Short-term Effects of Ferulic Acid on Ion Uptake and Water Relations in Cucumber Seedlings

Ferulic acid (FA) is commonly found in soils and is considered an allelochemical. Studies have suggested that FA and other phenolic acids decrease plant growth in part by decreasing the absorption of mineral nutrients and water. However, no studies have examined these parameters in a single experimental system to investigate how FA affected both ion uptake and plant-water relations in whole plants. Using intact cucumber (Cucumis sativus</it> L. cv. Early Green Cluster) seedlings, we examined short-term effects of FA on ion uptake kinetics, transport promoters and inhibitors, and water relations as indicated by a pressure-volume analysis. We found that after 3 h of treatment, 200 μM FA inhibited net ion uptake, particularly NO⊟<inf>3</inf>, and promoted net K+ efflux from seedling roots. The addition of fusicoccin, a K+ transport promoter, counteracted the inhibitory effect of FA on net K+ uptake. Concurrent treatment of seedlings with FA and tetraethylammonium, a channel-blocking salt, reduced average K+ efflux by 66%. Treatment of seedlings with FA also decreased leaf water potential (ψ<inf>1</inf> and turgor pressure (P<inf>T</inf>). However, decreased ψ<inf>1</inf> and P</it><inf>T</inf> were not caused by changes in the osmotic properties of the symplast or stomatal conductance. A decrease in water absorption is a likely explanation for the loss of P</it><inf>T</inf> observed. The results of our experiments indicate that both ion uptake and plant-water relations can be adversely affected by FA.