Abstract
The objective of this study was to reveal if reducing the concentration of methyl jasmonate (MeJA) solution applied to rice panicles just before flower opening can advance the flower opening time without the side effect of increasing sterility in rice plants. We used the main culms of four cultivars and treated the panicles with three concentrations of MeJA (0.04, 0.4, and 4 mmol L-1) a few days after heading. We determined the time to flower opening after the treatment (flower opening time) by photographing panicles at 10-min intervals. The number of opened flowers, sterility percentage, and pollination on the day of treatment were also examined. MeJA treatment advanced flower opening time in three cultivars (‘Hanaechizen,’ ‘Takanari,’ and ‘Asahi’), (p \< 0.05, analysis of variance). Application of 4 mmol L−1 MeJA to ‘Hanaechizen,’ which showed the highest response to MeJA treatment, advanced the flower opening time by 194 min. Application of 0.4 mmol L−1 MeJA to ‘Hanaechizen’ also shortened the interval by 98 min. However, application of 0.04 mmol L−1 MeJA to ‘Hanaechizen’ did not shorten the interval significantly, but that to ‘Asahi’ shortened the interval by 26 min (p \< 0.05). Fertilization occasionally failed when the MeJA application advanced the flower opening time more than 1 hour. We conclude that reducing the MeJA concentration advanced flower opening time but was accompanied by sterility.
