Fig. 2

Effect of population density on biomass allocation of two ragweed organs at different growth stages (Mean ± SE). a, b A. artemisiifolia.; c, d A. trifida. Different lowercase letters indicate significant differences in relative organ biomass at the same population density across growth stages (P < 0.05), while different uppercase letters indicated significant differences in relative organ biomass across different densities during one growth stage (P < 0.05)