低钾对钾迟钝型水稻不同叶位叶片光合活性的影响

Effect of low potassium levels on photosynthetic activities in different position leaves of potassium-insensitive rice plants

研究了低钾对抽穗期钾迟钝型水稻品种原丰早不同叶位的气体交换参数和叶绿素荧光参数的影响。结果表明,对照和低钾植株的净光合速率(Pn)、气孔导度(Gs)随叶位均显著下降,而对照植株的胞间CO2浓度(Ci)基本维持不变,但低钾植株的Ci却持续上升,说明正常和低钾条件下的叶片衰老时Pn的下降主要不是由气孔因素引起的。对叶绿素荧光参数的分析表明激发压(1-qP)和PSⅡ功能的相对限制(L(PSⅡ))随叶位上升,初始荧光(Fo)和非光化学猝灭(qN)无明显变化,而PSⅡ最大光化学量子产量(Fv/Fm)、PSⅡ有效光化学量子产量(F′v/F′m)、PSⅡ实际光化学量子产量(ФPSⅡ)和表观电子传递速率(ETR)明显下降。这些结果说明PSⅡ反应中心的受损导致了CO2同化的下降。另外,正常和低钾条件下剑叶的所有参数均无显著差异,暗示着低钾条件下剑叶功能的维持是原丰早耐低钾的一个重要原因。

To investigate the senescence among different position leaves at heading stage in rice plants, gas exchange and chlorophyll fluorescence properties in different leaf positions of the potassium-insensitive rice cultivar Yuanfengzao were examined. The results showed that both the net photosynthetic rate （ P. ）, stomatal conductance （ Gs ） declined significantly with lowering of leaf position, while intercellular CO2 concentration （ Ci ） in the control plants had little change, but C2 in low potassium-stressed plants greatly increased, which suggesting that the decrease in P. in both plants were not contributed to the stomatal factors. Further evidence of chlorophyll fluorescence measurement showed that, excitation pressure （ 1 - qe） and relative constrain of PSⅡ functionality （ L （PSⅡ）） increased with lowering of leaf position, and initial fluorescence value （ Fo ） and non-photochemical quenching coefficient （ qN ） maintained rather stable, but PS Ⅱ maximum photochemical effi- ciency （FJFm）, PS Ⅱ available photochemical efficiency （F＇v/F＇m ）, PS Ⅱ actual photochemical efficiency （ Ф PSⅡ ） and apparent electron transport rate （ETR） greatly declined. All these results indicated that the damage of PSⅡ reaction center resulted in the decline in CO2 assimilation. Because no significant differences of all the parameters studied between control and low potassium-stressed rice plants were observed, the photosynthetic functionality maintenance of flag leaf was probably associated with the fact that Yuanfengzao was insensitive to low potassium stress.