Root traits and taxonomic affiliation of nine herbaceous species grown in glasshouse conditions

Abstract

This study examines whether root traits differed between three major plant families (Asteraceae, Fabaceae and Poaceae) and whether they are related to root respiration and exudation. Nine traits related to biomass allocation, root topology, morphology, chemical composition and mycorrhizal colonisation were examined for nine C 3 herbaceous species grown in controlled conditions. Poaceae differed from Fabaceae for the whole set of root traits examined except mycorrhizal colonisation, while Asteraceae showed intermediate characteristics. As compared to Fabaceae, Poaceae allocated more biomass to roots; showed a more sparsely branched root system with a small average root diameter, a high root dry matter content and a low nitrogen concentration. Root respiration was weakly related to root mass ratio and root dry matter content; no significant relationship was found between root functions and root architecture or morphology. This study shows that plant classification based on taxonomic affiliation reflects differences in root system traits and functions. Whole root system traits do not allow strong predictions of root respiration and exudation, perhaps because these processes are more linked to fine root than to whole root system traits.

Root system variability in common legumes in Central Europe

“…On the other hand, species in the tribes Loteae, Galegeae and Genisteae were all perennial and therefore had relatively low root system variability. The differences between root systems of annuals and perennial species were also recorded by Fitter et al (1988), Gross et al (1992) and Roumet et al (2008).…”

“…Nodulation can be affected by soil salinity and pH, moisture, temperature and nutrient availability (Zahran 1999). In previous studies, the formation of nodules was recorded only when plants were grown in mineral nitrogen-deficient soils (Hirsch 1992), whereas high phosphorus together with high mineral nitrogen availability in the soil suppressed (Truongt & Brix 2009) or entirely inhibited nodulation (Roumet et al 2008). According to Corby (1988), nodule shape is associated with legume taxonomy and can be species-specific (Zahran 1998) or tribe-specific (Rejili et al 2007).…”

“…The root systems of perennials are more randomly branched and have larger diameter roots than annuals (Roumet et al 2006(Roumet et al , 2008. On the other hand, dichotomously branched root systems are more typical in annuals (Gross et al 1993).…”

Root structure–function relationships in 74 species: evidence of a root economics spectrum related to carbon economy

“…Graminoids and eudicots are often considered as contrasting functional groups because they differ in many aspects, such as root morphology and anatomy. Roots of graminoids are fibrous, with no secondary growth, and they generally have thin and Npoor roots compared with eudicots (Craine et al, 2001;Roumet et al, 2006Roumet et al, , 2008. Whether these differences translate into a disparity in root function and whether structure-function relationships are consistent across functional groups remain untested.…”

“…Using standardized methods, we measured specific root respiration (RR) rates and decomposition in controlled conditions (termed decomposability hereafter) together with four fine-root morphological traits (SRL, diameter, proportion of very fine roots with a diameter ≤ 0.2 mm and dry matter content, which is a proxy of tissue density; Birouste et al, 2014) and six chemical traits (N, C, water-soluble compound, hemicellulose, cellulose and lignin concentrations). We hypothesized that: (1) an RES exists in which species that possess thinner roots with a high SRL and a low dry matter content have high N and water-soluble compound concentrations and high respiration and decomposition rates, whereas the opposite pattern is expected for species with thick, dense roots, which are rich in structural compounds such as lignin and cellulose; (2) eudicots and graminoids show opposite patterns along the RES because eudicots are known to have N-rich roots with a high SRL and a lower tissue density compared with graminoids (Craine et al, 2001;Roumet et al, 2008;G. Freschet et al, unpublished); (3) respiration and decomposability covary and are driven by similar traits.…”