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gas exchange in plants
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gas exchange in plants
The net (overall) effect depends on the time of day and the light intensity. Photosynthesis doesn’t occur at night. When there is no photosynthesis, there is a net release of carbon dioxide and a net uptake of oxygen. If there is enough light during the day, then: the rate of photosynthesis is higher than the rate of respiration there is a net release of oxygen and a net uptake of carbon dioxide
C6H12O6 + 6O2 → 6CO2 + 6H2O (aerobic respiration) 6CO2 + 6H2O → C6H12O6 + 6O2 (photosynthesis)
The structure of the leaf is adapted for gas exchange. The cells in the spongy mesophyll (lower layer) are loosely packed, and covered by a thin film of water. There are tiny pores, called stomata, in the surface of the leaf. Most of these are in the lower epidermis, away from the brightest sunlight
the role of stomata
- The stomata control gas exchange in the leaf. Each stoma can be open or closed, depending on how turgid its guard cells are.
- In the light, the guard cells absorb water by osmosis, become turgid and the stoma opens.
- In the dark, the guard cells lose water, become flaccid and the stoma closes.
