Abscisic Acid Accumulation in Detached Leaves of Rice (Oryza sativa L.) in Response to Water Stress: A Correlation with Leaf Size

When water stress was imposed on detached leaves of two rice (Oryza sativa L.) cultivars, more ABA per unit fresh weight accumulated in IR20, a small-leaved cultivar, than in 63–83, a large-leaved cultivar; the difference being up to threefold. In an F2 population of a cross between the two cultivars ABA accumulation was found to be significantly negatively correlated with leaf fresh weight. This correlation persisted in the F3 generation. Such a correlation was not evident, however, when a number of rice cultivars, which varied widely in leaf size, were examined. The difference in ABA accumulation between IR20 and 63–83 was not accounted for by different spatial patterns of water loss or ABA accumulation within a leaf, and cultivar differences in ABA content were maintained both across, and at various positions along the leaf. No major differences in leaf anatomy were observed between the two cultivars. Differences found in leaf water relations characteristics were few and generally minor. It therefore seems unlikely that these properties account for the difference between the cultivars in the ability to accumulate ABA or for the correlation with leaf size.