Abstract Shifting toward stress-resistant planting material has become a pre-requisite for fruit tree culture under arid to the semiarid environment. No information currently exists on the physiological basis of water stress tolerance in Ziziphus jujuba at the saplings stage, an important fruit tree of semiarid regions of Central Punjab. Therefore, an experiment was conducted under controlled conditions where plants were subjected to three watering regimes: control irrigation, a medium, and a high-water deficit treatment. During the experiment, growth, biomass production and allocation in different plant organs (leaves, stem, and root) were measured. The physiological response of Z. jujuba under water deficit was determined through a gas exchange system and CO2 assimilation rate, stomatal conductance, and water use efficiency were evidenced. Biomass production/allocation in leaves and stem decreased significantly with an increase in soil water deficit. Root biomass production remained unchanged (p = 0.907), but allocation increased significantly under high soil water deficit (p < 0.001). Net CO2 assimilation rate (A) remained similar at 6.54 ± 0.32 μmol m−2 s−1 but, stomatal conductance (gs) decreased significantly from 94.0 to 69.2 mmol m−2 s−1 under high water deficit treatment. Water use efficiency (ratio between Net CO2 assimilation rate and transpiration rate) also increased significantly (p = 0.012) under high water deficit treatment. Ziziphus jujuba showed a medium degree of plasticity under water deficit conditions, which was mainly driven by a sustained CO2 assimilation rate and more biomass allocation for root development.

中文翻译：

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土壤水分亏缺条件下，一致的 CO2 同化率和增强的根系发育驱动了小枣的耐受机制

摘要 向抗逆种植材料转变已成为干旱至半干旱环境下果树栽培的先决条件。目前尚无关于在旁遮普中部半干旱地区的重要果树——幼树阶段小枣耐水胁迫的生理基础的信息。因此，在受控条件下进行了一项实验，其中植物接受三种浇水方案：控制灌溉、中等和高水分亏缺处理。在实验过程中，测量了不同植物器官（叶、茎和根）的生长、生物量产生和分配。枣树在缺水条件下的生理反应是通过气体交换系统确定的，并证明了 CO2 同化率、气孔导度和水分利用效率。随着土壤水分亏缺的增加，叶和茎中的生物量产生/分配显着下降。根生物量产量保持不变（p = 0.907），但在高土壤水分亏缺下分配显着增加（p < 0.001）。净 CO2 同化率 (A) 保持相似，为 6.54 ± 0.32 μmol m-2 s-1，但在高水分亏缺处理下，气孔导度 (gs) 从 94.0 显着降低至 69.2 mmol m-2 s-1。在高缺水处理下，水分利用效率（净 CO2 同化率与蒸腾率之间的比率）也显着增加（p = 0.012）。Ziziphus jujuba 在缺水条件下表现出中等程度的可塑性，这主要是由于持续的 CO2 同化率和更多的生物量分配用于根部发育。