Interspecific Root Recognition Driven by Root Exudates in Intercropping: From Field Phenominen to Processes

Experimental evidence suggests that root-root interactions among plant species can greatly affect plant productivity in natural and agricultural ecosystems. Studies have showed that root-root interactions were driven by limiting or increasing the access of neighboring plants to nutrient pools in soils. Beyond these nutrient-driven root interactions, plant roots can directly respond to the identity of neighbor plant species. We use a sequence of five greenhouse experiments to investigate (1) root-root recognitions between maize (Zea mays L.) and wheat (Triticum aestivum L.), barley (Hordeum vulgare L.) and maize plants, and (2) the role of specific root exudates from wheat. Maize roots tend to avoid wheat roots, but not to avoid barley or maize roots. Similar responses could be induced by adding either the root exudates of wheat to maize or 6-Methoxy-benzoxazolin-2-one (MBOA) in particular. We demonstrate how root-root recognition leads to avoidance of maize roots towards neighboring wheat, and provide an evidence that this response is caused by a specific component of wheat root exudates (i.e. MBOA). Our findings may have far reaching implications for the sustainability of cereal/cereal intercropping systems, which aim to maximize food production by enhancing plant species diversity.