Search

Copyright of Canadian Journal of Plant Science is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The article presents the biology of the Canadian weed Onopordum acanthium L. It is described as a biennials whose seedlings consist of a relatively large, fleshy and sparsely branched which is surmounted by a pair of 1.25-2 cm long, glabrous entire cotyledons that are pale green with whitish venation. It refers to Onopordum acanthium as a strongly competitive species that infests small grain fields in Nevada and northeastern California. It indicates its response to herbivory such as mammals and birds, disease and higher plant parasites.

Genus Sanicula encompasses about 40 species, mainly from temperate deciduous forests and exhibiting an Arcto-Tertiary relict distribution. It has previously been shown that stasis in physiological traits, such as seed dormancy, can occur in genera with an Arcto-Tertiary disjunct distribution. The aim of this study was to determine the requirements for dormancy break and seed germination in the Eurasian woodland herb Sanicula europaea L. Comparing our results with other Apiaceae in a phylogenetic and biogeographic framework enables us to determine whether stasis in seed dormancy has occurred in Sanicula. Experiments under natural conditions showed that the embryo elongates within the seed during winter, when temperatures are low. Seeds of S. europaea germinated immediately after growth of the embryo was completed, and seedlings subsequently emerged when temperatures had risen in spring. A series of tests under temperature-controlled conditions revealed that growth of the embryo and physiological dormancy break occur simultaneously at low temperatures (5 °C), irrespective of a pre-treatment at high temperatures. These results contrast with the dormancy traits of several eastern North American Sanicula species, which presumably require a high temperature pre-treatment before chilling becomes effective. This geographical distribution pattern of seed dormancy traits has also been established independently in several other Arcto-Tertiary relict genera. [ABSTRACT FROM AUTHOR]

Seed dormancy is an important factor regulating preharvest sprouting (PHS) but is a complex trait for genetic analysis. We previously identified a major quantitative trait locus (QTL) controlling seed dormancy on the long arm of chromosome 4A (4AL) in common wheat. To transfer the QTL from the dormant lines ‘OS21-5’ and ‘Leader’ into the Japanese elite variety ‘Haruyokoi’, which has an insufficient level of seed dormancy, backcrossing was carried out through marker-assisted selection (MAS) using PCR-based codominant markers. Nineteen BC5F2 plants with homozygous alleles of ‘OS21-5’ or ‘Haruyokoi’ were developed and evaluated for seed dormancy under greenhouse conditions. The seeds harvested from plants with ‘OS21-5’ alleles showed a clearly high level of dormancy compared with seeds from plants with ‘Haruyokoi’ alleles. Additionally, the dormancy phenotype of BC3F3 seeds harvested from 128 BC3F2 plants with homozygous alleles of ‘Leader’ or ‘Haruyokoi’ showed a clear difference between these alleles. The QTL on 4AL confers a major gene, Phs1, which was mapped within a 2.6 cM region. The backcrossed lines developed in this study can be important sources for improving PHS resistance in Japanese wheat and for analyzing the mechanism of seed dormancy. MAS was useful for the development of near-isogenic lines in this complex trait, to facilitate the molecular dissection of genetic factors. [ABSTRACT FROM AUTHOR]

The alien vine Vincetoxicum rossicum (Kleopow) Barbar. (Asclepiadaceae) is a major concern in natural areas of the Lower Great Lakes Basin. Reproduction in this perennial occurs largely by polyembryonic seeds that mature from August to November. Many seeds produced in autumn germinate the following spring, but the germinability of seeds produced in late summer is unknown. The influence of parent plant light environment on seed characteristics in this species is also poorly understood. We examined the characteristics of V. rossicum seeds harvested in late August and early November 2002 from three habitats in central New York State, USA, differing in light availability. Site had a significant effect on seed weight and germination percentage, but not on the number of embryos germinating per seed or radicle length. Seeds produced in the shaded habitat in August weighed significantly more and had lower germin ability than seeds produced in an adjacent open habitat, but this was not observed in a second open habitat. The probability of germination decreased with seed size for seeds ranging from 2 to 8 mg. For the open sites, fresh seeds produced in August had approximately double the germination percentages of those produced in November. However, for all sites, germination following 18 weeks of cold storage was greatest for seeds harvested in November. The probability of multiple embryos germinating was influenced by seed weight. The nature of this relationship varied by site, but not by harvest date or storage duration. Larger seed size resulted in longer total radicle length after 7 d, regardless of site. [ABSTRACT FROM AUTHOR]