[Effect of enhanced UV-B radiation on polyamine metabolism and endogenous hormone contents in rice (Oryza sativa L.)].

The results showed that the activities of Agrinine decarboxylase(ADC), Ornithine decarboxylase(ODC) and s-Adenosylmethionine decarboxylase(SAMDC) were increased by 165.74%, 104.60% and 89.60% in the leaves of Shan You63(Sy63) and by 59.91%, 41.30% and 23.68% in the leaves of Nancheum(NC). Only ADC and ODC activities were increase by 115.93%, 14.45%, but SAMDC activity was decreased by 33.01% in the leaves of IR65600-85 respectively in the exposure to enhanced UV-B radiation for 7-14 days. In late treatment time course(21-28 d), the activities of ADC and ODC were increased by 89.72% and 3.71% in the leaves of Sy63 exposed to UV-B radiation for 21-28 days and by 73.95% and 27.38% in the leaves of NC. The activity of ADC was also increased by 94.41%, but ODC activity was decreased by 13.57% in the leaves of IR65600-85 compared with the controls. As far as SAMDC was concerned, the enzymic activities in the leaves of Sy63, NC and IR65600-85 were reduced by 40.06%, 19.20% and 38.21% respectively in the exposure to enhanced UV-B radiation for 21-28 days. The reverse was true in the case of Polyamine Oxidase (PAO), this in turn resulted in increased contents of Polyamine(PA) especially putrescine(Put). In addition, the result also indicated that the contents of IAA and GA1/3 were significantly reduced in all rice cultivars used for this experiments with enhanced UV-B radiation treatments for 7-28 days, in which the contents of IAA and GA1/3 were decreased by 58.92% and 45.48% in the leaves of Sy63, by 43.31% and 56.20% in the leaves of NC, and by 38.60% and 47.33% in the leaves of IR65600-85. The contents of ZRs in the leaves of the three cultivars concerned were lower in earlier treatment time courses (7-14 d), but much higher in late courses(21-28 d) compared with the their counterparts. With regard to the endogenous hormone of ABA, the content was significantly increased by 14.4%, 99.6% and 56.7% respectively in the three rice cultivars concerned exposed to enhanced UV-B radiation for 7-28 days, thereby led to decreased values of IAA/ABA, GA1/3/ABA and ZRs/ABA, consequently suppressed growth and development of rice.