Biosynthesis of stress ethylene in soybean seedlings: Similarities to endogenous ethylene biosynthesis

The similarity of stress ethylene biosynthesis in whole plants to endogenous ethylene biosynthesis was investigated using two inhibitors of ethylene biosynthesis, aminoethoxyvinylglycine (AVG) and cobalt chloride (Co2+); and the intermediates, methionine, S‐adenosylmethionine (SAM), and 1‐aminocyclopropane‐1‐carboxylic acid (ACC), of basal ethylene biosynthesis. Stress ethylene production induced by ozone, cadmium, or 2,4‐dichlorophenoxyacetic acid was inhibited in hydroponically‐grown soybean seedlings in a concentration‐dependent manner by both AVG and CO2+. The ethylene intermediates evoked responses in intact seedlings similar to that described for endogenous ethylene production in isolated vegetative tissue. The addition of SAM to the hydroponic system relieved AVG inhibition of stress ethylene production. Feeding ACC to the seedlings resulted in increased ethylene production independent of stress application or prior AVG inhibition. Cobalt inhibition of stress ethylene production was relieved by increasing concentrations of ACC. A short lag period of 12–18 min was observed in stress ethylene production following a 30‐min ozone exposure. Addition of cycloheximide partially inhibited ozone‐induced ethylene production. These results suggest a common pathway in whole plants for stress ethylene production and endogenous ethylene biosynthesis.