Modelling rice roots reveals how to pick up phosphorus

Farmers growing upland rice face a couple of challenges, limited supplies of water and phosphorus (P). Pieterjan De Bauw and colleagues have been working on models to see what root traits help rice take up phosphorus from the soil. Their results could help farmers where upland rice is grown, in Asia, Africa and Central America.

To help build the models, the team first got data through growing rice in columns, so they could observe root growth. There were three different conditions, with deficient, suboptimal, non-limiting concentrations of phosphorus in the soil. The team grew the plants in varying conditions and then harvested them. The shoots were then examined for P concentration, but the roots underwent a different process.

“Immediately after removing the shoot, the soil cylinder was carefully taken out of the pot and precisely cut into three segments. One part comprised a segment (A) from 0 to 15 cm depth which included the ‘shallow roots’; another segment (B) comprised soil from 15 to 30 cm depth including the ‘intermediate roots’; and the last segment incorporated the ‘deep roots’ below a depth of 30 cm,” write the authors in their article.

The roots were then carefully examined using “shovelomics” to assess their traits. This provided the data to use CRootBox to create a functional structural-model of the plant roots.

“Multiple single root phenes (e.g. the number of nodal roots, nodal radius, lateral density, etc.) all contribute to the performance of a root system, but the utility of a root phene depends on other phenes, which can be either synergistic or antagonistic. Therefore, functional-structural modeling is the most practical approach to assess the large number of root phene interactions with other phenes or environmental variables… This work demonstrated how multiple co-occurring root phene responses can be integrated in CRootBox,” write De Bauw and colleagues.

The team of botanists found that the key to picking up phosphorus was in the root tips. “Quantification of the contribution of root types to both P and water uptake revealed the most relevant root characteristics enhancing low P and/or drought tolerance. The S-type roots are important for P uptake, but the L-types and their branches additionally improve water uptake under drying periods, hence potentially contributing to the combined tolerance against drought and P deficiency in soils for upland rice.”