Abscisic Acid Content and Effects During Dehydration of Detached Leaves of Desiccation Tolerant Plants

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Abstract
Borya nitida is an angiospcrm whose detached leaves develop complete tolerance to dehydration when they are equilibrated to air of 96% r.h. This treatment causes leaves to yellow as chlorophyll is destroyed, and abscisic acid contents increase several-fold. Exogenous ABA (at 0.038–0.38 mol m−3) promoted desiccation tolerance (a) in leaves undergoing tolerance induction at 96% r.h., (b) only slightly during rapid drying at rates which are normally injurious, and (c) considerably in turgid tissue treated with ABA 48 h before rapid drying. ABA content also increased with intense water stress in Myrothamnus flabellifolia, a desiccation tolerant angiosperm which, unlike Borya, retains most of its chlorophyll when dehydrated. Preliminary incubation in ABA of detached leaves of this ‘resurrection plant’ also promoted survival during rapid drying. The ability of ABA to substitute for the normal induction period suggests that this hormone participates in the development of desiccation tolerance.