السؤال 51

A leafy plant is sealed in a glass jar and kept in the dark. Which way do gases move between the plant and the air in the jar, and why?

It takes in oxygen and gives out carbon dioxide, because only respiration is going onالإجابة الصحيحة
It takes in carbon dioxide and gives out oxygen, because photosynthesis continues in the dark
It takes in oxygen and gives out carbon dioxide, because respiration only starts at night
No gases move at all, because the plant rests until morning

الشرح

In darkness the sugar-making reaction has stopped, so nothing is drawing in the one gas or giving out the other, and the exchange left on show is the one belonging to respiration alone. The wording matters here: the reason is that photosynthesis has switched off, not that respiration has switched on, because respiration was running all through the day as well.

الشرح

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