Differences between C3 and C4 plants
Cyclic Photophosphorylation
Significance of Cyclic Photophosphorylation 1. When cyclic photophosphorylation alone operates, the CO2 assimilation drops down because of the shortage of reduced NADP (NADPH2). 2. It generates only ATP molecules and as such can not drive dark reactions of photosynthesis. 3. It is an important system in providing ATP for synthetic processes (other than photosynthesis)like a synthesis of protein, lipids, nucleic acids, and pigments within chloroplasts. Limitations of Cyclic Photophosphorylation 1. This system operates if the activity of the PSII is blocked. 2. Under these conditions : a. only PS I remains active b. Photolysis of water does not take place c. blockage of non-cyclic ATP formation causes a drop in CO2 assimilation in dark reaction and, therefore, d. there is a shortage of reduced NADP. (i.e., NADPH2) 2. Non-cyclic Photophosphorylation It occurs in green plants and involves both PS I and PSII * During this process, the electron is excited by the absorption of a phot...
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