Abstract
Achieving novel improvements in crop management may require changing interrow distance in cultivated fields. Such changes would benefit from a better understanding of plant responses to the spatial heterogeneity in their environment. Our work investigates the architectural plasticity of wheat plants in response to increasing row spacing and evaluates the hypothesis of a foraging behavior in response to neighboring plants. A field experiment was conducted with five commercial winter wheat cultivars possessing unique architectures, grown under narrow (NI, 17.5 cm) or wide interrows (WI, 35 cm) at the same population density (170 seeds/m2). We characterized the development (leaf emergence, tillering), the morphology (dimension of organs, leaf area index), and the geometry (ground cover, leaf angle, organ spreading, and orientation). All cultivars showed a lower number of emerged tillers in WI compared to NI, which was later partly compensated by lower tiller mortality. Besides, the upper leaf blades were larger in WI. Finally the leaf area index at flowering showed little difference between WI and NI treatments. The rate of leaf emergence and the final leaf number were higher in WI compared to NI, except for one cultivar. Around the start of stem elongation, pseudo-stems were more erect in WI, while around the time of flowering, stems were more inclined and leaves were more planophile. Cultivars differed in their degrees of responses, with one appearing to prospect more specifically within the interrow space in WI treatment. Altogether, our results suggest that altering interrow distance leads to changes in the perceived extent of competition by plants, with responses first mimicking the effect of a higher plant density and later the effect of a lower plant density. Only one cultivar showed responses that suggested a perception of the heterogeneity of the environment. These findings improve our understanding of plant responses to spatial heterogeneity and provide novel information to simulate light capture in plant 3D models, depending on cultivar behavior.
Highlights
Interrow distance is an important aspect of crop management
The choice of row spacing reflects a compromise between optimizing resource capture by plants and practical constraints, such as allowing space between rows for the mechanical control of weeds in organic farming, or use of seeders adapted to no-till practices
Changing row spacing obviously impacts interactions between neighboring plants; such interactions involve competition for resources (Kirby and Faris, 1972; Alzueta et al, 2012), as well as active morphogenetic responses triggered by the perception of neighbors
Summary
Interrow distance is an important aspect of crop management. Generally, the choice of row spacing reflects a compromise between optimizing resource capture by plants and practical constraints, such as allowing space between rows for the mechanical control of weeds in organic farming, or use of seeders adapted to no-till practices. Wheat Architectural Response to Increasing Row-Spacing varies from 12 to 18 cm, whereas it can vary from 35 to 50 cm in organic or no-till farming conditions. These choices are largely empirical, and understanding how row spacing modulates plant growth and the possible genotypic variability in the responses would facilitate the design of new cultural practices. The increase of row spacing at constant density results in a non-isotropic change in density with an increase in the distance between plants of different rows and a decrease within a row, possibly altering the relationship between perception of neighbors and competition for resources. The existence of similar behavioral responses has not been documented for wheat
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