Flower development in Amelanchier alnifolia (Maloideae)

Abstract

The development of the flower of Amelanchier alnifolia from initiation to the onset of anthesis is described. Sepals are formed sequentially, but interprimordial zonal growth results in the initiation of the hypanthium. Petals and stamens arise in whorls around the floral meristem as the hypanthium extends. They show neither coalescence nor adnation and do not appear to contribute to the development of the hypanthium. Gynoecial primordia arise individually, give rise to the styles and stigmas, and are joined basally by zonal growth to produce the roof of the ovary. The wall of the inferior ovary is interpreted as a gynoecial hypanthium. It is difficult to determine the extent to which the gynoecial primordia contribute to the development of the ovary. They do not give rise to most of its structure but may be responsible for the initiation of the ovules. There is evidence of postgenital fusion of the septal margins as they converge in the centre of the ovary. The timing of events in floral development is recorded for the locality of the study. The observations are discussed in relation to current theories concerning the nature of the inferior ovary. Key words: Amelanchier, flower, development, inferior ovary, hypanthium.

Pollen development in relation to phenological stages of inflorescence expansion inAmelanchier alnifolia(saskatoon), with a comparison with buds forced out of dormancy

“…The timing of inflorescence and flower development corresponds with that reported previously in Saskatchewan pop- ulations of A. alnifolia Steeves et al 1991). Floral development generally commences after the second week of April, and anthesis occurs in May.…”

“…In 1991, in the present study, microsporogenesis commenced toward the end of the second week of April, and tetrad development occurred during the fourth week. Steeves et al (1991) observed premeiosis microsporocytes in the second week of April, tetrad formation in the third week, and mature pollen in the first week of May. Although these approximations are useful, our study has introduced an increased level of precision in predicting internal developmental events that is independent of yearly variation in weather .…”

“…Pierre and Kaminski 1993;Schroeder and Faye 1996), there has been considerable emphasis placed on understanding all aspects of the plant's reproductive biology to improve fruit production. Such studies include the relationship between shoot morphology and inflorescence and flower production (St. Pierre and Steeves 1990), inflorescence development , flower development with emphasis on the gynoecium (Steeves et al 1991), pollination biology (Olson 1984), and fruit development (Olson and Steeves 1982). Despite the importance of understanding the development of the anther and pollen grains, for example, in studies of male sterility and the development of haploid plants using microspores in breeding programs (Ferrie et al 1995), there have been no such studies in A. alnifolia.…”

“…The flowers of A. alnifolia are perfect, consisting of 5 green sepals, alternating with 5 white petals, an androecium of 20 stamens, and an inferior gynoecium of 5 fused carpels (Steeves et al 1991). The inflorescence bud is initiated, and partly developed, in the year prior to flowering.…”

“…In A. alnifolia, the timing of several events has been reported, including anthesis and petal drop (St. Pierre and Steeves 1990) and stages of inflorescence and flower development (Friesen 1986;Steeves and Steeves 1990;Steeves et al 1991). A useful tool for management of fruit crops is the development of phenophase models, which predict stages of floral and fruit development based on correlations with environmental events (Gianfagana and Mehlenbacker 1985).…”