Physiology of Stressed Crops, Vol. 5: Membrane System

Though plant cells are separated by cell walls, cells maintain their identity as they are delimited by semi-permeable membranes that permit them to function as autonomous units. The flow of materials in and out of the cell is regulated by channels, transporters, pumps, and acquaporins in these membranes. The cytoplasm is sandwiched between two membranes: the plasma membrane, which forms the outer boundary of the cytoplasm, and the tonoplast or the vacuolar membrane which forms the inner bou...