Ineffectiveness of Abscisic Acid in Stomatal Closure of Yellow Lupin, Lupinus luteus var. Weiko III |
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Authors: | LANCASTER, JANE E. MANN, JAY D. PORTER, N. G. |
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Abstract: | Stomata of yellow lupin leaves are remarkably insensitive toabscisic acid (ABA). Stomatal resistance was monitored usingboth a viscous now porometer and a diffusion porometer. Resultswere confirmed with scanning electron microscopy. When exogenousABA solutions were supplied via petioles, 106 M solutionshad no effect on stomatal resistance. Upper (adaxial) stomatawere not affected by 105 M ABA but lower stomata showed3-fold more resistance after 2 h. Stomata of both surfaces closedafter 30 min in 104 M ABA. Isolated epidermal peels of lupin leaves were floated on ABAsolutions yet upper surface peels showed no stomatal closingin 104 M ABA, while lower surface stomata closed to abarely significant extent. Stomata of intact leaves were not very sensitive to darkness,showing at most a doubling in resistance after 6 h darkness.Complete stomatal closure, however, was readily produced bywilting leaves. Hence, lupin stomata are physically capableof closing. Endogenous ABA levels of water-stressed leaves increased approximately10-fold, which corresponds to concentrations below 10 µMABA. It is concluded that ABA is unlikely to play a role incontrolling short-term stomatal response of lupins. |
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