There are two types of plants, C3 and C4. C3 plants use the Calvin Cycle to gene

Question

There are two types of plants, C3 and C4. C3 plants use the Calvin Cycle to generate sugar. C4 plants use phosphoenol pyruvate to make malate and oxaloacetate which will eventually be used to make sugar. Both types of plants have stomatas (openings on leaves that can be opened and closed) for CO2 entry. In addition, water is also lost through the stomata. C3 plants are only able to synthesize sugar at relatively high CO2 levels because photosynthesis will stop when CO2 production from the mitochondria equals the use of CO2 in the chloroplasts. C4 plants are able to continue photosynthesis even at low CO2 levels.   (1) Why are C4 plants able to survive in hot, dry conditions when C3 plants are not? (2) Plants can develop cancer but it is usually from an infection not from the ionizing rays of the sun. What part of the photosynthesis pathway do you think protects the plant form sun damage?

Explanation / Answer

1. C4 plants are more efficient than c3 plants. When its hot and dry, the c3 plants close their stomata to prevent excessive water loss due to transpiration due to which the entry of CO2 in cells also stop, and no photosynthesis takes place. Thus c3 plants cannot survive in hot dry environments such as deserts.

Whereas c4 plants have CAM that is crassulacean acid metabolism. It begins in the night itself, when stomata are opened the CO2 is fixed. Then malic acidis formed as a product which is used as the carbon source in c3 cycle next day. Hence these plants have evolved themselves to survive in such conditions.

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