Shade avoidance: an integral component of crop-weed competition

• Published in: Weed research Vol. 50; no. 4; pp. 281 - 288
• Main Authors: PAGE, E.R, TOLLENAAR, M, LEE, E.A, LUKENS, L, SWANTON, C.J
• Format: Journal Article
• Language: English
• Published: Oxford, UK Oxford, UK : Blackwell Publishing Ltd 01.08.2010; Blackwell Publishing Ltd; Wiley-Blackwell
• Subjects: Biological and medical sciences; corn; fitness; Fundamental and applied biological sciences. Psychology; harvest index; kernel number; light quality; maize; Parasitic plants. Weeds; Phytopathology. Animal pests. Plant and forest protection; red-to-far-red ratio; Weeds; Zea mays; Light effect; Monocotyledones; Vegetals; Zea mays; light quality; Weed; corn; Red light; Environmental factor; C4-Type; maize; Cereal crop; Spectral data; Harvest index; kernel number; Gramineae; Weed science; fitness; Angiospermae; Interspecific competition; Spermatophyta; Yield component; red-to-far-red ratio
• ISSN: 0043-1737; 1365-3180
• DOI: 10.1111/j.1365-3180.2010.00781.x

Crop-weed competition is comprised of both resource dependent and resource independent processes. While many studies have focused on the role that resource dependant competition plays in reducing crop yields, few have investigated whether resource independent effects may contribute to these losses. In this study, we identify the red-to-far-red ratio as a variable that contributing to resource independent competition and tested the hypothesis that the expression of shade avoidance in response to weeds reduces maize fitness (i.e., kernel number) in the absence of resource dependent competition. Seedlings were grown in a field fertigation system under two light quality environments: an ambient and a low red-to-far-red ratio environment, which were designed to simulate weed-free and weedy conditions respectively. Plants that expressed classic shade avoidance characteristics set fewer kernels per plant and partitioned less biomass to the developing ear. Shade avoidance also doubled the plant-to-plant variability in these yield parameters (i.e., kernel number and harvest index) without affecting the mean or frequency distribution of shoot biomass at maturity. We propose that shade avoidance should be viewed as an integral component of the process of competition. This resource independent response precedes and conditions the crop seedling for the onset of resource dependent competition.