Soluble and insoluble invertase activity in elongating Tulipa gesneriana flower stalks

Abstract

Previously ‘frozen’Tulipa gesneriana L. bulbs cv. Apeldoorn, were planted 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 internodes. After planting, flower stalks were left intact, or, the leaves and flower bud were both removed to inhibit internode elongation. In intact flower stalks, elongation of the internodes was accompanied by an accumulation of glucose and an initial decrease in the sucrose content g,−1 dry weight. Insoluble invertase activity g,−1 dry weight hardly changed, but soluble invertase activity showed a peak pattern, that was related, at least for the greater part, to the changes in the sugar contents. Peak activities of soluble invertase were found during (lower‐ 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 bud 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 increase (uppermost internode) or decreased abruptly to a low level. It is concluded that soluble invertase may be one of the factors contributing to glucose accumulation and internode elongation in the tulip flower stalk.