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.

Highlights

  • Phosphorus (P) is an essential macronutrient for plant growth and metabolism

  • The ANOVA analysis showed that shoot dry weight varied among species depending on differential P supply and soil types (Supplementary Table S1)

  • The general response of shoot dry weight to P application was greater in calcareous soils (CS) than acid soils (AS) (P < 0.01), despite a variation among different plant species

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Summary

Introduction

Phosphorus (P) is an essential macronutrient for plant growth and metabolism. It is a structural element in nucleic acids and membrane phospholipids. P nutrition is a major limiting factor for crop production in many soils due to relatively low P availability because P can be readily adsorbed or fixed by free lime present in some calcareous soils (CS) and by aluminium (Al) and iron (Fe) in acid soils (AS) (Hinsinger, 2001; Shen et al, 2011). Around 70–90% of P applied as fertilizer may become unavailable to plants (Holford, 1997), exacerbating economic losses from fertilizer-P overuse in intensive agriculture (Shen et al, 2011). Improvement of P-acquisition efficiency through mobilizing the residual P accumulated in soil, as well as enhancing root absorbing surface and acquisition capacity for P applied to soil, is critical for sustainable P management and food production (Shen et al, 2011, 2013; Li et al, 2014)

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