Nikiforou Constantinos, Manetas Yiannis
Laboratory of Plant Physiology, Department of Biology, University of Patras, Patras GR-26500, Greece.
Funct Plant Biol. 2011 Nov;38(11):848-855. doi: 10.1071/FP11040.
Although it is widely documented that CO2 assimilation rates are positively correlated with leaf nitrogen, corresponding studies on a link between this nutrient and photosynthetic light reactions are scarce, especially under natural field conditions. In this investigation, we exploited natural variation in the nitrogen content of mature leaves of Pistacia lentiscus L. (mastic tree) in conjunction with fast chlorophyll a fluorescence rise (the OJIP curves) analysed according to the 'JIP test', as this was recently modified to allow for the assessment of events in or around PSI. The results depended on the sampling season, with low nitrogen leaves displaying lower efficiencies for electron flow from intermediate carriers to final PSI acceptors, and lower relative pool sizes of these acceptors, both during the autumn and winter. However, parameters related to the PSII) activity (i.e. quantum yields for photon trapping and electron flow along PSII and the efficiency of a trapped exciton to move an electron from the first plastoquoinone electron acceptor of PSII to intermediate carriers) were limited by low nitrogen only during the winter period. As a result, parameters like the quantum yield of total electron flow along both photosystems as well as the total photosynthetic performance index (PItotal) were positively correlated with leaf nitrogen independently of the season. We conclude that nitrogen deficiency under field conditions preferentially affects PSI activity while the effects on PSII are evident only during the stressful period of the year.
尽管有大量文献记载二氧化碳同化率与叶片氮含量呈正相关，但关于这种养分与光合光反应之间联系的相应研究却很少，尤其是在自然田间条件下。在本研究中，我们利用乳香黄连木（乳香树）成熟叶片氮含量的自然变化，结合根据“JIP 测试”分析的快速叶绿素 a 荧光上升（OJIP 曲线），因为最近对其进行了修改，以便能够评估 PSI 内部或周围的事件。结果取决于采样季节，在秋季和冬季，低氮叶片从中间载体到最终 PSI 受体的电子流动效率较低，且这些受体的相对库大小也较低。然而，与 PSII 活性相关的参数（即光子捕获和沿 PSII 的电子流动的量子产率，以及捕获的激子将电子从 PSII 的第一个质体醌电子受体转移到中间载体的效率）仅在冬季受低氮限制。因此，诸如沿两个光系统的总电子流动量子产率以及总光合性能指数（PItotal）等参数与叶片氮呈正相关，且不受季节影响。我们得出结论，田间条件下的氮缺乏优先影响 PSI 活性，而对 PSII 的影响仅在一年中的压力时期才明显。
