Abscisic Acid Production and Water Relations in Wilty Tomato Mutants Subjected to Water Deficiency

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Abstract
Neill, S. J. and Horgan, R. 1985. Abscisic acid production and water relations in wilty tomato mutants subjected to water deficiency.—J. exp. BoL 36: 1222-1231. Abscisic acid (ABA) concentrations were determined in shoots of Lycopersicon esculentum Mill. cv. Ailsa Craig wild type and the three wilty mutants notabilis (not), flacca (flc) and sitiens (sit). ABA content of unstressed wild type leaves was 1.5 nmol g−1 fr. wt.; concentrations in not, flc and sit were 49, 26 and 15% of this respectively. Gradual water stress was imposed on potted plants and a more rapid stress imposed on detached leaves. Leaves of the wild type and not responded to both stresses by increasing their ABA content but leaves of flc and sit did not produce any more ABA under stress. Transpiration rates of flc plants were three times greater than those of the wild type and stomatal resistances correspondingly lower. Stomata of both flc and the wild type responded to darkness and externally supplied ABA by closing. However, only wild type stomata responded to water stress by dosing; those of flc leaves remained open until the leaves were severely desiccated. Thus, there was some relationship between the lack of stomatal response to water stress and the failure to synthesize ABA.