What causes the leaves to change colors in the fall?

Question

Does it have to do with the temperature change or the amount of sunlight in the day or both?

Answer 1

in the fall there is less sunlight so the tree isn't so dependent on chlorphyll for the leaves, so as the chlorophyll gets used up, the carotenoids (reds, yellows and oranges) are able to show hence giving the leaves the colours you see. The carotenoids are always present in the leaves when they are green but are just masked by the green chlorophyll

Answer 2

Both. The tree shifts gears and stops focusing on photosynthesis for leaf production. The green chlorophyl falls away and you see the tree's real color.
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