Abstract
Mixed cropping is practised widely in developing countries and is gaining increasing interest for sustainable agriculture in developed countries. Plants in intercrops grow differently from plants in single crops, due to interspecific plant interactions, but adaptive plant morphological responses to competition in mixed stands have not been studied in detail. Here the maize (Zea mays) response to mixed cultivation with wheat (Triticum aestivum) is described. Evidence is provided that early responses of maize to the modified light environment in mixed stands propagate throughout maize development, resulting in different phenotypes compared with pure stands. Photosynthetically active radiation (PAR), red:far-red ratio (R:FR), leaf development, and final organ sizes of maize grown in three cultivation systems were compared: pure maize, an intercrop with a small distance (25cm) between maize and wheat plants, and an intercop with a large distance (44cm) between the maize and the wheat. Compared with maize in pure stands, maize in the mixed stands had lower leaf and collar appearance rates, increased blade and sheath lengths at low ranks and smaller sizes at high ranks, increased blade elongation duration, and decreased R:FR and PAR at the plant base during early development. Effects were strongest in the treatment with a short distance between wheat and maize strips. The data suggest a feedback between leaf initiation and leaf emergence at the plant level and coordination between blade and sheath growth at the phytomer level. A conceptual model, based on coordination rules, is proposed to explain the development of the maize plant in pure and mixed stands.
Highlights
Intercropping is widespread in large parts of China, Africa, and Latin America (Vandermeer, 1989, 2011)
Evidence is provided that early responses of maize to the modified light environment in mixed stands propagate throughout maize development, resulting in different phenotypes compared with pure stands
The aim of this study was to assess the developmental response of maize to the growth conditions in mixed cultivation with wheat
Summary
Intercropping is widespread in large parts of China, Africa, and Latin America (Vandermeer, 1989, 2011). It has important advantages compared with single crop systems: greater crop production per unit land (overyielding) (Li et al, 2007), potential for improved water and nutrient capture (Morris and Garrity, 1993a, b), enhanced pest and disease suppression (Zhu et al, 2000), and overall lower production risks (Rao and Singh, 1990). Plants need to adapt to either tolerate (Gommers et al, 2013) or avoid shading by neighbours (Franklin and Whitelam, 2007). Little is known about the consequences of local adaptation (e.g. enhanced sheath length) on later development
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