what part of a tree is responsible for making it's leaves green
pweese at least one person !

Chlorophyll

Chlorophyll is important for doing photosynthesis, as you probably know. It breaks down when its exposed to light, so during the long days of the year, new chlorophyll keeps being delivered to the leaves. Its expensive for the plant to make it, so before a plant loses its leaves, it stops making and delivering new chlorophyll. The old chlorophyll still breaks down, leaving behind the pigments that last longer. 

The bergeron process.