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- Leaves are the food factories of plants.
- Water and minerals present in the soil are absorbed by the roots and transported to the leaves.
- Carbon dioxide from air is taken in through the tiny pores present on the surface of leaves called stomata.
- These pores are surrounded by guard cells.
- Water and minerals are transported to the leaves by the vessels which run throughout the root, the stem, the branches and the leaves.
- They form a continuous path or passage for the nutrients to reach the leaf.
- The leaves have a green pigment called chlorophyll.
- It helps leaves to capture the energy of the sunlight.
- This energy is used to synthesize food from carbon dioxide and water.
- The leaves other than green leaves also have chlorophyll, they also undergo photosynthesis. Algae can also prepare their own food by photosynthesis.
 Photosynthesis
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Photosynthesis
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- The synthesis of food occurs in the presence of sunlight, it is called photosynthesis
- Chlorophyll, sunlight, carbon dioxide and water are necessary to carry out the process of photosynthesis.
- It is a unique process on the earth.
- In the absence of photosynthesis, life would be impossible on the earth.
- The solar energy is captured by the leaves and stored in the plant in the form of food.
- Thus, the sun is the ultimate source of energy for all living organisms.
- Oxygen is produced during photosynthesis.
- During photosynthesis, chlorophyll containing cells of leaves in the presence of sunlight, use carbon dioxide and water to synthesize carbohydrates.
- The process can be represented in an equation:
- End Products: During this process oxygen is released.
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- The presence of starch in leaves indicates the occurrence of photosynthesis. Starch is also a carbohydrate.
Important Products:
- Carbohydrates: They are made of carbon, hydrogen and oxygen.
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- These are used to synthesize other components of food such as proteins and fats.
- Proteins: They are nitrogenous substances and contain nitrogen.
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Importance of Nitrogen for Plants:
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- The nitrogen is present in abundance in gaseous form in the air but plants cannot absorb nitrogen in this form.
- Soil has certain bacteria that convert gaseous nitrogen into a usable form and release it into the soil (Nitrogen Fixation).
- These are absorbed by the plants along with water.
- Fertilizers are also rich in nitrogen, which is added to the soil by farmers.
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