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Transpiration, Respiration and Photosynthesis

Large quantities of water are absorbed by the plant for photosynthesis. However, excess water escapes in the form of water vapor from the stomata of leaves, lenticels of the stem, and fruits or cuticle of leaves. The process of losing water in the form of water vapour from a living plant is known as transpiration.

Factors affecting transpiration

  1. More transpiration takes place on a hot day as compared to cold day.
  2. Transpiration rate is higher if the wind is blowing as the water vapor is removed faster from the leaves.
  3. If air is humid, transpiration is slow.

Respiration

Since plants are living beings, they also respire by taking in oxygen and giving out carbon dioxide. Plants don’t have any organs fro breathing. The exchange of oxygen and CO2 takes place by diffusion through small pores called stomata present in the leaves and stem. The expansion and shrinking of guard cells occurs due to supply of moisture and light, resulting in opening and closing of stomata. The rate of exchange of gases in plants is much slower than in animals.

In respiration glucose molecules react with O2 and break down into CO2 to release energy. Chemical reaction of respiration as follows.

C6H12O6 (Glucose) + 6O2 (Oxygen) —> 6CO2 (Carbon dioxide) + H2O (water) + Energy

Some energy released during respiration is used by our body. The rest is lost as heat.

Photosynthesis

Green plants are able to prepare their own food from simple raw materials around them CO2 from air, and water from soil. The energy is obtained from sunlight by chlorophyll.

Using the energy of sun, a chemical reaction takes place in the green parts of plant in which CO2 and H2O are converted into food in form of glucose.

6CO2 (Carbon dioxide) + H2O (Water) —> (Sunlight +Chlorophyll) —> C6H12O6 (Glucose) + 6O2 (Oxygen)

In most plant glucose is converted into starch and stored in leaves, stems. The process of manufacturing food in green plants is known as photosynthesis.