Abstract
Root morphological/physiological modifications are important for phosphorus (P) acquisition of plants under P deficiency, but strategies differ among plant species. Detailed studies on the response of maize roots to P deficiency are limited. Nitrogen (N) form influences root morphology/physiology, and thus may influence root responses to P deficiency. This work investigated adaptive mechanisms of maize roots to low P by comparison with white lupin and faba bean supplied with two N forms. Plants were grown for 7–16 days in hydroponics with sufficient (250 µmol L−1) and deficient P supply (1 µmol L−1) under supply of NH4NO3 or Ca(NO3)2. Plant growth and P uptake were measured, and release of protons and organic acid anions, and acid phosphatase activity in the root were monitored. The results showed that P deficiency significantly decreased shoot growth while increased root growth and total root length of maize and faba bean, but not white lupin. It enhanced the release of protons and organic acid anions, and acid phosphatase activity, from the roots of both legumes but not maize. Compared with Ca(NO3)2, NH4NO3 dramatically increased proton release by roots but did not alter root morphology or physiology of the three species in response to low P. It is concluded that the N form did not fundamentally change root morphological/physiological responses of the three species to P deficiency. Morphological variation in maize and morpho-physiological modifications in white lupin and faba bean were the main adaptive strategies to P deficiency.
Highlights
Low phosphorus (P) availability in the soil is one of the most limiting factors for crop production (Schachtman et al 1998; Lynch 2007)
LP supply did not affect the dry weights of shoot or roots of white lupin at all three harvests irrespective of N form [Table 1; see Supporting Information—Figure S1]
The study demonstrated that root morphological variation was the main adaptive strategy in maize in response to P deficiency under the present condition
Summary
Low phosphorus (P) availability in the soil is one of the most limiting factors for crop production (Schachtman et al 1998; Lynch 2007). Plants have evolved different mechanisms in roots in order to increase P acquisition under P-limiting conditions. These mechanisms include morphological modifications, mycorrhizal symbioses, rhizosphere acidification, release of carboxylates and phosphatases, and upregulation of P transporters (Neumann and Romheld 1999; Raghothama 1999; Hinsinger 2001; Lambers et al 2006).
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