Abscisic Acid Accumulation and Water Relations of Four Cultivars ofPhaseolus vulgarisL. under Drought

Larqué-Saavedra, A., Rodriguez, M. T., Trejo, C. and Nava, T. 1985. Abscisic acid accumulation and water relations of four cultivars of Phaseolus vulgaris L. under drought.—J. exp. Bot 36: 1787–1792. Plants of four cultivars of Phaseolus vulgaris L. differing in drought resistance were grown in pots under greenhouse conditions and prior to flowering water was withheld from the pots until the mid-day transpiration rate reached values below 1.0 μg H2O cm−2 s−1 (designated the ‘drought’ stage). At this point leaves were harvested on 3 or 4 occasions over 24 h to determine the abscisic acid (ABA) concentration, total water potential (ψω), solute potential (ψ1) and turgor potential (ψp). Results showed that values of ψω, ψ1, and ψp differed between cultivars when they reached the ‘drought’ stage. The stomatal sensitivity to changes in ψω and ψp, was as follows: Michoacán 12A3 > Negro 150 Cacahuate 72 > Flor de Mayo. These data correlated well with the pattern of drought resistance reported for the cultivars. ABA accumulation at the ‘drought’ stage differed between cultivars at each sampling time, but overall differences in ABA level between cultivars were not significant. ABA levels did not, therefore, correlate with the drought resistance properties reported for the cultivars. Results are discussed in relation to ψω and hour of the day when bean samples were taken for ABA analysis.