ABSTRACT
The presence of aquaporins increases membrane permeability to water and also controls the volume of water passing into the stele; if such control did not occur, more water could move into the transport system than could be lost through the leaves. Minerals ions dissolved in the soil water are taken up from films of water surrounding the soil particles, through the root cortex largely via the apoplast pathway. At the endodermis they are taken into the cells by active transport on specialized proteins embedded in the cell membrane. The stomatal complex is made up of a pair of guard cells surrounding a central pore or stoma. Behind the stoma is the substomatal cavity surrounded by the cells of the spongy mesophyll. When the guard cell is fully turgid it swells unevenly and the stomatal pore opens. They also often contain chloroplasts, unlike the surrounding epidermal cells which are involved in providing energy to regulate stomatal opening.
