Abstract: By using open-top chamber (OTC), this paper studied the effects of simulated warming on the growth and reproduction investment of invasive plant Plantago virginica during its growth season in 2012, with the plant height, root length, leaf number, length, and width, inflorescence number and length, biomass allocation pattern, and reproduction traits investigated. As compared with the control, simulated warming increased the plant height of P. virginica significantly by 38%, but decreased the root length. The leaf number of P. virginica in OTC group increased at its early growth stage, but reduced to less than that of the control at medium growth stage. The leaf length and width and the inflorescence number and length in OTC group increased significantly. Simulated warming increased the total biomass and aboveground biomass while decreased the leaf biomass, but no significant differences were observed between the OTC and CK groups. The root biomass and rootshoot ratio in OTC group decreased significantly. Simulated warming had little effects on the inflorescence number and spikelet biomass, but increased the inflorescence number, total flower number, inflorescence biomass, and peduncle biomass significantly by 17%, 21%, 18%, and 26%, respectively, with the reproduction investment ratio increased by 11%, as compared with the control. There were no significant differences in the seed setting rate and seed size between the OTC and CK groups, but the seed number in the OTC group increased significantly while the thousandkernel weight had a significant decrease. In sum, simulated warming could significantly promote the growth of P. virginica, improve its assimilation products allocated to reproductive organs, increase the numbers of flower and seed, and thus, enhance the reproduction capacity and invasiveness of the invasive plant P. virginica.

Key words: dye tracing, piston flow, infiltration., Loess Tableland, apple orchard, root