Plant antiperspirant

The leaf must ensure that gas exchanges take place only through its stomata. After all, what good would it do to close them to conserve water, if it were to lose just as much elsewhere? Similarly, you wouldn't want to waste your time watering your garden with a hose that was full of holes!

That's why the leaves are covered in a waxy coating called the cuticle (in white on the image opposite), which prevents them from losing water. Carbon dioxide can't penetrate it, but it greatly cuts down on the water lost by the leaf and limits gas exchanges to the part of the leaf that the tree can control – the stomata (A minute epidermal pore in a leaf or stem through which gases and water vapor can pass. ).