Detection of 12-oxo-phytodienoic acid (OPDA) in a protein fraction of corn leaves. OPDA was detected in a crude protein fraction isolated from maize leaves. 10 min after exposure to Z-3-hexenyl acetate (Z-3-HAC) almost 80% of the protein-associated OPDA disappeared and was presumable transformed into jasmonic acid. Error bars represent standard deviation. An * indicates a significant difference between Z-3-HAC-treated and control plants (t-test, p ≤ 0.05).