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What causes the leaves on trees to change color and fall off?

Is it a time-release type of thing? Or do the trees react to the weather change? And how come trees in some areas change color and others dont in nearby areas?

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its the weather change because of the different seasons

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I want to say photosynthesis maybe

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yes
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This is about survival. All of the leaves require substantial energy and resources. In the summer this is a net positive. In the winter, this is not possible. To survive the tree must largely shut down to protect against frost/freezing. Because of this, the leaves die and fall off. Now the tree can survive winter better, and is less likely to be injured by winter storms and snow, that would case significant damage if all of the leaves were there.

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Is it really about survival.
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Yes... Freezing weather would severely damage the tree if the trunk and branches were still full of sap. The sap runs in the layer immediately below the bark, and so would be vulnerable.
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You are the best, information was spot on.
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I think it's just the life cycle.

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Really is that what you think.
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it's a chemical called chlorophyll in the leaves that makes them green.That chemical is gone in Autumn.Making the leaves change colors.I'm not so sure about falling off though.But there's the color changing problem solved.But those "piney"trees with pricks and quills,stay green all year.I don't necessarily know why but you call always go Google,Bing,Wikipedia,or even ask.com search for answers

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It is due to low chlorophyll coming to the leaves ,that happens because the chemical is mad e by combing things with sunlight ,so the less sunlight the less green leafs .

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First, it is the genetic inheritance of the tree. Some maples, for instance, will turn "early" every year. Second, it is the length of sunlight in the day. The reds and yellows are in the tree all along, but when the green stops being made because of short sunlight in the days, then you see the reds and yellows. Third, it is the amount of water. If the tree does not have enough water, it may loose leaves earlier to preserve water. Fourth, it is the health of the tree.
Why do the leaves fall? The tree actually cuts off circulation to the leaves when they are not making enough food.

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i was wrong about the reds and purples already being in the leaves, Lar235 was right--the leaves start making them when the green stops being made.
But--the yellow is in the leaves along with the green from the chlorophyll--we just see it when the chlorophyll goes away.
And, i forgot to mention that temperature is a factor also
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The tree drops its leafs to protect it from freezing.

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What causes it is that the moisture in the air is leaving for winter is coming. When the moisture is leaving, the sun's rays hit the leaves making the green color figment to dissolve into the bark of the and over time, it slowly makes the color for the figment is leaving but you are seeing a colors for the different sizes of the leaves.

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To protect them from damage from the harsh winter (well depends where you are from Maine to central Virginia has harsh winters. Lower than them the south has mild winters hardly getting any snow)

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sometimes the leaves fall because of the wind

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Because they wanted to be like Michael Jackson, they wanted to change their color then crumble and die.

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The chlorophyll disappears. This shows their real colors which are masked by the chlorophyll. Once the chlorophyll dies, it disappears. The chlorophyll protects the leaf so when the chlorophyll dies the leaf dies with it.

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As a professor at the Illinois college of ACES I can confidently say that decomposition is what causes the leaves to turn the orange brown color but the leaves fall off of the trees because of the change in seasons.

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You should be able to look this up. There are two important organelles that are used by trees to transfer nutrients between the roots and the leaves. These are xylem and phloem. Nutrients are pulled through the trunk (through osmosis) to the leaves where they are processed with the aid of photosynthesis. Then they are moved back through the tree to make the roots and the tree itself grow. Water is used to dissolve the nutrients. Without water the nutrients cannot dissolve and the tree starves to death. In the winter this is a problem because water freezes and expands. To avoid this, a tree will discard the leaves which in turn will stop the water/nutrient flow. Failure to do this will cause the water inside the trunk to freeze cracking the trunk open and killing the tree. Obviously, trees that live in tropical areas do not have this problem and thus never loose their leaves in the winter. Conifers have a different biochemical adaption that allows them to survive in winter without loosing their leaves (which look like needles).

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Trees respond to the decreasing amount of sunlight by producing less and less chlorophyll. Eventually, a tree stops producing chlorophyll. When that happens, the carotenoid already in the leaves can finally show through. The leaves become a bright rainbow of glowing yellows, sparkling oranges and warm browns. What about red leaves? Read on. http://dnr.wi.gov/eek/veg/trees/treestruecolor.htm

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This article should shed some light on the matter.

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