Investigating root architectural differences in lines of Arabidopsis with altered stomatal density using high resolution X-Ray Synchrotron imaging.

Abstract Purpose Freshwater is an increasingly scarce natural resource, essential for agricultural production. As plants consume 70% of the world’s freshwater, a reduction in their water use would greatly reduce global water scarcity. Plants with improved Water Use Efficiency (WUE) such as those with altered expression of the Epidermal Patterning Factor (EPF) family of genes regulating stomatal density, could help reduce plant water footprint. Little however, is known about how this modification in Arabidopsis thaliana affects root architectural development in soil, thus we aim to improve our understanding of this growth. Methods We used X-Ray synchrotron and neutron imaging to measure in three dimensions, the root system architecture (RSA) of Arabidopsis plants of three different genotypes, namely that of the wild type Columbia (Col 0) and two different EPF mutants, EPF2OE and epf2-1 (which show reduced and increased stomatal density respectively). We also used total biomass and carbon isotope discrimination (Δ) method to determine now WUE varies in these genotypes when grown in a sandy loam soil under controlled conditions. Results Our results confirm that the EPF2OE line had superior WUE as compared to the wild type using both the Δ and total biomass method. The epf2-1 mutant on the other hand, had significantly reduced WUE using the Δ but not in the biomass method. In terms of root growth, the RSA of the different genotypes had no significant difference between each other. There was also no significant difference in rhizosphere porosity around their roots as compared to bulk soil for all genotypes. Conclusions Our results indicate that the EPF mutation altering stomatal density in Arabidopsis plants did not have an adverse effect on root characteristics thus their wide adoption to reduce the global freshwater footprint is unlikely to compromise their soil foraging ability.