(a) How do guard cells regulate opening and closing of stomata! pores ?
(b) Two similar green plants are kept separately in oxygen free containers, one in dark and the other in continuous light. Which one will live longer ? Give reasons.
A)Stomata are the tiny pores present on the surface of the leaves. Gaseous exchange takes place in leaves through these pores. A large amount of water is also lost through these pores. The plant closes these pores when carbon dioxide is not required for photosynthesis. Guard cells control the opening and closing of these pores. The guard cells swell when water flows into these pores and stomatal pores get open, and as the water shrinks the guard cell closes.
B)The plant kept in light would live longer. The plant in the dark would not be able to carry out photosynthesis and the container would soon be filled with carbon dioxide in a short span of time. Lack of oxygen would kill the plant whereas the plant in light would carry out photosynthesis and convert carbon dioxide to oxygen and hence live longer.