Interaction between benzyladenine and fusicoccin on the development of excised watermelon cotyledons. I. Growth and organelle development

Abstract

Benzyladenine (BA) stimulates growth and orgenelle development in watermelon cotyledons while fusicoccin (FC) stimulates growth, but has no effect on organelle development. Here, we have examined the effect of BA and FC when administered together to the cotyledon. Cotyledons of watermelon ( Citrullus vulgaris Schrad., cv. Fairfax) were excised from the embryo after 24 h of imbibition and cultured for several days in presence of BA and FC, both 10 −5 M. In some experiments the concentration of BA was varied from 10 −6 to 10 −4 M. In BA + FC the growth rate was higher than in either of the two substances alone. Conversely, all parameters related to organelle development (carotenoid and enzyme levels) were much lower than with BA alone and barely higher than in the water control. Thus FC appears to be a powerful inhibitor of BA-induced organelle development. The inhibition is nearly abolished if the cotyledons are grown in 10 −5 M BA for 2 days before transfer to BA + FC. Enhancement of growth by FC is maximal in the presence of BA concentrations that are not very effective while inhibition of BA-induced carotenoid synthesis is maximal in the presence of BA concentrations that have the highest stimulating effect.