Asked by  | 11th Nov, 2009, 09:40: PM

Expert Answer:

Respiration occurs always.


In dark reaction, CO2 is reduced to carbohydrates. This reaction takes place in stroma of chloroplasts. It is independent of light. Here, ATP and NADPH2 is utilized.

Dark phase or light-independent reactions is a synthetic process in which carbon dioxide is reduced to glucose. This process takes place in stroma and utilizes ATP and NADPH2. These reactions take the products of the light-dependent reactions and perform further chemical processes on them.

There are three phases to the light-independent reactions, collectively called the Calvin Cycle: Carbon Fixation, Reduction reactions, and ribulose 1,5-diphosphate (RuDP) regeneration.

Though the light-independent reactions are also referred to as the dark reactions, that term may be misleading as they do not actually require darkness to proceed. The term "light-independent" is used to emphasize that the reactions occur regardless of the amount of light present as long as the proper substrate compounds are available. Even this term can be criticized, however, as the availability of substrates in plants depends on the light reactions, so the reactions cannot be said to be entirely "light-independent."

Answered by  | 11th Nov, 2009, 11:00: PM

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