Rice undergoes leaf senescence accompanied with grain filling when the plants reach the end of their temporal niche, and a delay in leaf senescence ultimately improves the yield and quality of grain. To estimate the decline in photosynthesis during leaf senescence and to find an efficient and useful tool to identify rice genotypes with a longer duration of active photosynthesis, we examined PSII photosynthetic activity in the flag leaves of japonica rice Shennong265 (SN265) and Beigeng3 (BG3) during leaf senescence using chlorophyll a fluorescence kinetics. The results show that inhibition occurred in the electron transport chains, but the energetic connectivity of PSII units was not affected as dramatically during leaf senescence. PSII reaction centres (RCs) were transformed into ‘silent RCs,’ and the chlorophyll content decreased during leaf senescence. However the size of the ‘economic’ antennae increased. Further, the percentage of variation of the specific energy flux parameters can rationally be used to indicate leaf senescence from the perspective of energy balance. Although the performance indices were more sensitive than other functional and structural JIP-test parameters, they still did not serve as an indicator of crop yield.

当植物到达其时空生态位的末端时，水稻经历叶片衰老并伴随着籽粒充实，叶片衰老的延迟最终提高了谷物的产量和品质。为了评估叶片衰老过程中光合作用的下降，并找到有效和有用的工具来鉴定具有较长光合作用持续时间的水稻基因型，我们研究了粳稻神农265（SN265）和北庚3（BG3）旗叶的PSII光合作用活性。叶绿素a在叶片衰老过程中荧光动力学。结果表明，抑制作用发生在电子传输链中，但PSII单元的能量连接在叶片衰老过程中并未受到显着影响。PSII反应中心（RCs）转化为“沉默RCs”，叶衰老过程中叶绿素含量降低。但是，“经济”触角的尺寸增加了。此外，从能量平衡的角度来看，可以将比能通量参数的变化百分比合理地用于指示叶片衰老。尽管性能指标比其他功能和结构的JIP试验参数更敏感，但它们仍不能作为农作物产量的指标。