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Plant Physiology is the study of the functions of plants. It is a branch of study regarding the physiological processes and behaviors of plants. Plants are essential for the ecosystem just like other living organs. How do plants grow? How do they develop the seeds? are some of the field of study dealt with plant physiology. Plant Physiology also deals with the different parts of plants, its functions, growth, movements, and nutrition of plants.
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Keyterms: Plant, Ecosystem, Living organs, Respiration, Transportation, Photosynthesis, Mineral nutrition, Stem, Root, Physiology, Nutrition
Plant Physiology
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Plant Physiology is a branch of study which deals with the different structures of plants and their functions. It includes plant growth and development by analyzing the processes such as respiration, transportation, photosynthesis, and mineral nutrition.
Plant Physiology
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Different Parts
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Plants consist of various body parts like stem, roots, leaves, fruits, and flowers. Below are the different parts of plants and their functions.
Leaves
Leaves are one of the essential parts of a plant. They grow in different shapes and sizes. Leaves contain chlorophyll which aids the plants in photosynthesis. Carbon dioxide, water, and sunlight are being used in the process of photosynthesis. The food required for a plant is stored in its leaves and from there it carries to other parts using the stem.
Leaf Structure
The main parts of a leaf are leaf base, lamina, and petiole. Some leaves also help in the reproduction of new plants. The leaves of Bryophyllum can produce new Bryophyllum plants. Leaves also help in the process of photosynthesis. Water comes into leaves carried by the stem from its roots. Leaves collect carbon dioxide from the atmosphere in the presence of sunlight which helps the photosynthesis process. Also, through the process of transpiration, an excess amount of water can be removed from plants using leaves.
Stem
Stem is the part of the plant that is found above the ground. In its tender form, the color of the stems are green. As the plant grows, the color changes. As the plants mature and becomes a tree, its stem becomes thick and woody. Stem also helps in the photosynthesis process in plants.
Parts of a Stem
Stem provides a supporting structure to the plants. It helps in transporting minerals, water and other nourishment from the leaves to other areas of the plant. Phloem and xylem are responsible for the transportation and normal functioning of any plant. These are protected by the stem. The stem helps in carrying minerals and nutritions in the water from the roots to other parts of the plant.
Xylem and Phloem
Xylem and Phloem are also known as sap. They transport important substances such as water, sugar, and other minerals between the roots, leaves and stem. Xylem and Phloem form the vascular tissues of a plant. They help in navigating food and water to different parts of the plant. The water is being carried from roots to other parts, while the nutrition from leaves is conducted to other parts using the stem.
Xylem and Phloem
Roots
Roots are the foundation system of plants. They keep the plants grounded on the earth. The main function of roots is to absorb water and minerals from the soil. It helps the plant to grow and reserve minerals. With the help of roots, plants are able to stand in a particular place. Plants do not have mobility. Plants cannot move from one place to another. Roots not only provide nutrition to plants but also help the plants to be fixed on the surface. Roots can be classified into taproot and fibrous root system.
Regions of Root
Flowers and Fruits
Fruits are the most important part of a seed plant. When fertilized, the mature ovary in a plant with other portions like pollen grains produces a seed. This seed further evolves into a fruit. Flowers are other parts of a plant which participates in reproduction. The major parts of a flower are petals, carpels, sepals, and stamens. Petals make a flower more attractive. Stamens and carpels are the female and male reproductive parts of a plant. Sepals give a greenish color to the flower.
Parts of Flower
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Functions of Plants
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The physiological processes of plants are diverse. Plant Physiology also deals with the different functionings of plants.
Respiration in Plants
The food that is required for the adequate functioning of plants comes from photosynthesis. Cellular respiration helps in releasing the energy used for synthesis of ATP that involves glycolysis. In the presence of oxygen, aerobic respiration passes along to complete oxidation of organic substances. Oxidative phosphorylation and electron transport system takes place in order to release and use the energy stored in molecules.
Plant Respiration
Mineral Nutrition in Plants
Mineral nutrition is the naturally occurring nutrient found in the soil. It is necessary for the proper functioning of the plant body. Mineral nutrition is crucial for the growth of plants. Minerals in plants spot the deficiency symptoms, essentiality, and mechanisms of absorption elements. The small amounts of nutrients required by plants are known as micronutrients.
Mineral Nutrition in Plants
Some of the micronutrients are copper, iron, boron, manganese, molybdenum, and chlorine. Similarly, macronutrients are the nutrients required for the plant body in large amounts. Some of the macronutrients are nitrogen, carbon, sulfur, calcium, phosphorus, potassium, and magnesium. Nutrients play a vital role in the balancing function of plants, influencing the pH of cell sap, maintaining osmotic pressure, etc.
Nutrition Transportation in Plants
Xylem and phloem together make a definite system in plants. This helps in transporting water and nutrients from roots to other parts of the plant. The transportation of nutrients and water in plants is either unidirectional or multidirectional. The transportation modes can be passive that occur through facilitated diffusion. The transportation is also made through specific membrane proteins called pumps.
Nutrition Transportation in Plants
Photosynthesis in Higher Plants
Photosynthesis is the primary source of food for all living organs. It is the process where plants synthesize their own food. As a result of photosynthesis, plants release oxygen in the atmosphere.
Photosynthesis in Plants
The process takes place in chloroplasts over the light and dark reactions with the help of 4 pigments namely chlorophyll a, chlorophyll b, carotenoids, and xanthophyll. Phosphorylation is the process of extracting energy from oxidizable substances and stored in a bond energy form. Both cyclic, as well as non-cyclic photo-phosphorylations, take place in plants.
Growth and Development of Plant
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Growth and development of plants is a part of plant physiology. The plant development starts from germination. A plant's growth cannot be determined as it grows throughout its lifespan. However, the growth can be measured with parameters such as length, volume, area, dry weight, cell number, etc. The growth period of a plant can be categorized into meristematic, elongation, and maturation. Plants also form phytochromes (Light-sensitive) and stimulate growth in response to the environmental signals.
Germination in Plant
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Things to Remember
- Plant Physiology is an area of study that deals with various structures of plants and their functions.
- The different body parts of a plant are leaves, roots, stem, fruits, flowers, etc.
- The leaves consist of chlorophyll which helps plants in photosynthesis.
- Some leaves can also help in the reproduction of a new plant. For example, Bryophyllum leaf can produce a new Bryophyllum plant.
- The stem helps in transporting water, minerals, and other nutrients from the leaves to other parts of the plant using xylem and phloem.
- A seed further evolves into a fruit. Flowers are also important in the reproduction of a plant.
- Some of the major functions of a plant are mineral nutrition, transportation in plants, respiration, photosynthesis, plant growth and development.
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Sample Questions
Ques: What is chlorophyll? (2 marks)
Ans: It is a pigment present in all plants. Chlorophyll is present in all green plants and other organisms. Chlorophyll is necessary for photosynthesis (A process where light energy is converted into chemical energy).
Ques: Define plant physiology? (2 marks)
Ans: Plant physiology is a branch of science that deals with the study of plant structure, different parts, and its functions. It is basically the study of the functions of plants. The study of plant physiology consists of different plant parts such as leaves, stems, roots, fruits, flowers, etc. It also includes various functions such as transportation in plants, respiration, mineral nutrition, photosynthesis, etc.
Ques: Explain the process of plant growth and development? (3 marks)
Ans: The development of a plant begins from the germination itself. The growth of a plant cannot be determined as it grows throughout its lifespan. But the growth can be measured to an extent using the parameters such as cell number, area, volume, length, dry weight, increase in fresh weight, etc. The growth period of a plant can be categorized into meristematic, elongation, and maturation.
Ques: What is photosynthesis? Explain different stages and processes for photosynthesis (3 marks)
Ans: Photosynthesis is a process where all plants synthesize their own food. The process requires water, carbon dioxide and solar energy. The by-product of photosynthesis is oxygen. Photosynthesis happens in two stages, one is a light-dependent reaction and the other one is a light-independent reaction. Light-dependent reactions take place during the daytime. Light-independent reaction is also known as a dark reaction or the Calvin cycle.
Ques: What makes leaves a major part of the plant? (2 marks)
Ans: Leaves are a very important source of photosynthesis. Leaves also help in transporting food and water to the different parts of a plant. They also aid in the exchange of gasses and help in removing excess water using transpiration.
Ques: Define wilting? (2 marks)
Ans: Wilting is the process where leaves are dried out drop off from a plant due to the insufficiency of water supply or excessive transpiration or vascular diseases.
Ques: What is the difference between xylem and phloem? (2 marks)
Ans: Xylem and phloem are two types of vascular tissues which help in the transportation process. Xylem tissues have tubular-shaped structures which resemble the shape of a star. Xylem tissues are situated in the center of the vascular bundle. Phloem tissues have the structure of tubular and elongated shapes. They are located on the outside of the vascular bundle and the fibers are larger in size compared to xylem fibers.
Ques: What makes macronutrients differ from micronutrients? (2 marks)
Ans: Micronutrients are the nutrients required for a plant in smaller amounts and macronutrients are nutrients required in larger amounts. Protein, fat, and carbohydrates are macronutrients where vitamins and minerals are referred to as micronutrients.
Ques: Define the term osmotic pressure? (2 marks)
Ans: Osmotic pressure is a pressure required to stop the osmotic movement of pure water into a solution across the semipermeable membrane.
Ques: What is the meaning of transpiration? Is there any similarity between transpiration and translocation? (2 marks)
Ans: Transpiration and translocation are two different things. Transpiration is the loss of water vapor from plants, especially from the leaves. Transpiration takes place by stomata and at times through cuticles as well. The movement of particles from one part to another in the vascular system of a plant is known as translocation.
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