| Effect and its mechanism of jasmonates on floret opening were studied in rice (Oryza saliva L.), sorghum (Sorghum bicola,r Moench), sudenese grass (Sorghum sudenese Stapf) and orchard-grass (Dactylis glomerata L.), and the application of MeJA for the flowering synchronization of male sterile and restorer lines was investigated in seed production of hybrid rice.1.Exogenous MeJA significantly induced floret opening in rice, sorghum, sudenese grass and orchard grass of gramineous plants:Eighty mm after soaking the excised panicles in 40, 400 and 4000 l.tmol/L MeJA solutions for 2 mm, the percentage of opening floret per panicle of rice cv. Handao297 was 7.5%. 22.7% and 44.5%, respectively, while the floret opening in control panicles was not yet initiated. The intact panicles of a hybrid, cv. AnxiangS-Zhul 73, and the excised panicles of a male sterile line, cv. XinluA, were also responsible to 4 and I mmol/L MeJA solutions respectively, with the percentage of opening floret being 32.5% and 42.9% at 80 mm after the treatment, and the floret opening in control panicles not yet initiated. The time lag for MeJA action was in the range of 6 to 30 mm, and it deferred with the variety type and the temperature. Panicles were more sensitive to MeJA at higher (34C) than at lower (25XD) temperature.Excised panicles of normal sorghum varieties, cv. Qianjinghong and ARI, male sterile lines, cv. 3042A and TX623A, maintainer lines, cv. 3042B and TX623B, sudenese grass, cv. 599-4, and a hybrid from sorghum and sudenese grass, cv. TX623A X 722Xuan were all responsible to MeJA treatment. Seven to ten h after the 2 mm treatment of soaking in 2 inmolIL MeJA solution, the average percentages of opening floret per panicle were as follows: cv. Qianjinghong, 18.72%, 25 times that of its control (0.75%); cv. ARI, 2.96%, 8.1 times that of its control (0.37%); cv. 599-4, 18.42%, 14.9 times that of its control (1.24%); cv. TX623AX722Xuan, 24.02%, 13.3 times that of its control (1.8%); cv. TX623A and TX623B, 18.11% and 23.96, increased by 18.11% and 15.12%, respectively, compared with their controls. The time lag for MeJA action was between 60 and 300 mm. In cv. Qianjinghong, floret opening responded to MeJA in a concentration-dependent manner, 8 h after the treatment with 0.2, 0.5 and 2 mmol/L MeJA solution, percentages of opening floret were 8.63%, 11.03% and 22.76%,6respectively, which were increased by 0.5, 0.9 and 3.1 times compared with their respective controls.Floret opening in excised panicles of orchard-grass started at 4.5 h after the treatment of soaking the panicles in 2 mmol/L solution for 4 mm, while in the control panicles, floret opening was not initiated until 19.5 h after the treatment. 28.5 h after the treatment, the number of opening floret reached 132/panicle, 16.5 times that of the control (8/panicle).2. JA and coronatine induced rice floret opening, while TA, MeTA and theobroxide exhibited no effect on floret opening in rice:I mmol/L JA markedly promoted rice floret opening, with its activity being slightly lower than that of MeJA. The number of opening floret in rice cv. Michkogane was more than doubled by the treatment of soaking panicles in 0.1 mmol/L coronatine solution for 5 mm; the time lag for coronatine action was 25 mm. TA, MeTA or theobroxide exhibited no effect on floret opening in rice cv. Michkogane at the experiment conditions.3. SA/MeSA and MeJA showed an antagonistic effect on floret opening in sorghum and rice:SA, at the concentration of I and 10 mmol/L, exhibited inhibitory etlect onN抣eJA-induced floret opening in sorghum cv. TX623A, the inhibitory efficiency was91.34% and 100%, respectively, at 12 h after the treatment. In rice cv. XinluA, 2 rnmol/LMeJA-induced floret opening was suppressed by a treatment with 5 mmol/L SA.Airborne MeSA inhibited natural and MeJA-induced floret opening in rice cv.Michkogane, and this inhibition was overcome by MeJA treatment.4 Endogenous JA and other signal molecules in the octadecanoic pat...
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