ULTRASTRUCTURAL-CHANGES IN THE PETALS OF SENESCING FLOWERS OF DIANTHUS-CARYOPHYLLUS L

Ultrastructural changes associated with carnation petal senescence were investigated using ethylene levels of individual petals as a physiological monitor of the senescence process. Limited vacuolar and cytoplasmic vesiculation was observed in pre-senescent petals which became more extensive in pre-climacteric tissues, along with dilation of the outer mitochondrial membrane. Climacteric mesophyll tissue was characterized by widespread cytolysis. Intact cells possessed a highly reduced cytoplasm and vacuoles with electron-dense deposits. Degenerative changes became evident in the vasculature at this stage. These included occlusion of the sieve plate, and membrane abnormalities in the companion cells. Post-climacteric tissue was characterized by loosening of wall fibrillar structure in the vasculature, the appearance of intracellular cytoplasmic debns and cells completely devoid of contents. These changes are discussed in relation to developmental regulation on the one hand, and increasing levels of membrane disorgamsation on the other, leading to a possible 'error catastrophe' and final senescence. © 1992 Annals of Botany Company.