1-Aminocyclopropane-1-carboxylate-dependent biosynthesis of ethylene in soils of different texture

• Published in: Pedobiologia Vol. 51; no. 5; pp. 351 - 358
• Main Authors: Nazli, Zilli H., Khalid, Azeem, Khalid, Muhammad, Arshad, Muhammad
• Format: Journal Article
• Language: English
• Published: Elsevier GmbH 01.01.2008
• Subjects: ACC; Ethylene; Ethylene-forming enzyme; Kinetics; Soil amendments; ACC; Ethylene-forming enzyme; Kinetics; Soil amendments; Ethylene
• ISSN: 0031-4056; 1873-1511
• DOI: 10.1016/j.pedobi.2007.08.001

1-Aminocyclopropane-1-carboxylic acid (ACC) is an established intermediate in methionine-derived ethylene (C 2H 4) biosynthesis in plants. This study reports concentration-dependent ACC-derived C 2H 4 biosynthesis in two differently textured soils (silt clay loam and fine loam). The gas chromatographic analysis showed that addition of up to 10 mmol l −1 ACC significantly stimulated C 2H 4 biosynthesis in both soils while no C 2H 4 was detected in sterilized soils amended with a sterilized ACC solution. Kinetic analysis revealed that the ethylene-forming enzyme (EFE)-mediated reaction was more linear in the silt clay loam ( R 2=0.992) than in the fine loam soil ( R 2=0.668) when reaction velocity ( V) was plotted against substrate concentration [S] that ranged from 2.5 to 10 mmol l −1. Within this range of [S], a first-order reaction was observed. Amendment of soils either with glucose (C source) or NH 4NO 3 (N source) strongly inhibited ACC-dependent C 2H 4 production. Maximum C 2H 4 production in both soils was recorded at a substrate concentration of 10 mmol l −1 when reaction mixture was maintained at a pH of 7.0 and incubated for a period of 120 h at 35 °C while shaking. Among the nine trace elements tested, seven showed a positive effect on ACC-dependent biosynthesis of C 2H 4 in both soils, while Fe(III) and Ag(I) inhibited the biotransformation of ACC into C 2H 4. However, three of the five tested electron complexes, added at 1.0 mmol l −1, had inhibitory effects on ACC-derived C 2H 4 biosynthesis while mannitol and hydroquinone stimulated C 2H 4 production in both soils. The addition of antibiotics (1.0 mmol l −1) to ACC-amended soils significantly reduced C 2H 4 production in both soils. Overall, C 2H 4 production from ACC was greater in the silt clay loam soil than in the fine loam soil. Knowledge of the factors affecting C 2H 4 biosynthesis in soil could be of great significance since even very low concentrations (ppb) of C 2H 4 in the root environment are known to affect plant growth dramatically.