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Fluid Journal : Spring 2015
8 plants growing under drought conditions will require a large healthy rooting system for maximal root surface area to extract available water from the soil. So a large root mass with a large number of root hairs is beneficial. The root hair zone is the most water permeable in the rooting system and increases the root diameter, promoting increased water uptake. Calcium plays a vital role in root (Figure 3) and root hair production (Figure 4), since it is a major nutritional component of roots and aids in cell division during root and root hair development. With the increased production of larger roots and root hair with calcium application, rooting systems have greater surface area and become significantly more effective in increasing available water uptake by 55 percent in a sandy soil on a theoretical basis (Figure 5). During drought stress, plants release abscisic acid (ABA), a hormone that increases water conductivity (movement of water from roots to shoots) in the plant. With or without ABA, Ca also increases water conductivity. With ABA and Ca, water conductivity is significantly increased (Figure 6). So, water uptake efficiency, maximal root and root hair mass, and optimal water conductivity are necessary for strong healthy productive plants during drought. Calcium plays a vital role in both plant mechanisms. Transpiration Stomata. Available soil water is taken up by plant roots and translocated to the xylem, which moves the water in a continuous flow into leaves. Water is converted to water vapor near the stomata and when open, escapes into the atmosphere as the plant acquires CO2 and releses O2. Stomatal transpiration, as described, accounts for 90 to 95 percent of the water transpired through the leaves. The ability of the plant to regulate its stomatal opening and closing is imperative in order to obtain a carbon source for photosynthesis and to limit water loss from tissue and prevent desiccation. Tissue damage or plant death can occur when plant tugor is low and the stomata are open. It is well known that potassium is key