华南几种外来入侵植物对不同氮源的响应

Many studies have shown that exotic plant invasion has the potential to alter N availability in invaded ecosystem, and the increase of soil N facilitates invasion of exotic plants. However, nutritional preference of those plants toNO3- and NH4+ (two major forms of inorganic N in soil) are out of consideration. We chose 4 exotic invasive plants, Mikania micrantha, Ipomoea cairica, Wedelia trilobata and Bidens pilosa in southern China. They were cultured in nutrient solution with different ratios of NO3- : NH4+(100：0、50：50、0：100) to investigate the preference of the four invasive plants to different forms of N. Our results showed that: 1) From the point view of plant growth, the four invasive plants prefer NO3-. And NO3- was beneficial for them to increase root biomass, which could promote nutrient absorption. 2) From the perspective of physiology, net photosynthetic rate (Pn), stomatal conductance (Gs),Transpiration rate (Tr) of the 4 invasive plants increased significantly under NO3- nutrition relative to NH4+ nutrition. Except for Wedelia trilobata, maximal photochemical efficiency (Fv/Fm)、actual photochemical efficiency (ΦPSII)、photochemical quenching coefficient(qP)、chlorophyll a (Chl a)、chlorophyll b (Chlb)、and total chlorophyll (Total Chl) of the other 3 invasive plants under NO3- were significantly higher than those under NH4+. The results indicate that exotic invasive plants may have relatively stronger invasiveness under NO3﹣dominated condition. The native plants preferring to NO3﹣may be used to control the NO3﹣-fed invasive plants under NO3﹣dominated condition, while the native plants preferring to NH4+ may be used to control these invasive plants under NH4+ dominated condition. Further studies concerning nutrient preference or competition would be required to gain an insight into plant invasion and ecological control of invasive plants.