Comparison of achene characteristics within and among diploid and tetraploid clones of Solidago flexicaulis and their significance in germination and resource allocation studies

Abstract

Achene characteristics were examined within clones, among clones of a cytotype, and between the diploid and tetraploid cytotypes of Solidago flexicaulis. The pattern of intraclonal variation was similar in each of the three diploid and five tetraploid clones. In each of the clones, embryo weight increased with increasing achene weight and the number of days taken to germinate increased with increasing pericarp weight. Other significant correlations were not consistent among all clones. Generally, clones of the same cytotype were more similar to each other than to clones of the other cytotype. Additionally, the characteristics were generally larger among the tetraploid than diploid clones. However, a trend in decreasing size from southwestern to southeastern Ontario was observed. With respect to most measured characteristics, tetraploid clones occurring just west of the Frontenac Axis were intermediate between tetraploid clones occurring farther southwest in Ontario and diploid clones occurring just east of the Frontenac Axis. In this study, knowledge of ploidy level was important not only with respect to the analyses performed but also with respect to the interpretation of results and the correct assessment of causal factors of observed patterns of variation. Thus, knowledge of ploidy level is especially important in comparative ecological studies involving patterns of resource allocation and germination rates.

Significance of achene characteristics and within‐achene resource allocation in the germination strategy of tetraploid Aster pilosus var. pilosus (Asteraceae)

“…The independence of germination time and achene weight for tetraploid A. pilosus var. pilosus is in agreement with the results presented by Chmielewski (1991) for the cytotypes of A. lanceolatus. It is worth noting, however, that McEvoy (1984) found that germination time in Senecio jacobaea decreased with increasing achene weight in disk achenes, but increased with increasing achene weight in ray achenes.…”

“…The increased likelihood of germination as a consequence of increased achene weight is not a unique feature ofthis species or genus. Similar results have been reported within the tribe for both Aster acuminatus (Pitelka, Thayer, and Hansen, 1983) and A. lanceolatus (Chmielewski, 1991), Seneciojacobaea L. (McEvoy, 1984), and Solidago flexicaulis L. (Chmielewski et aI., 1989).…”

“…The importance of the timing of achene dispersal and subsequent germination has also been discussed (Keever, 1950;Baskin and Baskin, 1979;Chmielewski et al, 1989). Asters germinating in spring or summer usually form an overwintering rosette, then bolt and flower the following summer.…”

“…This low germination in lighter achenes is seen as the result of a proportionately thicker pericarp (Cook, 1980). Based on germination trials for the 4n, 6n, and 8n cytotypes of A. lanceolatus Willd., Chmielewski (1991) concluded that achene weight is one of the factors that apparently predetermines germination, and should not be overlooked [Vol. 81 (4) when similar studies are conducted on other species of Aster.…”

Structural, physiological and molecular aspects of heterogeneity in seeds: a review

“…Seed heteromorphism may occur at the level of the inflorescence (Cavers and Steel, 1984;Venable et al, 1995), individual (McGinley, 1989;Sakai and Sakai, 1996;Chmielewski, 1999), clone (Chmielewski et al, 1989), population (Venable et al, 1995) or species (Maun and Payne, 1989;Walck et al, 1997). Morphological heteromorphism may occur in seed size (Maun and Payne, 1989), seed shape (Venable and Burquez, 1989), seed colour (McGinley, 1989;Doucet and Cavers, 1997;Puga-Hermida et al, 2003a) (Fig.…”