Effects of foliar and root-applied benzylaminopurine on tillering of rice plants grown in hydroponics

Abstract

Many studies have confirmed that exogenous cytokinins increase tillering in grasses as wheat, oat and barley. In this study, the effects of benzylaminopurine (BA) on tillering of two rice cultivars, North Rose with low tillering ability and Sasanishiki with high tillering ability, were examined using hydroponics. Foliar spray of BA was applied to both cultivars at the 6-leaf stage. Root application of BA was used to Sasanishiki at the 8-leaf stage. Both root-applied and foliar-sprayed BA retarded the increase of tillers and resulted in significant decrease in tiller numbers per plant. The result indicated that primary tillers were much more affected than secondary tillers. Leaf production on the main stem was also temporarily inhibited with the exception of foliar spray to plants of cv. Sasanishiki. The effective concentration of BA on tillering was over 0.01 μM for root application and 100 μM for foliar spray. Magnitude of effect of root application was greater than that of foliar spray in cv. Sasanishiki. Foliar-sprayed BA mainly inhibited tillers that are at the stage of differentiation of tiller buds from appearance. Root-applied BA could further inhibit the growth of tiller buds into tillers. In conclusion, BA inhibited the tillering of rice plants rather than promoting it, which is inconsistent with general description of cytokinin roles.