The Senescence Process in Oat Leaves and its Regulation by Oxygen Concentration and Light Irradiance

摘要

The regulation of senescence by oxygen-concentration, light irradiance and H2O2has been studied in leaf segments ofAvena sativaL. cv. Suregrain.The development of the components of the senescence process, for example chlorophyll breakdown, proteolysis (as soluble amino acids), hydroperoxides (as malondi-aldehyde) and permeability (as conductivity) is accelerated in light as the O2-tension increases. In darkness, 0.3O2accelerates increases in hydroperoxides, permeability and proteolysis and delays the chlorophyll break-down, but 0.0005O2delays all the components studied. In every case the hydroperoxide content, permeability and proteolysis are closely related. Any treatment inducing an increase in membrane permeability causes chlorophyll bleaching (photo-oxidation) if leaf segments are then treated with light in an atmosphere containing oxygen. Light has a modulating effect on the senescence process. An irradiance lower or higher than 40 W m–2has an accelerating effect on the senescence proces