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To my knowledge, oregon grape (Mahonia aquifolium) is purportedly an evergreen shrub? Deciduous broadleaf plants lose their leaves in autumn usually and before that as the leaves die they oxidize and turn shades of yellow and red as carotenoids and anthocyanins are expressed.

For what reason does M. aquifolium turns red in the fall given that they DON'T drop their leaves? Does it somehow benefit the plant? Is it because oregon grape's ancestor used to drop leaves?

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    $\begingroup$ I don't know about Mahonia aquifolium, however, an "evergreen" plant does not mean the leaves will stay green forever. Normally, all leaves of all kinds of plants, get old ("senescent"), take retirement from metabolic functions, store only waste products; and new leaves take the major metabolic functions. Now; a Typical Deciduous plant sheds all the senescent leaves on a Particular Season of the Year, whereas, a so-called "Evergreen" plant, typically, does not shade all the leaves at a particular season. Rather, they shade some leaves throughout year without bias to a season. $\endgroup$ – Always Confused Aug 27 '16 at 16:27
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    $\begingroup$ The photo input continues while the enzymatic reactions decline with failing temperatures which would mean the thylacoid pH will get out of hand. Anthocyanin shading the light harvesting centers is one means to prevent this. Yellow xanthophylls (yellow) is another but accomplishes the same end differently. It's about reducing PS2 activity, IMHO. $\endgroup$ – Jim Young Aug 27 '16 at 22:54
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    $\begingroup$ @user17343 I edited your post to try to improve the format. Feel free to roll back if you don't like the edit. +1 btw $\endgroup$ – Remi.b Aug 28 '16 at 2:18
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    $\begingroup$ Thanks to all the helpful answers!! I'm a little put off by the condescension on here, particularly in the scientific topics. It's an app, not a journal. We're coming to YOU for YOUR expertise, so talking down to people about their grammar or use of Latin here seems exceeding condescending and priggish. Either way I appreciate all the input and time spent $\endgroup$ – Jaguar Domingo Aug 28 '16 at 4:44
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    $\begingroup$ Not directed at you @Remi.b $\endgroup$ – Jaguar Domingo Aug 28 '16 at 4:48

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