外源硅对纹枯病菌(Rhizoctonia solani)侵染下水稻叶片光合功能的改善

Exogenous application of sodium silicate improves the resistance of rice photosynthesis to Rhizoctonia solani infection

为了进一步探讨外源加硅增强水稻对纹枯病的抗性作用,以抗病品种91SP和感病品种Lemont为材料,研究了人工接种纹枯病菌条件下外源硅对水稻叶片叶绿素含量、光合作用、叶绿素荧光特性和MDA含量的影响。结果表明:(1)外源加硅能降低抗病品种91SP的纹枯病病级和病情指数,显著降低感病品种Lemont的病级和病情指数;(2)接种纹枯病菌后,水稻叶片叶绿素含量、净光合速率(Pn)、气孔导度(Gs)均明显降低,胞间CO2浓度(Ci)增大,而加硅处理的水稻叶片叶绿素含量、Pn、Gs不同程度增加,Ci有所降低;(3)接种纹枯病菌后,两个品种PSⅡ最大光化学效率(Fv/Fm)、PSⅡ有效光化学效率(Fv′/Fm′)、PSⅡ实际光化学效率(ΦPSⅡ)、光化学猝灭系数(qP)和表观光合电子传递速率(ETR)均降低,非光化学猝灭系数(qNP)增大,而对于加硅处理的水稻叶片,上述荧光参数在纹枯病菌侵染条件下的变化均受到不同程度的抑制。(4)外源硅可不同程度地减缓纹枯病菌侵染引起的丙二醛(MDA)含量的增加,对感病品种Lemont的缓解作用要大于抗病品种91SP。可见,外源硅处理可以不同程度地缓解纹枯病菌侵染条件下非气孔因素引起的水稻叶片光合速率的下降以及对光合机构的破坏作用,提高光化学效率,改善叶片的光合功能,减轻叶片膜脂过氧化程度,增强水稻对纹枯病的抗性。

Sheath blight caused by Rhizoctonia solani infection is one of the three major pathogen-caused diseases in rice. Sodium silicate has been reported to improve the resistance of rice to sheath bright. In this study, we invested the impacts of sodium silicate on rice photosynthesis under Rhizoctonia solani （ R. solani） infection. We hydroponically cultured two rice cultivars with different resistances to R. solani infection （resistant cultivar 91 SP, susceptible cuhivar Lemont ） and characterized different photosynthetic physiological parameters. Our experiments showed that ： （ 1 ） After being inoculated with R. solani, the rice with sodium silicate application （the Si ＋ rice） had lower （but not statistically significant） disease rating and disease index compared to the Si- rice plants in resistant cultivar 91SP, but the Si ＋ rice plants of susceptible cultivar Lemont had significantly lower rating and disease index with relative control effect of 27.42% compared to the Si- rice plants. （2） After being inoculated with R. solani, chlorophyll content, net photosynthetic rate （Pn） and stomatal conductance （Gs） of rice leaves were decreased significantly, while intercellular CO2 concentration （Ci） was increased. After treated with exogenous sodium silicate, chlorophyll content, Pn and Gs were increased, while Ci was decreased. （3） After being inoculated with R. solani, PS Ⅱ maximal quantum efficiency （ Fv/Fm）, PS Ⅱ effective quantum efficiency （ Fv＇/Fm＇ ）, PS II actual photochemical efficiency （ФPS Ⅱ ）, photochemical quenching （qP） and acyclic electron transfer late （ETR） were all decreased, but non- photochemical quenching （qNP） was increased. The Si ＋ rice plants showed less changes in these fluorescence parameters. （4） Si ＋ rice plants showed less boost in MDA contents upon R. solani inoculation in both cultivars. The results suggested that, exogenous sodium silicate application can alleviate the decreases of photosynthetic rate induced by non-stomata factors and the damage of photosynthesis system, increase photochemical efficiency, improve the foliar photosynthetic ability, reduce the degree of leaf lipid peroxidation, and enhance the rice plants resistance to sheath blight.