Plant Age and Soil Texture Rather Than the Presence of Root Hairs Cause Differences in Maize Resource Allocation and Root Gene Expression in the Field

Abstract

Understanding the biological roles of root hairs is key to projecting their contributions to plant growth and to assess their relevance for plant breeding. The objective of this study was to assess the importance of root hairs for maize nutrition, carbon allocation and root gene expression in a field experiment. Applying wild type and root hairless rth3 maize grown on loam and sand, we examined the period of growth including 4-leaf, 9-leaf and tassel emergence stages, accompanied with a low precipitation rate. rth3 maize had lower shoot growth and lower total amounts of mineral nutrients than wild type, but the concentrations of mineral elements, root gene expression, or carbon allocation were largely unchanged. For these parameters, growth stage accounted for the main differences, followed by substrate. Substrate-related changes were pronounced during tassel emergence, where the concentrations of several elements in leaves as well as cell wall formation-related root gene expression and C allocation decreased. In conclusion, the presence of root hairs stimulated maize shoot growth and total nutrient uptake, but other parameters were more impacted by growth stage and soil texture. Further research should relate root hair functioning to the observed losses in maize productivity and growth efficiency.

Root cap is an important determinant of rhizosphere microbiome assembly

“…Plant gene expression indicates roles of jasmonate and ethylene signals triggered by immune response and suggests pleiotropic effects on microbiome assembly through the expression of genes related to ROS signaling and flavonoid production. As the absence of root hairs caused an extremely low impact on root gene expression, in this experiment as well as in earlier studies (Ganther et al ., 2021, 2022), and the plants were not grown under nutrient deficiency that could potentially enhance their dependency on root hairs (Bienert et al ., 2021), pleiotrophic effects by the rth3 mutation appear unlikely.…”

The spatial distribution of rhizosphere microbial activities under drought: water availability is more important than root‐hair‐controlled exudation

“…In addition to the differences in the root hairs between the rth3 mutant and the wild‐type, less soil adhered to the root system of the rth3 mutant when grown under field conditions, the rth3 mutant had problems in organizing the newly synthesized cellulose (Hochholdinger et al ., 2018) and showed reductions in the grain yield, while the mutant phenotype remained stable under field conditions (Hochholdinger et al ., 2008). However, lack of root hairs had only a minor effect on root gene expressions (Ganther et al ., 2022). For a detailed description of the root‐hair‐defective rth3 mutant, refer to Hochholdinger et al .…”