Photosynthesis

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Chlorophyll

During summer time , leaves of plants undergo photosynthesis and appear green . Chlorophyll is the green pigment that gives the green color in leaves (The leaves of some trees , such as birches and cottonwoods , also contain carotene these leaves appear brighter green , because carotene absorbs blue-green light . The shorter days and cool nights of autumn produce changes in the tree . One of these changes is

the growth of a corky membrane between the branch and the leaf stem which interferes with the flow of nutrients into the leaf . Because of this interference chlorophyll production in the leaf declines and the green color in the leaf fade . What are left are the other pigments like carotene in the leaves of birch and hickory that change from green to bright yellow and orange . In some trees , as the concentration of sugar in the leaf increases , the sugar reacts to form anthocyanins . These pigments cause the yellowing leaves to turn red . Red maples , red oaks , and sumac produce anthocyanins in great quantity and show the brightest reds and purples in the autumn scenery

Since the low temperatures during autumn destroy chlorophyll the result of this is a lower rate of photosynthetic activities . According to Ottander and Oquist (1991 , winter-induced inhibition of photosynthesis is caused by the combined effects of light and freezing temperatures light causes photoinhibition of photosystem II , whereas frost causes inhibition of enzymatic steps of photosynthesis

References

The Chemistry of Autumn Colors ' Chemical of the Week . March 29 , 2008 http /scifun .chem .wisc .edu /chemweek /fallcolr /fallcolr .html

Ottander , C , TZquist ,G . Recovery of photosynthesis in winter-stressed Scots pine ' 1991 .Plant , Cell Environment 14 (3 345-349 doi :10 .1111 /j .1365-3040 .1991 .tb01511 .x April 2 , 2008 http /www .blackwellsynergy .com /doi /abs /10 .1111 /j .1991 .tb01511 x ?journalCode pce indicate your last name here PAGE \ MERGEFORMAT 2...