Comparison of the levels of endogenous plant growth substances in CPPU-treated and -untreated kiwifruit.

摘要

Seasonal changes in the endogenous levels of IAA-, gibberellin-, cytokinin- and abscisic acid-like substances in the seeds, mesocarp and endocarp of CPPU [forchlorfenuron]-treated and -untreated kiwifruits (cv. Hayward) were determined. The nucellusand endosperm in the seeds of treated and untreated fruits developed rapidly during stage I, whereas the embryo developed rapidly during stage II. Embryo development in CPPU-treated fruits was slightly slower than that of untreated fruits. The levels ofIAA- and gibberellin-like substances always tended to be higher in the seeds than they were in the flesh of treated and untreated fruits throughout the growing season. The levels of cytokinin-like substances were higher in the seeds than in the flesh during stage I, but the reverse occurred during stage II. The levels of ABA-like substances in the seeds and flesh were nearly equal throughout the fruit growth period. Among the growth substances tested, the level of IAA-like substances in the seeds correlated most strongly with fruit development and tended to increase towards fruit maturation. The seasonal levels of gibberellin- and cytokinin-like substances in the seeds paralleled the initially rapid development of the fruit and seed tissues. ABA-likesubstances in seeds and flesh increased towards maturity. Application of CPPU increased levels of IAA- and gibberellin-like substances in the seeds early in stage I and at the beginning of stage II; it also increased cytokinin-like substances in the flesh during stage II. It is suggested that CPPU enlarges fruits not only by its high cytokinin activity but also by activating endogenous IAA, gibberellins and cytokinins.