Abstract
The effects of Polaris and gibberellic acid (GA) on four month old plants of two sugar-cane cultivars were measured. Polaris inhibited stem elongation, reduced leaf fresh weight and increased both sucrose per cent cane and sucrose per stem, whereas GA increased stem elongation, stem and leaf fresh weight and sucrose per tern despite a reduction in sucrose per cent cane. The rate of 14C fixation by the topmost fully expanded leaf was increased by GA and reduced by Polaris, but the rate of translocation was increased by both chemicals. Acid invertase activity was also increased by GA and reduced by Polaris whereas neutral invertase activity tended to be affected in the reverse manner. The results are consistent with the view that the ripening activity of Polaris results from a combination of growth inhibition, increased translocation and reduced acid invertase activity. The increase in sucrose per stem in response to GA, on the other hand, resulted from the increase in storage capacity which was accompanied by increased rates of photosynthesis and translocation.
