A layer is where most gas exchanges occur in the the leaf.

Answer 1

This is correct. The layer responsible for gas exchange in leaves is called the mesophyll. Within the mesophyll are two types of cells, the palisade and spongy cells, where photosynthesis occurs and oxygen and carbon dioxide are exchanged through tiny pores called stomata. The stomata open and close to regulate the amount of gases exchanged and to prevent excessive water loss through transpiration.