Estimating the importance of maize root hairs in low phosphorus conditions and under drought

Ann Bot. 2019 Nov 27;124(6):961-968. doi: 10.1093/aob/mcz011.

Abstract

Background and aims: Root hairs are single-cell extensions of the epidermis that face into the soil and increase the root-soil contact surface. Root hairs enlarge the rhizosphere radially and are very important for taking up water and sparingly soluble nutrients, such as the poorly soil-mobile phosphate. In order to quantify the importance of root hairs for maize, a mutant and the corresponding wild type were compared.

Methods: The rth2 maize mutant with very short root hairs was assayed for growth and phosphorus (P) acquisition in a slightly alkaline soil with low P and limited water supply in the absence of mycorrhization and with ample P supply.

Key results: Root and shoot growth was additively impaired under P deficiency and drought. Internal P concentrations declined with reduced water and P supply, whereas micronutrients (iron, zinc) were little affected. The very short root hairs in rth2 did not affect internal P concentrations, but the P content of juvenile plants was halved under combined stress. The rth2 plants had more fine roots and increased specific root length, but P mobilization traits (root organic carbon and phosphatase exudation) differed little.

Conclusions: The results confirm the importance of root hairs for maize P uptake and content, but not for internal P concentrations. Furthermore, the performance of root hair mutants may be biased by secondary effects, such as altered root growth.

Keywords: Macronutrients; fine roots; micronutrients; phosphate; rhizosphere; water.

MeSH terms

  • Droughts*
  • Phosphorus
  • Plant Roots
  • Soil
  • Zea mays*

Substances

  • Soil
  • Phosphorus