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Abstract
Research completed from 2009 to 2011 evaluated the effects of exogenous abscisic acid (ABA) on the evapotranspiration, leaf gas exchange, and root conductance of tomato (Solanum lycopersicum). In the evapotranspiration study, tomatoes drenched with six rates (0-1000 mgL-1) of ABA exhibited a rate-dependent reduction in cumulative evapotranspiration and extensions of shelf life of unwatered plants by up to 6 d. Research on the short-term effects of ABA reported reduced stomatal conductance, photosynthesis, and transpiration within 60 min. One side effect of concentrated ABA drenches was an ABA-induced wilt occurring within 24 h after ABA application that was not related to low substrate water contents. The root conductance of tomato was evaluated following ABA drenches at six rates using decapitated root systems. ABA caused rate-dependent reductions in water flux through the roots. These results suggest that ABA reduces root conductance, limiting water transport to the leaves and causing the wilt.