How come leafs turn red??

Question

How come tree leafs change color in automn before falling??

Answer 1

There is not enough light in the winter time for photosynthesis. The trees will rest, and live off the food they stored during the summer. They begin to shut down their food-making factories. The green chlorophyll disappears from the leaves. As the bright green fades away, we begin to see yellow and orange colors. Small amounts of these colors have been in the leaves all along. We just can't see them in the summer, because they are covered up by the green chlorophyll.

Answer 2

because leaves have several differnt types of pigments. Some are chlorophylls which are green and involved in photosynthesis (because the green absorbs a specific wavelength of sun rays) and the other kind is cartenoids, which are red, yellow, and orange in color (There is one more main pigment, but it is not so important for this). So leaves turn red as a defense mechanism/energy conserving tecnique. When it starts to get cold, the tree (or plant) begins to withdraw it's chlorophylls which are much more worthy (expensive and usefull to the plant) than the cartenoids, which leaves the leaves (hee hee) red or orange. And then the plant will usually store the chlorophylls in undergound storage or something. Hope that helps! I was just telling a friend of mine about that a while back!

Answer 3

Carotenoids

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.

Carotenoids are common in many living things, giving characteristic color to carrots, corn, canaries, and daffodils, as well as egg yolks, rutabagas, buttercups, and bananas.

Their brilliant yellows and oranges tint the leaves of such hardwood species as hickories, ash, maple, yellow poplar, aspen, birch, black cherry, sycamore, cottonwood, sassafras, and alder.

Anthocyanins

The reds, the purples, and their blended combinations that decorate autumn foliage come from another group of pigments in the cells called anthocyanins. These pigments are not present in the leaf throughout the growing season as are the carotenoids. They develop in late summer in the sap of the cells of the leaf, and this development is the result of complex interactions of many influences - both inside and outside the plant. Their formation depends on the breakdown of sugars in the presence of bright light as the level of phosphate in the leaf is reduced.

During the summer growing season, phosphate is at a high level. It has a vital role in the breakdown of the sugars manufactured by chlorophyll. But in the fall, phosphate, along with the other chemicals and nutrients, moves out of the leaf into the stem of the plant. When this happens, the sugar-breakdown process changes, leading to the production of anthocyanin pigments. The brighter the light during this period, the greater the production of anthocyanins and the more brilliant the resulting color display. When the days of autumn are bright and cool, and the nights are chilly but not freezing, the brightest colorations usually develop.

Anthocyanins temporarily color the edges of some of the very young leaves as they unfold from the buds in early spring. They also give the familiar color to such common fruits as cranberries, red apples, blueberries, cherries, strawberries, and plums.

In our autumn forests, they show up vividly in the maples, oaks, sourwood, sweetgum, dogwood, tupelo, black gum and persimmon. These same pigments often combine with the carotenoids' colors to create the deeper orange, fiery reds, and bronzes typical of many hardwood species.

Answer 4

the colour change is based on the break down of sugars present in the leaves...temperature of the environment plays a large role in the colour change.

Answer 5

because the pigments die in the cold so it cannot photosynthasize due to the lack of chlorophil. so in a nutshell

it gets cold the chlorophill dies the chloroplasts change color and they fall because they are dead cuzthey cant eat

Answer 6

What are 'leafs?' What's 'automn?'

Answer 7

Vaio's answer is concise and precise ...