Effects and mechanism of paclobutrazol on drought resistance of Phyllostachys edulis seedlings

To reveal the mechanism of paclobutrazol (PP₃₃₃) on drought resistance of Phyllostachys edulis seedlings, we set the PP₃₃₃ concentrations with 0 and 40 mg/L and the relative water contents with 30% (drought stress) and 70% (normal water supply), and a total of four treatments in pot experiments. Membrane lipid peroxidases and the activities of antioxidant enzymes and contents of osmotic adjustment substances were determined at the 7th, 14th and 21st days under the drought stress, and the determination of height increment of seedlings, total biomass and leaf relative water content were conducted at the 21st day under the drought stress. The results showed that compared with the normal water supply, drought stress significantly reduced the height increment, total biomass, leaf relative water content, and the activities of catalase (CAT) and peroxidase (POD), but significantly increased the root shoot ratio, malondialdehyde (MDA) content, proline (Pro) content and superoxide dismutase (SOD) activity of P. edulis seedlings. Under the drought stress, the application of PP₃₃₃ significantly reduced the seedling height increment to the lowest value of 1.50 cm, while the root shoot ratio reached the maximum value of 1.35. The application of PP333 could significantly reduced MDA content and improved the leaf relative water content, proline content, and the activities of SOD, POD and CAT. Under the normal water supply condition, the effect of PP₃₃₃ was similar to that under the drought stress, while its efficacy was poor than that of the latter. In conclusion, the application of PP₃₃₃ can increase the relative water content, root shoot ratio, osmotic adjustment substance (Pro) content and antioxidant enzyme activities, and decrease the MDA content to improve the drought resistance of P. eduli seedlings.