Autotrophic nutrition is the process by which organisms produce their own food from simple inorganic substances, such as carbon dioxide and water. Plants are autotrophic organisms. They use the process of photosynthesis to produce food.

Photosynthesis

Photosynthesis is the process by which plants use sunlight, water, and carbon dioxide to produce food (glucose) and oxygen. The chemical equation for photosynthesis is as follows:

• 6CO₂ + 6H₂O + light energy → C₆H₁₂O₆ + 6O₂

The following events occur during this process –

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.

Factors Affecting Photosynthesis

The following factors affect photosynthesis:

• Sunlight: Sunlight is essential for photosynthesis. Plants need sunlight to split water molecules and to produce NADPH and ATP.
• Water: Water is another essential ingredient for photosynthesis. Plants use water to produce hydrogen atoms, which are needed to produce NADPH and ATP.
• Carbon dioxide: Carbon dioxide is the third essential ingredient for photosynthesis. Plants use carbon dioxide to produce glucose.
• Temperature: Temperature affects the rate of photosynthesis. The optimal temperature for photosynthesis is around 25°C.
• Mineral nutrients: Mineral nutrients, such as nitrogen, phosphorus, and potassium, are also essential for photosynthesis.

Importance of Autotrophic Nutrition

Autotrophic nutrition is important for the following reasons:

• Provides food for all living organisms: Autotrophic organisms produce the food that all other living organisms need to survive.
• Maintains the balance of oxygen and carbon dioxide in the atmosphere: Autotrophic organisms produce oxygen and consume carbon dioxide during photosynthesis. This helps to maintain the balance of oxygen and carbon dioxide in the atmosphere.
• Prevents soil erosion: The roots of autotrophic organisms help to hold the soil in place, which prevents soil erosion.

Stomata

Stomata (singular: stoma) are small openings or pores found on the surfaces of leaves, stems, and other plant organs. They play a crucial role in the physiology of plants, primarily in gas exchange and transpiration. Here are some key points about stomata:

1. Structure: Stomata consist of two specialized cells, known as guard cells, which surround a central pore. Guard cells can change shape, opening and closing the stomatal pore.
2. Function:
   • Gas Exchange: Stomata allow the exchange of gases, such as carbon dioxide (CO₂) and oxygen (O₂), between the plant and the surrounding environment. During photosynthesis, CO₂ enters the leaf through stomata, while O₂ and water vapor exit.
   • Transpiration: Stomata also enable the release of water vapor from the plant. This process, called transpiration, helps regulate the plant’s water balance and nutrient uptake.
3. Control of Opening and Closing:
   • Light: Stomata typically open in the presence of light and close in darkness. This is mediated by blue light receptors in the guard cells.
   • Water Availability: Stomata close to conserve water when a plant is under water stress. This closure is controlled by hormones like abscisic acid (ABA).
   • Carbon Dioxide Levels: High CO₂ levels can trigger stomatal closure to limit excessive water loss.
4. Regulation by Guard Cells: The turgidity (swelling) or flaccidity (shrinking) of the guard cells controls stomatal opening and closing. When the guard cells take up water, they swell and cause the stomata to open. Conversely, the loss of water from guard cells leads to stomatal closure.
5. Distribution: Stomata are more abundant on the lower surface of leaves in many plant species. This positioning minimizes water loss through transpiration.
6. Role in Photosynthesis: Stomata are essential for photosynthesis as they allow CO₂ to enter the leaf, which is a crucial component of the photosynthetic process.

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