Interactions between root hairs and the soil microbial community affect the growth of maize seedlings

Root hairs are considered important for rhizosphere formation, which affects root system functioning. Through interactions with soil microorganisms mediated by root exudation, root hairs may affect the phenotypes and growth of young plants. We tested this hypothesis by integrating results from two experiments: (1) a factorial greenhouse seedling experiment with Zea mays B73-wt and its root-hairless mutant, B73-rth3, grown in live and autoclaved soil, quantifying 15 phenotypic traits, seven growth rates, and soil microbiomes and (2) a semi-hydroponic system quantifying root exudation of maize genotypes. Possibly as compensation for lacking root hairs, B73-rth3 seedlings allocated more biomass to roots and grew slower than B73-wt seedlings in live soil, whereas B73-wt seedlings grew slowest in autoclaved soil, suggesting root hairs can be costly and their benefits were realized with more complete soil microbial assemblages. There were substantial differences in root exudation between genotypes and in rhizosphere versus non-rhizosphere microbiomes. The microbial taxa enriched in the presence of root hairs generally enhanced growth compared to taxa enriched in their absence. Our findings suggest the root hairs' adaptive value extends to plant-microbe interactions mediated by root exudates, affecting plant phenotypes, and ultimately, growth. An experiment with seedlings of Zea mays B73 and its root-hairless mutant (Z. mays B73-rth3) with contrasting soil microbiomes showed that root hairs are beneficial towards plant growth but can be costly. Root hairs' adaptive value was partly mediated by plant-microbe interactions involving exudates, which feedback to plant phenotypes and growth.

Automated summary

Root hairs play a crucial role in rhizosphere formation and root system functioning. They affect plant phenotypes and growth through interactions with soil microorganisms mediated by root exudation. Root hairs can be costly but their benefits are realized with more complete soil microbial assemblages. Root exudation and the presence of root hairs have significant effects on plant-microbe interactions and ultimately, plant growth.