EFFECTS OF WATER-STRESS APPLIED AT DIFFERENT PHENOLOGICAL PHASES ON YIELD COMPONENTS OF DWARF BEAN (PHASEOLUS-VULGARIS L.)

Drought treatments were applied to seven sets of dwarf bean plants in pots. Each was subjected to water stress during one of the seven pheno logical phases, ranging from bud stage to grain filling. Treatments co nsisted of withholding irrigation until 80% of the available water cap acity was used. Evidence of differential effects of water stress accor ding to the phase of application was obtained by tagging all the flora l organs (buds or pods) present during the phase. Fallen tags indicate d how many organs had aborted before physiological maturity. Periods o f flowering (pl: bud, p2: flower opening, p3: fruiting set) were more sensitive than pod elongation (p4 and p5) and grain filling (p6 and p7 ) phases. Bud abortion rate was 50% in non-stressed plants and 70% in stressed ones. The final pod number was 53% lower in plants stressed d uring the pi period (the most sensitive period) than in controls. Pod number was generally much more sensitive to drought than the seed numb er per pod, which was only 13% lower than in controls for plants stres sed during the pi period. ((C) Inra/Elsevier, Paris.).