Uniconazole inhibits stress-induced ethylene in wheat and soybean seedlings

Abstract

Abstract.Previous studies have shown that uniconazole inhibits ethylene synthesis and protects plants from various stresses. The present research was conducted to delineate the mechanism of ethylene inhibition by uniconazole [(E)-(p-chlorophenyl)-4,4-dimethyl-2-(1,2,4-triazol-1-yl)-l-penten-3-ol]. Following heat stress of 48~ for 3 h, the shoots of the control wheat seedlings became desiccated, and the seedlings lost 23% of their fresh mass 8 h after stress. The control soybean seedlings had epinastic unifoliate leaves 5 h after foliar application (4.4 g.a.i./ha) of the herbicide triclopyr [(3,5,6-trichloro-2-pyridinyl)oxyacetic acid]. Soil drench applications of uniconazole, a potent member of the triazole family, reduced these symptoms associated with heat and herbicide stress in wheat (5.0 mg/L) and soybean (0.4 mg/L) seedlings, respectively.Basal ethylene production was inhibited 32 and 48% by uniconazole in the wheat and acotyledonous soybean seedlings, respectively. Following a 48~ heat stress, 1-aminocyclopropane-1-carboxylic acid (ACC) levels increased 40% in both the control and uniconazole-treated wheat seedlings. After triclopyr application, ACC levels increased 400% in botl?, the control and uniconazoletreated soybean seedlings: The increased ACC levels, following stress, Were accompanied by increased ethylene production from the control, but not from the uniconazole-trea~ed wheat and acotyledonous soybean seedlings. ~iconazole treat-" ment did not significantly chang,e the basal or stress-induced N-malonyl-1-aminoc~r~lopropane-1-carboxylic acid (MACC) levels compa~ to controis. These results suggest that uniconazo"le inhibits ethylene synthesis by interfering with the conversion of ACC to ethylene in wheat and acotyledonous soybean seedlings. Ethylene production and ACC conversion were not inhibited by uniconazole in excised soybean cotyledons. These results indicate that different ethylene-forming enzyme (EFE) systems operate in the soybean acotyledonous seedling and cotyledon, and the system in the former is inhibited by uniconazole.

Effect of plant growth regulators on ethylene production, 1-aminocyclopropane-1-carboxylic acid oxidase activity, and initiation of inflorescence development of pineapple

“…Uniconazole-P, an active optical isomer of uniconazole, did not change indoleacetic acid or abscisic acid levels but promoted the biosynthesis of ethylene (1.8 times the control) and cytokinin (approximately 3 times for two zeatin compounds) in rice shoots (Izumi et al 1988). These triazol growth regulators interfered with sterol metabolism (Grossman 1990, Lurssen 1987) and also inhibited ethylene production by barley and oilseed rape (Grossman et al 1989), wheat and soybean (Krause et al 1991), and mung bean (Hofstra et al 1989). The delay or inhibition of E1 of pineapple in the uniconazole and paclobutrazol treatments could be due to decreased ethylene production or to other unknown factors, including altered plant susceptibility to ethylene.…”

“…We also evaluated PGRs that decrease plant tissue ethylene production but do not directly inhibit ACC synthase or ACC oxidase, such as uniconazole (Krause et al 1991), paclobutrazol (Wang and Steffens, 1985), and daminozide (Gussman et al 1993). GA 3 and CPA were also included in different experiments to evaluate their effects on El.…”

Modulation of ethylene synthesis in acotyledonous soybean and wheat seedlings

“…Samples were incubated in the dark at 24~ until a detectable quantity (12 ppb) of ethylene was present (1--4 h), then a 3-ml gas sample was withdrawn from the tubes or flasks, and the ethylene content of the sample was determined using a Hewlett-Packard gas chromatograph as previously described (Kraus et al 1991). The injector, column, and detector temperatures were 60 ~ 85 ~ and 250~ respectively, and the helium carrier gas flow was 24 ml/min.…”

“…Uniconazole [(E)-(pchlorophenyl)-4,4-dimethyl-2-(1,2,4,-triazol-l-yl)-lpenten-3-ol] is a potent member of the triazole family, which have been described as "plant multiprotectants" because of their ability to protect plants from several environmental and chemical stresses (Fletcher and Hofstra 1988). Kraus et al (1991) reported that uniconazole reduced basal and stress-induced ethylene production by inhibiting ethylene-forming enzyme (EFE) activity in wheat and acotyledonous soybean seedlings. They also reported that soybean appears to have two distinguishable EFE systems, since uniconazole inhibited EFE activity in the seedling, but not in the cotyledon.…”

Seed Treatment with Uniconazole Powder Improves Soybean Seedling Growth under Shading by Corn in Relay Strip Intercropping System

“…In addition, uniconazole protects plants from various stresses (Upadhyaya et al, 1990;Kraus et al, 1991;Leul and Zhou, 1998). Chen et al (2000) and Zhang et al (2002) reported that foliar application of uniconazole retarded soybean shoot elongation, and increased the stem diameter, and the numbers of branches, fl owers and pods under net cropping.…”