NCERT Gist: Nutrition in Plants | Additional Study Material for UPSC PDF Download

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- Carbohydrates, proteins, fats, vitamins and minerals are components of food.
- These components of food are necessary for our body and are called nutrients.
- Nutrition is the mode of taking food by an organism and its utilisation by the body.
- The mode of nutrition in which organisms make food themselves from simple substances is called autotrophic (auto = self; trophos = nourishment) nutrition, plants are called autotrophs.
- Animals and most other organisms take in readymade food prepared by the plants. They are called heterotrophs (heteros =other).
- The bodies of living organisms are made of tiny units called cells.
- Cells can be seen only under the microscope.
- Some organisms are made of only one cell.
- The cell is enclosed by a thin outer boundary, called the cell membrane.
- Most cells have a distinct, centrally located spherical structure called the nucleus.
- The nucleus is surrounded by a jelly-like substance called cytoplasm.
- Carbon dioxide from air is taken in through the tiny pores present on the surface of the leaves.
- These pores are surrounded by ‘guard cells’. Such pores are called stomata.
- The leaves have a green pigment called chlorophyll. It helps leaves to capture the energy of the sunlight. This energy is used to synthesise (prepare) food from carbon dioxide and water.
- Since the synthesis of food occurs in the presence of sunlight, it is called photosynthesis (Photo: light; synthesis : to combine).
- So we find that chlorophyll, sunlight, carbon dioxide and water are necessary to carry out the process of photosynthesis.
- During photosynthesis, chlorophyll containing cells of leaves in the presence of sunlight use carbon dioxide and water to synthesize carbohydrates.
- During the process oxygen is released.
- The carbohydrates ultimately get converted into starch.
- The presence of starch in leaves indicates the occurrence of photosynthesis.
- The starch is also a carbohydrate. You often see slimy, green patches in ponds  or in other stagnant water bodies.
- These are generally formed by the growth of organisms called algae.
- They contain chlorophyll which gives them the green colour.
- Algae can also prepare their own food by photosynthesis.
- The carbohydrates are made of carbon, hydrogen and oxygen.
- These are used to synthesise other components of food.
- Proteins are nitrogenous substances which contain nitrogen.
- Soil has certain bacteria that convert gaseous nitrogen into a usable form and release it into the soil.
- These soluble forms are absorbed by the plants along with water.
- Farmers adding fertilisers rich in nitrogen to the soil.
- In this way the plants fulfil their requirements of nitrogen along with the other constituents.
- Plants can then synthesise components of food other than carbohydrates such as proteins and fats.
- Humans and animals such plants depend on the food produced by other plants.
- They use the heterotrophic mode of nutrition.
- Yellow tubular structures twining around the stem and branches of a tree? This is a plant called Cuscuta (Amarbel).
- It does not have chlorophyll.
- It takes readymade food from the plant
- The plant on which it climbs is called a host.
- Pitcher plant showing lid and pitcher
- The apex of the leaf forms a lid which can open and close the mouth of the pitcher.
- Inside the pitcher there are hairs which are directed downwards.
- When an insect lands in the pitcher, the lid closes and the trapped insect gets entangled into the hair.
- The insect is digested by the digestive juices secreted in the pitcher. Such insecteating plants are called insectivorous plants.

Saprotrophs

- Cotton-like threads spread on the piece of bread
- These organisms are called fungi.
- They have a different mode of nutrition.
- They secrete digestive juices on the dead and decaying matter and convert it into a solution.
- Then they absorb the nutrients from it.
- This mode of nutrition in which organisms take in nutrients in solution form from dead and decaying matter is called saprotrophic nutrition.
- Plants which use saprotrophic mode of nutrition are called saprotrophs.
- Fungi also grow on pickles, leather, clothes and other articles that are left in hot and humid weather for long time
- Some organisms live together and share shelter and nutrients. This is called symbiotic relationship.
- For example, certain fungi live in the roots of trees.
- The tree provides nutrients to the fungus and, in return, receives help from it to take up water and nutrients from the soil.
- This association is very important for the tree.
- In organisms called lichens, a chlorophyll-containing partner, which is an alga, and a fungus live together.
- The bacterium called Rhizobium can take atmospheric nitrogen and convert it into a soluble form.
- But Rhizobium cannot make its own food.
- So it lives in the roots of gram, peas, moong beans and other legumes and provides them with nitrogen.
- Most of the pulses (dais) are obtained from leguminous plants.