The Growth and Development of Caltha introloba F. Muell. I. The Pattern and Control of Flowering

Abstract

The floral development of Caltha introloba F. Muell. was surveyed in the short alpine herbfield areas located in the vicinity of Charlottes Pass, in the Kosciusko National Park. This study included a detailed examination, by scanning electron microscopy, of changes occurring at the shoot apex. Floral initiation occurred in mid summer (January) and flowers were fully developed and in many instances ready to shed pollen, before the first snow fall in late autumn (May). The flowers generally remained closed until after the snow melted in spring (October), although some opening did occur under the snow if this remained until late in the year (mid November). Seed development was normally complete towards the end of summer (late January to February).

Controlled environment studies demonstrated that floral initiation and development were favoured by long days and high irradiance. These factors may represent important controls in the field where floral initiation occurs as daylength and irradiance reach their maximum levels. Also it was shown experimentally that there is a cold requirement before the flowers, that are otherwise fully developed, will open. This requirement should ensure that premature opening will not occur in autumn.