Completar frases PhotosynthesisVersión en línea A fill in the blanks activity to revise the parts of the leaf por Miss O'Boyle 1 The waterproof layer at the top of a leaf's surface is called the . The rows of cells in the upper mesopyll is called the layer . This is where takes place . These cells are tightly packed together and contain lots of which harness the light energy . Below this layer of cells is a layer called the . This is where gas exchange takes place through the on the bottom surface of the leaf .