Size-dependent growth and the development of inequality in maize, sunflower and soybean.
Links were investigated between allometry of plant growth and dynamics of size structure of well-fertilized, irrigated crops of soybean (Glycine max L.), sunflower (Helianthus annuus L.) and maize (Zea mays L.) grown at standard plant-population densities (D), as in commercial crops (D = 30, 6 and 8.5 plants m-2, respectively), and at high densities (2D). Patterns of size-dependent growth of shoot and seed mass accumulation were distinctly different among species. In soybean and sunflower, non-linear relationships between size and subsequent growth led to strong hierarchical populations in terms of both shoot and seed biomass. Curvilinear (soybean) and sigmoid (sunflower) size-dependent growth determined strongly asymmetrical (soybean) and bimodal (sunflower) frequency distributions of shoot biomass indicating predominantly size asymmetrical competition among individuals. In comparison, a lower plant-to-plant variation coupled with a typical linear allometry of growth to plant size indicated symmetrical two-sided plant interference in maize. Despite the weak development of hierarchies in shoot biomass, a strong inequality in reproductive output developed in crowded populations of maize indicating an apparent breakage of reproductive allometry.
Vega
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Facultad de Agronomía, UBA, Av. San Martín 4453, Buenos Aires, Argentina. clavega@mdp.edu.ar
Sadras
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D018533:Biomass; D005298:Fertility / Q000502:physiology; D006368:Helianthus / Q000254:growth & development; D019684:Magnoliopsida / Q000254:growth & development*; D008954:Models, Biological; D018520:Plant Shoots / Q000254:growth & development; D012639:Seeds / Q000254:growth & development; D013025:Glycine max / Q000254:growth & development; D003313:Zea mays / Q000254:growth & development