Q4. Assertion: increasing CO concentration raises the yield of greenhouse tomatoes. Reason: C plants respond to higher CO concentrations by showing increased rates of photosynthesis. Are both true, and does the reason explain the assertion?
Both are true, and the reason explains the assertion (NCERT page 150).
Q5. Why is light rarely a limiting factor in nature, according to NCERT? For which plants is it an exception?
Light saturation occurs at 10 per cent of full sunlight, so light is rarely limiting; the exceptions are plants in shade or in dense forests (NCERT page 149).
Q6. Give two ways in which water stress reduces photosynthesis.
It closes the stomata, reducing CO availability, and it makes leaves wilt, reducing their surface area and metabolic activity (NCERT page 150).