Global climate change is affecting important natural resources including water. Increasing temperature will change rate of evaporation and transpiration, leading to variations in water availability, ground water recharge, and water consumption by plants. Thus, competition for water will be a major future challenge for agriculture. Increasing water productivity at farm level is necessary to increase the efficiency of the irrigation system, plant water−use efficiency (WUE) and to optimize irrigation management. We test the hypothesis that in field−grown, drip−irrigated nectarine trees, the roots in the un−irrigated inter−row soil produce chemical signals that increase in summer to induce stomatal closure and so increase WUE. Concentrations of abscisic acid (ABA) were determined in leaf, root, and xylem sap of drip−irrigated (D) trees in which only about 25% of the soil volume was wetted and compared with those of trees irrigated using microjets (M) in which the whole soil volume was wetted. We also examined the effects of increased ABA on root−to−shoot dry matter ratio, the ratio ABA to indole−3−acetic acid (IAA), sap pH, and fruit and shoot growth. Both D and M trees were maintained at optimal water status as judged by pre−dawn leaf water potentials (about −0.3 MPa). There were no significant differences between treatments in mean fruit size (fruit diameter) or in tree yield (total fruit weight). However, shoot length was strongly reduced in D trees (to 75%) compared to M trees (100%). The concentrations of ABA in the inter−row roots of D trees were increased by 59% and that in the leaves by 13% compared to in the M trees. Despite the similar water status of D and M trees, a clear chemical signal was triggered in terms of a significant increase in the ABA/IAA ratio. This signal influenced leaf stomatal conductance which was 40% lower in D trees than in M trees. The associated responses in photosynthesis and transpiration raised the WUE of D trees by 7%–10% compared to M trees. This field study shows that in drip−irrigated trees, an ABA root−to−shoot signal issues from the inter−row roots growing in soil that dries out during a Mediterranean summer (hot, low rainfall). This ABA−induced WUE increase was achieved principally through reduced stomatal conductance and reduced transpiration.

中文翻译：

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局部灌溉下桃树的根到茎信号和叶片水分利用效率

全球气候变化正在影响包括水在内的重要自然资源。温度升高将改变蒸发和蒸腾速率，从而导致水利用量，地下水补给量和植物耗水量发生变化。因此，争夺水将是农业未来的主要挑战。要提高灌溉系统的效率，提高植物用水效率（WUE）并优化灌溉管理，必须提高农场一级的水生产率。我们检验了以下假设：在田间种植，滴灌的油桃树中，未灌溉的行间土壤中的根产生的化学信号在夏季增加，从而导致气孔关闭，从而增加WUE。测定了叶，根，根中脱落酸（ABA）的浓度 滴灌（D）的树木的木质部汁液仅润湿了约25％的土壤体积，并且与使用微喷头（M）灌溉的树木的木质部汁液相比，其全部土壤都被润湿了。我们还检查了ABA增加对根茎干物质比，ABA与吲哚-3-乙酸比（IAA），树液pH值以及果实和枝条生长的影响。根据黎明前的叶子水势（约-0.3 MPa）判断，D树和M树都保持在最佳水状态。处理之间在平均果实大小（果实直径）或树木产量（总果实重量）上没有显着差异。但是，与M树（100％）相比，D树的芽长明显减少（降至75％）。与M树相比，D树行间根中ABA的浓度增加了59％，叶中ABA的浓度增加了13％。尽管D和M树的水分状况相似，但根据ABA / IAA比的显着增加，触发了清晰的化学信号。该信号影响叶片气孔导度，D树的气孔导度比M树的低40％。光合作用和蒸腾作用的相关响应使D树的WUE比M树提高了7％–10％。这项田间研究表明，在滴灌的树木中，ABA的根部射击信号来自地中海夏季（干旱，低雨量）干燥的土壤中生长的行间根。这种ABA诱导的WUE增加主要是通过减少气孔导度和减少蒸腾作用来实现的。该信号影响叶片气孔导度，D树的叶片气孔导度比M树的叶片低40％。光合作用和蒸腾作用的相关反应使D树的WUE比M树提高了7％–10％。这项田间研究表明，在滴灌的树木中，ABA的根部射击信号来自地中海夏季（干旱，低雨量）干燥的土壤中生长的行间根。这种ABA诱导的WUE增加主要是通过减少气孔导度和减少蒸腾作用来实现的。该信号影响叶片气孔导度，D树的叶片气孔导度比M树的叶片低40％。光合作用和蒸腾作用的相关响应使D树的WUE比M树提高了7％–10％。这项田间研究表明，在滴灌的树木中，ABA的根部射击信号来自地中海夏季（干旱，低雨量）干燥的土壤中生长的行间根。这种ABA诱导的WUE增加主要是通过减少气孔导度和减少蒸腾作用来实现的。在地中海夏季（炎热，低降雨）中，土壤中生长的行间根部产生了ABA根对茎信号。这种ABA诱导的WUE增加主要是通过减少气孔导度和减少蒸腾作用来实现的。在地中海夏季（炎热，低降雨）中，土壤中生长的行间根部产生了ABA根对茎信号。这种ABA诱导的WUE增加主要是通过减少气孔导度和减少蒸腾作用来实现的。