Plants optimize water use and carbon assimilation via transient regulation of stomata resistance and by limiting hydraulic conductivity in a long-term response of xylem anatomy. We postulated that without effective hydraulic regulation plants would permanently restrain water loss and photosynthetic productivity under salt stress conditions. We compared wild type (WT) tomatoes to a transgenic type (TT) with impaired stomatal control. Gas exchange activity, biomass, starch content, leaf area and root traits, mineral composition and main stems xylem anatomy and hydraulic conductivity were analysed in plants exposed to salinities of 1 and 4 dS m-1 over 60 days. As the xylem cannot easily readjust to different environmental conditions, shifts in its anatomy and the permanent effect on plant hydraulic conductivity kept transpiration at lower levels under unstressed conditions and maintained it under salt-stress, while sustaining higher but inefficient assimilation rates, leading to starch accumulation and decreased plant biomass, leaf and root area and root length. Narrow conduits in unstressed TT plants were related to permanent restrain of hydraulic conductivity and plant transpiration. Under salinity, TT plants followed the atmospheric water demand, sustained similar transpiration rate from unstressed to salt-stressed conditions and possibly maintained hydraulic integrity, due to likely impaired hydraulic regulation, wider conduits and higher hydraulic conductivity. The accumulation of salts and starch in the TT plants was a strong evidence of salinity tolerance via osmotic regulation, also thought to help to maintain the assimilation rates and transpiration flux under salinity, although it was not translated into higher growth. This article is protected by copyright. All rights reserved.

中文翻译：

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宽阔的船只维持边际蒸腾通量，并且不会在水力控制和盐度受损的情况下优化低效的气体交换

植物通过瞬时调节气孔阻力和限制木质部解剖结构的长期响应中的水力传导率来优化水分利用和碳同化。我们假设如果没有有效的水力调节植物将在盐胁迫条件下永久抑制水分流失和光合生产力。我们将野生型 (WT) 番茄与气孔控制受损的转基因型 (TT) 番茄进行了比较。对暴露于 1 和 4 dS m-1 盐度超过 60 天的植物的气体交换活性、生物量、淀粉含量、叶面积和根性状、矿物质成分和主茎木质部解剖结构和导水率进行了分析。由于木质部不能轻易地重新适应不同的环境条件，其解剖结构的变化和对植物导水率的永久性影响使无压力条件下的蒸腾作用保持在较低水平，并在盐胁迫下保持，同时维持较高但效率低下的同化率，导致淀粉积累和植物生物量、叶和根面积减少和根长。未受胁迫的 TT 植物中的狭窄管道与水力传导率和植物蒸腾作用的永久抑制有关。在盐度下，由于水力调节可能受损、管道更宽和水力传导率更高，TT 植物遵循大气需水量，从无压力到盐压力条件保持相似的蒸腾速率，并可能保持水力完整性。TT 植物中盐和淀粉的积累是通过渗透调节的耐盐性的有力证据，也被认为有助于维持盐度下的同化速率和蒸腾通量，尽管它没有转化为更高的生长。本文受版权保护。版权所有。