Characterization of junglerice: growth habit and morphological plasticity determined by population density

Abstract

Background: Numerous studies have described junglerice (Echinochloa colona) competitiveness against crops, but its behavior concerning plant density as an outcome of intraspecific competition has not been well documented. Objective: This study aimed to characterize morphology based on population density and determine the degree of density dependence. Methods: Junglerice was grown in field conditions in a range of densities from 0.25 to 300 plants m -2 . Plant height and width, tillering, aerial dry weight, seed weight, seed number, and hundred-seed weight were determined and related to growth habits by principal components analysis. The variables were fitted to the growth habits using a general linear model. Aerial dry weight, tiller number, seed number, and seed weight per plant (pl -1 ) and per area (m -2 ) were fitted to plant density using non-linear functions. Results: Plants exhibited prostrate habit at 0.25 plants m -2 , semi-prostrate habit at 2-4 plants m -2 , and erect habit at 35 plants m -2 . Prostrate plants displayed a width of 196 cm, a height of 40 cm, 158 tillers per plant, and over 32,000 seeds per plant, whereas erect plants had an average width of 13.7 cm, a height of 114.5 cm, 10 tillers per plant, and approximately 1,700 seeds per plant. The aerial dry matter per area adhered to the law of constant final yield. In contrast, tiller number, seed number, and weight per area had a nonlinear dome-shaped relationship. Conclusions: Junglerice modifies its aerial structures according to population density, showcasing extensive morphological plasticity. This characteristic allows junglerice to adopt different growth habits.