MO FALL COLORS

We are "peaking" this week in middle Wisconsin in the autumnal colorfest department.  We are about 70% complete with color variations existing depending on the types of trees present.....everything from muted yellows to flame orange and reds.  
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This particular tree is typical of the Sugar Maples (Acer saccharum) in the area.  The red colors exist mainly because of the high concentration of sugars in the leaves which helps in the synthesis of anthocyanin pigments which cause the reddish colors.  Anthocyanin is an anti-oxidant that also makes the reds and purples in fruits and vegetables. It is important in maintaining the health of the leaves, repairs leaf damage and is, in effect, a kind of sunscreen.
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Chlorophyll, the green pigment found in leaves, is synthesized within the leaf and is important in photosynthesis (PNS).  Interestingly, UV light which is needed for PNS also destroys chlorophyll thus chlorophyll is constantly being manufactured to replace that which is destroyed by the UV light.
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In the autumn, an abscission layer forms between the leaf stem and the branch which cuts off the leaf's water supply.  As the residual chlorophyll in the leaf is slowly decomposed by UV light, no more can be synthesized due to the lack of water and nutrients....thusly the leaves slowly lose their green color and allow other pigments, mostly yellows (Carotene) to show through but were masked due to the abundance of chlorophyll.  Other pigments are synthesized as well if the proper nutrients are present which accounts for the riot of leaf colors seen in most mixed hardwood forests in middle latitudes.
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Where there are maples (Acer sp.) more reds will be seen....where there are mostly aspens (Populus sp.) yellow pigments, carotenoids are predominant.  Anthyocyanin and carotene (reds & yellows) can both show through and give the leaf an orange color.
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BTW....here's a concept most people do not clearly understand.  The COLOR of any object is a component of the light wavelengths that are reflected off the object and back to your eye.  If asked which color of the natural light spectrum (red-orange-yellow-green-blue-indigo-violet) is most important to photosynthesizing plants...most people would say green.  In fact, green is the least important color of the spectrum for PNS.  All the other "colors" (wavelengths) are absorbed by the leaf and only green is reflected precisely because it is not absorbed.  Leaves do not use green light.  Thus endeth the biology lesson for the day.
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Best in Large.