Fig. 1.

Response of Ws wt and mutant etiolated seedlings to ethylene. (A) For hypocotyl responsiveness, seedlings were grown for 4 d in the dark with 5 μM AgNO₃ (triangles) or 5 μM 2-aminoethoxyvinyl glycine (AVG) (circles), with the latter supplemented with increasing concentrations of ethylene ranging from 0 to 100 μl l⁻¹. (B) Relative hypocotyl length (length/length at 5 μM AgNO₃), with the ethylene concentration giving 50% inhibition denoted by a dashed line. The inset shows 4-d-old dark-grown seedlings of Ws wt and mutant exposed to 100 μl l⁻¹ ethylene. (C) The ratio of mutant to Ws wt hypocotyl length for each ethylene concentration tested, with the dashed line representing the predicted ratio if the mutant was not ethylene hyper-responsive. (D, E) For root responsiveness, Ws wt and mutant seedlings were grown in the dark for 4 d in the presence of air or increasing concentrations of ethylene. Actual root length is shown in (D), whereas (E) shows relative root length (length/length in air), with the ethylene concentration giving 50% inhibition denoted by a dashed line. (F) Ethylene biosynthetic rates for 4-d-old dark-grown seedlings of Ws wt and mutant. Ethylene was measured using a gas chromatography system with production rates calculated based on tissue fresh weight. Mean ±SE values were determined from five samples of 100 seedlings each.