Differential effects of non-structural carbohydrate allocation and C:N:P:K stoichiometry of rapeseed roots in diverse soil environments

The morphology, non-structural carbohydrate (NSC), and ecological stoichiometry of various roots have high degrees of plasticity under varying soil types, thereby conferring plants with ecological strategies for adaptation to heterogeneous soil environments. However, there have been few studies of NSC and stoichiometric characteristics of rapeseed roots in different soil types, particularly the interactive relationship of root morphology, NSC, stoichiometric traits with soil factors. Here, we compared the morphological features, NSC, and C:N:P:K stoichiometry of various roots of rapeseed across four main soils. The results indicated that root biomass, total root length, root surface area, root volume, and average root diameter were the highest in yellow-brown soil (YBS) while the lowest in red soil (RS). In the main root, the soluble sugar (SS), starch (ST), NSC contents, and element accumulation followed a descending order of YBS > alluvial soil (AS) > paddy soil (PS) > RS, while in the lateral and hair roots, the C, N, P, and NSC contents followed an order of YBS > PS > AS > RS. Correlation analysis showed that root P and K contents exhibited positive correlations with root SS, ST, and NSC contents in YBS, AS and RS, while soil N, P, and K contents exhibited substantial positive correlations with root NSC contents. Redundancy analysis revealed that total nitrogen (TN) and soil organic matter (SOM) were common significant limiting factors for the root growth of rapeseed in YBS, AS, and RS, while TN, total phosphorus (TP), and total phosphorus (TK) were significant limiting factors in RS. Based on the above results, it can be recommended that an appropriate amount of nitrogen fertilizer is applied for rapeseed seedlings at early growth stages in YBS, AS and PS, whereas an appropriate amount of NPK fertilizer should be applied in barren RS, which can facilitate the root growth of rapeseed seedlings in the tested soil types. The findings provide a theoretical basis for breeding high-yield rapeseed varieties for different soil types. • The root biomass was the highest in yellow-brown soil while the lowest in red soil. • The non-structural carbohydrates in different root tissues showed similar trends to root biomass. • Soil N, P and K contents were substantially positively correlated with non-structural carbohydrates. • Soil organic matter and total N were two important limiting factors in yellow-brown soil, alluvial soil and paddy soil. • The soil total N, total P and total K were important limiting factors in red soil.