通过盆栽实验研究了单一增强UV-B辐射(2.5、5.0和7.5 kJ.m-2.d-1)以及增强UV-B辐射和稻瘟病菌(Magnaporthe grisea,菌株Y98-16T和Y99-63C)侵染复合胁迫对水稻(Oryza sativa L.)品种‘黄壳糯’(‘Huangkenuo’)和‘合系41’(‘Hexi-41’)幼苗叶片相对电导率、MDA含量和SOD活性3个生理指标的影响。结果表明:在低剂量(2.5和5.0 kJ.m^-2.d-1)单一UV-B辐射条件下,2个水稻品种幼苗叶片的3个生理指标均较对照(自然光)有所降低;而在高剂量(7.5 kJ.m^-2.d^-1)单一UV-B辐射条件下,2个水稻品种幼苗叶片的3个生理指标均较对照有所增加。与对照(仅接种稻瘟病菌)相比,经低剂量(2.5和5.0 kJ.m^-2.d^-1)UV-B辐射后再接种稻瘟病菌,‘黄壳糯’幼苗叶片的3个生理指标总体上均降低;而经高剂量(7.5 kJ.m^-2.d^-1)UV-B辐射后再接种稻瘟病菌,‘黄壳糯’幼苗叶片的3个生理指标均有所增加。经不同剂量UV-B辐射后再接种稻瘟病菌,‘合系41’幼苗叶片的3个生理指标总体上均有所增加,且2个水稻品种幼苗叶片的相对电导率与SOD活性均有显著的正相关性(P<0.05)。与对照(仅接种稻瘟病菌)相比,接种稻瘟病菌后再经不同剂量UV-B辐射处理,‘黄壳糯’幼苗叶片的3个生理指标均有所增加;而‘合系41’幼苗叶片的3个生理指标变化各异。接种稻瘟病菌菌株Y98-16T后再用UV-B辐射处理,2个水稻品种幼苗叶片的3个生理指标间均有显著或极显著的正相关性(P<0.05或P<0.01);而接种稻瘟病菌菌株Y99-63C后再用UV-B辐射处理,2个水稻品种幼苗叶片的3个生理指标间无明显的相关性。研究结果显示,在增强UV-B辐射和稻瘟病菌侵染复合胁迫条件下,因2个胁迫因子的作用顺序不同、稻瘟病菌菌株不同、UV-B辐射量不同以及水稻品种的差异,水稻幼苗叶片的细胞膜透性、MDA含量和SOD活性呈现出不同的变化趋势。

Effects of single stress of enhanced UV-Bradiation (2.5, 5.0and 7.5kJ·m ^{- 2}·d^{- 1})and combined stress of enhanced UV-B radiation and inoculated Magnaporthe grisea(strainY 98-16T and Y 99-63C)on three physiological indexes (relative conductivity, MDA contentand SOD activity)in seedling leaf oftworice (Oryza sativa L.) cultivars (`Huangkenuo' and `Hexi-41')were studied by pot experiments. The results show that the three physiological indexes of seedling leaf of the two cultivars in low dose(2. 5and 5. 0kJ·m ^{- 2}·d^{- 1})of single stress of enhanced UV-B radiation all decrease compared with the control (natural light),while those all increase in high dose(7.5kJ·m ^{- 2}·d^{- 1}) of same UV-B stress. Compared with the control (only inoculated M.grisea), the three physiological indexes in seedling leaf of `Huangkenuo' decrease generally in combined stress of first enhanced UV-B adiation with  low dose(2.5and 5.0kJ·m <sup>- 2</sup>·d<sup>- 1</sup>) and then inoculated M. grisea, while those all increase in the same stress but treated with high dose(7.5kJ·m <sup>- 2</sup>·d<sup>-1</sup>). The three physiological  in dexes of `Hexi-41' seedling increase generally in combined stress of first enhanced UV-B radiation with different doses and then inoculated M. grisea, and there are significant positive correlations between relative conductivity and SOD activity of the two cultivars(P < 0. 05).In combined stress of first inoculated M. grisea and then enhanced UV-B radiation with different doses, the three physiological indexes in seedling leaf of `Huangkenuo' all increase compared with the control(only inoculated M. grisea),while those of `Hexi-41' seedling appear various changing trends. There are significant and extremely significant positive correlations among the three physiological indexes in seedling leaf of the two cultivars(P< 0.05orP< 0.01) in combined stress of first inoculated M. grisea strainY 98-16Tand then enhanced UV-B radiation, while there is no obvious correlation among those indexes in the same stress with M. grisea strainY 99-63C.It is suggested that because of different treating orders of the two stress factors, different strains of M. grisea, different radiation doses of UV-B and different rice cultivars, the relative conductivity ,MDA content and SOD activity in leaf of rice seedling could appear various changing trends under the combined stress of inoculated M. grisea and enhanced UV-B radiation.