Striga asiatica seed conditioning and 1-aminocyclopropane-1-carboxylate oxidase activity

• Published in: Weed research Vol. 41; no. 2; pp. 165 - 176
• Main Authors: Mohamed, A H, Ejeta, G, Housley, T L
• Format: Journal Article
• Language: English
• Published: Oxford UK Blackwell Science Ltd 15-04-2001; Blackwell Science
• Subjects: ACC oxidase; Biological and medical sciences; ethylene evolution; Fundamental and applied biological sciences. Psychology; Parasitic plants; Parasitic plants. Weeds; Phytopathology. Animal pests. Plant and forest protection; seed germination; witchweed; Gas emission; Seeds; Enzyme; Germination; Oxidase; Ethylene; Pest and disease control; Characterization; Dormancy; Enzymatic activity; Dicotyledones; Seed; Angiospermae; Scrophulariaceae; Plant growth substance; Spermatophyta; Oxidoreductases; Conditioning; Respiration; Parasitic plant
• ISSN: 0043-1737; 1365-3180
• DOI: 10.1046/j.1365-3180.2001.00229.x

Conditioned seeds of Striga asiatica (L.) Kuntze release ethylene, which elicits germination. We investigated the activity of 1‐aminocyclopropane‐1‐carboxylate (ACC) oxidase and respiration during conditioning. Seeds incubated in vivo with ACC, the substrate for ACC oxidase, produced negligible ethylene at the beginning of conditioning or if they were dormant (i.e. would not germinate after conditioning and treatment with stimulant). Non‐dormant seeds produced 3000 ηL of ethylene/600 seeds/24 h after 12 days of conditioning. In vitro ACC oxidase activity at day 0 of conditioning produced 500 ηL of ethylene/μg protein/h and 8000 ηL of ethylene/μg protein/h after 12 days of conditioning. Incubation of seeds in strigol before protein extraction did not enhance enzyme activity. Seeds released 4000 μL/L CO2 in the first 24 h of conditioning, with the rate increasing to 15 000 μL/L/24 h on day 4 and then remaining roughly unchanged. Maximum in vitro activity of ACC oxidase required ACC, catalase, O2, Fe2+, ascorbate and CO2. In vivo activity of ACC oxidase required ACC and/or germination stimulant(s), suggesting that stimulants may be involved in providing substrates for the ACC oxidase. No difference was observed in the separation of extracted proteins, which suggests that ACC oxidase is activated during conditioning, perhaps as a result of changes in co‐factor concentration. Application of these findings to Striga control is discussed.