Effects of water stress on chlorophyll fluorescence and growth of Rorippa amphibia: a well-adjusted invasive plant in China

Studying photosynthetic and growth-related characteristics of invasive plants under water stress is an important way to reveal their biological invasiveness. Rorippa amphibia native to Europe has invaded extensively the Liaoning Province, China, in recent years. Rorippa amphibia was cultured under waterlogging (flooded 2 cm over the soil surface), wet (25 similar to 30%, which means the soil water content corresponding to this treatment is 25 similar to 30% and the same goes for the following), CK (15 similar to 20%), or drought (5 similar to 10%) conditions in Shenyang for 1 month. Afterward, the chlorophyll fluorescence and growth indexes were measured. The results showed that in drought treatment, the V-J, V-K, M-0, Sm, phi Do and DI0/RC were significantly higher than CK, while Fm, Fv/Fo, Psi o, phi Po and PIABS declined significantly. In waterlogging treatment, only V-J increased significantly and Fm, Psi o, phi Eo, ET0/RC and PIABS decreased significantly. However, no significant difference between wet treatment and CK was found in chlorophyll fluorescence. Waterlogging, wet and CK treatments were conducive to Rorippa amphibia growth, while drought treatment harmed its growth. But some growth indexes including total leaf number and fresh and dry weight per leaf were higher than CK and root length, and fresh and dry weight of underground part and root-weight ratio increased with the decrease of soil water gradients. Rorippa amphibia showed a good performance under waterlogging and wet conditions, and it could also adapt to drought stress by adjustment of biomass allocation between the aboveground and underground parts. This may be the mechanism by which Rorippa amphibia successfully invades different habitats.