Growth Regulating Action of Isoprothiolane in Plants : II. Interactions between isoprothiolane and phytohormones in rice

Abstract

Isoprothiolane (diisopropyl-1, 3-dithiolan-2-ylidenemalonate, IPT) has been used as an agent controlling not only rice blast but also non-parasitic damping-off (MURENAE disease) of rice seedlings. It also accelerates the development of rice roots at the seedling stage. To study the plant hormone-like action of IPT, interactions between IPT and phytohormones with some biological assays were investigated. IPT stimulated the activity of auxin (IAA) -induced lamina inclination in the etiolated rice seedlings at high concentrations above 1O^-4M. As for the chlorophyll-retention in rice leaf disc system, IPT was more active than benzyl adenine, especially at high concentration. Though IPT suppressed both the shoot elongation of rice seedlings at 10^-4M and the proliferation of rice callus tissues, it enhanced the ethylene production both in seedlings and callus of rice. There was no interaction between IPT and GA on the growth of rice seedlings (cv. Tan-ginbouzu or Nipponbare) by the immersion method. These results indicate that IPT remarkably affects the growth process of rice seedlings through the enhancement or the modification of auxin activity, cytokinin activity and ethylene production system.