Relationships Between Growth and Competitiveness of Four Annual Weeds

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Abstract
(1) Competitive relationships among Amarantus retroflexus L., Chenopodium album L., Echinochloa crus-galli L. and Solanum nodiforum Jacq. were investigated under field conditions by replacement series experiments. Six complete series, matching each species with all other species, yielded a consistent hierarchy of aggressiveness among the four species. The primary interaction among the species was competition for similar resources. (2) Growth analysis for the four species was performed simultaneously with the competition experiments. Relative growth rate (RGR) did not vary significantly among the four species. However, plant weight and height, Canopy area index (CAI), Root/shoot ratio (R/S), Unit Leaf Rate (ULR), and Leaf Area Ratio (LAR) exhibited significant variation among the species. The parameters other than RGR suggest a general hierarchy that was consistent with the hierarchy obtained in the competition experiment. (3) RGR was poorly correlated with aggressivity (A) of the four species, with all other parameters exhibiting better correlations. The best-fitting linear regression relating competitiveness to growth ability described A as a function of plant weight, ULR, and LAR.