Tradeoffs among root morphology, exudation and mycorrhizal symbioses for phosphorus‐acquisition strategies of 16 crop species

Abstract

Summary Plant roots exhibit diverse root functional traits to enable soil phosphorus (P) acquisition, including changes in root morphology, root exudation and mycorrhizal symbioses. Yet, whether these traits are differently coordinated among crop species to enhance P acquisition is unclear. Here, eight root functional traits for P acquisition were characterized in 16 major herbaceous crop species grown in a glasshouse under limiting and adequate soil P availability. We found substantial interspecific variation in root functional traits among species. Those with thinner roots showed more root branching and less first‐order root length, and had consistently lower colonization by arbuscular mycorrhizal fungi (AMF), fewer rhizosheath carboxylates and reduced acid phosphatase activity. In response to limiting soil P, species with thinner roots showed a stronger response in root branching, first‐order root length and specific root length of the whole root system, Conversely, species with thicker roots exhibited higher colonization by AMF and/or more P‐mobilizing exudates in the rhizosheath. We conclude that, at the species level, tradeoffs occur among the three groups of root functional traits we examined. Root diameter is a good predictor of the relative expression of these traits and how they change when P is limiting.

The genetic architecture of host response reveals the importance of arbuscular mycorrhizae to maize cultivation

“…In wild species, host response appears to be centered around neutral commensalistic interactions, with equal occurrence of parasitism and mutualism (Klironomos, 2003). A range of host response is also seen in crop plants (Wen et al, 2019). In sorghum, a close relative of maize, host response varies from positive to negative depending on both the plant variety and the AMF species (Ramírez-Flores et al, unpublished observations;(Watts-Williams et al, 2019).…”

Root trait plasticity and plant nutrient acquisition in phosphorus limited soil

“…An increased AFRD will: (1) provide more root volume to be colonized by AMF (Reinhardt and Miller, 1990), (2) increase root longevity (Eissenstat, 1992;Comas et al, 2014), which is beneficial to maintain the active exchange of nutrients and C between AMF and roots, (3) increase the root surface area for a given unit of root length in rth3 versus WT maize (Haling et al, 2013), and (4) reduce the metabolic costs such as root respiration in rth3 maize (Lynch and Ho, 2005). Very recently, Wen et al (2019) showed that PHO activity and carboxylates amount increased with increasing root diameter under soil P limitation. Such plastic responses of roots (increased AFRD and AMF colonization) are complementary to increase plant P acquisition, which is also a case in the present study.…”

Innovations of phosphorus sustainability: implications for the whole chain

“…The first one is the spatial availability. Root growth and mycorrhizal association affect the spatial availability and acquisition of P [31] . Plants are able to respond to P deficiency by changing their root architecture.…”

“…Plant roots interact closely with soil microorganisms that enhance nutrient acquisition (e.g., AMF) and with pathogens that cause root necrosis or plant death [31,48,49] . Root and rhizosphere microbiomes, as part of the extended plant genome, are key determinants of plant health and productivity [50][51][52] .…”