Opening of Rice Floret in Rapid Response to Methyl Jasmonate.

Effects of methyl jasmonate (MeJA) on rice floret opening were investigated in seven cultivars or hybrid combinations covering various variety types. Intact or excised panicles, judged to have florets just before anthesis, were soaked in 4 x 10(-5) - 4 x 10(-3)M MeJA solutions for 2 min at different temperatures. The results indicated that MeJA significantly induced opening of rice florets within about 30 min, with the most rapid induction occurring just 6 min after treatment. Numbers of induced opening florets are correlated with MeJA concentrations. Higher concentrations of MeJA induced more florets. pH values had no influence on MeJA effect, but MeJA required less time and induced more florets at 34 degrees C than at 25 degrees C. As far as we know, this is the first evidence that floret opening is induced by plant hormones. CO(2) evolution from panicles was also increased by MeJA treatment. Field experiments revealed that perfect flowering synchrony between the cytoplasmic male sterile (CMS) and restorer lines in hybrid seed production could be obtained by spraying MeJA solution on CMS line plants at the rate of 25 mg/m(2). As a result, many more hybrid seeds were harvested.