缺钾对水稻不同品种光合和能量耗散的影响

试验测定了钾敏感型(二九丰)和钾钝感型(原丰早)两个水稻品种在缺钾处理41.d后其剑叶的生长、光合光响应曲线、叶绿素荧光参数光响应曲线和暗弛豫动力学曲线。结果表明,缺钾降低了水稻剑叶的光合作用,显著抑制了生长。但是缺钾条件下导致两个水稻品种净光合速率(Pn)下降的主导因子并不相同。在缺钾条件下,原丰早(YFZ)剑叶的Pn随气孔导度(Gs)和胞间CO2浓度(Ci)的下降而下降,但叶绿素荧光参数和叶绿素含量几乎没有变化,说明其Pn下降主要归于气孔的限制。缺钾处理41.d后,二九丰(EJF)在低光强下500mol/(m2.s)],Pn随Gs和Ci下降,但在更强的光强下,Pn和Gs继续下降,而Ci开始上升,并在1200mol/(m2.s)处超越了对照,说明此时主导因子不单受气孔限制,还受非气孔因子限制;它的光饱和点从1200mol/(m2.s)下降到大约500mol/(m2.s);同时,其荧光参数Fv/Fm、ФPSII、qP和ETR随光强上升而迅速下降,而L(PFD)、E和PP迅速增加,NPQ在1200mol/(m2.s)光强下上升,但是在高光强下却迅速降低,甚至低于对照,而且Fm、Fv/Fm下降,Fo上升,均说明缺钾处理可能使光合机构受到了伤害,发生了光抑制。对非光化学猝灭的分析得到其中间组分qNm可能起了更大的能量耗散作用,部分激发能从PSⅡ转移到PSⅠ,降低了PSⅡ耗散能量的压力。以上结果表明,两品种对钾敏感性不同极可能也与缺钾条件下光保护能力的差异有关。

Effects of potassium-deficiency on photosynthesis and energy dissipation in different rice cultivars

Our previous study has demonstrated that Erjiufeng(EJF) is one of potassium-sensitivity rice cultivars,and Yuanfengzao(YFZ) is an insensitive one. In this study,the growth,photosynthetic parameters and chlorophyll fluorescence parameters and dark relaxation kinetics of non-photochemical chlorophyll fluorescence quenching of these two rice cultivars were investigated after 41 days' potassium-deficiency treatment.The results showed that the net photosynthetic rate(Pn) of flag leaves was reduced,and the growth was significantly suppressed under the potassium deficient condition in both cultivars;however,the dominant factors induced Pn lower were different in two cultivars.Pn of flag leaves in YFZ was decreased with decreasing stomatal conductance(Gs) and intercellular CO₂ concentration(Ci),but chlorophyll fluorescence parameters and the content of chlorophyll content were quite stable,suggesting that the reduction in Pn could be accounted for the stomatal limitation.However,for EJF,Pn was decreased accompanied with Gs and Ci at lower photosynthetic photon flux densities(PFD) <500 μmol/(m2·s)].At higher PFD,Ci was increased with the decrease of Pn and Gs,and it exceeded the control at 1200 μmol/(m2·s), indicating that Pn suppression was mainly caused by the non-stomatal factors rather than stomatal limitation.Light saturation point(LSP) of EJF dropped to about 500 μmol/(m²·s) under potassium deficient condition,while LSP of YFZ was stable at 1200 μmol/(m²·s) in potassium-deficient plants.Under potassium deficient condition,F'v/F'm,ФPSII,qP and ETR were rapidly decreased with the increase of PFD;while L(PFD),E and PP were dramatically increased,NPQ was increased when PFD was less than 1200 μmol/(m²·s),but it was rapidly decreased to less than its control under higher PFD.Meanwhile,Fm and Fv/Fm were significantly decreased accompanied by the increase in Fo.All these results suggested that photosynthetic apparatus was damaged under potassium deficient condition,and photoinhibition occurred.Based on dark relaxation kinetics of non-photochemical chlorophyll fluorescence quenching,middle component(qNm) was observed to have a larger contribution to energy dissipation,and part of excited energy could be transferred from PSⅡ to PSⅠ,thus the pressure of dissipating energy was reduced.In conclusion,different rice cultivars of potassium sensitivity may also be partially related to their protection capacity against photodamage under prolonged potassium deficient conditions.