Purpose: Laboratory studies have identified fundamental processes and genetic determinants affecting the growth and stress tolerance of maize, yet they ignore complex field conditions where soil and climate variables interact. In this study, we assess the importance of plant development stage, substrate, and root hair formation on field-grown maize in terms of root gene expression and resource allocation, and shoot element status.

Methods: Wild type and root hairless rth3 mutant maize were grown on two substrates, sand and loam and sampled during the 4-leaf, 9-leaf and tassel emergence stages. This period was accompanied with a low precipitation rate. Youngest leaf and whole shoot elemental compositions were assessed by ionome analysis, root gene expression by RNA sequencing and qRT-PCR, and root resource allocation of C and N uptake by stable isotope labeling.

Results: Growth stage accounted for the main differences, followed by substrate and root hair formation in all analyses. Lack of root hairs led to significant impacts on shoot growth and total nutrient uptake, but had only a minor effect on root gene expression and momentary leaf nutritional status. During tassel emergence, the concentrations of several elements in leaves decreased, but nutrient transporter expression in roots increased; whereas cell wall formation-related root gene expression and C allocation to roots decreased.

Conclusion: Our results demonstrate that the presence and function of root hairs are a determinant of maize nutrient acquisition and growth, and provide insight on how maize acclimatizes to different substrates and a longer period of low precipitation.