The process by which green plants make their own food from carbon dioxide and water by using sunlight energy in the presence of chlorophyll is called photosynthesis. Green plants also need foos to acquire energy. All living organisms need energy to perform various life prosesses. This article deals with the modes of nutrition in plants. How plants prepare their own food, what all factors are responsible for photosynthesis etc.
Plants make their own food in the presence of sunlight and hence they are autotrophs. Plants convert sunlight energy into chemical energy. They use carbon dioxide, water and sunlight to make their own food in the presence of chlorophyll.
There are two types of modes of nutrition in plants. They are:
Since we are learning about mode of nutrition in plants we will discuss only about autotrophic mode of nutrition.
Autotrophic mode of nutrition
In autotrophic mode of nutrition organisms make their own food with the help of simple inorganic materials like carbon dioxide and water, in the presence of sunlight. Also in this nutrition organic food is made from inorganic materials.
Green plants have autotrophic mode of nutrition. These organisms are called autotrophs. The autotrophs have green pigments called chlorophyll which help in trapping sunlight energy. They use the sunlight to make food by the process of photosynthesis. The food produced by autotrophs is used by human beings and animals as well.
Nutrition in Plants
Green plants synthesize their own food by the process of photosynthesis. Photo means light and synthesis means to build, so photosynthesis means ‘building up by light. It is in the presence of chlorophyll that plants use energy of sunlight to make food from inorganic materials like carbon dioxide and water.
Green plants make their own food by photosynthesis
Chlorophyll is present in green coloured bodies called chloroplast. The leaves of a plant are green due to the presence of chlorophyll in them.
In the process of photosynthesis a lot of oxygen gas is released. Let us understand with the help of equation:
Food is prepared in the green leaves of the plant. Plant requires carbon dioxide to make food which it takes from air. The carbon dioxide enters the leaves through tiny pores in them called stomata. Water required to make food is taken from soil. This water is transported to the leaves through roots and stem. The sunlight provides energy to carry out chemical reactions and chlorophyll present in green leaves help in absorbing this energy. Oxygen produced as a by-product in this process which goes out in the air.
The food prepared by the leaves is in the form of simple sugar called glucose. This glucose is then sent to other parts of the plant. The extra glucose is stored in the leaves of the plant in the form of starch. Glucose and starch belong to a category called carbohydrates. Thus green plants convert sunlight energy into chemical energy.
The steps for photosynthesis are:
i) Sunlight energy is absorbed by chlorophyll.
ii) Sunlight energy is converted into chemical energy and water is split into hydrogen and oxygen.
iii) Carbon dioxide is reduced to hydrogen so that carbohydrate like glucose is formed.
It is not necessary that these steps of photosynthesis take place one after the other.
Conditions Necessary for Photosynthesis
Following are the conditions necessary for photosynthesis:
3) Carbon Dioxide
Let us discuss some experiments to prove that sunlight, chlorophyll, carbon dioxide and water are necessary for photosynthesis. This can be proven by getting the result that green leaves make starch as food and starch gives blue-black colour with iodine solution.
Experiment to Show that Sunlight is Necessary for Photosynthesis
There are certain plants that have partially white and partially green leaves. Such leaves are called variegated leaves. Croton and coleus have variegated leaves.
Experiment to show that sunlight is necessary for photosynthesis.
Experiment to Show that Chlorophyll is necessary for Photosynthesis
Experiment to show that chlorophyll is necessary for photosynthesis
Experiment to Show that Carbon Dioxide is Necessary for Photosynthesis
Experiment to show that carbon dioxide is necessary for photosynthesis.
How Plants Obtain Water for Photosynthesis?
Plants obtain water for the process of photosynthesis from soil. Roots of a plant absorb water from the soil which transported upward to the leaves through xylem vessel and utilised for photosynthesis.
Plants use carbon dioxide and water as raw materials to prepare energy food called carbohydrates. Other material like nitrogen, phosphorus, iron and magnesium which are required by the plant are taken from soil.
Site of Photosynthesis: Chloroplasts
The cell organelles of green plants which contain chlorophyll are called chloroplasts. It is here that the photosynthesis takes place. Chloroplasts are just below the upper epidermis of the leaf in palisade tissue.
The structure of a leaf to show chloroplasts in it (the small circles in above diagram are all chloroplasts).
From the article we have seen that how plants prepare theor own food.