Effects of waterlogging on some chemicals and antioxidant responses in Zanthoxylum armatum DC. seedlings

Zanthoxylum armatum DC. (Z. armatum), known as the prickly ash or toothache tree, shows higher productivity and interesting agronomic features for spices, oilseeds and medicinal values. Waterlogging is one of the major stresses restricting the growth, development and production of Z. armatum in Southwest China due to flash rainfall and floods. However, the effects of waterlogging stress on the growth and antioxidant responses in Z. armatum seedlings have not been reported. In this study, the physiological responses in Z. armatum seedlings were investigated under waterlogging with different depths (2.7, 5.5, 11 cm above the ground level) and durations (2, 4 and 6 days). No significant differences in the averages of height, stem diameter and number of leaves were observed. However, the apical leaflets of seedlings that were submerged to a depth of 11 cm above the ground become soft on day 6. Chlorophyll and malondialdehyde (MDA) content rose significantly with the waterlogging levels on different treatment days compared to the control. There were no significant differences in the relative electrical conductivity between the control and treatments on day 2, but the values of the treatment groups were higher than those of in the control on days 4 and 6. The generally increased content of soluble sugar and soluble proteins within a small range with prolonged duration of the stress showed little differences between waterlogging stress and the controls. Superoxide dismutase (SOD) and peroxidase (POD) activity showed different changes in different tested groups at different treatment times, as compared with controls. The morphological and physiological characteristics had different responses to stress duration and waterlogging degree as well as their interactions. These findings were strong evidence that these plants may develop strategies and have a certain tolerance to short-term waterlogging, especially mild waterlogging.