Phenotypic Analysis of <i>Arabidopsis</i> Mutants: Root Elongation under Salt/Hormone-Induced Stress

Abiotic stress, such as high salt or low temperature, adversely affects plant growth and development. Salt stress inhibits seed germination, retards plant growth, and accelerates senescence. Freezing or drought stress can cause cell damage and plant death. The following parameters can be used to evaluate plant tolerance to salt, drought, or freezing stress: root elongation (described here), fresh weight gain, seed germination, electrolyte leakage, or water loss measurement. Several stress mutants have been characterized using these tests, including hos1 and hos2, which show higher expression of some stress-regulated genes when exposed to low-temperature stress; hos5, which shows higher expression of some stress-regulated genes under abscisic acid (ABA) and salt treatments; sfr mutants, which are deficient in freezing tolerance; and eskimo1, which is constitutively freezing-tolerant. To determine whether a mutant shows altered response to osmotic stress or to specific ions, various concentrations of salts can be used. Mannitol can also be used to impose osmotic stress, and ABA can be used to impose hormone stress. Among the salts used in this protocol, Li(+) is considered a toxic analog of Na(+), whereas Cs(+) is a toxic cation related to K(+). The levels of stress suggested in this protocol may need to be adjusted, depending on the ecotype and growth conditions used.