Stimulation of auxin induced ethylene production in mung bean hypocotyl segments by 5,5' -dithiobis-2-nitrobenzoic acid

The non-permeant protein inhibitor 5,5'-dithiobis-2-nitrobenzoic acid (DTNB) was tested for its effects on auxin induced ethylene production. There was a stimulation in the rate of auxin induced ethylene production at all concentrations of DTNB tested (1, 2, 5, and 10 mM). The 5 mM DTNB treatment promoted the maximum stimulation of ethylene production with no further enhancement at the 10 mM concentration. After 12 hr ethylene production plateaued with 0.1 mM indoleacetic acid (IAA) alone and in combination with 1 and 2 mM DTNB. Although the DTNB treatments plateaued it was at a higher level than IAA alone. Both the 5 and 10 mM treatments of DTNB plus IAA did not show this leveling response even after 22 hr at which time these treatments were between 90 and 100% higher than the control. There was no stimulation of ethylene production by DTNB in the absence of IAA. Segments treated with 10^-4 M rβ-naphthaleneacetic acid (NAA) produced significantly higher levels of ethylene than IAA at the same concentration. Stimulation of ethylene production by DTNB was greatest at lower concentrations of IAA and NAA. The uptake of ¹⁴C-NAA by mung bean segments was 6-fold greater in the presence of DTNB than in its absence. Ca^$$ was required in the incubating media for DTNB to be effective. In the presence of Ca^$$ there was a highly significant increase in ethylene production while in its absence there was no significant effect. The stimulation of IAA induced ethylene production appeared to have a pH optima of 4.6, at higher pH values this response was not shown.