Rice increases phosphorus uptake in strongly sorbing soils by intra‐root facilitation

Abstract

Upland rice (Oryza sativa) is adapted to strongly phosphorus (P) sorbing soils. The mechanisms underlying P acquisition, however, are not well understood, and models typically underestimate uptake. This complicates root ideotype development and trait‐based selection for further improvement. We present a novel model, which correctly simulates the P uptake by a P‐efficient rice genotype measured over 48 days of growth. The model represents root morphology at the local rhizosphere scale, including root hairs and fine S‐type laterals. It simulates fast‐ and slowly reacting soil P and the P‐solubilizing effect of root‐induced pH changes in the soil. Simulations predict that the zone of pH changes and P solubilization around a root spreads further into the soil than the zone of P depletion. A root needs to place laterals outside its depletion‐ but inside its solubilization zone to maximize P uptake. S‐type laterals, which are short but hairy, appear to be the key root structures to achieve that. Thus, thicker roots facilitate the P uptake by fine lateral roots. Uptake can be enhanced through longer root hairs and greater root length density but was less sensitive to total root length and root class proportions.

Root phenotypes for the future

“…This unique form of lateral root, termed an S‐type (for short), is determinate and does not branch but contains many root hairs. In this issue, Kuppe et al (2022) propose that the development of S‐type lateral roots has enabled upland rice to adapt to strongly P sorbing soils. The authors developed a novel rhizosphere model that integrated key rice root architectural (e.g., different root classes) and physiological (e.g., P solubilisation) parameters.…”

Phenotypes and Molecular Mechanisms Underlying the Root Response to Phosphate Deprivation in Plants

“…The gramineous crops have a fibrous root system composed of PR, CRs, LRs, and RHs. Recently, Kuppe et al revealed that, with hairs on the respective root types, the CRs were responsible for 48.8% of the total P uptake, while large LRs and small LRs (<1 cm length and <80 μm diameter) took up 20.6% and 30.6% of the total P uptake, respectively [ 97 ], suggesting that genotypes with more and longer CRs and LRs would be better for adapting to low-Pi soils. One example is the OsPSTOL1 -overexpressing plants harbor larger root systems with more CRs and a higher root dry weight, which enables them to take up not only more Pi but also other nutrients, such as nitrogen and potassium, providing more nutrients for growth and yield [ 98 , 99 ].…”

Harnessing belowground processes for sustainable intensification of agricultural systems

“…Santi and Schmidt ( 2009 ) did not only decipher the underlying molecular mechanisms of Fe-deficiency induced proton release in Arabidopsis , they also reported differences in acidification capacity among Arabidopsis accessions indicating a genotypic diversity in Fe acquisition efficiency that is linked to the extent of rhizosphere acidification in all non-grass species (strategy I). Nutrient deficiency induced rhizosphere acidification (Nussaume et al 2011 ; Xu et al 2012 ; Yan et al 2002 ) but also alkalinization (Kuppe et al 2022 ) has also been reported upon P starvation and considerable acidification is typically found in the rhizosphere of N 2 fixing legumes (Marschner and Römheld 1983 ). Intercropping with legumes therefore might not only improve N nutrition in the co-crop but can also have a positive effect on P and micronutrient uptake (Gunes et al 2007 ).…”