Leaf Disc Stress Tolerance Assay for Tobacco Stress tolerance is a multigenic trait that depends on the coordinated action of several genes. Various physiological parameters, such as plant height and weight, total yield, chlorophyll content, photosynthesis rate, level of reactive oxygen species (ROS) and anti-oxidant activity could be correlated directly with the level of stress tolerance potential of any particular genotype. To evaluate the stress tolerance potential of a plant, leaf disc stress tolerance assay is a very rapid and widely acceptable experiment with minimum instrumentation facilities.