Specific features of meiosis in the Siberian fir (Abies sibirica Ledeb.) artificial populations

Morphological and cytogenetic characterization in experimental hybrid Aloe jucunda Reyn. x Aloe vera (L.) Burm. f. (Asphodelaceae)

“…Th ese authors argue that the plants analysed grew in two contrasting environments and that the high temperatures increased the frequency of meiotic aberrations. A cytogenetic study in Abies sibirica (gymnosperm) conducted by Bazhina et al (2008) revealed the same trend, noting that temperature fl uctuations in the diff erent months of the year aff ected the frequency of abnormalities. In this case, the plants evaluated during the dry season of summer registered a greater number of anomalies with respect to those analysed in the cool season of spring.…”

Fossilized pollen malformations as indicators of past environmental stress and meiotic disruption: insights from modern conifers

“…2), we summarize possible developmental origins of pollen malformation types observed in this study that are applicable to the fossil record by drawing upon historical observations in the cytological literature of extant conifers and seed plants. In studies to date, the developmental origins of certain malformation traits have not explicitly been discussed, given that cytological studies on conifer microsporogenesis mentioning them focus on genotypic rather than phenotypic implications of meiotic deviations (Andersson 1947; Runquist 1968; Bazhina et al 2007a,b, 2011; Noskova et al 2009), while morphological studies addressing malformations do not evaluate their developmental origins (Lakhanpal and Nair 1956; Srivastava 1961; Mehra and Dogra 1965). However, there are inferences that can be made about malformation origins based on what is known about microsporogenesis in saccate conifers and the nature of some morphological deviations.…”

“…Although certain morphological deviations in both fossil and modern pollen walls can be inferred to result directly from certain types of developmental disruptions, traceable to specific stages in meiosis I and II (Chira 1967; Bazhina et al 2007a,b, 2011; Noskova et al 2009) (Fig. 2), it can be difficult to infer presence of a specific environmental stress using higher frequencies of developmental deviations alone, as they arise from numerous genotype by environment interactions (Veilleux and Lauer 1981).…”

“…Some of these grains were unreduced (≥2 n ), among them trisaccates and conjoined dyads and tetrads, resulting predominately from simple and complex chromosome and chromatid bridges as well as parallel spindle arrangement in meiosis II. Additionally, Siberian A. sibirica growing under industrial pollution (Presnukhina and Kalashnik 2003) and under near-ambient conditions in an arboretum (Bazhina et al 2007b) have also displayed a wider spectrum of structural deviations during meiosis, including chromosome fragmentations, chromosome bridges, and ring chromosomes, as well as chromosome ejection and agglutination. Bazhina et al (2011) suggested that chromatin agglutination may have accounted for heterogeneity in sizes and shapes of pollen grains observed in studies of A. sibirica under changing climate in Siberia. Unreduced malformed grains such as giant grains (Fig.…”