Phytohormonal Regulation Of The Dwarfism And Floret Opening In Rice

To investigate the hormonal regulation of dwarfism and methyl jasmonate (MeJA)-induced floret opening of rice (Oryza satiava L.), rice varieties with different semidwarf genes, wild-abortive type cytoplasmic male-sterile (WA-CMS) rice, BT type cytoplasmic male -sterile (BT-CMS) rice and thermosensitive genetic male-sterile (TGMS) nce were used for research by exogenously treatment with hormone and chemical reagent and analysing the contents of endogenous hormone, hormone-binding proteins and respiration. Compared with control, seedling elongation was markedly promoted by 3 X 10~ mol/L gibberellic acid (GA3), slightly by 6X 10~ moIIL indo!e-3-acetic acid (IAA) or 100 ng/plant 24-epibrassinolde (24-epiBL) (ca 20%) , however was slightly inhibited by I X 10.6 tnol/L S,6-C12-indole-3-acetic acid (5,6-C12-IAA) or 4-Cl-indole-3-acetic acid (4-Cl-IAA) ( 6%-40拁,抩), and dramatically retarded by 1 X I & moIJL abscisic acid (ABA) or 1 X 10?mol/L MeJA (200/o.60%) . The second leaf sheath was much more sensitive to GA3 than seedling height, and the sensitivities of the semidwarf genes in rice seedlings were in order: sd-i>sd-n(t)>sd-t(t)>sd-g. Sensitivity of sd-i gene to GA3 was partially retarded by sd-g. sd-g was more sensitive to ABA, sd-t(1) was the most sensitive to IAA, sd-n(t) was IAA-and 24-epiBL-insensitive. When upper internode elongating, sd-I was the most sensitive to GA3, sd-g was GA3-insensitive. Promoting elongation of GA3 needed the occurrence of IAA, antagonistic relationship existed between GA3 and ABA, MeJA. Inhibitor of GA biosynthesis 桽-3307(1)< 10?molIL) had much more inhibitory effect on seedling elongation than 1,1-dimethylpiperidinium chloride (DPC) (6.7 X 10~ moIIL). 5 The contenb of endogenous IAA in (saai)dwarf varieties except Nanjingl 1 were less than that in high plant桸anjing No.6, the levels of endogenous ABA and ABA-binding proteins of seven (semi)dwarf species were much higher than those in Nanjing No.6, low levels of GA,+3 in varieties with sd-i or sd-n(t) were detected, however, the GA1+3 contents in species with sd-g or sd-t(t) were much higher than those in Nanjing No.6. The levels of GA-binding proteins in (semi)dwarf varieties were lower than that in Nanjing No.6, especially species with sd.g. Nanjingl I was a GA-deficient dwarf mutant , Xinguiai was a 2+ GA-insensitive dwarf mutant. Studies employing a Ca chelator, EGTA, and calmodulin (CaM) inhibitor, TFP (trifluoperazine) indicated that Ca~~-C~ involved in the response of semidwarf gene to GA3 . These results suggest that the dwarfism is jointly regulated by the levels of GA-, ABA-binding proteins and endogenous hormones (GA ,+~, ABA and IAA) MeJA induction on the rice floret opening could markedly be inhibited by 1-4 mmollL salicylic acid (SA), and the inhibition of SA on MeJA induction on floret opening of male-sterile rice could be nullified by MeJA treatment again . MeJA effect on floret opening of male-sterile rice could be clearly synergized by pretreatment of 8.4 X I ~ molIL 24-epiBL (90%), and slightly by 0.5 mmol/L IAA treatment in advance(30%). MeJA induction could be retarded by ethylene, however MeJA-induced rice floret opening was partially dependent on ethylene action. The lag time (time between treatment and first floret opening) of carbon dioxide (C02) and acetic acid (5mm) was significantly shorter than that of MeJA (30-40mm), MeJA enhanced floret respiration of male-s...