Restricted transpiration may not result in improved drought tolerance in a competitive environment for water

We have investigated how mutants with enhanced stomatal closure behave in a competitive situation with wild type plants for water. The abscisic acid oversensitive cbp20 and era1 Arabidopsis mutants retain more water when subjected to limited water supply due to restricted gas exchange, resulting in improved drought tolerance. This phenotype, however, was greatly reduced or disappeared when the root systems of neighboring wild type Arabidopsis plants competed for water in the soil around the mutants. These findings have implications in the potential use of this mutant class in agronomy as well as in designing genetic screens for drought tolerance.