立枯丝核菌侵染对花生光合机构活性的影响

Effects of Rhizoctonia solani infection on photosystems activities of peanut leaves

花生(Arachis hypogaea L.)根部接种立枯丝核菌(Rhizoctonia solani Kühn)后,通过对其叶片叶绿素荧光快速诱导动力学曲线、820 nm光吸收曲线及相关生理指标的测定,研究根部病原菌侵染对叶片光合机构活性的影响。结果表明,接种病原菌后5 d,侵染率为0%,接种后50 d,侵染率为58.3%,接菌花生地上部干重比对照降低10.5%,地下部干重降低20.0%。同时,花生叶片的净光合速率(Pn)和叶绿素含量显著下降,气孔导度下降较慢,而CO2浓度无显著变化;叶片中H2O2和丙二醛含量显著升高,Fv/Fm和PIABS均显著下降;光系统Ⅱ电子供体侧、反应中心和受体侧活性均受到抑制,但电子受体侧所受伤害较大;病原菌侵染显著降低了光系统Ⅰ(ΔI/Io)活性。丝核菌侵染花生根部,叶片中H2O2积累,破坏膜系统,对光系统功能造成伤害,致使光合电子传递能力下降,过剩激发能增加,导致活性氧积累,进一步加剧对光系统的伤害,从而抑制了花生的光合作用,进而降低了花生生长量。

In order to investigate the effects of root infection of Rhizoctonia solani on photosystems activities of peanut leaves, Chlorophyll fluorescence transient, light absorbance at 820 nm and some related physiological indexes of peanut leaves were detected. The results showed that, 5 days after peanut inoculation, the infection rate was 0%, and 50 days after inoculation, the infection rate was 58.3%. Compared with the control, the aboveground mass of peanut reduced by 10.5%, the belowground mass reduced by 20.0%, the net photosynthetic rate （ Pn ） and chlorophyll content significantly decreased, stomatal conductance declined slowly, whereas intercellular C02 concentration had no significant change. Furthermore, significant increase of H202 and malondialdehyde content and significant decline of F/ Fm and P1A^s were observed in infected peanut leaves. The electronic donor sides, reaction centers and acceptor sides of PS II were significantly damaged by R. solani infection, and the acceptor side was harmed more seriously than the donor side. Meanwhile, the PSI activity was also damaged severely. R. solani infection resulted in an increase of H202, which damaged the photosystem functions and hindered the electronic transferring from PS II to PSI. Accumulation of excessive excitation energy led to an increase of reactive oxygen species, which damaged photosystems further and then inhibited the photosynthesis in peanuts, thus reduced their biomass.