Quantification of Water Stress-Induced Osmotic Adjustment and Proline Accumulation for Arabidopsis thaliana Molecular Genetic Studies

For the genetic potential of model systems such as Arabidopsis thaliana to be most effectively used to understand drought resistance, reliable and rapid protocols are needed for laboratory study of phenotypes relevant to stress responses in the field. Osmotic adjustment, the amount of additional solutes accumulated by plants under water stress, is often measured in drought physiology studies and requires quantification of both relative water content and solute content (osmotic potential) of the plant tissue. Water stress also elicits high levels of proline accumulation. Protocols are presented here to measure both of these parameters in Arabidopsis seedlings that have been exposed to controlled water stress treatments using polyethylene glycol–agar plates. For the ninhydrin-based assay of proline, a protocol for performing the assay in 96-well format to increase sample throughput is presented.