Faculty of Agriculture, Iwate University, 3-18-8 Ueda, Morioka, 020-8550 Japan.
Graduate School of Agricultural Science, Kobe University, 1-1 Rokkodai, Nada-ku, Kobe, 657-8501 Japan.
Plant Cell Physiol. 2021 Oct 29;62(7):1121-1130. doi: 10.1093/pcp/pcab020.
Although N levels affect leaf photosynthetic capacity, the effects of N levels on the photochemistry of photosystems II and I (PSII and PSI, respectively) are not well-understood. In the present study, we examined this aspect in rice (Oryza sativa L. 'Hitomebore') plants grown under three different N levels at normal or high temperatures that can occur during rice culture and do not severely suppress photosynthesis. At both growth temperatures, the quantum efficiency of PSII [Y(II)] and the fraction of the primary quinone electron acceptor in its oxidized state were positively correlated with the amount of total leaf-N, whereas the quantum yields of non-photochemical quenching and donor-side limitation of PSI [Y(ND)] were negatively correlated with the amount of total leaf-N. These changes in PSII and PSI parameters were strongly correlated with each other. Growth temperatures scarcely affected these relationships. These results suggest that the photochemistry of PSII and PSI is coordinately regulated primarily depending on the amount of total leaf-N. When excess light energy occurs in low N-acclimated plants, oxidation of the reaction center chlorophyll of PSI is thought to be stimulated to protect PSI from excess light energy. It is also suggested that PSII and PSI normally operate at high temperature used in the present study. In addition, as the relationships between Y(II) and Y(ND) were found to be almost identical to those observed in osmotically stressed rice plants, common regulation is thought to be operative when excess light energy occurs due to different causes.
虽然氮水平会影响叶片的光合能力，但氮水平对光合系统 II 和 I（分别为 PSII 和 PSI）的光化学的影响还不太清楚。在本研究中，我们在正常或高温下（在水稻种植过程中可能会出现高温，但不会严重抑制光合作用），研究了三种不同氮水平下生长的水稻（Oryza sativa L. 'Hitomebore'）植株的这一方面。在两种生长温度下，PSII 的量子效率 [Y(II)] 和其氧化态的初级醌电子受体的分数与总叶片氮量呈正相关，而非光化学猝灭和 PSI 供体侧限制的量子产率 [Y(ND)] 与总叶片氮量呈负相关。这些 PSII 和 PSI 参数的变化与彼此之间密切相关。生长温度对这些关系的影响很小。这些结果表明，PSII 和 PSI 的光化学主要根据总叶片氮量的变化进行协调调节。当低氮适应植物中出现过量的光能时，PSI 反应中心叶绿素的氧化被认为会受到刺激，以保护 PSI 免受过量的光能。此外，研究还表明 PSII 和 PSI 在本研究中使用的高温下正常运行。另外，由于 Y(II)和 Y(ND)之间的关系与在渗透胁迫下的水稻植株中观察到的关系几乎相同，因此当由于不同原因出现过量的光能时，认为会有共同的调节作用。
