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1985. Relationship of steroidai structure to ethylene production by etiolated mung bean segments, -PhysioL Plant, 64: 13-16.Several brassinosteroid (BR) analogues, cholesterol and aldosterone were evaluated for their effectiveness alone and in combination with indole-3-acetic acid (IAA) in stimulating ethylene production by etiolated mung bean {Vigna radiata L. Rwilcz cv. Berken) hypocotyl segments. Changing the conformation of the two hydroxyl groups on C-22 and C-23 positions from a to ^ did not greatly reduce the efficiency of these compounds to stimulate ethylene production alone or in combination with IAA, There was little difference in activity observed when the conformation of the methyl group in the C-24 position was changed from a to fi. However, when hydroxyls were deleted from the side chain in the C-22 and C-23 positions, the compound was rendered inactive alone or in combination with IAA. The compound was also inactivated by removing the 7-oxa function on the B-ring and by substituting an ethyl group for the methyl group in the C-24 position. Both aldosterone and cholesterol were ineffective in promoting ethylene production. This study shows that very stringent structural features are required for a steroid to have BR-like activity and to act synergistically with auxin in the promotion of ethylene synthesis.Additional key word -Vigna radiata.

Fusicoccin was evaluated for its effects on brassinosteroid (BR), indole‐3‐acetic acid (IAA) and BR + IAA‐induced ethylene, 1‐aminocyclopropane‐1‐carboxylic acid (ACC) and ACC‐synthase production by etiolated mung bean (Vigna radiata L. Rwilez cv. Berken) hypocotyl segments. Fusicoccin inhibition of ethylene and ACC production induced by 2 μM BR started at concentrations as low as 0.05 μM. Maximum inhibition occurred at a 1 μM concentration with no further inhibition at higher concentrations tested. Fusicoccin (1 μM) was effective in the inhibition of BR‐induced ethylene, ACC and ACC‐synthase production at low and high concentrations of BR. Fusicoccin at concentrations as high as 2 μM had no effect on ethylene and ACC production promoted by low concentrations of IAA (1 to 10 μM). When higher concentrations (100–1000 μM) of IAA were used, fusicoccin (1 μM) had an inhibitory effect on ethylene and ACC production. Interestingly, fusicoccin (1 μM) had little or no effect on ACC‐synthase promoted by high concentrations of IAA (1000 μM). When BR and IAA were used in combination, fusicoccin inhibited ethylene and ACC production at concentrations as low as 0.05 μM with maximum inhibition occurring at 0.5 μM. At a 1 μM concentration, fusicoccin was effective in inhibiting the synergistic stimulation of ACC‐synthase promoted by BR and IAA.