The carboxylate‐releasing phosphorus‐mobilizing strategy can be proxied by foliar manganese concentration in a large set of chickpea germplasm under low phosphorus supply

Abstract

Summary Root foraging and root physiology such as exudation of carboxylates into the rhizosphere are important strategies for plant phosphorus (P) acquisition. We used 100 chickpea (Cicer arietinum) genotypes with diverse genetic backgrounds to study the relative roles of root morphology and physiology in P acquisition. Plants were grown in pots in a low‐P sterilized river sand supplied with 10 μg P g−1 soil as FePO4, a poorly soluble form of P. There was a large genotypic variation in root morphology (total root length, root surface area, mean root diameter, specific root length and root hair length), and root physiology (rhizosheath pH, carboxylates and acid phosphatase activity). Shoot P content was correlated with total root length, root surface area and total carboxylates per plant, particularly malonate. A positive correlation was found between mature leaf manganese (Mn) concentration and carboxylate amount in rhizosheath relative to root DW. This is the first study to demonstrate that the mature leaf Mn concentration can be used as an easily measurable proxy for the assessment of belowground carboxylate‐releasing processes in a range of chickpea genotypes grown under low‐P, and therefore offers an important breeding trait, with potential application in other crops.

Plasticity in root symbioses following shifts in soil nutrient availability during long‐term ecosystem development

“…Acacia rostellifera foliar Mn increased with soil age in all soil treatments, and this trend was particularly strong in the “field soil” as soil P declined. Increase in foliar Mn is consistent with greater reliance on carboxylates for P acquisition in P‐poor soils (Abrahão, Ryan, Laliberté, Oliveira, & Lambers, ; Lambers et al., ; Pang et al., ). Interestingly, this trend remained in the average and specific inoculum soil treatments suggesting that specific fungi may have led to increased carboxylate exudation.…”

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

“…Typical root morphological strategies include vigorous root branching, high specific root length, and increased frequency and length of root hairs; together, these result in a larger volume of soil being explored (Vance et al ., ; Postma et al ., ; Haling et al ., ). Additionally, plants can also employ root physiological or P‐mining strategies such as increased carboxylate, phosphatase and proton release (termed P‐mobilizing exudates here) into the rhizosphere to mobilize sparingly soluble inorganic and organic P (Hinsinger et al ., ; Richardson et al ., ; Pang et al ., ). Furthermore, P deficiency can also induce establishment of symbioses with arbuscular mycorrhizal fungi (AMF); the external hyphae of AMF can access P from the labile inorganic soil P pool beyond root P‐depletion zones, and explore micropores that roots or even root hairs cannot enter (Clark & Zeto, ; Smith et al ., ; van der Heijden et al ., ).…”

Vellozioid roots allow for habitat specialization among rock‐ and soil‐dwelling Velloziaceae in campos rupestres

“…Community‐weighted manganese concentrations [Mn] in mature leaves can be used as a proxy for nutrient‐acquisition strategies (Lambers, Hayes, Laliberté, Oliveira, & Turner, ), because carboxylates release both soil P and soil‐bound Mn (Lambers, Chapin, & Pons, ; Lambers et al, ). As a result, carboxylate‐releasing plants accumulate Mn in leaves (Gardner & Boundy, ; Lambers et al, ; Pang et al, ). Conversely, AM fungi intercept Mn, decreasing leaf [Mn] in host plants (Kothari, Marschner, & Römheld, ).…”