College of Resources and Environment, Shandong Agricultural University, Tai'an, 271018, People's Republic of China.
College of Resources and Environment, Shandong Agricultural University, Tai'an, 271018, People's Republic of China.
Plant Physiol Biochem. 2020 Oct;155:93-104. doi: 10.1016/j.plaphy.2020.06.033. Epub 2020 Jul 22.
Plants are always suffering periods of soil water deficit and sustained soil salinity during their life cycle. Unraveling the mechanisms underpinning the responses of plants, especially the photosynthesis, to drought, salinity, and co-occurring stresses is critical for both the protection of natural vegetation and the stabilization of crop production. To better understand the downregulation of photosynthetic capability induced by soil salinity and drought, gas exchange parameters, leaf pigment contents, and chlorophyll (Chl) a fluorescence transients were analyzed in leaves of Hybrid Pennisetum. Our results showed that long-term moderate salinity, short-term drought, and the combination of these stressors decreased leaf pigment content by 11.4-31.5% and net photosynthetic rate (P) by 14.6-67.6% compared to those in untreated plants. The reduction of P in Hybrid Pennisetum under long-term salinity stress mainly occurred by stomatal limitation, whereas non-stomatal limitation played a dominant role under short-term drought stress. The changes in Chl a fluorescence kinetics (especially the appearance of the L-band and K-band) in both stress treatments showed that salinity and drought stress damaged the structural stability of photosystem II (PSII) and disturbed the equilibrium between the electrons at the acceptor and donor sides of PSII. Furthermore, although the negative effect of drought stress on leaf photosynthesis was much greater than that of salinity stress, moderate salt stress alleviated the negative effect of drought stress on the photosynthetic performance of Hybrid Pennisetum after long acclimation times.
在其生命周期中，植物总是会经历土壤水分亏缺和持续土壤盐渍化时期。揭示植物对干旱、盐胁迫和共同发生的胁迫的响应机制，特别是光合作用的响应机制，对于保护自然植被和稳定作物生产至关重要。为了更好地理解土壤盐度和干旱诱导的光合作用能力下调的机制，我们分析了杂交狼尾草叶片的气体交换参数、叶片色素含量和叶绿素（Chl）a 荧光瞬变。我们的结果表明，与未处理的植物相比，长期中度盐度、短期干旱以及这些胁迫因素的组合使叶片色素含量降低了 11.4-31.5%，净光合速率（P）降低了 14.6-67.6%。在长期盐胁迫下，杂交狼尾草 P 的减少主要是由气孔限制引起的，而在短期干旱胁迫下，非气孔限制起主导作用。两种胁迫处理中 Chl a 荧光动力学的变化（特别是 L 带和 K 带的出现）表明，盐度和干旱胁迫破坏了光系统 II（PSII）的结构稳定性，并扰乱了 PSII 受体和供体侧电子的平衡。此外，尽管干旱胁迫对叶片光合作用的负面影响远大于盐胁迫，但在长期适应时间后，适度盐度胁迫减轻了干旱胁迫对杂交狼尾草光合性能的负面影响。
