Shade avoidance: an integral component of crop–weed competition

Abstract

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.

Competitividade relativa de cultivares de arroz irrigado com Aeschynomene denticulata

“…This trend in relation to height is probably associated with the plant strategy to capture more light, thereby forming stems with longer internodes in the case of rice and more etiolated stems in the case of joint-vetch, with lower investment of energy for growth and development. This is because light is the main limiting resource in the community (Almeida & Mundstock, 2001), with a key role in the initial response of a plant with higher competitive potential (Galon et al, 2011;Page et al, 2010). In wheat, Agostinetto et al (2008) and Rigoli et al (2008) registered an increase in the height of the plants when in competition with ryegrass or radish.…”

Interação competitiva de genótipos de arroz e papuã

“…Provavelmente, o menor prejuízo da interação, no tocante à estatura das plantas, esteja associado à estratégia da planta para captar mais luminosidade, o que leva à formação de colmos mais longos, com menor investimento de energia para o perfilhamento e para o desenvolvimento de AF ou MS (Galon et al, 2011). Convém destacar que a luz é o principal recurso limitado na comunidade e desenvolve papel importante na resposta inicial de uma planta com maior potencial competitivo (Page et al, 2010).…”

Competitive Ability of Lettuce with Ryegrass1

“…Probably, this fact is connected to the strategy of the plant to capture more luminosity, which leads to the formation of longer stems, with lower energy investment to develop the leafs, leaf area and dry mass (Galon et al, 2011). It is noteworthy that light is the main limited resource in the community and it has an important role for the initial response of a plant with higher competitive potential (Page et al, 2010). Studying the interference periods in lettuce, Machado et al (2009) observed a reduction on NL when in competition with weeds during the entire culture cycle.…”