Major Crop Species Show Differential Balance between Root Morphological and Physiological Responses to Variable Phosphorus Supply

Abstract

The relationship between root morphological and physiological responses to variable P supply in different plant species is poorly understood. We compared root morphological and physiological responses to P supply in seven crop species (Zea mays, Triticum aestivum, Brassica napus, Lupinus albus, Glycine max, Vicia faba, Cicer arietinum) treated with or without 100 mg P kg-1 in two soils (acidic and calcareous). Phosphorus deficiency decreased root length more in fibrous root species (Zea mays, Triticum aestivum, Brassica napus) than legumes. Zea mays and Triticum aestivum had higher root/shoot biomass ratio and Brassica napus had higher specific root length compared to legumes, whereas legumes (except soybean) had higher carboxylate exudation than fibrous root species. Lupinus albus exhibited the highest P-acquisition efficiency due to high exudation of carboxylates and acid phosphatases. Lupinus albus and Cicer arietinum depended mostly on root exudation (i.e., physiological response) to enhance P acquisition, whereas Zea mays, Triticum aestivum and Brassica napus had higher root morphology dependence, with Glycine max and Vicia faba in between. Principal component analysis using six morphological and six physiological responses identified root size and diameter as the most important morphological traits, whereas important physiological responses included carboxylate exudation, and P-acquisition and P-utilization efficiency followed by rhizosphere soil pH and acid phosphatase activity. In conclusion, plant species can be grouped on the basis of their response to soil P being primarily via root architectural or exudation plasticity, suggesting a potential benefit of crop-specific root-trait-based management to cope with variable soil P supply in sustainable grain production.

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

“…These results suggest that two contrasting plant strategies exist between species with thinner and thicker roots (i.e. opportunistic vs conservative strategies), thin‐root species preferentially modifying the root growth to improve the efficiency of soil exploration in response to resource (P)‐limited conditions (Liu et al ., ; Lyu et al ., ; Zhang et al ., ; Ma et al ., ).…”

“…Case studies have provided valuable insights through comparison of the root responses of crop species to varying P supply. Some crops, such as maize ( Zea mays ) and wheat ( Triticum aestivum ), show stronger root morphological responses than physiological responses to P deficiency (Lyu et al ., ; Deng et al ., ; Wen et al ., ). Other crops, such as faba bean ( Vicia faba ) and Chickpea ( Cicer arietinum ), exhibit a poor root morphological response to changing P supply, but a significant modification in root exudation (Liu et al ., ; Lyu et al ., ; Zhang et al ., ).…”

“…Some crops, such as maize ( Zea mays ) and wheat ( Triticum aestivum ), show stronger root morphological responses than physiological responses to P deficiency (Lyu et al ., ; Deng et al ., ; Wen et al ., ). Other crops, such as faba bean ( Vicia faba ) and Chickpea ( Cicer arietinum ), exhibit a poor root morphological response to changing P supply, but a significant modification in root exudation (Liu et al ., ; Lyu et al ., ; Zhang et al ., ). Increasing P application markedly decreases arbuscular mycorrhizal (AM) colonization of Z. mays and T. aestivum roots (Teng et al ., ; Deng et al ., ), but a slight suppression in V. faba roots (Tang et al ., ).…”

“…This experimental evidence indicates potential coordination or tradeoffs among diverse root functional traits in response to low P among crop species; as a result, species may exhibit distinct below‐ground strategies to enhance P acquisition. However, most studies focused on independent changes or pairwise combinations of root morphology, exudation and mycorrhizal symbioses with a limited number of crop species (Brown et al ., ; Lyu et al ., ; Deng et al ., ; Wen et al ., ). Thus, it is necessary to examine the three groups of root functional traits simultaneously across a large number of crop species.…”

Phosphorus leaching from riparian soils with differing management histories under three grass species

“…This can increase P mobilization into soil solution through a range of mechanisms and/or cause inorganic P to become immobilized within the microbial biomass in organic form (Dinkelaker, Mheld, & Marschner, 1989;Hinsinger, 2001;Richardson et al, 2009a). Even though farmers apply fertilizer to increase the supply of P to the soil solution, plants still release exudates, albeit sometimes at lower rates (Lyu et al, 2016;Ratnayake, Leonard, & Menge, 1978). If by the action of its roots, a plant mobilizes more soil P into solution than it needs or has the ability to take up during growth, then excess P could Core Ideas • Mobilization of soil P by plants could contribute to P leaching.…”