Inflorescence development in Amelanchier alnifolia

Abstract

The morphology and development of the inflorescence of Amelanchier alnifolia, a potential fruit crop, are described. Although racemelike in appearance, the 8- to 12-flowered inflorescence is determinate, and the occasional branching of the basal member indicates its compound nature. This basal member in the axil of a foliage leaf frequently bears three to four bracteoles instead of the two characteristic of the remaining lateral flowers, and an arrested bud may be found in the axil of one or more of the bracteoles. The inflorescence is thus interpreted as a much reduced panicle. The phenology of inflorescence development in relation to seasonal shoot growth has been documented. Transformation of vegetative shoot apices to the flowering condition begins after the differentiation of a set of cataphylls and as the current fruit crop is ripening. It is marked by the accelerated formation of bract primordia with precocious axillary buds, culminating after about 2 weeks with the initiation of a terminal flower. Although the last to be formed, the terminal flower at all subsequent stages is equivalent in development to those at the base of the inflorescence. The buds in the axils of three to five bracts immediately below the terminal flower are arrested at an early stage and variation in inflorescence size may in part be due to variability in their development.

Microsporogenesis inAmelanchier alnifolia: sporogenous cells, microsporocytes, and tetrads

“…There have been several studies aimed at improving our understanding of the reproductive biology of A. alnifolia. However, most of these have focussed on the development of the inflorescence with an emphasis on the gynoecium (e.g., St-Pierre and Steeves 1990;Steeves and Steeves 1990). On the other hand, Olson (1984) investigated aspects of the pollination biology and Sumner et al (1999) developed a system for identifying the sequential stages of microspore development in relation to the external morphology of the expanding inflorescence and its flowers.…”

Correlation of microsporangial and megasporangial differentiation along racemes of Phytolacca americana L. (Phytolaccaceae)

“…Solely descriptive investigations have been used most frequently for taxonomic comparisons or establishment of classification schemes (L4bbe, 1974), as well as for determination of organ initiation and differentiation within inflorescences (Barnard, 1955). Even much of the descriptive work is open to question, as evidenced by erroneous interpretations of inflorescences (Steeves & Steeves, 1990;Nemoto & Ohashi, 1993). These latter projects relate to inflorescence ontogeny, as influenced by individual components of the inflorescence; e.g.…”

“…However inflorescence studies are classified, it has been suggested that there is a paucity of information (Abbe, 1974). Even much of the descriptive work is open to question, as evidenced by erroneous interpretations of inflorescences (Steeves & Steeves, 1990;Nemoto & Ohashi, 1993). The general scarcity of inflorescence work combined with incorrect conclusions would seem to make such work appropriate for updating information as well as providing baseline data for additional studies.…”

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

“…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).…”

“…In A. alnifolia, a phenophase model has been developed that relates stages of inflorescence expansion to temperature degree-days (Friesen and Stushnoff 1985;Friesen 1986). Moreover, Steeves and Steeves (1990) suggest that variation in timing of the development of the floral structures related to site, clone, and year differences can be "corrected by observation of external phenological events." Therefore, a useful tool to facilitate research on reproductive biology at the cellular level is the identification of external morphological markers of inflorescence development that can be correlated with cellular events such as microspore and pollen development Sparks 1992a, 1992b).…”