Plant growth regulators (PGRs) improve crop growth and mitigate the adverse effects of drought stress. This study explores the effects of various PGRs including melatonin (MT), indole‐butyric acid (IBA) and gibberellic acid (GA3) on drought‐tolerant Zhongzhe 9 (ZZ9) and Xintaitang 22 (ROC22), as well as drought‐sensitive varieties Guitang‐44 (GT44) and Funong 41 (FN41) varieties. A pot experiment was conducted to evaluate the foliar application of these hormones alone or in combination on sugarcane seedlings under drought stress conditions. At the sixth leaf stage, drought stress was induced by reducing soil moisture to 40%–45% field capacity. Results showed that the drought‐sensitive variety GT44 had the highest plant height (17.97 cm), while PGRs application enhanced the relative water content (RWC) in FN41 by 0.96%. PGRs treatment also increased plant height by 33.98% and RWC by 3.26% compared to controls. MT application significantly increased chlorophyll a and b contents in FN41 by 4.82% and 4.51%, respectively. Antioxidant enzyme activities superoxide dismutase and peroxidase increased by 16.39% and 12.57%, respectively, indicating enhanced oxidative stress defence. Moreover, PGRs applications reduced hydrogen peroxide and malondialdehyde (MDA) accumulation, signifying decreased oxidative damages. The combinations of MT + GA3 and MT + IBA + GA3 significantly improved the plant growth attributes, antioxidant enzymes, osmolytes and reduced the accumulation of ROS and MDA content in both tolerant and sensitive varieties under drought stress. Thus, combined application of MT + GA3 and MT + IBA + GA3 treatments effectively mitigated drought stress in sugarcane seedlings, providing valuable insights for sustainable agricultural practices.

中文翻译：

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叶面施用植物生长调节剂通过调节甘蔗品种的生长和生化反应来提高耐旱性


植物生长调节剂 （PGR） 可改善作物生长并减轻干旱胁迫的不利影响。本研究探讨了褪黑素 （MT）、吲哚丁酸 （IBA） 和赤霉酸 （GA3） 等多种 PGR 对耐旱中浙 9 号 （ZZ9） 和新台塘 22 号 （ROC22） 以及干旱敏感品种桂塘 44 （GT44） 和福农 41 （FN41） 品种的影响。进行了盆栽试验，以评估在干旱胁迫条件下这些激素单独或联合对甘蔗幼苗的叶面施用。在第六叶期，通过将土壤水分降低到 40%–45% 的田间容量来诱导干旱胁迫。结果表明，对干旱敏感的品种 GT44 的株高最高 （17.97 cm），而 PGRs 的应用使 FN41 中的相对含水量 （RWC） 提高了 0.96%。与对照相比，PGRs 处理还使株高增加了 33.98%，RWC 增加了 3.26%。MT 施用显著提高了 FN41 中叶绿素 a 和 b 的含量，分别提高了 4.82% 和 4.51%。抗氧化酶活性超氧化物歧化酶和过氧化物酶分别增加了 16.39% 和 12.57%，表明氧化应激防御增强。此外，PGRs 应用减少了过氧化氢和丙二醛 （MDA） 的积累，标志着氧化损伤减少。MT + GA3 和 MT + IBA + GA3 的组合在干旱胁迫下显著提高了耐性和敏感品种的植物生长属性、抗氧化酶、渗透液，降低了 ROS 和 MDA 含量的积累。因此，MT + GA3 和 MT + IBA + GA3 处理的联合应用有效缓解了甘蔗幼苗的干旱胁迫，为可持续农业实践提供了有价值的见解。