Root morphology

Soil resources and root morphology

Nitrogen (N) is the quantitatively most important nutrient in cropping systems. However, a considerable N fraction is lost through runoffs with detrimental consequences for the environment and human health. Increasing the plant N uptake by optimizing the degree of root branching for exploring a larger soil volume in search of the mobile nitrate resource may contribute to limit soil leaching.

This research highlights the natural variability of root morphology in Brassicaceae species, especially in the Arabidopsis model and rapeseed crop.

• Arabidopsis model

There is a great deal of genetic variation in root morphological traits among natural Arabidopsis accessions worldwide (Mech Dev 130: 45-53, Nitrogen 3: 444-454). We focused on root hairs, which are key components of the rhizosheath contributing to water and nutrient uptake. In collaboration with Prof C. Vincent (University of Florida, USA), a method was developed to quantify root hairs at the whole root organ level (J Exp Bot 73: 3304-3307). That way, we evaluated the role of root phenes in biomass production and N acquisition in a coreset of Arabidopsis accessions (J Exp Bot 73: 3569-3583). Greater biomass production can be achieved through an increased root system size or specific root hair characteristics. Greater number of root hairs may provide a low-resistance pathway under elevated N conditions, while root hair length may enhance root zone exploration under low N. Root system size correlated positively with high-affinity nitrate uptake, emphasizing the benefits of an exploratory root organ in N acquisition.

• Rapeseed crop

Considerable improvement in input efficiencies is required to achieve the full potential of rapeseed crop, parented with Arabidopsis. We documented a considerable degree of variability in root morphology among commercial cultivars, and a positive relationship between root system size and shoot biomass (Nitrogen 2: 491-505). Furthermore, root morphological traits observed at a young developmental stage in laboratory setups, positively correlated with seed N and protein concentrations measured in the field (Front Plant Sci 7: 70). This supports our premise that optimizing root morphology may lead to greater biomass production or improved nutritional value.

Multiple quantitative genetic approaches for root traits are conducted with large diversity sets, and the identified QTL regions could serve as selection targets for redesigning the root morphology of rapeseed (Physiol Plant 176: e14315).