Rhododendron delavayi is an alpine evergreen ornamental plant with strong tolerance to drought stress. Brassinosteroids are promising agents for alleviating the negative effects of drought on plants, but the mechanism by which BRs induce plant resistance to drought is not well understood. The present study investigated the effects of exogenous spray of 24‐epibrassionlide (EBR) at different concentrations (0~1 mg l⁻¹) on the physiological response of R. delavayi to drought caused by no watering for 10 days. With the increase in EBR concentration, net photosynthetic rate, stomatal conductance, transportation rate, light saturated photosynthetic rate, light compensation point, light saturation point, excitation energy capture efficiency of reaction center, actual photochemical efficiency of photosystem II (PSII), photochemical quenching and electron transport rate significantly increased, but there were no significant effects on photosynthetic pigment content. These results suggested that the EBR‐induced improvement in CO₂ assimilation under drought was mainly related to stomatal and non‐stomatal factors, and partially attributed to the increased photochemical efficiency of PSII. In addition, the leaf water potential increased with the increase in EBR concentration, while the malondialdehyde, superoxide dismutase, catalase, proline and soluble protein decreased. The results suggested EBR application partially alleviated the negative effect of drought on R. delavayi by improving water relations and decreasing lipid peroxidation and reactive oxygen species production. We concluded that exogenous application of EBR improved photosynthesis and alleviated the negative effects of drought‐induced membrane peroxidation and severe oxidative stress.

中文翻译：

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24-吡草醚内酯可改善杜瓦杜鹃对干旱的光合响应

杜鹃花杜鹃是一种高山常绿观赏植物，对干旱胁迫具有较强的耐受性。油菜素类固醇是减轻干旱对植物的不利影响的有前途的药物，但是对BRs诱导植物抗旱的机理尚不清楚。本研究调查了不同浓度（0〜1 mg l ^-1）的24-表皮内酯（EBR）的外源喷雾对德拉瓦罗非鱼生理反应的影响。10天没有浇水导致的干旱。随着EBR浓度，净光合速率，气孔导度，传输速率，光饱和光合速率，光补偿点，光饱和点，反应中心的激发能捕获效率，光系统II（PSII）的实际光化学效率，光化学猝灭的增加电子传输速率显着增加，但对光合色素含量没有显着影响。这些结果表明，EBR可以改善CO ₂干旱下的同化作用主要与气孔和非气孔因素有关，部分归因于PSII的光化学效率提高。此外，随着EBR浓度的增加，叶片水势增加，而丙二醛，超氧化物歧化酶，过氧化氢酶，脯氨酸和可溶性蛋白质降低。结果表明，EBR的应用通过改善水的关系并减少脂质过氧化作用和活性氧的产生，部分缓解了干旱对德拉瓦伊的不利影响。我们的结论是，外源施用EBR可以改善光合作用，并减轻干旱引起的膜过氧化和严重的氧化应激的负面影响。