Evidence that brassinosteroid stimulates auxin‐induced ethylene synthesis in mung bean hypocotyls between S‐adenosylmethionine and 1‐aminocyclopropane‐1‐carboxylic acid

Brassinosteroid (BR) stimulation of auxin‐induced ethylene production and the particular step at which BR acts to promote such synthesis were studied in mung bean (Vigna radiata L. Rwilcz cv. Berken) hypocotyl segments. Increasing concentrations of methionine alone and in combination with 3 μM BR and 10 μM IAA had a minimal effect on ethylene production. With increasing concentrations of 1‐aminocyclopro‐pane‐1‐carboxylic acid (ACC), however, ethylene production increased. BR or IAA further enhanced ethylene production with maximum rates occurring when these compounds were added together with ACC. The addition of 10 μM CoCl₂ in conjunction with BR and/or IAA resulted in 85–97% inhibition of ethylene production. When 20 μM cycloheximide was used in conjunction with BR and/or IAA there was a complete inhibition of ethylene production. Total inhibition also resulted when 1.0 μM aminoethoxy‐vinylglycine (AVG) was used in combination with BR and/or IAA. AVG alone had no effect on ACC conversion to ethylene.