Water scarcity restricts citrus growth and productivity worldwide. In pot condition, tetraploid plants tolerate water deficit more than their corresponding diploids. However, their tolerance mechanisms remain elusive. In this study, we focused on which mechanisms (i.e., hydraulic, osmotic, or antioxidative) confer water-deficit tolerance to tetraploids. We exposed diploid and tetraploid Volkamer lemon rootstock (Citrus Volkameriana Tan. and Pasq.) to quickly (fast) and slowly (slow) developing water-deficit conditions. We evaluated their physiological, antioxidative defense and osmotic adjustment responses and mineral distribution to leaves and roots. Water deficit conditions decreased the photosynthetic variables of both diploid and tetraploid plants. Moreover, the corresponding decrease was greater in diploids than tetraploids. Higher concentrations of antioxidant enzymes, osmoprotectants and antioxidant capacity were found in the leaves and roots of tetraploids than diploids under water deficit. Diploid plants showed fast response in slow water deficit condition, but that response did not persist as the deficit intensified. Meanwhile, tetraploids had lower water loss, which slowed the onset of slow water deficit relative to diploids. This response allowed stronger photosynthesis, while antioxidant and osmoprotectant production allowed for further tolerance once desiccation began. Overall, our results concluded that Volkamer lemon tetraploid plants tolerate rapid and slow water deficit by maintaining their photosynthesis due to low conductance (stem or roots) which helps to avoid desiccation and stronger biochemical defense machinery than their corresponding diploids.

中文翻译：

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不同的策略导致共同的结果：不同的缺水情景突出了二倍体与四倍体 Volkamer 柠檬中水分亏缺耐受性的生理和生化策略

水资源短缺限制了全球柑橘的生长和生产力。在盆栽条件下，四倍体植物比其相应的二倍体更能耐受水分不足。然而，它们的耐受机制仍然难以捉摸。在这项研究中，我们关注哪些机制（即水力、渗透或抗氧化）赋予四倍体缺水耐受性。我们暴露了二倍体和四倍体 Volkamer 柠檬砧木 ( Citrus Volkameriana谭。和 Pasq.）快速（快速）和缓慢（缓慢）发展的缺水状况。我们评估了它们的生理、抗氧化防御和渗透调节反应以及对叶和根的矿物质分布。缺水条件降低了二倍体和四倍体植物的光合变量。此外，二倍体的相应减少大于四倍体。在缺水条件下，四倍体的叶和根中的抗氧化酶、渗透保护剂和抗氧化能力的浓度高于二倍体。二倍体植物在缓慢缺水条件下表现出快速反应，但随着缺水加剧，这种反应并没有持续存在。同时，四倍体的失水量较低，相对于二倍体而言，这减缓了缓慢失水的发生。这种反应允许更强的光合作用，而一旦开始干燥，抗氧化剂和渗透保护剂的产生允许进一步的耐受性。总体而言，我们的研究结果得出结论，Volkamer 柠檬四倍体植物通过维持其光合作用由于低电导（茎或根）而耐受快速和缓慢的缺水，这有助于避免干燥和比其相应的二倍体更强的生化防御机制。