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Investigations into the possible causes of flower abscission in French beans, phaseolus vulgaris
(University of Dar es Salaam, 1981) Hoza, Julia T
One hundred and sixty four varieties of French beans, Phaseolus vulgaris L. were screened for their pronness to flower abscission. The effect of water stress on flower abscission in varieties UAC 77 and UAC c,w. 121 was investigated. Of the two varieties, variety UAC 77 was resistant to flower abscission whereas vexiety UAC c.w. 121 was prone to flower abscission. The endogenous levels of Indole-3-acetic acid (IA.A) and Abscisic acid (ABA) under droughting condition were also estimated. The results indicate that the rate of flower abscission in P. vulgaris L. is varietal specific and that water stress increases the incidence of flower abscission in this species. The endogenous levels of IAA and ABA were found to increase with increasing water stress. The lower transpiration rates observed in the stressed plants of both varieties are due to the closure of stomata under droughting conditions. Spraying the plants with 10 ppm ABA increased the rate of flower abscission. Ultrastructural studies of the abscission zones indicated that water stress stimulates quick maturation of the abscission layer and that flower abscission in P. vulgaris L. progresses.through middle lamella dissolution and cell wall breakage.