3. Results
3.1. Effects of mannitol at various concentrations on stem length and
the number of total buds and open flowers
Mannitol at 10 mM or higher concentrations delayed the wilting of spike tips and stimulated stem growth, and the optimal concentration was 250 mM (Table 1, Fig. 1A). The stimulation of stem growth was accompanied by an increase in the number of buds. In control flower spikes, several flowers opened within the first few days (Fig. 1C). Mannitol at 1 and 10 mM slightly affected flower opening, whereas mannitol at 100 mM or higher concentrations markedly promoted flower opening. Mannitol at 100 mM or higher concentrations caused abortion of buds on about the 15th node from the base of spikes, but flowers on the upper part of the spikes opened almost fully. The time from harvest to the time when open flowers without wilting were not observed in each flower spike was 11.8 0.4 days at 0 mM, 11.8 0.6 days at 1 mM, 14.3 0.6 days at 10 mM,27.8 1.5 days at 100 mM, 31.0 1.0 days at 200 mM, and 28.4 2.0 days at 500 mM (means of eight replicates SE).