Abstract
M.Sc.
The commercial value of cut flowers, whether for ornamental use or as an export product, has
increased significantly over the years. Much attention is given to flower quality and flower
longevity. These two factors are influenced by preharvest and postharvest treatments. The major
postharvest loss reduction techniques in carnation flowers include regulation of preharvest
growing, use of improved harvesting techniques, use of various storage techniques, use of growth
regulators and use of floral preservatives. Senescence of carnation flowers (Dianthus
caryophyllus L. cv. White Candy), is accompanied by a climacteric rise in ethylene synthesis and
an increased sensitivity of the flowers to ethylene. A pulse treatment with sucrose caused a delay
and suppression of the climacteric rise in ethylene synthesis. The action of sucrose, with reference
to ethylene, was similar to that of cytolcinins. Dry storage also caused an increase in flower
longevity. This is due to the flower's ability to maintain water balance by lowering the cells
osmotic potential. Dry storage is of importance, as transportation of the flowers occurs under
these conditions. Although sucrose increased the longevity of freshly cut carnations, it caused
a decrease in longevity of flowers that were subjected to water stress. With the lowering of the
tissue water potential through treatment with sucrose and thereafter by dry storage, the flowers
are subjected to stress, and are not able to recover even after rehydration. Applied sucrose
increased the carbohydrate pool, thereby resulting in a gradual decline of starch. Administering
both sucrose and water stress to the carnation flowers resulted in an early peak in the sugar
content, as well as an early depletion of sugar in the flower petals. Cytokinin activity in untreated
carnation flowers appeared to be higher compared to flowers treated with sucrose. Water stress
have the effect of decreasing cytokinin levels and activity. It is thus clear from the results of this
study, that carnations subjected to water stress through dry storage, should not be pretreated with
any preservative containing sucrose, as it leads to a reduction in vase life.