The Metabolism of Oat Leaves during Senescence

The senescence of the first leaves of light-grown Avena seedlings when detached and placed in the dark is inhibited by alpha, alpha'-dipyridyl and alpha, alpha', alpha''-tripyridyl at concentrations between 10(-5) and 10(-4) M. Five other chelating agents exert similar inhibiting effects at concentrations 3 to 30 times higher. The senescence of etiolated leaves, as shown by loss of carotenoid and protein, is similarly inhibited. Ethylene-diaminetetraacetate has a similar effect in the dark, though only at 10 mM and above, but in the light it causes bleaching of chlorophyll. It is deduced that an iron-containing system plays an essential part in the initiation of the senescence process.