Role of Some Growth Regulating Substances on Seed Germination and Seedling Growth of Asteracantha longifolia Nees

Abstract

Summary The presence of gibberellic acid compensated the requirement of light when the seeds of Asteracantha longifolia were germinated in total darkness, although they were found to prefer light for germination. The onset of seed germination in total darkness with gibberellic acid concentrations above 10 ppm was delayed. The pace of germination decreased both in continuous white light as well as in total darkness above 10 ppm. The presence of gibberellic acid in continuous white light did not affect the mean percentage of germination, although in total darkness 10 ppm solution appeared to exert the optimum stimulatory effect. The growth of the radicle in the presence of gibberellic acid in continuous white light and total darkness remained less than that of the control, although suffered retarding effect to a lesser degree in light than in dark. The growth of the hypocotyl was, however, promoted with 5 ppm and 10 ppm solutions in continuous white light and total darkness respectively as compared to that of the controls. 2,4-Dichlorophenoxy acetic acid proved to be extremely retarding both as regards seed germination and seedling growth. The pace of germination and percentage of germination decreased with increasing concentrations of this chemical. The growth of the hypocotyl was drastically reduced in as low a concentration as 1 ppm. The effect of coumarin inhibiting seed germination and suppressing seedling growth was not so drastic as that of 2,4-D. In fact coumarin promoted the growth of hypocotyl in lower concentrations, but proved to be growth retarding agent in the case of radicle.