Physiological response of the invasive weed Mikania micrantha and the native species Pueraria lobata var. thomsonii to water stress.
Mikania micrantha is the most dangerous invasive weed in South China, due to its harmful effects on natural secondary forest habitats and other habitats. In order to illustrate the possibility of using the native legume Pueraria lobatavar. thomsoniito replace M. micrantha, three water gradients (soil water content <10%, 60-70% and 120-130%) that simulate drought, normal soil water content (as control) and waterlogged conditions, respectively, were established to study the physiological response of these two plant species to drought and waterlogging. Results showed that under drought stress, the total biomass of M. micrantha decreased significantly by 72% as compared to controls. Under waterlogging stress, the total biomass of P. lobata var. thomsonii increased by 16% compared to the control treatment, while M. micrantha decreased by 15%. Under drought conditions, the root-shoot ratio and chlorophyll content of native species P. lobata var. thomsonii were significantly greater than those found in the control (P<0.05); while there were no significant differences in the root-shoot ratio of M. micrantha compared to the control (P>0.05), but the chlorophyll content was significantly higher than that found in the control but lower than the normal level after rewatering. This may be the result of a significant increase in the proline and soluble sugar in P. lobata var. thomsonii. Following waterlogging stress, the malondialdehyde content of P. lobata var. thomsoniiwas approximately 2.1 times higher than the control, while that of M. micrantha was 3 times the control. After soil water content returned to normal levels, the malondialdehyde content of M. micrantha and P. lobata var. thomsoniimaintained high levels, which were 1.72 times and 1.45 times the control group, respectively, indicating that the membrane lipid peroxidation level of P. lobata var. thomsonii was lower than that of M. micranthaas affected by waterlogging. Thus, it was concluded that P. lobata var. thomsonii exhibited better drought and waterlogging tolerance than M. micrantha. The resistance index also confirmed this conclusion. The results provide theoretical support for the control of M. micrantha through replacement by applying the native legume P. lobata var. thomsonii to natural habitats like forest edges or windows in areas of South China.