Role of soluble carbohydrates in flower senescence: A survey

The life of many flowers is extended by application of sugars such as sucrose or glucose, but in most flowers the levels of soluble sugars in the petals are still high at the time of flower wilting. This seems to indicate that the cells still have adequate reserves at the time of wilting, which is contradictory to the effect of exogenous sugars. This review is meant to address this discrepancy. A major problem in the interpretation of the data is the lack of information on the distribution of soluble sugars in the various cell types and inside cells. Some cell types and some cellular compartments may well contain a low sugar concentration, despite the overall high sugar levels. The mitochondria of some cell types may no longer be able to import sugars from the cytosol, for example, or they are no longer able to use the available sugars after these have been imported. It is also possible that sugar levels in the cytosol become limiting for vase life, in the presence of high sugar concentrations in the vacuole. Vacuolar sugars may be unavailable for respiration as they serve to counteract adverse water relations. The determination of soluble sugars, therefore, should distinguish both tissues and cell compartments. Without these distinctions, it is suggested, our understanding in this field will remain rather limited.