Senescence of leaf sheaths of ryegrass stubble: changes in enzyme activities related to H2O2 metabolism

• Published in: Plant growth regulation 2000, Vol.30 (1), p.71-77
• Main Authors: PIQUERY, L, DAVOINE, C, HUAULT, C, BILLARD, J.-P
• Format: Article
• Language: English
• Subjects: Agronomy. Soil science and plant productions; Biological and medical sciences; Detoxification; Economic plant physiology; Enzymatic activity; Fundamental and applied biological sciences. Psychology; Growth and development; Hydrogen peroxide; Morphogenesis, differentiation, rhizogenesis, tuberization. Senescence; Plant physiology and development; Senescence and abscission; Vegetative apparatus, growth and morphogenesis. Senescence
• ISSN: 0167-6903; 1573-5087
• DOI: 10.1023/A:1006308928018

Changes in the levels of reactive oxygen species (O2^sup .-^, H^sub 2^O^sub 2^), and of activities of enzymes involved in their detoxification were investigated during senescence of leaf sheaths of ryegrass stubble. The accumulation of H^sub 2^O^sub 2^ in the medium leaf sheaths coincided with a drop in the levels of total glutathione, of pyridine nucleotides and of activities of monodehydroascorbate reductase and dehydroascorbate reductase. Conversely, a paradoxical increase in the ascorbate/ascorbate plus dehydroascorbate ratio was observed, which appears to be inconsistent with H^sub 2^O^sub 2^ accumulation. Our results suggest that oxalate might be an essential source of H^sub 2^O^sub 2^ in senescent leaf sheaths, and that oxalate oxidase might be involved in the defence of foliar tissue against pathogens during the progress of senescence. Moreover, it is assumed that glucid catabolism of the ryegrass stubble might be a starting point of a metabolic drain leading to ascorbate, then to oxalate during the late phase of leaf sheath senescence.[PUBLICATION ABSTRACT]