State one artificial condition which may stop non-cyclic photophosphorylation and trigger cyclic photophosphorylation ?
The process of formation of ATP in chloroplast in the presence of sunlight is known as photophoshorylation. Photophosphorylation is of two types:
* Noncyclic photophosphorylation
* Cyclic photophosphorylation
Cyclic photophosphorylation yields only ATP and involves only one photosystem (PSI).
Cyclic photophosphorylation is favoured in plants when concentration of ATP is low in plants and NADPH is high.
Electrons from P700 (PSI) are returned to it via the cytochrome b6f complex. There is no NADP+reduction, but protons are pumped across the membrane and therefore ATP is generated.
Cyclic photophosphorylation also occurs when only light of wavelengths beyond 680 nm are available for excitation.
So, artificiallly we can only control the wavelength of light to stop noncyclic photophosphorylation and to trigger cyclic photophosphorylation.