Question

C4 plants and CAM plants have adapted the Calvin Cycle to work more efficiently in hot climates by reducing the impact of photorespiration. Describe photorespiration and explain the problem that these plants are solving.

Answer 1

Photorespiration is also known as oxidative photosynthetic carbon cycle or C2 cycle . Here 2- phosphoglycolate produced by RuBisCo when it oxygenates RuBP that cannot be utilized within the Calvin cycle. The pathway by which 2-phosphoglycolate is further metabolized is known as C2 cycle.

High temperature promotes oxygenation , and hence the photorespiration, because the solubility of CO2 in in water declines more rapidly than that of oxygen as the temperature is increased.

C4 plants- concentrate CO2 at the site of caboxylation , keeping the CO2 concentration high enough for RuBisCo to bind carbon dioxide rather than oxygen. This is how c4 evolved to minimize photorespiration.

CAM plants - these plants open their stomata during the night and close them during the day.closing stomata during the day helps these plants conserve water but it also prevents carbon dioxide from entering the leaves. During the night, when there is stomata are open, these plants take up carbon dioxide. Assimilation of carbon dioxide occurs in to malic acid at night which is stored in the vacuoles. So plenty of carbon dioxide is stored in plants to avoid photorespiration.