The Effect of Intraspecific Competition on the Growth and Development of Johnsongrass under Greenhouse Conditions

Various levels of intraspecific competition influenced johnsongrass [Sorghum halepense(L.) Pers.] reproduction. Increases in density, from one to eight plants per 20-cm pot, delayed for formation of rhizomes and panicles and reduced the final dry weight accumulation in these reproductive structures under greenhouse conditions. Tillering was delayed by medium density (4 plants per pot) and inhibited by the highest density (8 plants per pot). At all densities, the dry weight accumulation in reproductive structures was associated with a decrease in dry weight of the shoot material. Most of the reproductive effort was in the formation of rhizomes rather than panicles. Crowding of johnsongrass plants delayed the formation of the reproductive structures and reduced their final dry weight.