why the leaves of some trees appear green in the summer but turn different colour in autumn?

Answer 1

All summer long the trees keep making chlorophyll as the existing chlorophyll "wears out". There are orange and yellow pigments in the leaves all during this time, but the green does not allow them to show.

Trees make red colors in the fall when there are plenty of sugars in the leaves. When trees stop making chlorophyll in the shorter days of fall, the reds, yellows, and greens can show through.

We have done experiments covering parts of leaves with aluminum foil during the fall. Our tests showed that when leaves do not get light, they do not make the red color. See photos of the results at:http://www.carlinvilleschools.net/linke/Biology/bio.htm

Answer 2

The technical term is senessence, this is whilst the chlorophyll tiers drop because of the fact the sunlight tiers drop in autumn i think of, and the leaf loses the eco-friendly shade. additionally the abscission layer between the tip of the leaf stalk and the main important branch seperate and then the leaf falls.