Salinity is often a great limitation in marginal environments with potential for developing alternative non‐edible crops for biodiesel, and the physiological responses involved in the recovery of plants subjected to high salinity are poorly studied. The aim of this study on Jatropha curcas is to identify salinity tolerance responses of net photosynthesis rate under saturating irradiances (A_max), its recovery capacity and the role of mesophyll conductance (g_m) over A_max. Two experiments were performed with seedlings in pots under outdoor conditions and hydroponic conditions, respectively, with salinity intensities ranging from 3 to 12 dS/m, their isosmotic treatments with polyethylene glycol (PEG) and controls without abiotic stress. A_max and growth rate were mainly affected by salinity effects in all the ranges, with a drastic 60% drop in dry biomass under 6 dS/m, revealing a significant sensitivity of this species. However, a surprising increase in A_max was promoted by the presence of NaCl, with respect to their respective isosmotic treatments with PEG, although it was still lower than the unstressed plants. This advantage disappeared from 9 dS/m, but negative effects of NaCl toxicities were never detected. The photochemical apparatus resulted extremely resistant in this species, since Fv/Fm and leaf greenness were affected only at 12 dS/m. So, g_m was strongly and linearly associated with A_max. This association derives from the overall range of stress intensities tested, thus appearing as the main useful trait for enhancing photosynthesis depletion under salinity stress, without losses of the water use efficiency. A drastic 75% drop was also detected in the electron use for photosynthesis, revealing that A_max would also be modulated by metabolic impairments under salinity. Moreover, full recovery after only 8 days was observed, confirming the high resistance of the species to NaCl stress even under very high salinities. This study contributes to a better understanding of the physiological processes involved in the response of J. curcas to salinity during early vegetative stage, generating possibilities for improving tolerance of this species under environments exposed to salinity.

中文翻译：

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营养早期阶段麻疯树光合作用，荧光和叶肉电导对盐度升高的响应

在边缘环境中，盐度通常是一个很大的限制，有可能开发出替代性非食用作物来生产生物柴油，而盐度高的植物恢复过程中涉及的生理反应研究也很少。这项针对麻风树的研究的目的是确定饱和辐照度（A _max）下净光合作用的盐度耐受性响应，其恢复能力以及叶肉电导率（g _m）在A _{max上的作用。}。分别在室外条件和水耕条件下在盆中的幼苗进行了两个试验，盐度强度为3至12 dS / m，分别用聚乙二醇（PEG）等渗处理和无非生物胁迫的对照。甲_最大和生长速率主要受在所有范围盐度效果，与干生物质下6 DS /米的急剧下降60％，这揭示物种的显著灵敏度。但是，A _max令人惊讶地增加就其各自的PEG等渗处理而言，NaCl的存在促进了NaCl的生长，尽管它仍低于未胁迫的植物。这种优势从9 dS / m起消失，但从未检测到NaCl毒性的负面影响。由于Fv / Fm和叶片绿度仅在12 dS / m时受到影响，因此光化学仪器对该物种具有极强的抵抗力。因此，g _m与A _max强烈且线性相关_。这种联系源自所测试的压力强度的整个范围，因此似乎是在盐分胁迫下增强光合作用耗竭而又不损失水分利用效率的主要有用性状。在用于光合作用的电子中，也检测到急剧下降了75％，这表明一个_最大也将通过在盐代谢障碍调制。此外，仅在8天后就观察到完全恢复，这证实了该物种即使在非常高的盐度下也具有对NaCl胁迫的高抗性。这项研究有助于人们更好地了解植物营养早期阶段麻疯树对盐分的响应所涉及的生理过程，从而为提高该物种在盐分环境下的耐受性提供了可能性。