Some physiological effects of podolactone‐type inhibitors

Abstract

Podolactone‐type inhibitors, including harringtonolide and lycoricidinol, affect several bioassays at 1 to 10 μ M. Although these compounds were less active than abscisic acid in inhibiting growth of coleoptiles of wheat embryos, podolactone A significantly decreased the number of mature spikelets of Lolium temulentum at a lower concentration than abscisic acid. Lycoricidinol was more active than podolactone E, the most active of the podolactones, in three bioassays. Inhibition of growth induced by gibberellic acid or zeatin with podolactone‐type compounds was not competitive. Harringtonolide was a strong inhibitor of growth at higher concentrations but did not affect auxin transport, while podolactone E and lycoricidinol inhibited it. Lycoricidinol, podolactone E and harringtonolide did not retard senescence of leaf‐discs. The promotive effects of gibberellic acid in the barley endosperm bioassay were counteracted by podolactone A.