Unravelling the functional relationship between root anatomy and stress tolerance

Salinity is a major environmental constraint limiting the yield of crop plants in many semi-arid and arid regions. A recently developed biophysical model for plant growth in saline environments confirms a critical role for root morphology and hydraulic properties in salinity and soil water deficit tolerance. The identification of genes based on correlations between exposure to salt stress and gene expression in roots and other organs has to date proved to be only marginally successful as a strategy for improving plant salt tolerance. Recently, the identification of genes that function in stress tolerance has advanced considerably by using genetic mutation analysis. However, the power of a genetic approach to understanding the specific mechanisms of root adaptation to saline and osmotic stress environments has not been fully exploited. A review of the available, yet still incomplete, collection of root mutants in Arabidopsis and other species demonstrates the potential usefulness of such mutants as tools in the genetic dissection of root function under osmotic stress. Identification of genes responsible for changes in root morphology that might also be advantageous in the presence of salt stress may open new avenues towards the elucidation of critical mechanisms for plant salt tolerance.