Effects of species and soil‐nitrogen availability on root system architecture traits – study on a set of weed and crop species

Abstract

Better managing crop : weed competition in cropping systems while reducing both nitrogen and herbicide inputs is a real challenge that requires a better understanding of crop and weed root architecture in relation to soil-nitrogen availability. An original approach was used which considered the parameters of a simulation model of root architecture as traits to analyse (a) the interspecific diversity of root system architecture, and (b) its response to soil-nitrogen availability. Two greenhouse experiments were conducted using three crop and nine weed species grown at two contrasted concentrations of soil-nitrogen availability. Plant traits were measured to characterise both overall plant growth and root architecture, with a focus on primary root emergence, root elongation and branching. The studied root traits varied among species (from a twofold to a fourfold factor, depending on the trait), validating their use as indicators to analyse the interspecific variability of root architecture. The largest interspecies differences were for two traits: 'maximal apical root diameter' and 'interbranch distance' (distance between two successive laterals on the same root). Conversely, most of the studied root traits varied little with soil-nitrogen availability (from no variation to a 1.1-fold factor, depending on the trait) even though soil-nitrogen availability varied with a 17-fold factor and impacted the overall shoot and root biomass. So, the root traits used in this article are stable whatever soil-nitrogen availability. As they reflect processes underlying root system architecture, this low effect of nitrogen suggests that the rules governing root architecture are little affected by plant nitrogen status and soil-nitrogen availability. We propose that the determinants of differences in root system architecture between soils with contrasted nitrogen availability mainly originate from differences in the amount of carbon allocated to and within the root system. Characterising each plant species by a combination of root traits gave insights regarding the potential species competitive ability for soil resources in agroecosystems.

Genetic Variation in Root Architectural Traits in Lactuca and Their Roles in Increasing Phosphorus-Use-Efficiency in Response to Low Phosphorus Availability

“…Six root traits were investigated: depth, dmax, elong, dmin, DlDm and ibd. These traits form useful descriptors of the root system architecture and its variability and they can summarize the developmental processes (e.g., elongation and branching) as well as the developmental characteristics (e.g., distribution of the root diameters) of roots, as previously shown in other studies that focus on intra-and interspecific root diversity (Pagès, 2014;Pagès and Picon-Cochard, 2014;Bui et al, 2015;Moreau et al, 2017;Salinier et al, 2019). These variables can also be used in modeling approaches such as the one proposed in the Archisimple model, which was elaborated by .…”

Integrating plant-plant competition for nitrogen into a 3D individual-based model simulating the effects of cropping systems on weed dynamics

“…Note that soil-nitrogen availability may affect plant root architecture (Jeudy et al, 2016). However, this effect is mainly mediated by the effect of plant nitrogen nutrition on biomass allocation to roots (Brun et al, 2010;Moreau et al, 2017). So, in accordance with our objective to limit the complexity of our new model version, we considered that modifications of plant root architecture (i.e., the shape and size of the root system envelope and the distribution of root biomass within this envelope) in response to soil-nitrogen availability was entirely mediated by modifications of biomass allocations to roots.…”

Vulpia myuros, an increasing threat for agriculture

“…Vulpia myuros is generally described as having a shallow, but dense root system (Moreau et al ., 2017; Rossiter, 1966). However, in a study presenting a new tool for root monitoring, Jeudy et al .…”

“…Its Ellenberg value for nitrogen classifies it as an indicator species of infertile soils (Hill et al ., 1999; Moreau et al ., 2013). It has been shown to be able to grow with low soil phosphorus concentration, because of its higher phosphate absorption capacity (Scott and Blair, 1987), probably linked to its dense root system (Moreau et al ., 2017). Its dominance is greater in moderately acidic soils (Rossiter, 1966; Hill et al ., 1999).…”