Carbohydrate traffic during opening of gladiolus florets.

摘要

The source of the carbohydrate increase that accompanies petal expansion in gladiolus florets was evaluated. Flower spikes were harvested immediately after harvest or after being held in a vase solution of 250 mg 8-hydroxyquinoline citrate/litre for5 days. The fresh weight of the florets on freshly-harvested gladiolus cv. New Rose spikes was highest in the fully open florets at the base of the spike, and decreased towards the tip. After 5 days in the vase, the fresh weight of the lowest florets had decreased, and that of the middle florets had increased significantly (with bud opening). The fresh weight of the newly-opened florets was somewhat lower than that of the open flowers on the freshly-harvested spikes. The maximum dry weight in freshly harvested spikes was in the lowest (open) florets. After 5 days, the dry weight of the lower florets, which were now senescent, had fallen significantly in the cultivars New Rose and Sierra Snow, whereas that of the opening florets at positions 6 to 13 had increased. The dry weight of the newly opened florets in these cultivars was significantly less than that of the open florets on freshly-harvested spikes. In cv. St. Patrick, there was a loss of dry weight in the senescing florets, and newly opened florets had a dry matter content equal to that of open florets on the freshly harvested spike. The ratio of fresh to dry weight of the florets on a freshly-harvested spike of New Rose declined slowly and steadily up the spike. After 5 days in the vase, thesenescent flowers had a low fresh weight:dry weight ratio, whereas the newly opened florets between the 6th and 13th positions had increased the fresh weight:dry weight ratio in the harvested spikes. In the youngest buds measured (buds 17 to 20), the ratio was the same in buds of fresh spikes as in those that had been in the vase for 5 days. The sugar content of the florets changed markedly during the postharvest life of the spikes, mirroring the changes in flower dry weight. In the senescent florets ofspikes held in the vase solution for 5 days, the storage carbohydrate content had decreased whereas it had increased in the younger florets; in these younger florets, glucose formed a larger proportion of the total sugar content (fructose, glucose and sucrose). Removal of the 3 open and opening lower florets at harvest markedly changed the dry matter content of the newly opening florets. After 5 days in solution, the dry matter in senescent flowers of control spikes had decreased , and it had increasedsignificantly in the opening florets. The dry matter content of opening florets on the spikes where 3 open flowers had been removed at the start of the experiment was consistently lower than that of those on the control spikes.