Boron deficiency responses in maize (Zea mays L.) roots

Background: Boron (B) is an essential micronutrient for plants. Dicot plants respond to insufficient B supply by altering root architecture and root hair growth. How root systems of rather low-B demanding monocot species such as maize (Zea mays L.) respond to B deficiency in terra has not been experimentally resolved, yet.Aims: The study aims to investigate root responses and their physiological consequences under B deficiency during the vegetative growth of maize.Methods: B73 wild-type (WT) maize and its root hairless rth3 mutant were grown under varying B supply conditions in soil columns and in an automated root phenotyping facility. Biomass data, root system architecture traits, the mineral elemental composition and molecular B-deficiency responses were quantified.Results: Though having very low leaf B concentrations, no major growth deficit, apart from chlorotic stripes on leaves, was recorded on maize root and shoot development, with or without root hairs, on B-deficient conditions. Although leaf B concentration of the rth3 mutant is significantly lower under B-deficient and under B-surplus conditions compared to the WT, the rth3 mutant neither developed a larger total root length, more fine roots nor displayed a higher expression of B uptake transporters as compensatory adaptations.Conclusions: Strikingly, maize plants did neither react with an inhibited root growth nor by a compensatory root foraging behaviour to severe B-deficient in terra growth conditions. This is rather atypical for plants. The performance and altered leaf B concentrations of rth3 mutants may be biased by secondary effects, such as an overall reduced root growth.

Automated summary

This study investigated the root responses and physiological consequences of maize under boron deficiency. The results showed that maize plants did not inhibit root growth or show compensatory root foraging behavior under boron-deficient conditions. This atypical response provides important information for understanding the root responses of maize to boron deficiency.