Condition favouring cyclic photophosphorylation is
(a) Anaerobic environment
(b) Aerobic and low light intensity
(c) Aerobic and optimum light
(d) Anaerobic and low light intensity

Options

A. Anaerobic environment
B. Aerobic and low light intensity
C. Aerobic and optimum light
D. Anaerobic and low light intensity.

Answer

To determine the conditions favoring cyclic photophosphorylation, let's analyze the options given in the question step by step:

### Step 1: Understand Cyclic Photophosphorylation
Cyclic photophosphorylation is a process that occurs in photosystem I of the chloroplasts. In this process, electrons are expelled from photosystem I, travel through a series of electron carriers, and ultimately lead to the production of ATP. Importantly, the electrons return to photosystem I, completing the cycle.

### Step 2: Identify the Light Intensity Requirement
Cyclic photophosphorylation does not require high light intensity. Instead, it can occur under low light conditions. This is a key characteristic of the process.

### Step 3: Determine the Oxygen Requirement
Cyclic photophosphorylation occurs in an aerobic environment, meaning that oxygen is present. It is important to note that this process does not produce NADPH, which is typically required for carbon fixation. Therefore, the absence of carbon dioxide fixation indicates that oxygen must be available.

### Step 4: Analyze the Options
Now, let's evaluate the options provided:

- **(a) Anaerobic environment**: Incorrect, as cyclic photophosphorylation requires oxygen.
- **(b) Aerobic and low light intensity**: Correct, as it occurs in the presence of oxygen and can function under low light conditions.
- **(c) Aerobic and optimum light**: While it can occur in aerobic conditions, optimum light is not necessary; low light is sufficient.
- **(d) Anaerobic and low light intensity**: Incorrect, as it cannot occur without oxygen.

### Conclusion
Based on the analysis, the condition that favors cyclic photophosphorylation is **(b) Aerobic and low light intensity**.

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