Hormonal Regulation of Source-sink Relationship: Effect of Hormones on Excised Source and Sink Organs of Cereals

The regulatory role of plant growth substances in relation tosource and sink activity was studied. Leaching of electrolytesfrom flag leaf cells increased with age. Abscisic acid, however,increased the permeability of leaf cells at 10^–4 M andlower concentrations. Plant growth regulators like auxin, gibberellinand cytokinin at 10^–5 M inhibited the leaching of electrolytesbut slightly enhanced the process at 10^–3 M. The effluxof ¹⁴C-sucrose loaded on the flag leaves was not detectablein the very early stage of panicle development but was prominentin the later stages. While auxin prevented sucrose efflux atall stages of panicle development, gibberellin and cytokininwere effective only in different degrees. All the three growthregulators enhanced the activity of -amylase in the flag leafcells but protease activity was enhanced only by gibberellin.Synthesis of polymers like starch, DNA, RNA and protein in developingrice grains was stimulated by gibberellin, cytokinin and auxinlargely in the order mentioned. (Received September 2, 1986; Accepted May 22, 1987)