High root absorption of silicon (Si) in sugarcane plants that accumulate the element attenuates water deficit-induced damage. However, there is a lack of research to identify whether the low relative absorption of Si via leaf spraying compared to root application has an immediate antioxidant effect on plants under water restriction. For this purpose, the objective of this research was to evaluate the effect of Si applied via leaf spraying and via nutritive solution (root) in mitigating the damage caused by short-term water deficit induced by PEG-6000 in pre-sprouted sugarcane seedlings. The treatments were arranged in a 3 × 2 factorial scheme, consisting of the forms of Si supply: via nutrient solution (SiR) (2.0 mmol/L), via foliar spraying (SiL) (3.4 mmol/L) plus the absence of Si (−Si), combined with the presence (−0.6 MPa) and absence of water deficit, arranged in randomized blocks with 6 repetitions. The experiment was developed in a hydroponic system, in which Si was initially supplied during the seedling production phase; subsequently, water deficit was induced with PEG-6000 for a period of 72 hr. Plants under water deficit increased the accumulation of Si with the supply of the element via root application and via foliar spraying by 2118% and 98%, respectively, in comparison to the absence of Si. However, although Si foliar absorption was relatively low in comparison to the root, the physiological effects in relieving water deficit-induced stress were equal to or even higher than those of root application. In conclusion, the amount of Si absorbed by the plant is not a major factor to induce an antioxidant defence response to mitigate the immediate effects of water deficit, since the two forms of application of Si were similar. Si foliar spraying promotes physiological and biochemical effects that alleviate damage done water deficit short term, even on plants with an active absorption mechanism such as sugarcane.

中文翻译：

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与根部施用相比，通过叶面施用的硅的低吸收具有直接的抗氧化作用，可减轻甘蔗的缺水损害

积累元素的甘蔗植物中硅 (Si) 的高根吸收可减轻缺水引起的损害。然而，缺乏研究来确定与根部施用相比，通过叶喷施对硅的低相对吸收是否对水分限制下的植物具有直接的抗氧化作用。为此，本研究的目的是评估通过喷叶和通过营养液（根）施用硅在减轻 PEG-6000 对发芽前的甘蔗幼苗造成的短期水分亏缺造成的损害方面的效果。处理以 3 × 2 因子方案排列，由 Si 供应形式组成：通过营养液 (SiR) (2.0 mmol/L)、通过叶面喷施 (SiL) (3.4 mmol/L) 加上不存在 Si （-Si），结合存在（-0. 6 MPa）并且没有缺水，随机排列，重复 6 次。该实验是在水培系统中进行的，其中最初在幼苗生产阶段提供硅；随后，用 PEG-6000 诱导缺水 72 小时。与不存在 Si 的情况相比，缺水的植物通过根施和叶面喷施提供的元素分别增加了 2118% 和 98% 的 Si 积累。然而，尽管与根部相比，Si 叶面吸收相对较低，但在缓解水分亏缺引起的胁迫方面的生理作用与根部施用相当甚至更高。综上所述，植物吸收的硅量不是诱导抗氧化防御反应以减轻水分不足的直接影响的主要因素，因为硅的两种应用形式相似。硅叶面喷施促进生理和生化作用，缓解短期缺水造成的损害，即使对甘蔗等具有主动吸收机制的植物也是如此。