Monday, 28 March 2016
2.42 describe the role of stomata in gas exchange
Guard cells control the opening and closing of stomata. During daytime (when photosynthesis occurs) stomata are open allowing for CO2 and O2 to enter (by diffusion). At night time, the stomata close. This is because photosynthesis doesn't occur so there is no need to have stomata open all the time (as no CO2 needs to be taken into the leaf). However, during the night stomata may open periodically to allow oxygen to diffuse in for respiration of cells.
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ReplyDeleteHi there! Basically, guard cells are turgid during the night as this closes stomata to reduce water loss. During the day they are more flaccid which opens stomata allowing gas exchange to occur:)
DeleteThe guard cells are turgid during the day because the cells take up water by osmosis and are flaccid during the night because the water has been dragged to the neighbouring epidermis cells, which makes the guard cells sag pressing them together.
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