Inhibition of IAA‐induced ethylene production in etiolated mung bean hypocotyl segments by 2,3,5‐triiodobenzoic acid and 2‐(p‐chlorophenoxy)‐2‐methyl propionic acid

Abstract

1984. Inhibition of IAA-indueed ethylene production in etiolated mung bean hypocotyl segments by 2,3,5-triiodoben2oic acid and 2-(pclilorophenoxy)-2-methyl propionic acid, -Physiol. Plant. 62: 448-452.The effect of two auxin antagonists, 2,3,5-triiodobenzoic acid (TIBA) and 2-(p-chIorophenoxy)-2-methyl propionic acid (CMPA) on IAA-indueed ethylene production in etiolated mung bean hypocotyl {Vigna radiata L. Rwiicz cv. Berken) segments was studied. Both TIBA and CMPA inhibited IAA-indueed ethylene production and CO2 production at concentrations from 0.001 mM to 0.1 mM and 0.01 mM to 1,0 mM, respectively. The optimum concentration for inhibition of ethylene production by TIBA was 0.05 mM and CMPA was 0.5 mM. At the optimum concentration of TIBA and CMPA, there was a significant decrease in IAA-indueed ethylene production without a decrease in respiration rates below control levels. After 18 h, mung bean hypocotyl segments treated with 0.05 mM TIBA for 6 h or 0.5 mM CMPA for 8 h showed a maximum inhibition of IAA-indaced ethylene production. Treatments longer than 8 h caused no further inhibition. The uptake of ['''C]-naphthaleneaeetic acid by mung bean segments was greatly reduced by the addition of either TIBA (0,05mM) or CMPA (0.5 mM) to the incubation media. The results of treatment sequences showed that TIBA needed to be applied prior to IAA in order to inhibit IAA-indueed ethylene production, but CMPA caused the same inhibitory effect whether applied before or after IAA treatment. These findings provide evidence that TIBA inhibits auxin-induced ethylene production in etiolated mung bean hypocotyl segments by blocking auxin movement into the tissue whereas CMPA may work on both auxin transport and action.Additional key words -Vigna radiata.

Identification and characterization of a full-length cDNA encoding for an auxin-induced 1-aminocyclopropane-1-carboxylate synthase from etiolated mung bean hypocotyl segments and expression of its mRNA in response to indole-3-acetic acid

“…Today the induction of ethylene by auxin is generally thought to be one of the most common plant-hormone interactions. In fact, it has been suggested that ethylene production by vegetative tissues is naturally regulated by the internal levels of auxin [1,2,26,30], although there is no direct evidence to support this idea. Sakai and Imaseki [22], working with etiolated mung beans, and Kang et al [11 ], studying etiolated pea segments, both showed that after a one-hour lag, the rate of ethylene production increased with time and this increase was dependent on the auxin concentration applied.…”

p-Chlorophenoxyisobutyric Acid Impairs Auxin Response in Arabidopsis Root

“…On the other hand, the effect of PCIB was often attributed to the inhibition of auxin transport (Katekar and Geissler, 1980;Tsai and Arteca, 1984), the regulation of auxin metabolism (Frenkel and Haard, 1973), or nonspecific toxic effect (Yip and Yang, 1986). Although the effects of PCIB presented in this study such as inhibition of lateral root development, loss of gravitropic re- sponse, and inhibition of primary root growth are also caused by auxin influx or efflux inhibitors (Fujita and Syono 1996;Luschnig et al, 1998;Casimiro et al, 2001;Malamy and Ryan, 2001;Rahman et al, 2001Rahman et al, , 2002, some of the PCIB effects are crucially different from the effects of auxin influx and efflux inhibitors.…”

Development of Erect Leaves in a Modern Maize Hybrid is Associated with Reduced Responsiveness to Auxin and Light of Young Seedlings in vitro

“…It was reported that PCIB itself can inhibit polar auxin transport. [63][64][65] However, since the capacity of PAT was similar in the modern and older hybrids, we could possibly exclude differential inhibitory effects of PCIB on PAT in the hybrid seedlings.…”