Chaves M M, Flexas J, Pinheiro C
Instituto Superior de Agronomia, Technical University of Lisbon, Lisbon, Portugal.
Ann Bot. 2009 Feb;103(4):551-60. doi: 10.1093/aob/mcn125. Epub 2008 Jul 28.
Plants are often subjected to periods of soil and atmospheric water deficits during their life cycle as well as, in many areas of the globe, to high soil salinity. Understanding how plants respond to drought, salt and co-occurring stresses can play a major role in stabilizing crop performance under drought and saline conditions and in the protection of natural vegetation. Photosynthesis, together with cell growth, is among the primary processes to be affected by water or salt stress.
The effects of drought and salt stresses on photosynthesis are either direct (as the diffusion limitations through the stomata and the mesophyll and the alterations in photosynthetic metabolism) or secondary, such as the oxidative stress arising from the superimposition of multiple stresses. The carbon balance of a plant during a period of salt/water stress and recovery may depend as much on the velocity and degree of photosynthetic recovery, as it depends on the degree and velocity of photosynthesis decline during water depletion. Current knowledge about physiological limitations to photosynthetic recovery after different intensities of water and salt stress is still scarce. From the large amount of data available on transcript-profiling studies in plants subjected to drought and salt it is becoming apparent that plants perceive and respond to these stresses by quickly altering gene expression in parallel with physiological and biochemical alterations; this occurs even under mild to moderate stress conditions. From a recent comprehensive study that compared salt and drought stress it is apparent that both stresses led to down-regulation of some photosynthetic genes, with most of the changes being small (ratio threshold lower than 1) possibly reflecting the mild stress imposed. When compared with drought, salt stress affected more genes and more intensely, possibly reflecting the combined effects of dehydration and osmotic stress in salt-stressed plants.
植物在其生命周期中经常会经历土壤和大气水分亏缺的时期，而且在全球许多地区还会面临高土壤盐分问题。了解植物如何应对干旱、盐分及同时出现的多种胁迫，对于稳定干旱和盐碱条件下的作物表现以及保护自然植被可能起着重要作用。光合作用以及细胞生长是受水分或盐分胁迫影响的主要过程。
干旱和盐分胁迫对光合作用的影响要么是直接的（如通过气孔和叶肉的扩散限制以及光合代谢的改变），要么是间接的，例如多种胁迫叠加产生的氧化胁迫。植物在盐分/水分胁迫及恢复期间的碳平衡，可能既取决于光合恢复的速度和程度，也取决于水分亏缺期间光合作用下降的程度和速度。目前关于不同强度水分和盐分胁迫后光合恢复的生理限制的知识仍然匮乏。从大量关于遭受干旱和盐分胁迫的植物转录谱研究的数据来看，很明显植物通过与生理和生化改变同时快速改变基因表达来感知和应对这些胁迫；即使在轻度至中度胁迫条件下也是如此。从最近一项比较盐分和干旱胁迫的综合研究来看，很明显这两种胁迫都会导致一些光合基因的下调，大多数变化较小（比值阈值低于1），这可能反映了所施加的轻度胁迫。与干旱相比，盐分胁迫影响的基因更多且更强烈，这可能反映了盐胁迫植物中脱水和渗透胁迫的综合作用。
