Nutrition in Plants

Autotrophic Nutrition: In this type of nutrition organisms makes its food itself by the process of photosynthesis. The organism takes CO2 and H2O from the environment and in the presence of chlorophyll and sunlight makes its food in the form of carbohydrates (Glucose). It is the source of energy to the plants. Excess glucose is stored in the form of starch.
CO2 + H2O Chlorophyll C6H12O6 + 6H2O+ 6O2
Sunlight
Steps of photosynthesis:
1. Chlorophyll absorbs light energy and converts it into chemical energy.
2. Splitting of water molecule and O2 is released.
3. Carbon dioxide is reduced to form carbohydrates.
Site of photosynthesis:
Transverse Section of leaf: In leaf two surfaces are present, upper epidermis and lower epidermis. In between the two epidermises mesophyll cells are present which are rich in chloroplast. Chlorophyll pigments are present in the chloroplast. Photosynthesis occurs in the chlorolopast of mesophyll cell of leaf.

Raw materials required for photosynthesis
Carbon dioxide: The epidermis of leaf has minute pores called stomata through which exchange of gases takes place between leaf and environment. CO2 from environment enters into the leaf cells through stomata.
Water: Water is absorbed by roots of the plant from the soil. Water is conducted through xylem up to the leaves.
Q How do desert plants, in which the stomata are closed at day time, carry out photosynthesis?
Ans: In desert plants the stomata are closed during day time. At night stomata opens CO2 diffuses into the leaf cells and is converted into an intermediate compound called malic acid. In the day time CO2 is released from malic acid and used to form food in the presence light.
Q. Explain the structure of stomata with the help of diagram.

Stomata are minute pores present in the leaf epidermis. The opening and closing of stomata is regulated by two guard cells. Nucleus and cloroplasts are also present in the guard cells.They are protected by surrounding epidermal cells.
Q Write the mechanism of opening and closing of stomata?
Ans. When the guard cells gain water they become turgid or swollen and stomata opens. When the guard cells lose water they shrink and stomata closes.
Q When plants do close their stomata?
Ans. When plants do not need CO2 for plants their stomata are closed. This also prevents the loss of water from the plant by transpiration.
Q,. How do plants get other materials for its growth and developments?
Plants need other minerals like N, S, Mg, Zn, Ca, P etc .Plants take these materials from the soil with the help of roots. The most important mineral is N. It is absorbed in the form of nitrate or nitrite and are used to form proteins.