[Objective] The aim of the work was to study the effects of 24-epibrassinolide (EBR) added to nutrient solution on carbohydrate metabolism of cucumber {Cucumis sativus L.) under root-zone hypoxia. [Method] Seedlings of a relatively hypoxia-resistant cultivar, 'L(u)bachun No.4', and a relatively hypoxia-sensitive cultivar, 'Zhongnong No.8', were hydroponically grown for 8 days in normoxic and hypoxic nutrient solutions with and without addition of EBR at 1 μg L-1. And the effects of EBR on contents of carbohydrates in leaves and roots and activities of glycolytic enzymes in the roots were investigated. [Result] Application of EBR to normoxic nutrient solution promoted the accumulation of total soluble sugars in leaves and roots, but had no effects on activities of glycolytic enzymes in the roots. Changes in contents of starch and glucose, and activities of acid invertase and ATP-dependent phosphofructokinase enzymes in the roots showed obviously different between two genotypes cucumber in response to root-zone hypoxia. EBR added to hypoxic nutrient solution caused an increase in the concentrations of fructose and sucrose and activities of major glycolytic enzymes in the roots, but exerted little influence on carbohydrate concentrations in the leaves. [Conclusion] These results suggest that EBR added to hypoxic nutrient solution may stimulate the photosynthate allocation down to roots and activities of major glycolytic enzymes, and eventually enhanced tolerance of cucumber plants to root-zone hypoxia.%[目的]探讨外源EBR(24-表油菜素内酯)对低氧胁迫下黄瓜(Cucumis sativus L.)幼苗碳水化合物代谢的影响.[方法]采用营养液水培法,以耐低氧能力较强的黄瓜品种'绿霸春4号'和耐低氧能力较弱的品种'中农8号'为材料,研究根际低氧胁迫下外源施用EBR对黄瓜幼苗碳水化合物含量及根系糖酵解代谢酶活性的影响.[结果]通气条件下正常栽培,EBR处理显著促进两黄瓜品种叶片和根系中可溶性总糖的积累,但对根系糖酵解代谢酶活性的影响较小;低氧胁迫下,耐低氧能力不同的两品种幼苗根系淀粉、葡萄糖含量及酸性转化酶、ATP依赖的磷酸果糖激酶活性的变化表现出明显的品种差异;低氧条件下,EBR处理进一步提高了两品种根系中蔗糖和果糖含量及主要的糖酵解代谢酶活性,对叶片中大部分碳水化合物含量均无显著影响.[结论]低氧胁迫下,外源EBR通过促进碳水化合物从叶片向根系的分配及根系糖酵解代谢酶活性的提高,增强黄瓜植株耐低氧胁迫的能力.
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