BRAINCAKEGas Exchange in Plants
Plants, like animals, respire all the time, so their cells need a constant supply of oxygen and must remove carbon dioxide. Photosynthesising cells also need carbon dioxide and produce oxygen. The net exchange of gases depends on the balance between these two processes:
• in bright light, the rate of photosynthesis is greater than the rate of respiration, so a leaf takes in carbon dioxide and gives out oxygen
• in the dark, only respiration occurs, so the leaf takes in oxygen and gives out carbon dioxide
• at the compensation point, the rates of photosynthesis and respiration are equal, so there is no net exchange of either gas
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Key terms in this lesson
- stomata
- Small pores, mainly in the lower epidermis of a leaf, through which gases diffuse in and out, each surrounded by a pair of guard cells.
More in Gas Exchange
- Very Active Insects
- Gas Exchange in Fish
- Fish Gills
- Ventilating the Gills
- The Countercurrent Exchange System
- Stomata
- Opening and Closing the Stomata
- Lenticels
All 23 lessons in Gas Exchange · All Edexcel AS-level Biology topics