Stimulation of Root Thickening and Inhibition of Bolting by Jasmonic Acid in Beet Plants

Abstract

Beet is a biennial plant. In the first season, it develops leaf rosette on a dwarf stem and forms a thick storage root. Based on the idea that some growth-inhibiting compound may participate in these developmental events, the effects of jasmonic acid (JA) on root thickening and stem elongation (bolting) were examined using beet plants cultured in vitro. JA failed to induce thickening of the tap root, but greatly promoted thickening of lateral roots. Furthermore, JA strongly inhibited bolting induced by chilling or exogenous gibberellic acid. The presence of JA in the tops (leaves and dwarf stems) of field-grown plants was confirmed by mass spectrometry. Although the content of JA seems to be insufficient to account for the induction of root-thickening and for the inhibition of bolting, the results suggest that JA-related compounds are involved in the thickening growth of storage root and in the formation of leaf rosette.