Cell wall changes during the expansion and senescence of carnation (Dianthus caryophyllus) petals

Senescence of carnation (Dianthus caryophyllus L. ev. White Sim) petals coincided with a decrease on a per flower basis in the yield of cell wall and ethanol‐insoluble solids. The decrease in cell wall yield per flower was due largely to a loss of neutral sugars, primarily galactose (45%) and arabinose (23%). On a per flower basis, water‐and chelator‐soluble pectins increased throughout development, comprising in senescent petals 18 and 58%, respectively, of total pectin. Alkali‐soluble pectins ranged from 35 to 45% of the total pectin and decreased during senescence. Gel chromatography of chelator‐ and alkali‐soluble pectins revealed no change in molecular size and polygalacturonase activity was not detected. Large‐molecular‐size hemicelluloses decreased during development, an observation reminiscent of the changes affecting hemicelluloses during the ripening of a number of fruit types. Compositional analysis of the large hemicellulosic polymers revealed a decrease in xylose and galactose content.