Why are ivy leaves thicker in the sun than in the shade?

What is the bilogical reason for this. I can't find information anywhere.

The type of ivy leaves i am researching is Hedera Helix, if anyone knows...please do answer soon!

Why are ivy leaves thicker in the sun than in the shade?
The reason is because of the plants response to the drier conditions of the sun. The leaves are thicker because in the hot heat from the sun dries out leaves quicker than in the shade. If the leaves were put in the shade they'd get back to thin and papery. It's a special technique the English Ivy has adapted because in the forest it starts in a shady dark shadow of a tree and as it grows up it gets hotter and drier so the leaves get gradually thicker and thicker as well as smaller too. Many other vining plants do this also.
Reply:they are thicker so as they can retain more water ie less transpiration. the thinner the leaf the more transipration and photosynthesis
Reply:i would guess that because the sun is their source of energy, the plant sends most of it's resources into better harvesting that energy, through more leaf coverage
Reply:I don't know for sure but leaves process chlorophyll through sunlight, so I would wager that the sun makes the leaves thicker because they are processing more light.



Hope that helps.