when the leaf dries so why they jace the brown colour in them
Answers
Leaves are nature's food factories. The process of leaves turning sunlight, water and carbon dioxide into oxygen and glucose (sugar) is called photosynthesis. A chemical called chlorophyll helps make photosynthesis happen. Chlorophyll is what gives plants their green color.
Why do leaves change colour?
Chlorophyll is found in abundance in the cells of leaves. This pigment is supposed to be the busiest among all. Because of the busy nature of the green pigment chlorophyll, it is dominant and covers the yellow and the orange pigment. The function of chlorophyll (photosynthesis) goes on from summer to monsoon. Post-monsoon, as winter approaches, plants start preparing themselves for the cold weather.
During winter, there is not enough light or water 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. A thin layer of cells grow on the water tubes of the leaves to make sure that no more water enters the leaves or plants. Since there is no water, chlorophyll is not able to perform its normal task of photosynthesis and it slowly starts disappearing or turning less dominant. And due to this, the yellow and orange pigment start showing. Leaves do not change their colour but just lose their green.
Sometimes leaves are red and purple in colour. This happens when the cells block the water tubes of the leaves; the sugar that is being carried to other parts of the plant is left behind or is trapped due to lack of water lending. Sunlight and the cool nights of autumn cause the leaves turn this glucose into a red color.
When all the pigments; green, yellow and orange die because of lack of water, the leaf starts turning brown in colour and later withers away to give way for a new leaf to be grown. Because of no pigments and water, the brown leaves are dry and crunchy.