The fine root systems of ericaceous plants possess both absorptive fibrous roots and skeletal pioneer roots. This functional differentiation (heterorhizy) can be coupled with a specific mycorrhization pattern, in which fibrous roots form more ericoid mycorrhizas than pioneer roots. However, the behaviors of root-associated fungi on the different individual roots remain largely unknown. We investigated the colonization patterns and root modifications of Leohumicola verrucosa, Oidiodendron maius, and Leptobacillium leptobactrum strains on Vaccinium oldhamii hypocotyl cuttings in vitro. Three putative and true mycorrhizal fungal strains (one L. verrucosa and two O. maius) exhibited typical heterorhizic colonization patterns and tended to increase pioneer root branching. However, a root endophytic fungus (L. leptobactrum) uniformly exhibited a lower colonization across the different roots and did not increase the number of pioneer root branches. The colonization patterns and root modification ability of mycorrhizal fungi may be linked, thereby ensuring sufficient colonization sites.
Water stress such as drought and waterlogging is considered to be a major limiting factor in crop production. Roots play important roles in crop adaptation to water stress. This study aimed to characterize the vertical root distribution patterns and analyze the root-shoot relationships of different cereal species with different water requirements in response to different soil moisture conditions. Sorghum, maize, and rice were grown under 5% w/w soil moisture content (SMC5), 20% w/w soil moisture content (SMC20) and in waterlogged soil (WL) for 35 days using root box pin-board method. For sorghum and maize, the optimal soil water condition was SMC20 which produced the greatest shoot and root growth, while rice had greatest shoot and root growth under WL. Sorghum significantly increased root to shoot ratio in both water stress conditions, suggesting that sorghum prioritizes carbon partitioning of assimilates towards the roots. Although whole root dry weight and total root length were reduced by water stress, vertical distribution of root traits varied with soil water conditions and promoted root response was observed in specific soil layer. A highly positive relationship between root and shoot traits was observed in rice, suggesting that root and shoot trait responses are coupled with changing soil water conditions. Further studies are needed to confirm root architectural changes focusing on different root component traits as well as other root traits related to root architectural structure.