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Students can Download Chapter 9 Environment Sustainable Development Notes, Plus One Economics Notes helps you to revise the complete Kerala State Syllabus and score more marks in your examinations.

Kerala Plus One Economics Notes Chapter 9 Environment Sustainable Development

Environment
The environment is defined as the total planetary inheritance and the totality of all resources. It includes all the biotic and abiotic factors that influence each other. While all living elements – the birds, animals and plants, forests, fisheries, etc. are biotic elements and abiotic elements include air, water, land, etc. Rocks and sunlight are all examples of abiotic elements of the environment. A study of the environment then calls for a study of the interrelationship between these biotic and abiotic components of the environment.

Functions of the Environment
The environment performs four vital functions

• It supplies resources: resources here include both renewable and non-renewable resources.
  Renewable resources are those which can be used without the possibility of the resource becoming depleted or exhausted. That is, a continuous supply of the resource remains available.
• It assimilates waste
• It sustains life by providing genetic and bio-diversity
• It also provides aesthetic services like scenery, etc.

Global Warming and Ozone Depletion
Two important issues faced by our environment is global warming and ozone depletion.

Global warming: Global warming is a gradual increase in the average temperature of the earth’s lower atmosphere as a result of the increase in greenhouse gases since the Industrial Revolution. Much of the recent observed and projected global warming is human-induced. It is caused by man-made increases in carbon dioxide and other greenhouse gases through the burning of fossil fuels and deforestation.

Ozone Depletion: Ozone depletion refers to the phenomenon of reductions in the amount of ozone in the stratosphere The problem of ozone depletion is caused by high levels of chlorine and bromine compounds in the stratosphere The origins of these compounds are chlorofluorocarbons (CFC), used as cooling substances in airconditioners and refrigerators, or as aerosol propellants, and bromo fluorocarbons (halons), used in fire extinguishers. As a result of depletion of the ozone layer, more ultraviolet (UV) radiation comes to Earth and causes damage to living organisms. UV radiation seems responsible for skin cancer in humans; it also lowers production of phytoplankton and thus affects other aquatic organisms. It can also influence the growth of terrestrial plants.

State of India’s Environment
India has abundant natural resources in terms of rich quality of soil, hundreds of rivers and tributaries, lush green forests, plenty of mineral deposits beneath the land surface, vast stretch of the Indian Ocean, ranges of mountains, etc. The black soil of the Deccan Plateau is particularly suitable for the cultivation of cotton, leading to a concentration of textile industries in this region. The Indo-Gangetic plains – spread from the Arabian Sea to the Bay of Bengal – are one of the most fertile, intensively cultivated and densely populated regions in the world.

India’s forests, though unevenly distributed, provide green cover for a majority of its population and natural cover for its wildlife. Large deposits of iron ore, coal and natural gas are found in the country. India alone accounts for nearly 20% of the world’s total iron-ore reserves. Bauxite, copper, chromate, diamonds, gold, lead, lignite, manganese, zinc, uranium, etc. are also available in different parts of the country. However, the developmental activities in India have resulted in pressure on its finite natural resources, besides creating impacts on human health and well-being.

The threat to India’s environment poses a dichotomy -threat of poverty-induced environmental degradation and, at the same time, threat of pollution from affluence and a rapidly growing industrial sector. Air pollution, water contamination, soil erosion, deforestation and wildlife extinction are some of the most pressing environmental concerns of India.
The priority issues identified are :

• land degradation
• biodiversity loss
• air pollution with special reference to vehicular pollution in urban cities
• management of fresh water and
• Solid waste management. Land in India suffers from varying degrees and types of degradation stemming mainly from unstable use and inappropriate management practices.

Sustainable Development
The concept of sustainable development was emphasized by the United Nations Conference on Environment and Development (UNCED), which defined it as: ‘Development that meets the need of the present generation without compromising the ability of the future generation to meet their own needs’.

Strategies for sustainable development
Strategies for sustainable development include the following.

• Use of Non-conventional Sources of Energy: LPG, Gobar Gas in Rural Areas:
• CNG in Urban Areas
• Wind Power
• Solar Power through Photovoltaic Cells
• Mini-hydel Plants
• Traditional Knowledge and Practices
• Bio-composting
• Bio-pest Control

Students can Download Chapter 8 Infrastructure Notes, Plus One Economics Notes helps you to revise the complete Kerala State Syllabus and score more marks in your examinations.

Kerala Plus One Economics Notes Chapter 8 Infrastructure

Infrastructure
Infrastructure means some kinds of permanent installation, which are used over a long period of time for the supply of basic inputs like railway lines, schools, colleges, universities, hospitals, etc. Infrastructural facilities are often referred to as economic and social overheads.

1. The economic infrastructure consists of energy, transport, communication
2. The social infrastructure consists of education, health, and housing.

Relevance of Infrastructure
Infrastructure plays important role in economic growth and development. Developed nations have good record of social and economic infrastructure. The contributions of infrastructure are:
• It invites investment which leads to growth.
• It enhances productivity.
• It improves the quality of life of people.

State of Infrastructure in India
Two important infrastructures in India are energy and health. We shall examine their details below:

Energy: Energy is very vital for rapid economic growth. There is a big gap between consumer demand and the supply of electricity in India. Energy is a critical aspect of the development process of a nation. It is, of course, essential for industries. Now it is used on a large scale in agriculture and related areas like the production and transportation of fertilizers, pesticides, and farm equipment. It is required in houses for cooking, household lighting, and heating.

Sources of Energy: There are commercial and non-commercial sources of energy. Commercial sources are coal, petroleum, and electricity as they are bought and sold. Non-commercial sources of energy are firewood, agricultural waste, and dried dung. These are non-commercial as they are found in nature/ forests. While commercial sources of energy are generally exhaustible, non-commercial sources are generally renewable.

Non-conventional Sources of Energy: Both commercial and non-commercial sources of energy are known as conventional sources of energy. There are three other sources of energy which are commonly termed as non-conventional sources – solar energy, wind energy and tidal power.

Power/Electricity: The most visible form of energy, which is often identified with progress in modern civilization, is power, commonly called electricity; it is one of the most critical components of infrastructure that determines the economic development of a country.

Health: Health is an essential element of human resource development. Health is a holistic process related to the overall growth and development of the nation. WHO defines health as Economists judge the health conditions of the people of a country by looking at the following indicators.

• Infant mortality
• Maternal mortality
• Life expectancy
• Nutritional levels
• Incidence of communicable and non-communicable diseases
• Health infrastructures

Health System in India: India’s health infrastructure consists of a three-tier system such as primary, secondary, and tertiary. Primary health care includes health education, health problems, prevention and control of diseases, promotion of nutrition, issues relating to potable water and sanitation, maternal and child health care, immunization against major infectious diseases like Polio, T.B, diphtheria, promotion of mental health and provision of essential drugs, etc.

Primary health care is provided through, sub-centers catering to a population of about 5000, Primary health care centres (PHCs) at block level and community health centres (CHCs) at the district level. The primary health care centres have only limited facilities. When the patient need advanced health care they are referred to secondary or tertiary hospitals.

Secondary care institutions are those which have facilities for clinical investigations like X-ray, clinical laboratory, scanning, etc., specialist doctors like a surgeon, gynecologists, pediatricians, etc. It is mostly available in district headquarters and big towns and cities.

Tertiary health care institutions these are health care institutions at the top of the three-tier system, devoted in health care, health education and research: Medical colleges, super-specialty hospitals and multi-specialty hospitals. All India Institute of Medical Sciences (AIIMS) Delhi, National Institute of Mental Health and Neuro Sciences (NIMHANS) Bangalore, Sree Chithra Institute of Medical Science (SCIM) Trivandrum, etc., are tertiary health care institutions.

Indian Systems of Medicine (ISM): Natural systems of medicine have to be explored and used to support public health. There is a great scope of advancement of medical tourism in India. It includes six systems: Ayurveda, Yoga, Unani, Siddha, Naturopathy and Homeopathy (AYUSH). At present, there are 3,004 ISM hospitals, 23,028 dispensaries and as many as 6,11,431 registered practitioners in India. But little has been done to set up a framework to standardize education orto promote research. ISM has huge potential and can solve a large part of our health care problems because they are effective, safe and inexpensive.

Students can Download Chapter 7 Employment-Growth, Informalisation and Related Issues Notes, Plus One Economics Notes helps you to revise the complete Kerala State Syllabus and score more marks in your examinations.

Kerala Plus One Economics Notes Chapter 7 Employment-Growth, Informalisation and Related Issues

Workers and Employment
Those activities that contribute to Gross National Product (GNP) or national income are known as economic activities. When farmers work in a field or a labour work in a factory, or doctor works in a hospital they produce goods or services. All those who are engaged in economic activities including self-employed are called workers. The employment situation is diverse and complex in India. It is due to the developing nature of the economy and the socio-economic and demographic factors that influence it.

Participation of People in Employment
The worker-population ratio is an important indicator of the employment situation in an economy.
Worker population-ratio refers to the ratio of workers to the population. It is computed by dividing the number of workers(W) by the total population (P) and express it in terms of percentage (W/P)*100. This ratio is useful in knowing the proportion of the population actively contributing to the production of goods and services in a country. The worker-population ratio in India for 2011 was 39.3%.

Employment in Firms, Factories, and Offices
In the course of the economic development of a country, labour flows from agriculture and other related activities to industry and services. Generally, we divide all economic activities into eight different industrial divisions. They are:

1. Agriculture
2. Mining and quarrying
3. Manufacturing
4. Electricity, gas and water supply
5. Construction
6. Trade
7. Transport and storage
8. Services.

For simplicity, all the working persons engaged in these divisions can be clubbed into three major sectors, viz.

• Primary sector includes (1) and (2)
• Secondary sector which includes (3), (4), and (5)
• Service sector which includes divisions (6), (7), and (8).

Unemployment and Types of Unemployment
The unemployment situation in India is highly complex. There are different types of unemployment in our country like open unemployment, disguised unemployment, seasonal unemployment, etc. Unemployment is a situation in which people are willing to work at the prevailing wage rate, but do not get any work.

Open Unemployment: Open unemployment is the situation in which people above a certain age who are able to work and willing to work at the prevailing wage remain unemployed. Open unemployment is involuntary in nature. They are willing to work, but employment opportunities are not available to them. People standing in some selected areas waiting to be recruited as the hired worker is a case of open unemployment.

Disguised Unemployment: When more persons are working in a job than actually required, the situation is termed as disguised unemployment or hidden unemployment. If some workers are withdrawn from work, either total production or productivity falls. This type of unemployment is prominent in Indian agriculture.

Seasonal Unemployment: The type of unemployment caused by a change in seasons is termed as seasonal unemployment. This is normally found in the agricultural sector of India. Agriculture normally provides only seasonal employment and people are employed during the busy sowing and harvesting seasons. Seasonal unemployment could also be found in agro-based industries such as sugar mills, rice mills, cotton-spinning mills, etc.

Students can Download Chapter 6 Rural Development Notes, Plus One Economics Notes helps you to revise the complete Kerala State Syllabus and score more marks in your examinations.

Kerala Plus One Economics Notes Chapter 6 Rural Development

Rural Development
Rural development is quite a comprehensive term but it essentially means a plan of action for the development of areas which are lagging behind in socio-economic development. It essentially focuses on the action for the development of areas that are lagging behind in the overall development of the village economy. Some of the areas which are challenging and need fresh initiatives for development in India include:

• Development of human resources including- literacy, more specifically, female literacy, education, and skill development-health, addressing both sanitation and public health
• Land reforms
• Development of the productive resources of each locality
• Infrastructure development like electricity, irrigation, credit, marketing, transport facilities including construction of village roads and feeder roads to nearby highways, facilities for agriculture research and extension, and information dissemination
• Special measures for alleviation of poverty and bringing about significant improvement in the living conditions of the weaker sections of the population emphasizing access to productive employment opportunities.

Credit and Marketing in Rural Areas
Credit: Growth of rural economy depends primarily on the infusion of capital, from time to time, to realize higher productivity in agriculture and non-agriculture sectors. As the time gestation between crop sowing and realization of income after production is quite long, farmers borrow from various sources to meet their initial investment on seeds, fertilizers, implements and other family expenses of marriage, death, religious ceremonies.

A major change occurred after 1969 when India adopted social banking and a multi-agency approach to adequately meet the needs of rural credit. Later, the National Bank for Agriculture and Rural Development (NABARD) was set up in1982 as an apex body to coordinate the activities of all institutions involved in the rural financing system.

The institutional structure of rural banking today consists of a set of multi-agency institutions, namely, commercial banks, regional rural banks (RRBs), co-operatives and land development banks. Recently, Self-Help Groups (henceforth SHGs) have emerged to fill the gap in the formal credit system because the formal credit delivery mechanism has not only proven inadequate but has also not been fully integrated into the overall rural social and community development. By March end 2003, more than seven lakh SHGs had reportedly been credit linked. Such credit provisions are generally referred to as micro-credit programmes.

Agricultural Market System
Agricultural marketing is a process that involves the assembling, storage, processing, transportation, packaging, grading and distribution of different agricultural commodities across the country. Let us discuss four such measures that were initiated to improve the marketing aspect.

1. The first step was regulation of markets to create orderly and transparent marketing conditions.

2. Second component is provision of physical infrastructure facilities like roads, railways, warehouses, godowns, cold storages and processing units.

3. Co-operative marketing, in realizing fair prices for farmers’ products, is the third aspect of a government initiative.

4. The fourth element is the policy instruments like

• assurance of minimum support prices (MSP) for 24 agricultural products
• maintenance of buffer stocks of wheat and rice by Food Corporation of India and
• distribution of food grains and sugar through PDS.

These instruments are aimed at protecting the income of the farmers and providing food grains at subsidized rate to the poor.

Diversification into Productive Activities
Diversification of farm products has two aspects: The first one relates to the diversification of crop production. The second one relates to the shift of the workforce from agriculture to other allied activities such as livestock, poultry, fishers, etc., and to non-farm sectors like food processing. Diversification of agriculture helps to provide alternative employment opportunities in the non-farm sector and will minimize the risk of depending exclusively on agriculture. These activities related to diversification are given below:

• Animal husbandry
• Fisheries
• Horticulture

Sustainable Development and Organic Farming
In recent years, awareness of the harmful effect of chemical-based fertilizers and pesticides on our health is on a rise. Conventional agriculture relies heavily on chemical fertilizers and toxic pesticides, etc., which enter the food supply, penetrate the water sources, harm the livestock, deplete the soil and devastate natural eco-systems. Efforts in evolving technologies which are eco-friendly are essential for sustainable development and one such technology which is eco-friendly is organic farming.

Benefits of Organic Farming:
1. Organic agriculture offers a means to substitute costlier agricultural inputs (such as HYV seeds, chemical fertilizers, pesticides, etc.) with locally produced organic inputs that are cheaper and thereby generate good returns on investment.

2. Organic agriculture also generates income through international exports as the demand for organically grown crops is on a rise.

3. Studies across countries have shown that organically grown food has more nutritional value than chemical farming thus providing us with healthy foods.

4. Since organic farming requires more labour input than conventional farming, India will find organic farming an attractive proposition.

5. Finally, the produce is pesticide-free and produced in an environmentally sustainable way.

Students can Download Chapter 4 Poverty Notes, Plus One Economics Notes helps you to revise the complete Kerala State Syllabus and score more marks in your examinations.

Kerala Plus One Economics Notes Chapter 4 Poverty

Poverty and Poverty Line
Poverty is a multi-dimensional concept. It is defined as a situation in which a section of society is unable to fulfill even the basic necessities of life or deprived of basic necessities of life. Poverty is measured on the basis of the poverty line. One way is to determine it by the monetary value (per capita expenditure) of the minimum calorie intake that was estimated at 2,400 calories for a rural person and 2,100 for a person in the urban area.

Causes of Poverty
Important causes of poverty in India are:

• Low income
• Lack of assets
• Unemployment
• Inequality
• Exploitation
• Population explosion
• Undesirable economic growth
• Inflation
• Absence of industrialisation.

Poverty Eradication Programmes
Poverty eradication programmes in India are classified as follows:

Self-employment Programmes
Integrated Rural Development Programme (IRDP): The IRDP was introduced in 2nd October 1980. This programme has been renamed as
Swarnajayanthi Grama Swarojgar Yojana (SGSY) from 1st April 1999. The SGSY is a very holistic programme compared to IRDP. SGSY is developed by merging various programmes such as TRYSEM (Training of Rural Youth for Self-employment), DWCRA (Development of Women and Children in Rural Areas), GKY (Ganga Kalyan Yojana), MSW (Million Well Scheme), and SITRA (Supply of Improved Tool Kits to Rural Artisans). It forms SHG’s (Self-Help Groups) of poor people and formulates self-employment programmes under their leadership. It includes development of infrastructure, technology, credit and marketing managements, etc. Unlike other programmes, the priority of the employment programme can be fixed by the beneficiaries.

Wage Employment Programmes
1. National Rural Emptoyment Programme (NREP): NREP was the new name given to Food for Work Programme. It was launched in 1980 as a centrally sponsored scheme with state and central governments sharing equal amounts. The aim of this programmer the development of community assets like drinking water wells, irrigation wells, rural roads, schools, etc.

2. The Rural Landless Employment Guarantee Programme (RLEGP): This programme was launched on 15th August 1983 to supplement NREP. This is a centrally sponsored scheme with 100 percent fund by the union government.

3. Jawahar Rozgar Yojana (JRY) and Nehru Rozgar Yojana (NRY): NREP and the RLEGP were merged and renamed into a single rural employment programme known as Jawahar Rozgar Yojana. JRY came into effect from 1st April 1999. The aim of the programme was to provide gainful employment for unemployed rural areas. The urban version of JRY is known as Nehru Rozgar Yojana (NRY).

4. The Million Well Scheme (MWS) was to provide open irrigation well, free of cost, to poor small and marginal farmers belonging to SC/ST category.

5. Indira Awas Yojana (IAY) was introduced for providing houses, free of cost to SC/ST families. Now this facility is extended to other poor families too.

6. Pradan Manthri Gramodaya Yojana: Gramin Awas (PMRY)
The PMRY: GAwas launched on 1st April, 2000. The programme aims at providing the housing needs of the rural people.

7. National Rural Employment Guarantee Programme (NREGP) 2005: In August 2005, the Parliament has passed a new Act known as National Rural Employment Guarantee Act 2005. The act provides guaranteed wage employment to every household whose adult volunteer is to do unskilled manual work for a minimum of 100 days in a year. Thj act came into force from 2nd February 2006 and implemented in India’s 200 most backward districts. Later on it was extended to all over the country in two phases. The programme was later on renamed as Mahatma Gandhi National Rural Employment Guarantee Programme (MGNREGP) or commonly called Employment Assurance Scheme.

Social Security Programmes: There are not many programmes for the social security of the poor. However, there are some centrally sponsored schemes. They are as follows:

• Old-age pension for the elderly who are without support.
• Financial support in the event of the death of the breadwinner.
• Support for women of poor households on pregnancy.

Food Security Programmes: It is essential to ensure food security to the masses. As we know, though there js sufficient production of food grains, millions of people are starving in the country. The problem is mainly of distribution. To overcome these several measures are taken by the government. They are as follows:

1. Public distribution system (PDS): Foodgrains are made available at cheaper prices and distributed through Fair Price Shops, ration shops, Maveli Stores, Neethi Stores etc.

2. Targeted Public Distribution System (TPDS): The TPDS initiated in June 1997 aims at ensuring the availability of food grains to BPL families.

3. Integrated Child Development Schemes (ICDS): A nutrition programme meant for children below 6 years of age, pregnant and lactating women.

4. Mid-day Meal at School: Mid-day Meal at School is in operation in several states. The programme was launched in all India level on 15th August 1995.

5. Annapurna Scheme: This programme was commenced from 2000-01. Poor old people who are not getting old-age pensions are covered under this scheme.

6. Antyodaya Anna Yojana: This scheme is launched for the poorest of the poor. Under this scheme, food grains are made available to very poor families at a highly subsidised price.

Students can Download Chapter 11 Plant Growth and Development Notes, Plus One Botany Notes helps you to revise the complete Kerala State Syllabus and score more marks in your examinations.

Kerala Plus One Botany Notes Chapter 11 Plant Growth and Development

Growth
Growth is defined as an irreversible permanent increase in the size of an organ or its parts of an individual cell.
It is accompanied by metabolic processes (both anabolic and catabolic), that occur at the expense of energy.
Eg: expansion of a leaf.

Plant Growth Generally is Indeterminate
Plant growth is unlimited growth due to the presence of meristems.
Root apical meristem and the shoot apical meristem are responsible for the primary growth of the plants and contribute to the elongation of the plants along their axis.

Role of lateral meristem in plants
In dicotyledonous plants and gymnosperms, the lateral meristems, (vascular cambium and cork-cambium) cause an increase in the girth of the organs. This is known as secondary growth.

Growth is Measurable

• Growth is measured in terms of increase in fresh weight, dry weight, length, area, volume, and cell number.
• One single maize root apical meristem can give rise to more than 17,500 new cells per hour, cells in a watermelon increase in size by up to 3,50,000 times.
• In the former, growth is expressed as an increase in cell number.
  latter expresses growth as an increase in the size of the cell.
• While the growth of a pollen tube is measured in terms of its length, an increase in surface area denotes the growth in a dorsiventral leaf.

Phases of Growth
The period of growth is generally divided into three phases.

1. Meristematic: The constantly dividing cells, both at the root apex and the shoot apex, represent the meristematic phase of growth.
2. Elongation: The cells proximal to the meristematic zone represent the phase of elongation.
3. Maturation: Proximal to the phase of elongation represents the phase of maturation.

Growth Rates
The increased growth per unit time is termed as growth rate. The growth rate may be

1. Arithmetic
2. Geometrical

On plotting the length of the organ against time, a linear curve is obtained, it is expressed as

L_t = L₀ + rt
L_t = length at time ‘t’
L₀ = length at time ‘zero’.
r = growth rate/elongation per unit time.

Different phases of the Sigmoid curve

1. lag phase
2. log or exponential phase
3. stationary phase

In most systems, the initial growth is slow (lag phase), and it increases rapidly at an exponential rate (log or exponential phase)
In the end, due to the limited nutrient supply, the growth slows down leading to a stationary phase. It is the typical sigmoid or S-curve.

The exponential growth can be expressed as
W₁ = W₀ e rt
W₁ = final size (weight, height, number etc.)
W₀ = initial size at the beginning of the period
r = growth rate
t = time of growth
e = base of natural logarithms

Quantitative comparisons between the growth of a living system can also be made in two ways:

• Measurement and the comparison of total growth per unit time is called the absolute growth rate.
• The growth of the given system per unit time expressed on a common basis.

In Figure two leaves, A and B, are drawn that are of different sizes but show an absolute increase in area in the given time to give leaves, A1 and B1.

Conditions for Growth
Water, oxygen, and nutrients as very essential elements for growth.
The plant cells grow in size by cell enlargement it requires water.
Turgidity of cells helps in extension growth. Water also provides the medium for enzymatic activities
Oxygen helps in releasing metabolic energy essential for growth activities.
Nutrients (macro and micro essential elements) are required by plants for the synthesis of protoplasm and act as a source of energy.
An optimum temperature range is best suited for plant growth.
Environmental signals such as light and gravity also affect certain phases/stages of growth.

Differentiation, Dedifferentiation, and Redifferentiation
1. The cells derived from root apical and shoot-apical meristems and cambium differentiate and mature to perform specific functions. This is termed as differentiation.
For example, during differentiation, tracheary elements lose their protoplasm and develop a very strong, elastic, lignocellulosic secondary cell wall, to carry water too long distances.

2. The living differentiated cells, that have lost the capacity to divide can regain the capacity of division This phenomenon is termed dedifferentiation.
For example, interfascicular cambium and cork cambium is formed from fully differentiated parenchyma cells.

3. Meristems are able to divide and produce cells that once again lose the capacity to divide but mature to perform specific functions. This is called a redifferentiation.
For example, secondary tissues develop from vascular cambium and cork cambium

Development
It is the stage of the life cycle in which germination of the seed to senescence.

The plant shows a response to the environment to form different kinds of structures. This ability is called plasticity
Heterophylly is an example of plasticity

Types of Heterophylly
1. The leaves of the juvenile plant are different in shape from those in mature plants.
e.g cotton, coriander, and larkspur.
2. Shapes of submerged leaves are different from those produced in the air.
Eg buttercup.

Development is considered as the sum of growth and differentiation.
Development in plants is under the control of intrinsic and extrinsic factors.

A) Intrinsic factors

1. Intracellular (genetic)
2. Intercellular factors (chemicals such as plant growth regulators)

B) Extrinsic factors
Light, temperature, water, oxygen, nutrition, etc.

Plant Growth Regulators

Characteristics
The plant growth regulators (plant hormones or phytohormones) include

1. Indole compounds (indole-3-acetic acid, IAA);
2. Adenine derivatives (N6-furfurylamino purine, kinetin),
3. Derivatives of carotenoids (abscisic acid, ABA);
4. Terpenes (gibberellic acid, GA3) or
5. Gases (ethylene, C2H4).

The PGRs are divided into two groups based on their functions in a living plant body.
One group of PGRs are involved in growth-promoting activities, e.g., auxins, gibberellins, and cytokinins.
The other group mainly involved in growth-inhibiting activities such as dormancy and abscission. Eg-abscisic acid and ethylene.

The Discovery of Plant Growth Regulators
1. Auxin
At first, Charles Darwin and his son Francis Darwin observed that the coleoptiles of canary grass responded to unilateral illumination by growing towards the light source.
After a series of experiments, it was concluded that the tip of the coleoptile was the site of transmittable influence that caused the bending of the entire coleoptile.
Auxin was isolated by F. W. Went from tips of coleoptiles of oat seedlings.

2. Gibberellin
The ‘balance’ (foolish seedling) disease of rice seedlings, was caused by a fungal pathogen Gibberalla fujikuroi.
In this experiment, the uninfected rice seedlings were treated with sterile filtrates of the fungus. It led to the development of the disease. The active substance was gibberellic acid.
It was demonstrated by E. Kurosawa.

3. Cytokinin
The internodal segments of tobacco stems- the callus proliferated in the presence of auxins along with the extracts of vascular tissues, yeast extract, coconut milk or DNA.
Skoog and Miller later identified and crystallized the cytokinesis promoting active substances that they termed kinetin.

4. Abscisic acid(ABA)
During the mid-1960s inhibitory hormones were identified: inhibitor-B, abscission II and dormin.
Later all the three were named abscisic acid (ABA).

5. Ethylene
Ripened oranges that hastened the ripening of stored unripened bananas. Later this volatile substance was identified as ethylene, a gaseous PGR.

Physiological Effects of Plant Growth Regulators
Auxins
Auxins were first isolated from human urine.
They are generally produced by the growing apices of the stems and roots, from where they migrate to the regions of their action.

Two types of auxins

1. Natural (IAA and indole butyric acid (IBA)
2. Synthetic. NAA (naphthalene acetic acid) and 2, 4-D (2, 4-dichlorophenoxyacetic)

1. They help to initiate rooting in stem cuttings
2. Auxins promote flowering e.g. in pineapples.
3. They help to prevent fruit and leaf drop at early stages but promote the abscission of older mature leaves and fruits.
4. In most higher plants, the growing apical bud inhibits the growth of the lateral (axillary) buds, a phenomenon called apical dominance.
5. Removal of shoot tips (decapitation) usually results in the growth of lateral buds Hence it is widely applied in tea plantations, hedge-making, etc.
6. Auxins also induce parthenocarpy.
7. They are widely used as herbicides. 2, 4-D is used to kill dicotyledonous weeds, So it is used to prepare weed-free lawns by gardeners.
8. Auxin controls xylem differentiation and helps in cell division.

Gibberellins
Gibberellic acid (GA3) was one of the first gibberellins to be discovered and remains the most intensively studied form.
GA3 is acidic.

1. GA3 causes an increase in the length of grapes stalks. .
2. Gibberellins, cause fruits like apple to elongate and improve its shape
3. They delay senescence. Hence the fruits are keeping as fresh.
4. GA3 is used to speed up the malting process in the brewing industry.
5. Spraying sugarcane crop with gibberellins increases the length of the stem, thus increasing the yield by as much as 20 tonnes per acre.
6. Spraying juvenile conifers with GAs hastens the maturity period, thus leading to early seed production.
7. Gibberellins also promote bolting(internode elongation just prior to flowering) in beet, cabbages and many plants with rosette habit.

Cytokinins
Cytokinins were discovered as kinetin (a modified form of adenine, a purine) from the autoclaved herring sperm DNA.
Naturally occurring cytokinin-zeatin was isolated from corn-kernels and coconut milk.
Natural cytokinins are synthesised in regions where rapid cell division occurs, for example, root apices, developing shoot buds, young fruits, etc.

1. It helps to produce new leaves, chloroplasts in leaves, lateral shoot growth and adventitious shoot formation.
2. Cytokinins help to overcome apical dominance.
3. They promote nutrient mo8/+9bilisation which helps in the delay of leaf senescence.

Ethylene
The most widely used compound as a source of ethylene is ethephon.
It is readily absorbed and transported within the plant and releases ethylene slowly.
Ethephon hastens fruit ripening in tomatoes and apples and accelerates abscission in flowers and fruits

1. Ethylene is a gaseous hormone that promotes senescence and ripening fruits.
2. It promotes horizontal growth of seedlings, swelling of the axis, and apical hook formation in dicot seedlings.
3. Ethylene promotes senescence and abscission of plant organs, especially of leaves and flowers.
4. Ethylene is highly effective in fruit ripening. It enhances the respiration rate during the ripening of the fruits (respiratory climactic).
5. Ethylene breaks seed and bud dormancy and initiates germination in peanut seeds, sprouting of potato tubers.
6. Ethylene promotes rapid internode/petiole elongation in deepwater rice plants.
7. Ethylene also promotes root growth and root hair formation, thus helping the plants to increase their absorption surface.
8. Ethylene is used to initiate flowering and fruit-set in pineapples.
9. It also induces flowering in mango.
10. It promotes female flowers in cucumbers

Abscisic acid

1. It promotes abscission and dormancy.
2. It acts as an inhibitor of plant metabolism.
3. ABA inhibits seed germination.
4. ABA stimulates the closure of stomata and increases the tolerance of plants to various kinds of stresses. Hence it is called the stress hormone.
5. ABA plays an important role in seed development, maturation, and dormancy.
6. ABA helps the seeds to withstand desiccation
7. ABA acts as an antagonist to GA3.

Photoperiodism
It is the phenomenon of relative day and night length for the initiation of flowering.

Based on the exposure to photoperiod there are three types of plants

1. Long day plants: They require exposure to light for a period greater than critical duration (12 hr).
2. Short-day plants: They require less than critical duration before flowering.
3. Day-neutral plants: In this type, there is no such correlation between exposure to light duration and induction of flowering response.

Which is the organ of a plant perceives light for photoperiodism?
The site of perception of light/dark duration is the leaves. After receiving the required photoperiod, the hormonal substance migrates from leaves to shoot apices for inducing flowering. The shoot apices become changed into flowering apices prior to flowering.

Vernalisation
It is the phenomenon of exposure of low temperature for the initiation of flowering
Some important food plants, wheat, barley, rye have two kinds of varieties: winter and spring varieties.

Nature of spring and winter varieties
The ‘spring’variety are normally planted in the spring and come to flower and produce grain before the end of the growing season.
Winter varieties, planted in spring fail to flower or produce mature grain within a span of a flowering season.
If they are planted in autumn .they germinate and overwinter come out as small seedlings, resume growth in the spring, and are harvested usually around mid-summer.

Biennials and low-temperature treatment
Biennials are monocarpic plants that normally flower and die in the second season. Biennial plants are subjected to a cold treatment, it stimulates photoperiodic flowering response. Sugarbeet, cabbages, carrots are some of the common biennials.

NCERT Supplementary Syllabus

Seed Germination
The seeds germinate under favourable conditions after the period of dormancy.
After dormancy embryo becomes metabolically active and starts growing. This process is known as seed germination.
The conditions necessary for seed germination are the availability of water and oxygen.

A physiological phenomenon in seed germination
The physical phenomenon associated with seed germination is imbibition. It causes the swelling of seed then rupturing of the seed coat, through which radical emerges out.
It develops into a root system but the shoot system arises from the plumule of another end of the embryonal axis.
The metabolic activities require oxygen for breaking down the food reserves such as polysaccharides, proteins and lipid.
It is converted into soluble materials with the help of enzymes and mobilized to the embryonal axis.
The growth of radical and plumule is due to cell extension, cell division, and several biochemical processes.
The seed also needs a suitable temperature (optimum between 25 to35). The rate of respiration increases rapidly during seed germination.

What is the Viviparous type of germination?
Vivipary is the germination of a seed while it is still attached to the parent plant and is nourished by it. The plants grow in marshy land such as Rhizophora and Sonneratia (halophytes)show this type of germination.
During germination, radical elongates, and the weight of the germinating seed increases. As a result, the seedling separates and fail down vertically into the mud and grow into a new plant.

Seed Dormancy
It is the period of rest or a period of suspended growth due to this

1. water content, the metabolic activities become extremely low.
2. the seed coat becomes impermeable to oxygen and moisture and hardens.

The suspension of growth is due to exogenous (environmental conditions) or endogenous control during which metabolic activity of the seed is greatly reduced.

Causes of Dormancy

1. Impermeable or mechanically resistant seed coats.
2. Rudimentary or physiologically immature embryos or
3. Due to the presence of germination inhibitors such as abscisic acid, phenolic acid, short-chain fatty acids, and coumarin.

How can overcome seed dormancy?

1. Mechanical or chemical scarification of the seed coat (scratching of seed coat or seeds soaked in chemicals to break the dormancy)
2. Stratification of seeds or changing environmental conditions such as temperature, light, and pressure. Stratification of seeds is subjecting the moist seeds to oxygen for variable periods of low or high temperatures.

Students can Download Chapter 10 Respiration in Plants Notes, Plus One Botany Notes helps you to revise the complete Kerala State Syllabus and score more marks in your examinations.

Kerala Plus One Botany Notes Chapter 10 Respiration in Plants

How are respiration and photosynthesis-related?
Green plants and cyanobacteria can prepare their own food by the process of photosynthesis, they trap light energy and convert it into chemical energy that is stored in the bonds of carbohydrates (Macromolecules) like glucose, sucrose, and starch.
By Cellular respiration, food materials undergo breakdown that release energy and the trapping of this energy for the synthesis of ATP.

ATP is called the energy currency of the cell why?
ATP is broken down whenever (and wherever) energy needs to be utilised. Hence, ATP acts as the energy currency of the cell.

Seat of photosynthesis and respiration
Photosynthesis takes place within the chloroplasts whereas the breakdown of complex molecules to yield energy takes place in the cytoplasm and in the mitochondria (also only in eukaryotes).
The compounds that are oxidized during respiration are known as respiratory substrates.
Eg. Proteins, fats, and even organic acids.

Do Plants Breathe?
Plants require O₂ for respiration and give out CO₂ and H₂O as end products and release energy most of which is given out as heat.

Respiration is least important to plants than animals
Roots, stems, and leaves respire at rates far lower than animals When cells photosynthesize O₂ is released within the cell.
But some cells live where oxygen may or may not be available.
All living organisms retain the enzymatic machinery to partially oxidise glucose without the help of oxygen. This breakdown of glucose to pyruvic acid is called glycolysis.

Glycolysis
The term glycolysis -(Greek words, glycols for sugar, and lysis for splitting).
The scheme of glycolysis was given by Gustav Embden, Otto Meyerhof, and J. Parnas, Hence glycolysis is called an EMP pathway.
In anaerobic organisms, it is the only process in respiration.
Glycolysis occurs in the cytoplasm of the cell and is present in all living organisms.
In this process, Glucose undergoes partial oxidation to form two molecules of pyruvic acid.

Steps lead to end products of glycolysis

1. Glucose and fructose are phosphorylated to give rise to glucose-6-phosphate by the activity of the enzyme hexokinase.

2. This phosphorylated form of glucose then isomerises to produce fructose-6-phosphate.

3. In this pathway, ATP is utilised at two steps: first in the conversion of glucose into glucose 6-phosphate and second in the conversion of fructose 6-phosphate to fructose 1,6 diphosphate).

4. The fructose 1,6-diphosphate is split into dihydroxyacetone phosphate and 3 phosphoglyceraldehydes (PGAL). In this step NADH +H+ is formed from NAD+.

5. 3-phosphoglyceraldehyde (PGAL) is converted to 1,3 bisphosphoglycerate (DPGA).

6. The conversion of DPGA to 3-phosphoglyceric acid (PGA), is also an energy-yielding process; this energy is trapped by the formation of ATP.

7. 3-phosphoglyceric acid (PGA) is converted into 2 phosphoglycerates.

8. 2 phosphoglycerates are converted into 2 phosphoenol pyruvic acid. ATP is synthesized during the conversion of PEP to pyruvic acid.

9. 2 phosphoenol pyruvic acid undergoes dephosphorylation to form 2 molecule of pyruvic acid

The fate of pyruvic acid
It involves

1. Lactic acid fermentation
2. Alcoholic fermentation
3. Aaerobic respiration.

Fermentation takes place under anaerobic conditions in many prokaryotes and unicellular eukaryotes.

The complete oxidation of glucose to CO₂ and H₂O occurs in organisms that adopt Krebs’ cycle which is also called as aerobic respiration. This requires an O₂ supply.

Fermentation
In fermentation, glucose undergoes incomplete oxidation and forms CO₂ and ethanol
The enzymes, pyruvic acid decarboxylase, and alcohol dehydrogenase catalyze these reactions.
Fermentation occurs in the presence of yeast
Yeasts poison themselves to death when the concentration of alcohol reaches about 13 percent. Some organisms like bacteria produce lactic acid from pyruvic acid.

The lactic acid in eukaryotic cell
In animal muscle cells during exercise, when oxygen is inadequate for cellular respiration, pyruvic acid is reduced to lactic acid by lactate dehydrogenase.
The reducing agent is NADH+H* which is re oxidised to NAD+ in both the processes.
In both lactic acid and alcohol fermentation, less than seven percent of the energy in glucose is released.
In eukaryotes second step after glycolysis take place within the mitochondria and this requires O₂.
It is aerobic respiration leads to complete oxidation of carbohydrate in the presence of oxygen and releases CO₂, water and a large amount of energy.
This type of respiration is most common in higher organisms.

Aerobic Respiration
The second step of Aerobic respiration takes place within the mitochondria.
The product of glycolysis- pyruvate is transported from the cytoplasm into the mitochondria.

First step of oxidation of pyruvic acid
In the mitochondrial matrix, pyruvate undergoes oxidative decarboxylation by pyruvic dehydrogenase. The reactions require the participation of several coenzymes, including NAD+ and Coenzyme A.

During this process, two molecules of NADH are produced from the metabolism of two molecules of pyruvic acid.
The acetyl CoA then enters a cyclic pathway, tricarboxylic acid cycle(Krebs’ cycle) after the scientist Hans Krebs who first elucidated it.

Tricarboxylic Acid Cycle
The TCA cycle starts with the condensation of acetyl group with oxaloacetic acid (OAA) and water to yield citric acid.
The reaction is catalysed by the enzyme citrate synthase and a molecule of CoA is released.
It is followed by two successive steps of decarboxylation, leading to the formation of alpha-ketoglutaric acid and then succinyl-CoA. In the remaining steps, Succinic acid is oxidised to OAA.

Which step of the Krebs cycle substrate-level phosphorylation occurs?
During the conversion of succinyl-CoA to succinic acid, a molecule of GTP is synthesised. This is substrate-level phosphorylation.

At three sites in the cycle where NAD+ is reduced to NADH + H+ and one site where FAD+ is reduced to FADH₂.

In the mitochondrial matrix, pyruvate is broken down to release.
8 molecules of NADH + H+
2 molecules of FADH₂
2 molecules of GTP and
3 molecules of CO₂

Electron Transport System (ETS) and Oxidative Phosphorylation

The metabolic pathway through which the electron passes from one carrier to another is called the electron transport system (ETS).
It is present in the inner mitochondrial membrane.
Reduced coenzyme like NADH(complex) in the mitochondrial matrix is oxidised and release 2 electrons and 2protons
Electrons and protons are transferred to FMN, it reduced to FMNH2
It breaks and releases protons and electrons .protons go to intermembrane space but electrons reach ubiquinone.
Ubiquinone also receives reducing equivalents via FADH2 (complex II).
The reduced ubiquinone is then oxidised with the transfer of electrons to cytochrome c via cytochrome bc1 complex (complex III).

Electron Transport System (ETS)
Cytochrome c acts as a mobile carrier for the transfer of electrons between complex III and IV.
Complex IV refers to cytochrome c oxidase complex containing cytochromes a and a3.

Oxidation of one molecule of NADH gives rise to 3 molecules of ATP, while that of one molecule of FADH2 produces 2 molecules of ATP.
Oxygen acts as the final hydrogen acceptor.

Oxidative phosphorylation in mitochondria
In ETS the energy of oxidation-reduction is utilised for the production of proton gradient required for phosphorylation. This process is called oxidative phosphorylation.

Chemiosmosis (proposed by peter Mitchel)
The energy released during the electron transport system is utilised in synthesizing ATP with the help of ATP synthase (complex V) called chemiosmosis.

F1 – F0/exosomes
This complex consists of two major components, F1 and Fo.
The F1 headpiece is a site for synthesis of ATP from ADP and inorganic phosphate.
F0 is an integral membrane protein complex act as a channel through which protons cross the inner membrane.
For each ATP produced, 2H+ passes through F0 from the intermembrane space to the matrix down the electrochemical proton gradient.

The Respiratory Balance Sheet
How many ATP molecules are produced in Aerobic respiration?
In aerobic respiration, the number of ATP molecules produced or utilized in glycolysis, TCA cycle and ETS gives the net gain of 36 ATP molecules
Fermentation accounts for only a partial breakdown of glucose whereas in aerobic respiration it is completely degraded to CO₂ and H₂O.

How many ATP molecules are produced in Fermentation?
In fermentation there is a net gain of only two molecules of ATP for each molecule of glucose degraded NADH is oxidized to NAD+ rather slowly in fermentation.

Amphibolic Pathway
It involves two processes anabolism and catabolism.
For example, fats is broken down into glycerol and fatty acids. Then fatty acids degraded to acetyl CoA and enter the pathway.
Glycerol enters the pathway after being converted to PGAL.
The proteins are degraded by proteases and the individual amino acids enter the pathway at some stage within the Krebs’cycle as pyruvate or acetyl CoA.

Is it true both catabolism and anabolism occur in fat metabolism?
Fatty acids( substrate) are broken down to acetyl CoA before entering the respiratory pathway. But when the organism needs to synthesize fatty acids, acetyl CoA withdrawn from the respiratory pathway for it.
Hence, the respiratory pathway involves the breakdown and synthesis of fatty acids, i.e catabolism, and anabolism respectively. Hence it is considered as an amphibolic pathway.

Respiratory Quotient
Definition: The ratio of the volume of CO₂ evolved to the volume of O2 consumed in respiration is called the respiratory quotient (RQ) or respiratory ratio.

Respiratory quotient of some respiratory substrates
1. Carbohydrates: When carbohydrates are completely oxidised, the RQ is 1, because equal amounts of CO₂ and O₂ are evolved and consumed, respectively

2. Fats: If fats are used in respiration, the RQ is less than 1.

3. Proteins: When proteins are respiratory substrates the ratio is 0.9.

4. Organic acids: When organic acids are respiratory substrates, the ratio is more than one.

Students can Download Chapter 9 Photosynthesis in Higher Plants Notes, Plus One Botany Notes helps you to revise the complete Kerala State Syllabus and score more marks in your examinations.

Kerala Plus One Botany Notes Chapter 9 Photosynthesis in Higher Plants

What Do We Know?
Role of light, CO₂, H₂O, and Chlorophyll
Actually, chlorophyll (green pigment of the leaf), light, and CO₂ are required for photosynthesis. A variegated leaf ora leaf that was partially covered with black paper, and one that was exposed to light. On testing these leaves for starch it was clear that photosynthesis occurred only in the green parts of the leaves in the presence of light.

Half leaf experiment and the importance of CO₂ in photosynthesis
In this, a part of a leaf is enclosed in a test tube containing some KOH soaked cotton (which absorbs CO₂), while the other half is exposed to air. The set up is then placed in light for some time. Then conducted the starch test, showed that the exposed part of the leaf tested positive for starch while the portion that was in the tube, tested negative. This showed that CO₂ is required for photosynthesis.

Early Experiments

Historical aspects of photosynthesis
1. Priestley
He observed that a candle burning in a closed space – a bell jar, soon gets extinguished. Similarly, a mouse would soon suffocate in a closed space.

He concluded that a burning candle or an animal that breathes the air, both damage the air. But when he placed a mint plant in the same bell jar, he found that the mouse stayed alive and the candle continued to burn.

2. Jan Ingenhousz
He showed that sunlight is essential to the plant process that purifies the air fouled by burning candles or breathing animals. In aquatic habitat, during bright sunlight, small bubbles were formed around the green parts while in the dark they did not. Later he identified these bubbles are oxygen. So the green part of the plants could release oxygen.

3. Julius von Sachs
Glucose is usually stored as starch. He found that the green parts in plants where glucose is made.

4. T.W Engelmann
By using a prism he split light into its spectral components and then illuminated a green alga, Cladophora, placed in a suspension of aerobic bacteria. The bacteria were used to detect the sites of O₂ evolution. He observed that the bacteria accumulated mainly in the region of blue and red light of the split spectrum.

An empirical equation for photosynthesis

[CH₂O] represent a carbohydrate (e.g., glucose, a six-carbon sugar).

Hydrogen donor in bacteria and green plants
Some organisms do not release O₂ during photosynthesis
When H₂S, instead is the hydrogen donor for purple and green sulphur bacteria, the ‘oxidation’ product is sulphur or sulphate depending on the organism and not O₂. In the green plants, the O₂ evolved from H₂O, not from carbon dioxide.

The modern equation for photosynthesis

C₆H₁₂O₆ represents glucose. The O₂ released is from water

Where Does Photosynthesis Take Place?
It takes place in the chloroplast of leaves that contain grana, the stroma lamellae, and the fluid stroma.

Where is the energy production site in chloroplast?
The energy-rich molecules like ATP and NADPH are synthesized in grana and stroma lamellae by light reactions.

Where is the Glucose production site in chloroplast?
In stroma by dark reactions, CO₂ fixation leading to the synthesis of glucose, which in turn forms starch

Structure of chloroplast

Diagrammatic representation of an electron micrograph of a section of chloroplast

How Many Pigments are Involved in Photosynthesis?
Chromatographic separation of the leaf pigments shows that different types of pigments in leaves i.e
Chlorophyll a (bright or blue-green in the chromatogram)
chlorophyll b (yellow-green)
xanthophylls (yellow)
carotenoids (yellow to yellow-orange)

a) Graph showing the absorption spectrum of chlorophyll a, b, and the carotenoids.

b) Graph showing the action spectrum of photosynthesis.

c) Graph showing action spectrum of photosynthesis superimposed on the absorption spectrum of chlorophyll a.

Wavelengths of light absorbed by pigments
Chlorophyll pigments absorb light, at specific wavelengths of blue and the red regions while carotenoids absorb the blue and green wavelength
Chlorophyll is the major pigment responsible for trapping light, other thylakoid pigments like chlorophyll b, xanthophylls, and carotenoids, which are called accessory pigments, also absorb light and transfer the energy to chlorophyll a. but also protect chlorophyll a from photo-oxidation.

What is Light Reaction?
It is the photochemical phase include

1. light absorption
2. water splitting
3. oxygen release
4. Formation of high-energy rich molecules ATP and NADPH.

The pigments are organised into two light-harvesting complexes(LHC)

1. Photosystem I (PS I)/P700
2. Photosystem II (PS II)/P680

Each photosystem has single chlorophyll a molecule forms the reaction centre, all the pigments except chlorophyll-a forming a light-harvesting system also called antennae.

In PS I the reaction centre, chlorophyll a has an absorption peak at 700 nm while in PS II it has absorption maxima at 680 nm, and is called P680.

The Electron Transport
How does electron flow in electron carriers that connect two photosystems?
Initially, excitation of chlorophyll molecule occurs due to light, then electrons are emitted from Ps II (uphill) that are accepted by electron acceptor, electron flows through electron carriers cytochromes, (downhill) and (Loss of electrons of PSII is compensated by electrons coming from water and loss of electrons of PS I is compensated by electrons coming from PS II).

PS I is also excited due to light and electrons are emitted (uphill), it transfers an electron to another accepter, and finally down the hill to NADP+ causing it to be reduced to NADPH + H+ is called the Z scheme.

Result of Z-scheme

1. production of ATP and NADPH
2. O₂ evolution

Splitting of Water
Photolysis
It is the splitting of water into H+, [O] and electrons in the presence of light and these electrons are available to PSII.
This process takes place on the inner side of the membrane of the thylakoid.
Oxygen released is one of the net products of photosynthesis.
2H₂O → 4H⁺ + O₂ + 4e^–

Cyclic and Non-cyclic Photo-phosphorylation
Phosphorylation
The process of which ATP from ADP and inorganic phosphate in the presence of light (in mitochondria and chloroplasts) is named phosphorylation.

Electron in a cyclic process
When only PS I is functional, the cyclic flow of electrons within the photosystem and the phosphorylation occurs in the stroma lamellae.
Cyclic photophosphorylation also occurs when only light of wavelengths beyond 680 nm are available for excitation i.e at 700 nm

Result of cyclic photophosphorylation
ATP is produced.

Where does the light-harvesting complex work for acyclic and noncyclic processes?
The membrane or lamellae of the grana have both PS I and PS II so a noncyclic process occurs,
The stroma lamellae membranes lack PS II as well as NADP reductase enzyme So a cyclic process occurs.

Chemiosmotic Hypothesis
It is the ATP synthesis linked to the development of a proton gradient across a membrane
In chloroplast, the proton accumulation is towards the inside of the membrane, i.e., in the lumen. In respiration, protons accumulate in the intermembrane space of the mitochondria when electrons move through the ETS.
The proton gradient develops due to,

a. Splitting of the water molecule takes place on the inner side of the membrane, the protons accumulate within the lumen of the thylakoids

b. As electrons move through the photosystems, protons are transported across the membrane moves into the lumen side of the membrane

c. The NADP reductase enzyme is located on the stromal side of the membrane. Along with electrons that come from the accepter of electrons of PS I, protons are necessary for the reduction of NADP+ to NADPH+ H+. These protons are also removed from the stroma.

In chloroplast, protons in the stroma decrease in number, while in the lumen there is an accumulation of protons. This creates a proton gradient across the thylakoid membrane The gradient is broken down due to the movement of protons across the membrane to the stroma through the transmembrane channel of the F₀ of the ATP.
ATPase have a channel that allows diffusion of protons back across the membrane; this releases enough energy to activate the ATPase enzyme that catalyses the formation of ATP.

Where are the ATP and NADPH Used?
It is used in the biosynthetic phase of photosynthesis. This process does not directly depend on the presence of light but is dependent on the products of the light reaction, i.e., ATP and NADPH.
Melvin Calvin studied the algal photosynthesis by using radioactive 14C led to the discovery that the first CO₂ fixation product was identified as 3-phosphoglyceric acid or PGA.

The Primary Acceptor of CO₂
The studies showed that the accepter molecule was a 5-carbon sugar -ribulose bisphosphate (RuBP) in the Calvin cycle.

The Calvin Cycle
It involves three stages:

1. carboxylation
2. reduction
3. regeneration

1. Carboxylation:
Carboxylation is the fixation of CO₂ into a stable compound catalysed by the enzyme RuBisCO that results in the formation of two molecules of 3-PGA.

2. Reduction: These are a series of reactions that lead to the formation of glucose.
The steps involve the utilization of 3 molecules of ATP for phosphorylation and two NADPH for reduction per CO₂ molecule fixed. For the fixation of six molecules of CO₂, 6 turns of the cycle are required and one molecule of glucose is generated

3. Regeneration: Regeneration of the CO₂ acceptor molecule require one ATP for phosphorylation to form RuBP.
Hence for every CO₂ molecule entering the Calvin cycle, 3 molecules of ATP and molecules of NADPH are required

The Calvin cycle proceeds in three stages:
1. carboxylation, during which CO₂ combines with ribulose- 1, 5- bisphosphate
2. reduction, during which carbohydrate is formed at the expenses of the photochemically made ATP and NADPH; and
3. regeneration during which the CO₂ acceptor ribulose- 1, 5-bisphosphate has formed again so that the cycle continues

The C₄ Pathway (Hatch and Slack Pathway)
Plants that are adapted to dry tropical regions have the C₄ pathway, C₄ plants have a special type of leaf anatomy. They tolerate higher temperatures. They lack a process called photorespiration and have greater productivity of biomass.

Special leaf anatomy-kranz anatomy
Large cells around the vascular bundles are centripetally arranged bundle sheath cells such anatomy is called ‘Kranz’ anatomy. Eg- maize or sorghum

Primary CO₂, accepter, first stable product and Enzyme of C₄ Pathway
The primary CO₂ acceptor is a 3-carbon molecule- phosphoenolpyruvate (PEP) present in the mesophyll cells. The enzyme responsible for this fixation is PEP carboxylase or PEPcase.
The first stable product C₄ acid OAA is formed in the mesophyll cells.

Diagrammatic representation of a Hatch arid Slack Pathway
OAA converted into 4-carbon compounds like malic acid or aspartic acid in the mesophyll cells .which are transported to the bundle sheath cells. In the bundle sheath cells, these C4 acids are broken down to release CO₂ and a 3-carbon molecule. The 3-carbon molecule is transported back to the mesophyll where it is converted to PEP again, thus, completing the cycle.
Thus the basic pathway that results in the formation of the sugars, the Calvin pathway, is common to the C₃ and C₄ plants.

Photorespiration
In C₃ plants, under high concentration of O₂ and low CO₂ concentration, RUBP binds with O₂ to form one molecule of PGA and phosphoglycolate and a large quantity of CO₂ is released.

Can you say photorespiration is a wasteful process?
This process utilise ATP but neither synthesis of sugars, nor of ATP. Hence photorespiration is a wasteful process.

The specialty of C₄ plants to avoid Photorespiration
In C₄ plants photorespiration does not occur because C₄ acid from the mesophyll is broken down in the bundle cells to release CO₂ – this results in increasing the intracellular concentration of CO₂. Here RuBisCO functions as a carboxylase minimizing the oxygenase activity, productivity, and yields are better in these plants.

Factors Affecting Photosynthesis
Photosynthesis is influenced by several factors, both internal (plant) and external. The plant factors include the number, size, age, and orientation of leaves, mesophyll cells and chloroplasts, internal CO₂ concentration, and the amount of chlorophyll. The external factors include the availability of sunlight, temperature, CO₂ concentration, and water.

Blackman s Law of Limiting Factors
If a chemical process is affected by more than one factor, then its rate will be determined by the factor which is nearest to its minimal value: it is the factor that directly affects the process if its quantity is changed.
For example, In the green leaf, the light and CO₂ conditions are optimum but the plant does not photosynthesize if the temperature is very low.

Light
The availability of light shows a direct relationship with CO₂ fixation rates at low light intensities At higher light intensities the rate does not show further increase because other factors are not in optimal amount. The intensity of light beyond a point causes the breakdown of chlorophyll and a decrease in photosynthesis.

Carbon dioxide Concentration
The concentration of CO₂ is very low in the atmosphere (between 0.03 and 0.04 percent). An increase in concentration up to 0.05 percent can cause an increase in CO₂ fixation rates. The C₃ and C₄ plants respond differently to CO₂ concentrations.

Graph of light Intensity on the rate of photosynthesis

C₄ plants show saturation at about 360µL^-1 while C₃ responds to increased CO₂ concentration and saturation is seen only beyond 450µL^-1 Thus, the current availability of CO₂ levels is limiting to the C₃ plants.

C₃ plants respond to higher CO₂ concentration by showing increased rates of photosynthesis leading to higher productivity The above concept is used for some greenhouse crops such as tomatoes and bell pepper.

Temperature
The dark reactions that take place in stoma are enzymatic and temperature controlled. C₄ plants respond to higher temperatures and show a higher rate of photosynthesis while C₃ plants have a much lower temperature optimum.

Water
Water stress causes the closure of stomata and it is difficult to receive CO₂ for photosynthesis. The stress condition also makes leaves wilt and reducing the surface area of the leaves and their metabolic activities.

Students can Download Chapter 8 Mineral Nutrition Notes, Plus One Botany Notes helps you to revise the complete Kerala State Syllabus and score more marks in your examinations.

Kerala Plus One Botany Notes Chapter 8 Mineral Nutrition

Methods to Study the Mineral Requirements of Plants
In 1860, Julius von Sachs a German botanist demonstrated that plants could be grown in a nutrient solution in the complete absence of soil.

Hydroponics and its Importance

• This technique of growing plants in a nutrient solution is known as hydroponics.
• The nutrient solutions must be aerated to obtain optimum growth.
• In this method, essential elements are used and their deficiency symptoms can be studied.
• Hydroponics is used in the commercial production of vegetables such as tomato, seedless cucumber, and lettuce.

Hydroponic plant production. Plants are grown in a tube or trough placed on a slight incline. A pump circulates a nutrient solution from a reservoir to the elevated end of the tube. The solution flows down the tube and returns to the reservoir due to gravity. Inset shows a plant whose roots are continuously bathed in the aerated nutrient solution. The arrows indicate the direction of the flow.

Essential Mineral Elements

Some minerals are not essential to plants

• More than sixty elements are found in different plants.
• Some plant species absorb selenium, some others gold, while some plants growing near nuclear test sites take up radioactive strontium.

Criteria for Essentiality
The criteria for the essentiality of an element are given below:

• The element must be supporting normal growth and production.
  In the absence of the element, the plants do not complete their life cycle or set the seeds.
• The requirement of the element must be specific and not replaceable by another element.
• The element must be directly involved in the metabolism of the plant.

Based upon the above criteria 17 elements are essential for plant growth and metabolism. They are
i. Macronutrients:
Carbon, hydrogen, oxygen, nitrogen, phosphorous, sulphur, potassium, calcium, and magnesium
They are present in plant tissues in large amounts(in excess of 10 m mole/ Kg of dry matter).

ii. Micronutrients:
Iron, manganese, copper, molybdenum, zinc, boron, chlorine, and nickel
They are needed in very small amounts (less than 10 m mole /Kg of dry matter).

In addition to the essential elements, sodium, silicon, cobalt, and selenium are required by higher plants. Essential elements are grouped into four broad categories on the basis of their diverse functions.
i. Essential elements as components of biomolecules (e.g., carbon, hydrogen, oxygen, and nitrogen).

ii. Essential elements that are components of energy-related chemical compounds (e.g, magnesium in chlorophyll and phosphorous in ATP).

iii. Essential elements that activate or inhibit enzymes, (Mg²⁺ is an activator for both ribulose bisphosphate carboxylase oxygenase and phosphoenolpyruvate carboxylase, both of which are critical enzymes in photosynthetic carbon fixation
Zn²⁺ is an activator of alcohol dehydrogenase and Mo of nitrogenase during nitrogen metabolism.

iv. Essential elements alter the osmotic potential of a cell.
Potassium plays an important role in the opening and closing of stomata.

Role of Macro- and Micro-nutrients
Essential elements participate in various metabolic processes in the plant cells. The various forms and functions of mineral elements are given below.

Nitrogen

• It is absorbed mainly as NO₃^– Some taken up as NO₂ or NH₄⁺
• Nitrogen is required in meristematic tissues and the metabolically active cells.
• It is one of the major constituents of proteins, nucleic acids, vitamins and hormones

Phosphorus

• It is absorbed in the form of phosphate ions (either as HPO₄^2- or H₂PO₄^–)
• Phosphorus is a constituent of cell membranes, certain proteins, all nucleic acids, and nucleotides.
• It is required for all phosphorylation reactions.

Potassium

• It is absorbed as a potassium ion (K⁺).
• It is required in abundant quantities for meristematic tissues, buds, leaves, and root tips.
• Potassium helps to maintain an anion-cation balance in cells
• It is involved in protein synthesis
• It is involved in the opening and closing of stomata and activation of enzymes
• It helps in the maintenance of the turgidity of cells.

Calcium

• It is absorbed in the form of calcium ions (Ca²⁺).
• Calcium is required by meristematic and differentiating tissues.
• It is important in the formation of calcium pectate in the middle lamella.
• It is also needed during the formation of the mitotic spindle.
• It activates certain enzymes and plays an important role in regulating metabolic activities.

Magnesium

• It is absorbed by plants in the form of divalent Mg²⁺
• It activates the enzymes of respiration, photosynthesis, and are involved in the synthesis of DNA and RNA.
• Magnesium is a constituent of the ring structure of chlorophyll
• It helps to maintain the ribosome structure.

Sulphur

• It is absorbed in the form of sulphate (SO₄^2-)ion.
• Sulphur is present in two amino acids – cysteine and methionine
• It is the main constituent of several coenzymes, vitamins (thiamine, biotin, Coenzyme A), and ferredoxin.

Iron

• It is absorbed in the form of ferric ions (Fe³⁺)
• It is an important constituent of proteins involved in the transfer of electrons like ferredoxin and cytochromes.
• It activates the catalase enzyme and is essential for the formation of chlorophyll.

Manganese

• It is absorbed in the form of manganous ions (Mn²⁺).
• It activates many enzymes involved in photosynthesis, respiration, and nitrogen metabolism.
• It is also involved in the splitting of water to liberate oxygen during photosynthesis.

Zinc

• Plants obtain zinc as Zn²⁺ ions.
• It activates various enzymes, especially carboxylases.
• It is also needed in the synthesis of auxin.

Copper

• It is absorbed as cupric ions (Cu²⁺).
• It is essential for the certain enzymes involved in redox reactions

Boron

• It is absorbed as BO₃^3- or B₄O₇^2-
• It is required for uptake and utilisation of Ca²⁺
• it helps in membrane functioning
• it helps pollen germination
• it helps cell elongation and cell differentiation
• it is involved in carbohydrate translocation.

Molybdenum

• Plants obtain it in the form of molybdate ions (MoO₂²⁺).
• It is a component of nitrogenase and nitrate reductase both of which participate in nitrogen metabolism.

Chlorine

• It is absorbed in the form of chloride anion (Cl^–).
• Along with Na⁺ and K⁺, it helps in determining the solute concentration and the anion cation balance in cells.
  It is essential for the water-splitting reaction in photosynthesis, a reaction that leads to oxygen evolution.

Deficiency Symptoms of Essential Elements
If the concentration of the essential element below the critical concentration plants shows certain morphological changes. These are indications of deficiency symptoms.

Mobility of element determines deficiency symptoms
Deficiency symptoms in older tissues
Deficiency symptoms also depend on the mobility of the element in the plant. It first appears in the older tissues.
For example, the deficiency symptoms of nitrogen, potassium, and magnesium are visible first in the senescent leaves.
In the older leaves, biomolecules containing these elements are broken down and available for mobilising to younger leaves.

Deficiency symptoms in younger tissues
Sometimes the deficiency symptoms appear first in the young tissues. If the elements are immobile, they are not transported from mature organs to younger organs.
For example, Elements like sulphur and calcium are structural components of the cell and hence are not easily released.

The deficiency symptoms are

1. Chlorosis
2. Necrosis
3. stunted plant growth
4. premature fall of leaves and buds
5. and inhibition of cell division.

Chlorosis is the loss of chlorophyll leading to yellowing in leaves. It is due to the deficiency of elements like N, K, Mg, S, Fe, Mn, Zn, and Mo.
Necrosis, or death of tissue, particularly leaf tissue. It is due to the deficiency of Ca, Mg, Cu, K.
Lack or low level of N, K, S, Mo causes inhibition of cell division.
Deficiency of elements like N, S, Mo delay flowering

Toxicity of Micronutrients
If the supply of micronutrients at a moderate decreased level shows deficiency symptoms but the moderate increase causes toxicity, i.e the excess of an element inhibits the uptake of another element.

Symptoms and other effects of Manganese toxicity

• Symptom of manganese toxicity is the appearance of brown spots surrounded by chlorotic veins.
• Manganese competes with iron and magnesium for uptake and for binding with enzymes.
• Manganese also inhibits calcium translocation in the shoot apex.
• Symptoms of manganese toxicity induce
• Deficiency symptoms of iron, magnesium, and calcium.

Mechanism of Absorption of Elements
The process of absorption occurs in two main phases-

1. Apoplast (passive). The passive movement of ions into the apoplast occurs through ion- channels and the transmembrane proteins.
2. Symplast(active) The inward movement of ions into the cells is called influx and the outward movement efflux. This movement occurs by using metabolic energy.

Translocation of Solutes

• Mineral salts are pulled up through the plant by the transpirational pull.
• Analysis of xylem sap shows the presence of mineral salts in it.
• Radioisotopic studies support the xylem transport of mineral elements.

Soil as a Reservoir of Essential Elements

• Soil consist of a variety of minerals, nitrogen-fixing bacteria, and other microbes holds water and supplies air to the roots, and acts as a matrix that stabilises the plant.
• If the amount of nutrients in the soil is decreased, it is supplied from outside as fertilizers in the form of macronutrients (N, P, K, S, etc.) and micronutrients (Cu, Zn, Fe, Mn, etc.)

Metabolism of Nitrogen
Nitrogen Cycle
Nitrogen is a constituent of amino acids, proteins, hormones, chlorophyll, and many vitamins.
Atmospheric nitrogen consists of two nitrogen atoms joined by a very strong triple covalent bond main nitrogen pools-atmospheric soil, and biomass.

1. N₂ Fixation: The process of conversion of atmospheric nitrogen (N₂) to ammonia is termed nitrogen fixation.

2. Nitrification:

• Ammonia is converted into nitrate.
• Ammonia is first oxidized to nitrite by Nitrosomonas or Nitrococcus.
• The nitrite is further oxidized to nitrate with the help of the bacterium Nitrobacter

3. Ammonification: Decomposition of organic nitrogen of dead plants and animals into ammonia is called ammonification

4. Denitrification: It is the conversion of soil nitrate into molecular N₂ by Thiobacillus and pseudomonas

Formation of nitrogen oxides

• In nature, lightning and UV provide energy to convert nitrogen to nitrogen oxides (NO, NO₂, N₂O).
• Industrial combustions, forest fires, automobile exhausts, and power generating stations are also sources of atmospheric nitrogen oxides.

Biological Nitrogen Fixation
The nitrogen-fixing microbes are free-living or symbiotic. ‘Free-living nitrogen-fixing aerobic microbes are Azotobacter, Beijernickia Rhodospirillum Bacillus Anabaena Nostoc.

Development of root nodules in soyabean

Development of root nodule sin soyabean:

• Rhizobium bacteria contact susceptible root hair, divide near it.
• Upon successful infection of the root hair cause it to curl.
• Infected thread carries the bacteria to the inner cortex. The bacteria get modified into rod-shaped bacteroids and cause inner cortical and pericycle cells to divide. Division and growth of cortical and pericycle cells lead to nodule formation.
• A mature nodule is complete with vascular tissues continuous with those of the root.

Basic steps are given below

• Rhizobium bacteria attach the root hair.
• Root hair curls.
• Infected thread carries the bacteria to the inner cortex.

The bacteria get modified into rod-shaped bacteroids and cause inner cortical and pericycle cells to divide. Division and growth of cortical and pericycle cells lead to nodule formation, d) A mature nodule is complete with vascular tissues continuous with those of the root.

Overall equation for N2 fixation
N₂ + 8e^– + 8H⁺ +16ATP → 2NH₃ + H₂ + 16ADP + 16Pt

Fate of ammonia

• At first, ammonia protonated to form NH⁴⁺.
• This ammonium ion is used to synthesise amino acid in plants

There are two ways for the synthesis of amino acids in plants

1. Reductive animation
In this, ammonium ion reacts with alpha-ketoglutaric acid and forms glutamic acid.

2. Transamination
It involves the transfer of an amino group from one amino acid to the keto group of a keto acid.
Glutamic acid is the main amino acid from which the transfer of amino groups takes place and other amino acids are formed in the presence of transaminase.

Amides

• The important amides are asparagine and aspartate.
• Amide is formed when the hydroxyl group of one amino acid is replaced by an amino group.
• Since amide contains more nitrogen than amino acids. They are transported through xylem vessels.