Influence of pretreatment stresses on inhibitory effects of ferulic acid, an allelopathic phenolic acid

Experiments were conducted to determine the potential for acclimation (i.e. , increased tolerance) to allelopathic phenolic acids resulting from pretre atment of seedlings with allelochemical (ferulic acid), drought, or nutrien t stress. Cucumber seedlings were exposed to pretreatment stresses in a nut rient culture system for nine days, starting with day 3. Seedlings were sub sequently treated for 5 hr with 0, 0.25, 0.5, or 0.75 mM ferulic acid. Accl imation (tolerance) was quantified by percentage inhibition of net phosphor us uptake. Seedlings grown with ferulic acid or drought pretreatment stress es were more tolerant to subsequent ferulic acid treatments (i.e., inhibiti on of net phosphorus uptake by ferulic acid was reduced). Nutrient pretreat ment stress eliminated the inhibitory activity of ferulic acid on net phosp horus uptake. The results suggest that a general acclimation response to a variety of pretreatment stresses can confer an increased tolerance of plant s to allelopathic phenolic acids such as ferulic acid.