Root morphological responses to localized nutrient supply differ among crop species with contrasting root traits

Roots have morphological plasticity to adapt to heterogeneous nutrient distribution in soil, but little is known about crop differences in root plasticity. The objective of this study was to evaluate root morphological strategies of four crop species in response to soil zones enriched with different nutrients. Four crop species that are common in intercropping systems [maize (Zea mays L.), wheat (Triticum aestivum L.), faba bean (Vicia faba L.), and chickpea (Cicer arietinum L.)] and have contrasting root morphological traits were grown for 45 days under uniform or localized nitrogen and phosphorus supply. For each species tested, the nutrient supply patterns had no effect on shoot biomass and specific root length. However, localized supply of ammonium plus phosphorus induced maize and wheat root proliferation in the nutrient-rich zone. Localized supply of ammonium alone suppressed the whole root growth of chickpea and maize, whereas localized phosphorus plus ammonium reversed (maize and chickpea ) the negative effect of ammonium. The localized root proliferation of chickpea in a nutrient-rich zone did not increase the whole root length and root surface area. Faba bean had no significant response to localized nutrient supply. The root morphological plasticity is influenced by nutrient-specific and species-specific responses, with the greater plasticity in graminaceous (eg. maize) than leguminous species (eg. faba bean and chickpea).