SOLUBLE AND INSOLUBLE INVERTASE ACTIVITY IN ELONGATING TULIPA-GESNERIANA FLOWER STALKS

Previously 'frozen' Tulipa gesneriana L. bulbs cv. Apeldoorn. were pla nted and grown at higher temperatures to study the role of invertase ( EC 3.2.1.26) in the cold-induced elongation of the flower stalk intern odes. After planting, flower stalks wire left intact, or, the leaves a nd flower bud were both removed to inhibit internode elongation. In in tact flower stalks, elongation of the internodes was accompanied by an accumulation of glucose and an initial decrease in the sucrose conten t g(-1) dry weight. Insoluble invertase activity g(-1) dry weight hard ly changed, but soluble invertase activity showed a peak pattern, that was related, at least for the greater part, to the changes in the sug ar contents. Peak activities of soluble invertase were found during (l ower- and uppermost internodes) or around the onset of the rapid phase of internode elongation (middle internodes). Internode elongation and glucose accumulation immediately ceased when the leaves and flower bu d were removed. Insoluble invertase activity g(-1) dry weight remained at its initial level (lowermost internode) or increased more towards the upper internodes. Soluble invertase activity did not further incre ase (uppermost internode) or decreased abruptly to a low level. It is concluded that soluble invertase may be one of the factors contributin g to glucose accumulation and internode elongation in the tulip flower stalk.