why do leaves change colour?

Question

why do leaves change colour?

Answer 1

The chlorophyll in the leaves is green and provides the dominant color. It starts to break down as autumn approaches, revealing other colors in the leaves begin to show themselves. They were actually there all along, but you couldn't see them because of all the green chlorophyll in the leaves.

Answer 2

The green pigment chlorophyll, which absorbs red and blue light, is not a very stable compound and bright sunlight causes it to break down. So, to maintain the amount of chlorophyll in their leaves, plants continuously have to make or synthesize it. The production of chlorophyll in plants requires sunlight and warm temperatures, so it is continuously broken down and re-made in the leaves of plants and trees during the spring and summer months.


Another pigment found in the leaves of many plants is carotene, which absorbs blue-green and blue light, and the light reflected from it appears yellow. The energy of the light absorbed by carotene is transferred to the chlorophyll to be used in photosynthesis. When carotene and chlorophyll occur in the same leaf together, they remove red, blue-green and blue light from the sunlight that falls on the leaf and, therefore, the light reflected by the leaf then appears a very bright green.

The shortening days and cooler nights of autumn trigger changes in the tree. At the point where the stem of the leaf is attached to the branch, a special layer of cells develops and gradually severs the tissues that support the leaf. Because the nutrient flow is interrupted, the production of chlorophyll in the leaf declines, and the green colour of the leaf fades. At the same time, the tree seals the cut, so that when the leaf is finally blown off by the wind or falls from its own weight, it leaves behind a leaf scar.

Carotene is a much more stable compound than chlorophyll and persists in leaves even when all the chlorophyll has disappeared, so the remaining carotene causes the fading leaf to appear yellow.

A third class of pigments that occur in leaves are the anthocyanins, which absorb blue, blue-green and green light. Therefore, the light reflected by leaves containing anthocyanins appears red or purple, depending on the acidity of their sap. Anthocyanin pigments are responsible for the red skin of ripe apples and the purple skin of ripe grapes. Anthocyanins are formed by a reaction between sugars and certain proteins in cell sap and this reaction does not occur until the concentration of sugar in the sap is quite high. The reaction also requires light which is why apples often appear red on one side and green on the other. The red side was in the sun and the green side was in shade. In some trees, as the concentration of sugar in the leaf increases, the sugar reacts to form anthocyanins, and these pigments cause the yellowing leaves to turn red.

The range and intensity of autumn colours is greatly influenced by the weather. Low temperatures destroy chlorophyll, but if they stay above freezing, they promote the formation of anthocyanins. Bright sunshine also destroys chlorophyll and enhances anthocyanin production. Dry weather, by increasing sugar concentration in sap, also increases the amount of anthocyanin. So the brightest autumn colours are produced when dry, sunny days are followed by cool, dry nights.

Many trees and shrubs lose their leaves when they are still very colourful. Some plants retain a great deal of their foliage through much of the winter, but the leaves do not retain their colour for long. Like chlorophyll, the other pigments eventually break down in light or when they are frozen. The only pigments that remain are tannins (bitter compounds that are produced in plants to deter foraging animals and insects and help them resist decay), which are brown. Hence the leaves that remain on deciduous trees in the winter are always brown.

Answer 3

As all living things,,,,,,,,,, even leaves dies,,,,,,,,,,,, leaves are generally green becoz of chorophyll pigments which are green in colour which helps in photosynthesis,,,,,,,,,, it contains chlorophyll a , chrophyll b, xanthophill and etc,,,,,,,,,,,, as the chlorphyll pigments lasts,,,,,,,,,,, it faints its colour,,,,,,,,, as results of which leaves turns yellow,,,,,,,,,,, and its shades and which is replaced by juvenile leaves

Answer 4

When winter comes, trees start to cut nutrients to leaves to conserve water and energy. The leaves actually start to die and decompose. The greenish color is the first to decompose and then the remaining colors start to appear.

Answer 5

May be chlorophyll turns to other pigment like Xanthophyll etc or due to deposition of excretary materils of plant.

Answer 6

Three things cause fall/autumn leaf color: leaf pigmentations (make-up of tree/leaf), length of night where you live, and the weather.

As days grow shorter, and nights grow longer and cooler, biochemical processes in the leaf begin to change. The amount and brilliance of the colors that develop in any particular autumn season are related to weather conditions that occur before and during the time the chlorophyll in the leaves is dwindling. Temperature and moisture are the main influences.
In early autumn, in response to the shortening days and declining intensity of sunlight, leaves begin the processes leading up to their fall. The veins that carry fluids into and out of the leaf gradually close off as a layer of cells forms at the base of each leaf. These clogged veins trap sugars in the leaf and promote production of anthocyanins. Once this separation layer is complete and the connecting tissues are sealed off, the leaf is ready to fall.


Colors come from:

Chlorophyll, gives leaves their green color and is necessary for photosynthesis (chemical reaction that enables plants to use sunlight to manufacture sugars for food.) Trees store sugars for their winter dormant period.

Carotenoids, which produce yellow, orange, and brown colors in such things as corn, carrots, and daffodils, as well as rutabagas, buttercups, and bananas.

Anthocyanins, which give color to such familiar things as cranberries, red apples, concord grapes, blueberries, cherries, strawberries, and plums. They are water soluble and appear in the watery liquid of leaf cells.

Chlorophyll and carotenoids are present in the chloroplasts of leaf cells throughout the growing season in spring and summer.

Most anthocyanins are produced in the autumn, in response to bright light and excess plant sugars within leaf cells. During the growing season, chlorophyll is continually being produced and broken down and leaves appear green. As night length increases in the autumn, chlorophyll production slows down and then stops and eventually all the chlorophyll is destroyed. The carotenoids and anthocyanins that are present in the leaf then show their colors.

Certain colors are characteristic of certain trees/bushes, etc. Oaks turn red, brown, or russet; hickories, golden bronze; aspen and yellow-poplar, golden yellow; dogwood, purplish red; beech, light tan; and sourwood and black tupelo, crimson. Maples differ species by species-red maple turns brilliant scarlet; sugar maple, orange-red; and black maple, glowing yellow. Striped maple becomes almost colorless. Leaves of some species such as the elms simply shrivel up and fall, exhibiting little color other brown.

The timing of the color change also varies by species. Sourwood in southern forests can become vividly colorful in late summer while all other species are still vigorously green. Oaks put on their colors long after other species have already shed their leaves. The evergreens-pines, spruces, cedars, firs, and so on-are able to survive winter because they have toughened up. Their needle-like or scale-like foliage is covered with a heavy wax coating and the fluid inside their cells contains substances that resist freezing. Thus the foliage of evergreens can safely withstand all but the severest winter conditions, such as those in the Arctic. Evergreen needles survive for some years but eventually fall because of old age.


The differences in timing among species seem to be genetically inherited, for a particular species at the same latitude will show the same coloration in the cool temperatures of high mountain elevations at about the same time as it does in warmer clients.

Needles and leaves that fall are not wasted. They decompose and restock the soil with nutrients and make up part of the spongy humus layer of the forest floor that absorbs and holds rainfall for trees and plants. Fallen leaves also become food for numerous soil organisms which are important to the forest ecosystem. Another benefit of the annual leaf fall is that the forest could not survive without its annual replenishment from leaves than the individual tree could survive without shedding these leaves.

The “Indian summer” days of autumn/fall provide an almost irresistible lure to those who enjoy the outdoors and the fall colors.

Answer 7

An elf paint then... ( I read this somewhere and it's a funny picture). Just kidding, you 've already got a great and correct answer...(the third, and also the one that talks about pigments.)

Answer 8

because they go through weather and "age" changes

Answer 9

because of the sun they get and how healthy they are

Answer 10

loss of chlorophyll!