Leaves change color with seasons

When I was asked to go to Japan to support our IC design last autumn 2003, anywhere I found colored broadleaved trees, from reds, oranges, to golds of the mixed deciduous woodlands! The colors are truly breathtaking.

Do you wonder why leaves change color with season? How does autumn color happen?
We knew from early years that photosynthesis is the process by which plants use the energy from sunlight to produce sugar for its food. Water and carbon dioxide, which are the raw materials of photosynthesis, enter the cells of the leaf, and then sugar and oxygen leave the leaf, which are the products of photosynthesis. When leaves appear green, it is because they contain an abundance of chlorophyll.
Scientists have worked to understand the changes that take place in the leaf. According to research length of daylight, temperature, light and water supply are the common factors. Changes in the length of daylight and changes in temperature make leaves stop their food-making process. And light, and water supply have an influence on the intensity and the duration of color of the leaf.
The combination of red, purple, orange and yellow is what that take place in the leaf as the seasons change from summer to autumn to winter and to spring. Since nighttime is longer than daytime during autumn, as night length increases chlorophyll production stops until all the chlorophyll is destroyed. Decreasing light levels destroys the chlorophyll. Thus the green color disappears, and the yellow to orange colors become visible. According to experts, the carotenoids and anthocyanins that are present in the leaf are unmasked and reveal their colors. Leaves containing more anthocyanins will appear red. Leaves with good amounts of both anthocyanins and carotenoids will appear orange. Leaves with carotenoids but little or no anthocyanins will appear yellow.