Temporal and spatial patterns in the production of pollen, ovules and seeds in pseudogamous blackberries (Rubus subgenus Rubus)

Abstract

Significant variation in the number of stamens and ovules per flower, the stamen/ovule ratio, and the number of seeds per berry was found among seven blackberry species, each represented by one clone, and to a much lesser extent among inflorescences within species. Inflorescence size and architecture were found to have no major influence on these reproductive parameters. The position of a flower within the inflorescence strongly influences its onset of anthesis, which in turn is closely correlated with these reproductive parameters. Ovule number decreases with time, although in some species it increases again at the end of the flowering season. Number of seeds decreases more or less linearly with time, although there is an unexpectedly high number of the earliest berries of the triploid species, which is probably the result of interspecific pollination. Pollen production estimated in one species decreases with time, per theca, per flower and per ovule, whereas the percentage of good pollen grains remains unaltered.

Pollen profile, spatial structure, and access to sex in asexual hermaphrodites

“…Hence, through several causes, much of the pollen produced by asexuals can be of poor quality compared with that produced by sexual relatives (Van Baarlen et al ., 2000; Verduijn et al ., 2004; Mogie et al ., 2007; Rotreklová, 2008; Hörandl & Temsch, 2009). However, even though a reduction in pollen quality may be unavoidable, the extent to which it is reduced can show considerable variation (Nybom, 1989; Meirmans et al ., 2006; Rotreklová, 2008; Rich, 2009). For example, a cline in male fertility from 4.7% to 42.3% has been observed in apomictic Townsendia hookeri (Thompson & Whitton, 2006).…”

Floral trait variation in Spergularia marina (Caryophyllaceae): ontogenetic, maternal family, and population effects

“…sequence on characters such as flower size, gender expression, or gamete production (Bawa & Webb, 1983;Holtsford, 1985;Solomon, 1985;Thomson, 1985Pellmyr, 1987;Lee, 1988;Nybom, 1989;Thompson & Pellmyr, 1989;Kang & Primack, 1991;Thomson & Barrett, 1991;Ashman & Baker, 1992;Emms, 1993). Very few studies, however, provide measures of both ontogenetic and genetic sources of variation in floral traits (Young & Stanton, 1990;Armbruster, 1991;Diggle, 1993).…”