Departamento de Biología Vegetal y Ecología, Facultad de Ciencia y Tecnología, Universidad del País Vasco, UPV/EHU, Apdo. 644, 48080 Bilbao, Spain.
Photosynth Res. 2012 Mar;111(3):269-83. doi: 10.1007/s11120-012-9721-1.
The future environment may be altered by high concentrations of salt in the soil and elevated [CO(2)] in the atmosphere. These have opposite effects on photosynthesis. Generally, salt stress inhibits photosynthesis by stomatal and non-stomatal mechanisms; in contrast, elevated [CO(2)] stimulates photosynthesis by increasing CO(2) availability in the Rubisco carboxylating site and by reducing photorespiration. However, few studies have focused on the interactive effects of these factors on photosynthesis. To elucidate this knowledge gap, we grew the barley plant, Hordeum vulgare (cv. Iranis), with and without salt stress at either ambient or elevated atmospheric [CO(2)] (350 or 700 μmol mol(-1) CO(2), respectively). We measured growth, several photosynthetic and fluorescence parameters, and carbohydrate content. Under saline conditions, the photosynthetic rate decreased, mostly because of stomatal limitations. Increasing salinity progressively increased metabolic (photochemical and biochemical) limitation; this included an increase in non-photochemical quenching and a reduction in the PSII quantum yield. When salinity was combined with elevated CO(2), the rate of CO(2) diffusion to the carboxylating site increased, despite lower stomatal and internal conductance. The greater CO(2) availability increased the electron sink capacity, which alleviated the salt-induced metabolic limitations on the photosynthetic rate. Consequently, elevated CO(2) partially mitigated the saline effects on photosynthesis by maintaining favorable biochemistry and photochemistry in barley leaves.
未来的环境可能会受到土壤中高浓度盐分和大气中升高的[CO2]的影响。这两者对光合作用有相反的影响。一般来说，盐胁迫通过气孔和非气孔机制抑制光合作用；相比之下，升高的[CO2]通过增加 Rubisco 羧化部位的 CO2 可用性和减少光呼吸来刺激光合作用。然而，很少有研究关注这些因素对光合作用的相互作用影响。为了阐明这一知识空白，我们在有或没有盐胁迫的情况下，分别在大气[CO2]浓度为 350 或 700 μmol mol(-1)（分别为 ambient 和 elevated）的条件下种植大麦（cv. Iranis）。我们测量了生长、几种光合作用和荧光参数以及碳水化合物含量。在盐胁迫条件下，光合作用速率下降，主要是由于气孔限制。随着盐度的增加，代谢（光化学和生物化学）限制逐渐增加；这包括非光化学猝灭的增加和 PSII 量子产量的降低。当盐度与升高的 CO2 结合时，尽管气孔和内部导度较低，但 CO2 向羧化部位的扩散速率增加。更大的 CO2 可用性增加了电子汇的容量，从而缓解了盐胁迫对光合作用速率的代谢限制。因此，升高的 CO2 通过维持大麦叶片中有利的生物化学和光化学特性，部分减轻了盐对光合作用的影响。
