Abstract: The expression of RbohA and RbohD genes in different tissues of Brassica campestris L. cultivars “Longyou 6” and “Tianyou 2” seedlings under different treatments was detected by realtime fluorescence quantitative PCR. The results showed that RbohAandRbohD genes were expressed in roots, stems, leaves, and hypocotyls of both cultivars without tissue specificity. The expression of RbohA and RbohD was induced by different treatments, including low temperature (2 ℃), salt stress (200 mmol·L^-1), and PEG-6000 simulated drought stress. The expression of both genes was higher in “Longyou 6” than in “Tianyou 2”. The expression of RbohA and RbohD genes increased with various degrees in seedlings under exogenous ABA and H₂O₂ treatments. Compared to the treatment of low temperature or salt stress alone, the expression of RbohA andRbohD was significantly decreased in both cultivars when they were pretreated with DPI (NADPH oxidase inhibitor), U0126 (MPKK specific inhibitor) and DMTU (H₂O₂ scavenger) with low temperature or salt stress. Such a result indicated that RbohA and RbohD are important for responses to low temperature, salt, and PEG-6000 simulated drought stress. ABA and H₂O₂ induced the expression of RbohA and RbohD. H₂O₂ and MAP kinase were involved in the induction of RbohA and RbohD gene expression under low temperature and salt stress.

Key words: sap flow, neural network, Populus bolleana, water consumption