Effects of ferulic acid, an allelopathic compound, on leaf expansion of cucumber seedlings grown in nutrient culture.

Cucumber seeds and seedlings at various ages (7-19 days old) were treated with a single treatment or multiple treatments (at 2-day intervals) of ferulic acid in nutrient culture. Ferulic acid treatments of cucumber seeds during stages of germination and radicle growth did not significantly reduce subsequent seedling growth. Ferulic acid treatments to seedlings reduced leaf area, leaf expansion, and dry weight of cucumber seedlings. Pretreatment of seeds and seedlings with 0.1 or 0.2 mM ferulic acid did not modify the effects of a single 1 mM ferulic acid treatment on leaf expansion when a single treatment was given at various times to seedlings ranging from 7 to 19 days of age. Treatments of 1mM or greater induced rapid wilting of leaves, but visible recovery occurred within 24-48 hr and subsequent treatments did not cause wilting. Once seedlings were removed from ferulic acid treatments, leaf expansion resumed. The magnitude of recovery depended on the concentration of ferulic acid, frequency of ferulic acid application and age of the seedling. Mean relative rates of leaf expansion recovered rapidly even in the presence of ferulic acid. Recovery of leaf expansion after ferulic acid treatments was faster for seedlings grown in an adequate nutrient environment than for seedlings grown in a limited nutrient environment. Ferulic acid disappeared from nutrient solutions with time, and two microbial metabolic products of ferulic acid (i.e., vanillic and protocatechuic acid) were identified in nutrient solutions.