Quantitative differences in leaf abscisic acid (ABA L ) among four cultivars of red maple ( Acer rubrum L.) and one freeman maple ( Acer × freemanii E. Murray) cultivar were investigated. This study tested the hypothesis that ABA L concentration can be used to compare the effects of water stress on the gas exchange response of five different maple genotypes, including four red maple cultivars [`Summer Red', `October Glory', `Autumn Flame', and `Franksred' ('Red Sunset')] and one hybridized freeman maple cultivar ['Jeffersred' ('Autumn Blaze')]. Two-year-old cloned genotypes of red maple and freeman maple were subjected to two treatments: irrigated daily to container capacity or irrigation withheld for one drought and recovery cycle. Leaf abscisic acid concentration, gas exchange, and wholetree sap flow measurements were conducted under well-watered and drought stress conditions. Over the course of the drought stress and recovery phase, net photosynthesis (A net ), stomatal conductance (g s ), and transpiration (E) declined as ABA L and instantaneous water use efficiency (A/g s ) increased. Until severe water stress conditions were prominent, water use was higher in `Summer Red' as compared to `October Glory'. This study found that ABA L tracked g s and that stomatal responsiveness to substrate moisture deficit is likely mediated by ABA accumulation in leaf tissue. This research demonstrates a leaf level physiological response to substrate volumetric water content that appears to depend on ABA L concentration. In addition, the evidence in this study indicates that ABA L may be used as a potential surrogate for the g s response to substrate water stress and could become part of a cultivar drought tolerance selection strategy for red maple and freeman maple.
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Bauerle et al. (2006) studied this question.