Factors affecting seed and cone development in Pacific silver fir (Abies amabilis)

Abstract

The reproductive development from pollination until seed maturity for Pacific silver fir (amabilis fir; Abies amabilis (Dougl. ex Loud.) Dougl. ex J. Forbes) was studied at two sites in British Columbia. Ten trees growing at varying elevations at each site were flagged and two or more cones were collected from each tree every 1 or 2 weeks. Following size measurements, cones were dissected and 20 ovules from each cone were sampled, fixed, embedded in paraffin, sectioned, and stained for anatomical study. Ovule, megagametophyte, and embryo size was measured and stage of ovule or seed and embryo was determined. At both sites the phenology and details of development were similar. The major causes of cone loss were frost at pollination and insect damage following pollination. The seed potential per cone was 359-408, but the filled seeds per cone based on cutting tests and X-raying was only 18-22%. The major causes of seed loss were insect damage (32-39%) during ovule and seed development and failure of ovules to be pollinated (26-31%). Although the amount of insect damage was similar at both sites, damage at Site 1 was primarily caused by Megastigmus sp. larvae in the seeds whereas at Site 2, damage was to seeds, scales, and the cone axis and due to Earomyia abietum larvae. Megagametophyte and embryo development is described and the time and causes of the seed loss are related to development. Anomalous types of development are described and possible causes discussed.Résumé : Le développement reproductif du sapin gracieux (sapin amabilis; Abies amabilis (Dougl. ex Loud.) Dougl. ex J. Forbes), de la pollinisation à la graine, a été étudié sur deux sites de la Colombie-Britannique. Sur chaque site, 10 arbres ont été sélectionnés à différentes élévations et, à toutes les 1 ou 2 semaines, au moins deux cônes ont été récoltés sur chaque arbre. Après avoir été mesuré, chaque cône a été disséqué et 20 ovules ont été prélevés, fixés, enrobés de parafine, sectionnés et colorés pour fins d'étude anatomique. La dimension des ovules, des mégagamétophytes et des embryons a été mesurée et le stade de l'ovule ou de la graine et de l'embryon a été déterminé. La phénologie et les détails du développement étaient similaires sur les deux sites. Les deux principales causes de pertes de cônes étaient le gel lors de la pollinisation et les dégâts occasionnés par les insectes suite à la pollinisation. Le nombre potentiel de graines par cône était de 359 à 408 mais les dissections et les rayons X ont révélé que seulement 18 à 22% des graines contenaient des embryons. Les causes majeures de pertes de graines étaient les dégâts occasionnés par les insectes (32-39%) pendant l'ovulation et le développement de la graine, de même que l'échec de la pollinisation des graines (26-31%). Bien que l'ampleur des dégâts d'insectes ait été similaire aux deux sites, les dégâts enregistrés au site 1 étaient principalement causés aux graines par des larves de Megastigmus sp., alors qu'au site 2, des larves d'Earomyia abietum avaient endommagé les graines, les ...

Critical phases in the seed development of common juniper (Juniperus communis)

“…During the first seed phase, the percentage of viable seeds decreased by up to 50%, mainly because no pollination took place. Amongst conifers, losses of up to 30% due to a lack of pollination are not uncommon (Owens 1995; Owens & Morris 1998). Being a dioecious species, it is possible that pollination success in common juniper is even lower than in most monoecious trees (Anderson & Owens 2000).…”

“…Hence, it is possible that because of the accelerated tube growth, the male–female synchrony for successful mating in seeds that ripen in <3 years is disturbed (Herrero 2003), but the expression of this perturbation is delayed until seed phase three. Owens (1995) and Owens & Morris (1998) also state that irregularities causing abortion or abnormal development of a reproductive structure can take place long before the anomaly has occurred.…”

Patterns of Cross-Continental Variation in Tree Seed Mass in the Canadian Boreal Forest

“…Short term variation in weather conditions at the reproductive stage can influence the periodicity of seed production [22], and the quantity and quality of seeds [21], [23]. Warm and sunny weathers during flowering and seed development favour the production of large seeds [24]. However, high rainfall may lead to low success of pollination and fertilization and low seed quality [25].…”

Microsporogenesis in the endangered species Cupressus dupreziana A. Camus: evidence for meiotic defects yielding unreduced and abortive pollen

“…Generally, the mechanisms governing good seed production are classi®ed as prezygotic (male and female structure development, production of functional gametophytes and gametes, incompatibility, pollination and fertilisation success) and post-zygotic events (success of embryo and endosperm development; Brink and Cooper 1947;Burd 1994;Lester and Kang 1998). In conifers, it has been shown that pollination is the most important pre-zygotic factor controlling reproductive success (Owens et al 1990a, b;Owens and Morris 1998). Indeed, in some species the presence of viable and functional pollen grains in the ovule is necessary for the development of female reproductive structures (Owens et al 1990b, and references therein;Wilson and Owens 1999).…”