Drought tolerance in maize through altered root system architecture

Photo: Maize. Pixabay, CC0 Public Domain.

Under drought conditions, the hypothetical steep, cheap and deep ideotype of maize would be expected to do best, and in a stand-out paper in Journal of Experimental Botany, Yingzhi Gao and Jonathan Lynch describe critical experiments to demonstrate that this holds true. Frank Hochholdinger puts these findings into context for the non-specialist in his Insight article in the same issue, and reflects on ways in which research on roots can catch up with other areas. 

Reduced crown root number improves water acquisition under water deficit stress in maize (Zea mays L.)

Untapping root system architecture for crop improvement

Gao and Lynch focused on the crown roots, which make up the bulk of the maize rootstock – these emerge from the shoot, and vary hugely in number (25–62 among the genotypes considered) and soil penetration. Various parameters were tested in different conditions – including, in the simplified mesocosm environment, stomatal conductance, leaf and net canopy CO2 assimilation, and shoot biomass; and in the more-complex field environment, stem water oxygen isotope enrichment (δ18O) signature, leaf relative water content, shoot biomass at anthesis and yield. Both types of study confirmed that, among the various combinations possible, it was an intermediate number of these roots growing deep to access scarce water which performed best under limited water availability.

Discussing the work, Frank Hochholdinger notes: ‘An intermediate number of crown roots is essential for the superior performance of plants. If the number of these roots is too low, plants become susceptible to lodging; if the number is too large, competition for soil and metabolic resources becomes uneconomic.’

He goes on to highlight the significant correlation between crown root number and rooting depth found by Gao and Lynch: ‘This is of particular interest because the specification of crown root number and their subsequent elongation are different developmental processes.’

Interdisciplinary approaches

The work is clearly significant for breeding maize that can be grown successfully in challenging, water-limited environments, and there is certainly a need for more progress in root research. Hochholdinger advocates interdisciplinary approaches, with a vision of obtaining ‘a full understanding of how exogenous signals are translated into cellular responses, and how this knowledge can be implemented into future rootbased increases in plant productivity.’

Read more

Read more about research on roots in the recent Special Issues from Journal of Experimental Botany – From Inspiration to Impact: Delivering Value from Global Root Research and Plant Roots: New Challenges in a Changing World

Journal of Experimental Botany publishes an exciting mix of research, review and comment on fundamental questions of broad interest in plant science. Regular special issues highlight key areas.

Author: Jonathan Ingram