Effects of drought and rewatering on growth and physiology characteristics of Wedelia chinensis and Wedelia trilobata.
Objective: This experiment was conducted to examine effects of drought and rewatering on growth, osmotic adjustment substances and antioxidant enzymes parameters of native Wedelia chinensis and alien invasive W. trilobata to explore ecological adaptability mechanism of these two species under drought stress. This study provides basis for the inhibition of W. trilobata invasion. Method: The cutting seedlings of these two species were selected to investigate growth index, chlorophyll content, soluble sugar, soluble protein,as well as activities of antioxidant enzymes including superoxide dismutase (SOD), peroxidase (POD), catalase (CAT) and ascorbate peroxidase (APX) after 15 days of natural drought and 3 days of rewatering. Result: (1) Drought treatment caused decreases in plant height, single leaf area, and total biomass, and increases in root-to-shoot ratio of these two species. Plant height, single leaf area and total biomass of W. chinensis were significantly higher than those of W. trilobata, but the ratio of root to shoot of W. chinensis was significantly lower than that of W. trilobata. After rewatering, plant height, single leaf area, and total biomass increased in both species, while the ratio of root to shoot decreased. Plant height, single leaf area and total biomass of W. trilobata increased faster, and the root-to-shoot ratio of W. trilobata decreased more significantly. However, there was no significant difference between indicators of W. chinensis and W. trilobata.(2) Drought caused significant increases in chlorophyll a, total chlorophyll, and chlorophyll a/b in W. chinensis, but they decreased significantly in W. trilobata. After rewatering, chlorophyll indexes of W. chinensis decreased and recovered to normal level of the control treatment. Conversely, chlorophyll indexes increased in W. trilobata(except for chlorophyll b content), and Chla/b in W. trilobata was significantly higher than in W. trilobata.(3) Soluble protein and soluble sugar contents of both species increased under drought treatment, and decreased under rewatering. Although contents of the two osmotic adjustment contents in W. trilobata recovered to normal level after rewatering, they were significantly lower in W. trilobata than in W. chinensis.(4) Activities of antioxidant enzymes (SOD,POD, CAT and APX) of W. chinensis increased first under drought treatment, and then decreased under rewatering. SOD, CAT and POD activities quickly recovered to normal level after rewatering, which inhibited the increase of MDA content. Activities of SOD, POD and APX of W.trilobata increased first under drought treatment, while decreased under rewatering, and CAT activity had opposite trend. After rewatering, only POD and APX activities recovered to normal level. Conclusion: The invasive W. trilobata had better recovery after rewatering, but it had worse drought tolerance than W.chinensis.It is suggested to control soil water content to inhibit W. trilobata growth in the management of green space.