Increased oxidative stress, lipid peroxidation and protein degradation trigger senescence in Iris versicolor L. flowers

Dynamics in various physiological and biochemical aspects were studied during various stages (I-tight bud stage to VI-senescent stage) of flower development in Iris versicolor. Floral diameter, fresh & dry mass and water content increased during flower opening and decreased towards senescence. Senescence was found to be related to the increased lipid peroxidation which was reflected in the decreased membrane stability index towards senescence. This increase in the lipid peroxidation was probably initiated by increased lipoxygenase activity which shot up just prior to the increase in lipid peroxidation. Soluble protein content showed a marginal decrease towards senescence with a corresponding increase in specific protease activity. Sugar fractions and alpha-amino acids showed a significant decrease towards senescence. Superoxide dismutase and ascorbate peroxidase activity increased as the flowers opened and thereafter a significant decrease was registered towards senescence. Catalase activity improved as the flower matures, but decreased prior to flower opening through senescence. The protein patterns from the tepal tissues resolved through electrophoresis showed a consistency in proteins upto the flower opening but a marginal decrease was registered in both high and low molecular weight proteins towards senescence. However, a protein of molecular weight 76.5 kDa showed up during senescent stages which may have a role in flower senescence.