Mode of Nutrition in Plant - Autotrophic Plants

Plants also need food for their growth. Carbon and energy requirements of the autotrophic organism are fulfilled by photosynthesis.

Autotrophic nutrition is fulfilled by the process by which autotrophs take in CO₂ and H₂O and convert these into food (glucose) in the presence of chlorophyll; sunlight is called photosynthesis.

Photosynthesis

\[\ce{\overset{Carbon dioxide}{6CO2}+\overset{water}{6H2O} ->[Sunlight][Chlorophyll]\overset{food(glucose)}{C6H12O6} + \overset{oxygen}{6O2}}\]

• Sunlight: It is an inorganic material
• Chlorophyll: It is a substance that absorbs sunlight.
• CO₂: Enters through stomata and oxygen is released as a by-product through stomata on leaf
• Water: water + dissolved minerals like nitrogen, phosphorus and other are taken up from the roots of the soil

Site of Photosynthesis: Some cells contain green pigments, which are cell organelles called chloroplasts, which contain chlorophyll.

Chloroplasts in a leaf

1. Absorption of light energy by chlorophyll.
2. Conversion of light energy to chemical energy and splitting of water molecules into hydrogen and oxygen.
3. Reduction of carbon dioxide to carbohydrates.

Water used in photosynthesis is taken up from the soil by the roots in terrestrial plants. Other materials like nitrogen, phosphorus, iron and magnesium are taken up from the soil. Nitrogen is an essential element used in the synthesis of proteins and other compounds.

Stomata:

• Stomata are tiny pores present on the surface of the leaves.
• Stomata do the exchange of large amounts of gases (O₂/CO₂)
• Stomata is responsible large amounts of water is lost through the stomata.
• The opening and closing of the pore is a function of the guard cells. The guard cells swell when water flows into them, causing the stomatal pore to open. Similarly, the pore closes if the guard cells shrink.