Flower Development and Senescence in Digitalis purpurea L., cv. Foxy

Abstract

Flowers of Digitalis purpurea L. cv. Foxy, take just over a week to develop from the smallest buds and open. Both the anthers and the stigma are closed when the flower opens, the anterior anthers dehisce 2 days after flower opening and the posterior anthers a day later. The stigma opens 2 days later still and the corolla remains attached for a further 2 days. The maximum size of the corolla is reached soon after opening and then remains constant. The fresh weight increases throughout the attached life of the corolla, whereas the dry weight reaches a maximum at flower opening and decreases during the remainder of the corolla's attached life. The content of antho-cyanin varies greatly from spike to spike. In some spikes the maximum content is at flower opening, in others it is much later, but in all cases the loss of anthocyanin with ageing is very small and the corollas are abcissed without visible wilting or fading. Maximum protein, RNA and glucose contents occur at, or soon after, flower opening and the levels decrease in the corollas as they age. Fructose reaches a maximum at the same time as glucose but does not decrease as rapidly, so that fructose becomes the major reducing sugar in the older corollas. Sucrose cannot be detected in any flowers. Ethylene production increases steadily with flower age, but the maximum production is recorded from flowers which have recently ab-scissed the corolla regardless of whether this occurs before detachment from the spike or within the collection tube.