In
the spring and the summer is when the leaves create food needed for the trees
growth, this process is known as photosynthesis. This process requires cells
containing chlorophyll, which gives the leaf its green color, to convert the
light energy into food. Chlorophyll is only found in plant cells, which is why
humans aren't green. In the fall, the amount of light and changes in
temperature stop the leaves from making food. The cholorophyll breaks down and
the other pigments like xanthophyll (yellow) and carotenes (orange) that were
masked by the green are visible. While this is happening a special layer of
cells develop at the stem of the leaf which gradually severs the supporting tissues,
making the leafs fall. Weather also has an impace on what color the leaves
turn. Above freezing temperatures will make bright red maples, while early
frost will dull this bright red. Rainy/Overcast days also increase the
intensity of fall colors.
Evergreen
trees do not lose their needles in the winter. This is due to the difference in
the kind of leaves that Evergreens have compared to other trees. Evergreens
have needles, needles have less surface area than larger, flatter leaves, and
can resist changes in temperature and humidity easier. This allows the
chloroplasts to survive and continue to produce food for the tree all year
round.
PoS
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