Why do leaves change color in the fall?

Answer 1

One of the sure signs of fall (besides the beginning of a new school year) is the change in color of leaves from green to bright yellow, orange and red. Trees are sort of like bears—they store up food during the spring and summer and then rest for the winter.

Over the spring and summer, trees use a process called photosynthesis to make food and energy. A green pigment called chlorophyll makes photosynthesis happen. During the fall and winter, there isn’t enough light or water for photosynthesis to occur, so the chlorophyll begins to fade way. As the green disappears, the other colors begin to emerge. These colors were present in the leaves all along, but they were dominated by the chlorophyll..

Answer 2

This is a great question!! I love it because we have all wondered this, and nobody I asked had a complete answer so I did some research two years ago.

Many answers above are partially right. Chlorophyl is responsible for the green color. When light levels decrease in fall and temperatures drop, the trees will start shutting down leaf activity, and will start recovering ("translocating") nutrients from the leaves. Chlorophyl is one of the first to go, and the organelles ("chloroplasts") that have this pigment are produced at slower and slower rates. Thus, the other pigments (carotenoids, yellow and orange), which are present in much lower amounts in the leaves, are revealed. A blue pigment (xanthene) is present as well but in very tiny amounts.

If the trees are still in the process of shutting down leaf activity, but there is still a lot of sun, the trees will produce an ADDITIONAL pigment, one that wasn't there before. This is because the sun's heat is damaging to the leaves, now that the chloroplasts are no longer capturing the sun's energy for sugar production. This additional compound is an anti-oxidant to keep free radicals (damaging chemical compounds that ravage cells in the leaf) from being produced, for the length of time that the tree is still translocating nutrients down to the roots..

This pigment gives the leaves the gorgeous intense reds and , oranges you see in Sugar Maples, and the bright crimson and purple hues you see in Sweet Gums. These colors are GREATLY muted or absent if the autumn season is mostly cloudy or rainy, because the bright sun is not out to pose a threat to the integrity of the leaf cells, so the tree will not produce the defensive anti-oxidants.

You may have noticed nutritionists recommending we eat "brightly colored" vegetables and fruits for their high antioxidant content? Also, have you ever noticed that some fruits are more brightly colored on one side (the sun-facing side) than the other? Bingo! Antioxidants in action.

Cool, huh! Hope this answers your question.

Answer 3

According to my research in the encyclopedia:

"A green leaf is green because of the presence of a group of pigments known as chlorophylls. When they are abundant in the leaf's cells, as they are during the growing season, the chlorophylls' green color dominates and masks out the colors of any other pigments that may be present in the leaf. Thus the leaves of summer are characteristically green.

"In late summer, the veins that carry fluids into and out of the leaf are gradually closed off as a layer of special cork cells forms at the base of each leaf. As this cork layer develops, water and mineral intake into the leaf is reduced, slowly at first, and then more rapidly. It is during this time that the chlorophyll begins to decrease.

"As autumn approaches, certain influences both inside and outside the plant cause the chlorophylls to be replaced at a slower rate than they are being used up. During this period, with the total supply of chlorophylls gradually dwindling, the "masking" effect slowly fades away. Then other pigments that have been present (along with the chlorophylls) in the cells all during the leaf's life begin to show through. These are carotenoids and they provide colorations of yellow, brown, orange, and the many hues in between.

"The carotenoids occur, along with the chlorophyll pigments, in tiny structures called plastids within the cells of leaves. Sometimes they are in such abundance in the leaf that they give a plant a yellow-green color, even during the summer. Usually, however, they become prominent for the first time in autumn, when the leaves begin to lose their chlorophyll."

There is more there at that link and several nice websites on the subject too. Hope that answers your question.

Answer 4

The green color in the leaves is due to chlorophyll.At the time of fall,the chlorophyll in the leaves get degraded & hence the color of the falling leaves change.

Answer 5

The green chlorophyll becomes depleted from the leaves in preparation for the coming cold season.

Answer 6

trees shed their leaves to reduce transpiration (loss of water to environment) This happens due to some chemical substances such as ethylene gas in the plant Before shedding the leaves the tree sucks up water , starch and all nutrients in the leaves This changes the leaves' colour

Answer 7

Chemical changes accrues, due to light condition and amount of water... colours are not always that vivid on same tree, from year to year. It also depends on the type of trees.

Some trees go though lots of colour changes and some just turn yellow.

Answer 8

The lack of sun light,frost and cold only highlight or brighten the colors.

Answer 9

when humans die they turn blue after sm hrs???????????????

leaves are also living breath and when they seperate from the tree it is like the connection of body's part is deconected from the heart......you can try it on u...try to tie a tight knot on ur half finger for sm time and when it does not get blood for sm time it will start turning blue and if u keeep it for long it will make ur finger feel numb....


******ps don't keep it for long it can kill ur finger like a leave is separated from the tree same will hapen to ur finger....take care