MadSci Network: Cell Biology |
There are several references on the web as to the function of chloroplasts in the guard cells of the stomatal apparatus. I had always heard that the chloroplasts were non-functional but, this is apparently not the case according to these references. If the chloroplasts are functional, sugars would be produced, changing the osmotic potential within the guard cell. Water would enter in response to this change in potential and the guard cells would open the stoma wider. http://www .microscopy-uk.org.uk/mag/articles/stomata.html http://www.le arn.co.uk/default.asp?WCI=Lesson&WCU=1446 http ://www.rrz.uni-hamburg.de/biologie/b_online/e32/32f.htm#co2 As to why other epidermal cells lack chloroplasts I can only offer some logical thinking. The epidermis is often covered by a cuticle making it difficult for water to exit the cells and equally difficult for gases, such as carbon dioxide, to enter the cells. If carbon dioxide can't enter the cells, photosynthesis does not occur and there would be no need for chloroplasts.
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