5. Conclusion
Mannitol treatment delayed senescence of spike tips, resulting in marked stem growth and promotion of bud development in cut snapdragon flowers. This effect was not observed in glucose, sucrose, and sorbitol treatments, resulting in the marked extension of overall vase life. Pulse-chase experiments with 14C-carbohydrates showed that mannitol metabolized slower than glucose and sucrose. Degradation of nuclei, a parameter of PCD, in the spike tips was suppressed by mannitol treatment, compared with other carbohydrates. Treatment with mannitol suppressed an increase in soluble carbohydrate concentrations in spike tips more than the other carbohydrates. Water potential and osmotic potential in the spike tips was modestly decreased by the mannitol treatment, resulting in the suppression of senescence. The other carbohydrates increased the carbohydrate concentrations in spike tips and decreased osmotic potential, resulting in their senescence.
Acknowledgement
The authors thank Mrs. K. Matsuda for her technical assistance.