Kornyeyev Dmytro, Logan Barry A, Tissue David T, Allen Randy D, Holaday A Scott
Department of Biological Sciences, Texas Tech University, Lubbock, TX 79409, USA.
Plant Cell Physiol. 2006 Apr;47(4):437-46. doi: 10.1093/pcp/pcj010. Epub 2006 Jan 31.
The extent to which PSII photoinactivation affects electron transport (PhiPSII) and CO2 assimilation remains controversial, in part because it frequently occurs alongside inactivation of other components of photosynthesis, such as PSI. By manipulating conditions (darkness versus low light) after a high light/low temperature treatment, we examined the influence of different levels of PSII inactivation at the same level of PSI inactivation on PhiPSII and CO2 assimilation for Arabidopsis. Furthermore, we compared PhiPSII at high light and optimum temperature for wild-type Arabidopsis and a mutant (npq4-1) with impaired capacities for energy dissipation. Levels of PSII inactivation typical of natural conditions (< 50%) were not associated with decreases in PhiPSII and CO2 assimilation at photon flux densities (PFDs) above 150 micromol m(-2) s(-1). At higher PFDs, the light energy being absorbed was in excess of the energy that could be utilized by downstream processes. Arabidopsis plants downregulate PSII activity to dissipate such excess in accordance with the level of PSII photoinactivation that also serves to dissipate absorbed energy. Therefore, the overall levels of non-photochemical dissipation and the efficiency of photochemistry were not affected by PSII inactivation at high PFD. Under low PFD conditions, such compensation is not necessary, because the amount of light energy absorbed is not in excess of that needed for photochemistry, and inactive PSII complexes are dissipating energy. We conclude that moderate photoinactivation of PSII complexes will only affect plant performance when periods of high PFD are followed by periods of low PFD.
光系统II（PSII）光失活对电子传递（光化学效率，PhiPSII）和二氧化碳同化的影响程度仍存在争议，部分原因是它经常与光合作用的其他组分（如光系统I，PSI）的失活同时发生。通过在高光/低温处理后操纵条件（黑暗与弱光），我们研究了在相同PSI失活水平下不同程度的PSII失活对拟南芥PhiPSII和二氧化碳同化的影响。此外，我们比较了野生型拟南芥和能量耗散能力受损的突变体（npq4-1）在高光和最适温度下的PhiPSII。自然条件下典型的PSII失活水平（<50%）与光子通量密度（PFDs）高于150微摩尔 米-2 秒-1时PhiPSII和二氧化碳同化的降低无关。在较高的PFDs下被吸收的光能超过了下游过程可利用的能量。拟南芥植物根据PSII光失活的水平下调PSII活性以耗散这种过量能量，而PSII光失活也有助于耗散吸收的能量。因此，在高PFD下非光化学耗散和光化学效率的总体水平不受PSII失活的影响。在低PFD条件下，这种补偿是不必要的，因为吸收的光能不超过光化学所需的能量，并且失活的PSII复合体正在耗散能量。我们得出结论，只有当高PFD时期之后紧接着低PFD时期时，PSII复合体的适度光失活才会影响植物性能。
