Development and aging of leaf etioplasts in maize cultured with and without sucrose

The vital cycle of etioplasts has been compared in leaves of etiolated plants of maize grown on inorganic medium with or without sucrose, in order to ascertain how much starvation might affect the start of senescence. The results showed that the sucrose supply lengthened leaf survival and delayed the appearance of the late ultrastructural symptoms of etioplast senescence, but did not affect the beginning of senescence, which can be evaluated as a decrease in protochlrophyll(ide) contents. The start of senescence in etiolated leaves of maize seems to be a preprogrammed event rather than one dependent on the occurrence of tissue starvation.