Abstract: A hydroponic experiment was conducted to investigate the effects of exogenous 24-epibrassinolide (EBR) on the root growth and anaerobic respiration isozyme expression of cucumber seedlings under hypoxia stress. Hypoxia stress induced the isozyme expression of root pyruvate decarboxylase (PDC), alcohol dehydrogenase (ADH), and lactate dehydrogenase (LDH), while the application of EBR increased the expression of PDC and ADH isozymes by 18.8% and 28.8% on the 3rd day and decreased the expression of PDC, ADH,and LDH isozymes by 19.5%, 25.6% and 53.4%, and 26.4%, 26.0% and 28.4% on the 6th and 9th day, respectively. On the 9th day of hypoxia stress, the root growth was inhibited significantly (P<0.05), while the application of EBR alleviated the growth inhibition, as indicated by the significant increase of root length, dry weight, and root tips (P<0.05). These results indicated that hypoxia stress inhibited the root growth of cucumber seedlings, whereas EBR could alleviate the inhibitory effect of hypoxia stress via regulating the isozyme expression of anaerobic respiration enzymes in seedling roots.

Key words: Caragana intermedia Rhizobia, Diversity, Resistance