In this study, the role of hydrogen sulfide (H 2 S) in growth and metabolism of zucchini ( Cucurbita pepo L.) was explored in a hydroponic culture system under both normal and nickel (Ni) stress conditions. Exposure of zucchini seedlings to 50 mg/l Ni(NO 3 ) 2 reduced root elongation and dry weight of roots and aerial parts. These reductions were attributed to Ni accumulation and depletion of essential bivalent cations in tissues. Excessive Ni resulted in the induction of oxidative stress, as evidenced by increased levels of electrolyte leakage (EL) and hydrogen peroxide (H 2 O 2 ) content in roots and leaves. Moreover, Ni stress increased the endogenous H 2 S content in parallel with the accumulation of proline, soluble sugars, phenolics, and flavonoids in roots and leaves. Exogenous application of 100 µM sodium hydrosulfide (NaHS) as a donor of H 2 S singly or associated with Ni solution significantly improved zucchini growth but the impacts of NaHS were more pronounced in Ni-stressed plants than control seedlings. Notably, NaHS amplified the endogenous H 2 S content and maintained Ni and the homeostasis of cation in roots and aerial parts of Ni-stressed seedlings. Applying NaHS significantly lowered the accumulation of proline, whereas it elevated the content of soluble sugars in roots and leaves of Ni-stressed seedlings. Furthermore, applying NaHS decreased the EL and H 2 O 2 content which were correlated to the enhancement of the phenolic and flavonoids content as well as 1,1-diphenyl-2-picrylhydrazyl radical and hydroxyl radical scavenging power in roots and leaves. By contrast, adding hypotaurine (HT), as a H 2 S scavenger, weakened the beneficial effect of NaHS on all above-mentioned traits that further confirmed the signaling role of H 2 S in regulating growth, membrane integrity, the content of phenolics and osmolytes, and mineral homeostasis under both control and Ni stress conditions.

中文翻译：

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硫氢化钠调节镍胁迫下西葫芦的膜完整性、阳离子稳态以及酚类物质和渗透物的积累

在这项研究中，在正常和镍 (Ni) 胁迫条件下，在水培培养系统中探索了硫化氢 (H 2 S) 在西葫芦 (Cucurbita pepo L.) 生长和代谢中的作用。将西葫芦幼苗暴露于 50 mg/l Ni(NO 3 ) 2 会降低根的伸长率和根和地上部分的干重。这些减少归因于镍的积累和组织中基本二价阳离子的消耗。过量的 Ni 会导致氧化应激，如根和叶中电解质泄漏 (EL) 和过氧化氢 (H 2 O 2 ) 含量增加所证明的那样。此外，Ni 胁迫增加了内源性 H 2 S 含量，同时促进了脯氨酸、可溶性糖、酚类物质和类黄酮在根和叶中的积累。外源施用 100 µM 硫氢化钠 (NaHS) 作为 H 2 S 供体单独或与 Ni 溶液结合显着改善了西葫芦的生长，但 NaHS 对 Ni 胁迫植物的影响比对照幼苗更显着。值得注意的是，NaHS 增加了内源性 H 2 S 含量并维持了 Ni 和 Ni 胁迫幼苗根部和地上部分的阳离子稳态。施用NaHS显着降低了脯氨酸的积累，而提高了Ni胁迫幼苗根和叶中可溶性糖的含量。此外，施用NaHS降低了EL和H 2 O 2 含量，这与酚类和类黄酮含量以及根和叶中1,1-二苯基-2-苦基肼自由基和羟基自由基清除能力的增强相关。相比之下，添加亚牛磺酸（HT），