Phytotoxic activity of middle-chain fatty acids I:: effects on cell constituents

Phytotoxic activity of several middle-chain fatty acids, especially pelargonic acid (C9 acid) was investigated. C9-C11 acids caused strong non-selective damage to plants such as crabgrass, cucumber, velvetleaf, and tobacco, while C6 and C14 fatty acids had almost no activity. Middle-chain fatty acids caused a strong and rapid electrolyte leakage. They reached highest conductivity in 3 h in the case of cucumber cotyledons. Middle-chain fatty acids caused a decrease of the amount of polar lipids, particularly MGDG and PG, and chlorophylls. They also caused an increase of free fatty acids in 24 It after treatment. These results suggested that middle-chain fatty acids caused severe damage to cell membranes and thylakoid membranes of treated leaves. C6 volatile compounds such as cis-3-hexenal, trans-2-hexenal, and cis-3-hexenol were generated in less than 1 h after spraying pelargonic acid to tobacco leaves. The application of pelargonic acid was thought to be the trigger for linolenic acid degradation in the thylakoid membranes. (C) 2004 Elsevier Inc. All rights reserved.