Colors of leaves

Season changes
Leaves turns brown when it is autumn, but why is that so? Well, to find out the answer, we must first know what are the functions of leaves

Basically, leaves gets it's water throught the plant's root, and they also take in carbon dioxide throught their stomata. They then uses the sunlights to turn water and carbon dioxide into oxygen and glucose. The way plants uses the sunlights to turn carbon dioxide and water into oxygen and glucose is by photosynthesis. Chorophyll, which is present in chloroplast in the plant is involoved in photosynthesis. It is chloroplast which gives the plant it's green colour

As the summber ends, there somes autumn. The days also gets shorter and shorter. This is how the plants "know" to get prepared for winter.

During winter, there is very little water and sunlight for the plant to photosynthesis. Thus, the trees will rest, and live off the food they stored during the summer. They began to shut down their "food-making factory", and their green chlorophyll will disappear. As the greens fade, the leave will turn yellow-orange color. But why that color? These color is actually the actual color of the plant all along, we just can't see it during summer as the chlorophyll in the plant is still present for photosynthesis

In fall, we would usually see plants with bright red or puple color leaves. Glusoce in the leaves(Like the maple leaves) is trapped in the leaves as photosynthesis stops, and with the sunlight and the cool nights from the autumn, the leaves began to turn glucose into red color. The brown color of trees(Like the oak tree) is made from wastes left in the leaves-(More explaination on colors below)

Preparations for winter
In winter, the days are shorter and it is very hard to find water. But how do plants survive throught the winter? They have lots of method to doing so.

Some plants are called "annual" which means they would complete their life cycle in one growing season. They would die as the sinter approches, but their seeds remain, ready to germinate and sprout again in the spring. "Perennial"live for more then 2 years. This includes treesand shrubs and other herbaceous plant which have soft fleshy stems. When winter comes, their woody parts of these plants are able to survive the cold, but the above ground of the plant's part, which are the leaves and stems, will die, leaving the underground parts alive. Thus in the winter, these plants will rest and use the stored food until spring

As the plants get older, they tend to shed their older leaves and grow new ones. This is important as theis helps the plants to replace damaged leaves made by the insects, diseases, or weather. The shedding and replacments continues all the time. Thus, leaves like maple, will shed their leaves in preparations for the cold winter

"Evergreen" plants, however, keeps their leaves throught the winter. They have special leaves which are somehow resistance to the cold and moisture lost. many plants have different shape of leaves to adapt to the cold winter. Some leaves, like the pine and fir tree have long thin needle like leaves, while others, like the holly, have board leaves with tough waxy surfaces. This leaves somtimes reduce their exposed area by curling up. Evergreen plants may continue to photosynthesis, as long as they have enough water, but reaction occurs slower as the temperature is low.

During the summer, the leaves would make more food then it needs. The excess food are turned into starch. These starch are used for the autumn when daylight gets shorter. The plants will then shut down their food production
Many things occurs in the leaves of the deciduous trees before they finally fall off the branches. The leaves have always been preparing food for the trees since the start of spring. At the base of the leaves, there is a special layer called "abscission" or seperating layer. During the summer, small tubes which passes throught this layer is carrying water into the leaves, and the food back to the tree. Whereas in the fall, the cells of the abscission layer began to swell and form cork like material, reducing the cut off flow between the leaves and the trees. Glucose, as well as waste products, is trapped in the leave. Without water to renew it, the chlorophyll begin to fade off.

Does color matters?
The red and purple colors comes from anthocyanin pigments. These pigments are potent antioxidents common in many plants. For intense, red apple, purple grapes, and red wine, flowers like violets and hyacinths. In some leaves, like the maple, these pigments are formes during the autumn from the trapping of starch. But why would the leaves use energy to make these pigment even thought the leaves are going to fall off? Some scientist thought the pigments anthocyanin will help the trees keep their leaves abit longer. The pigments will protect the leaves from the sun and also lower their freezing point, thus giving frst protection. The longer the leaves remain on the tree, and more sugar, and other valuble substances can be remove from the leaves before they fall. There is another possible reason: When the leaves decay, the anthocyanin will seep into the ground, preventing other plants species from growing in the spring

The brown color comes from tannin, which is the bitter waste product. Other colors, which has been all along on the plant, become visible without the chlorophyll. The orange color come from carotene and the yellow from xantheophyll. They are all common pigments found in flowers, and even food like carrots, egg yolks, etc. We do not know their exact functions in the leae, but scientist do know that they are somehow involved in photosynthesis.

Banana and autumn leaves...? What's there in common?
Do you know that while banana are still unripe, the color green is actually chloropyll? It is the same pigment that gives the green it's green color! However, as the banana becomes ripen, the chlorophyll will break down and disappear, revealing the yellowish color which has been the banana's real color form. During the autumn, the leaves also show off theit true colors as the chloroplast breaks down. There are also another changes in the banana as it ripen. The starch changes to sugar and the flesh soften as the pectin(a carbohydrate) breaks down.