Changes of chloroplasts density and heterogeneity during the senescence of barley leaves

The equilibrium density of chloroplasts from barley (Hordeum vulgare L. cv. Hassan) was analyzed by sucrose gradient centrifugation. Natural and detachment-induced leaf senescence were associated with a decrease in density and an increase in heterogeneity of the chloroplast population. Treatments (with growth regulators and light) which retarded or accelerated senescence, respectively, retarded or accelerated chloroplast density decrease. Accelerators as well as retardants of senescence decreased the heterogeneity of the chloroplast population.