1,720,980 research outputs found
Effects of seed age and dormancy-breaking treatments on the viability and germination of the Gulf of Saint Lawrence aster (Symphyotrichum laurentianum)
No full textThe upland hardwood component of Prince Edward Island's remnant Acadian forest: determination of depth of edge and patterns of exotic plant invasion
No full textThe upland hardwood component of Prince Edward Island's Acadian forest is among the best remaining examples of the precolonial landscape, but it has been severely fragmented during the past 300 years of human use and settlement. Despite the ecological importance of this remnant habitat and its level of fragmentation, there has been no assessment of depth of edge or exotic plant invasion in these areas. Three 300 m long edge-interior transects were established in each of six study sites. Nine 100-m^sup 2^ circular plots were sampled along each transect at distances from 5.7 to 300 m; one external plot was established at each transect to sample species in adjacent habitats. In each plot, all vascular plants were identified, a visual estimate of percent cover was made, and soil temperature, canopy cover, and tree diameters were measured. An edge-interior plant community gradient was found within these forests; a plant community characteristic of interior conditions was not reached until a distance of more than 120 m from an edge. This suggests that upland hardwood protected areas smaller than 240 m on a side (5.75 ha) are unlikely to include interior habitat, and sites should be greater than 320 m on all sides (10.24 ha) to ensure at least some interior habitat for vascular plants. Invasion by exotic species was found to be more extensive than that reported from other jurisdictions, and innermost (300 m) plots were not free from exotics. Fifteen exotic species were found within the study sites, with Veronica officinalis (common speedwell) and Hieracium lachenalii (hawkweed) being the most invasive, both in terms of distance penetrated and area covered. [PUBLICATION ABSTRACT] Key words: Acadian forest, fragmentation, depth of edge, protected area, Veronica, Hieracium.Source type: Electronic(1
Phyllotactic patterns in some members of the Vitaceae
No full textIn addition to two opposite cotyledons, germinating seedlings of V. riparia and Vitis cv. Vivant display two other phyllotactic patterns: (1) immediately following the emergence of the cotyledons, leaves are initiated individually in a spiral pattern, usually 2/5; (2) upon the initiation of the first tendril the phyllotactic pattern changes to alternate and opposite leaves (distichous) with leaf-opposed tendrils at two consecutive nodes out of three. The mean divergence angle observed at the primordial level in young seedlings with spiral phyllotaxy was different from the reported divergence angle of 144 degrees (2/5) observed between mature leaves. The transition between spiral and distichous leaf arrangement is abrupt, the first tendril being initiated opposite a leaf. Later in development, the tendrils are shifted to one side of the axis giving the shoot a dorsiventral symmetry. The distichous "mature" dorsiventrally symmetrical pattern in seedlings of V. riparia and cv. Vivant was compared to other members of the Vitaceae, which did not show this striking dorsiventrality..RE: 44 ref.; MS: 24 pl., 1 fig.; SC: HO; CA; 0CSource type: Electronic(1
Developmental morphology of normal and atypical flowers of Philodendron insigne (Araceae): A new case of homeosis
No full textThe early stages of development of the inflorescence of Philodendron insigne were examined using scanning electron microscopy. Pistillate flowers are initiated on the lower portion of the inflorescence and staminate flowers are initiated on the distal portion. The male flowers have three to five stamens. The female flowers have a multilocular ovary consisting of three to five locules. A transition zone consisting of sterile male flowers and atypical bisexual flowers with fused or free carpels and staminodes is located between the male and female floral zones. Generally, the portion of the bisexual flower facing the male zone forms stamens, and the portion facing the female zone develops one or two carpels. In P. insigne, the incomplete separation of staminodes from the gynoecial portion of the whorl shows that the staminodes and carpels belong to the same whorl. The atypical bisexual flowers of P. insigne are believed to be a case of homeosis where carpels have been replaced by sterile stamens on the same whorl. However, there is no regularity in the number of organs involved in the homeotic transformation taking place in atypical bisexual flowers. The presence of atypical bisexual flowers may correspond to a morphogenetic gradient at the level of the inflorescence as a whole.Source type: Electronic(1)http://proquest.umi.com/pqdweb?did=279053581&Fmt=7&clientId=65345&RQT=309&VName=PQ
Development of the inflorescence and flower of Philodendron fragrantissimum (Araceae): A qualitative and quantitative study
No full textThe early stages of inflorescence development in Philodendron fragrantissimum (Hook.) G. Don are examined using scanning electron microscopy. Pistillate flowers are initiated on the lower portion of the inflorescence and staminate flowers are initiated on the distal portion. Male flowers have 6-8 stamens (sometimes 5) and female flowers have a multilocular ovary consisting of 6-10 locules. A transition zone consisting of sterile male flowers and bisexual flowers with fused or free carpels and staminodes is also present. This zone is located between the male- and female- flower zones. Generally, the portion of the bisexual flower adjacent to the male zone forms staminodes and the portion bordering the female zone develops an incomplete gynoecium with few carpels. The different floral organs of the bisexual flowers are all inserted in the same whorl. Pistillate and staminate flowers are inserted on the same contact parastichies along the inflorescence; there is no spatial discontinuity between the female zone, the bisexual zone, and the male zone. The presence of bisexual flowers is believed to correspond to a morphogenetic gradient at the level of the inflorescence as a whole. A quantitative analysis of a series of parameters (i.e., length and width of flower types and inflorescence zones) indicates that each zone of the inflorescence has its own particular nature as far as rhythm of growth and geometry are concerned. There appears to be evidence for some form of partitioning in the global development of the inflorescence. The growth of a zone seems to be more variable in size and geometry than that of individual flowers. During later stages of development, the size of the flowers of the intermediate zone, especially the sterile male flowers, increases considerably, until it exceeds that of both male and female flowers.Source type: Electronic(1
Development of the flower and inflorescence of Arum italicum (Araceae)
No full textThe spadix of Arum italicum Miller consists of two main parts: a clavate sterile portion (appendix) and a cylindroid fertile portion. In the fertile portion with both male and female zones, there are two zones of sterile flowers (bristles). The basal portion of bristles is surrounded by a verrucose structure consisting of a mass of tissular excrescences. During early stages of development, there is no free space between the different zones of the inflorescence. The elongation of the inflorescence axis is what eventually separates the different zones from each other. There are no atypical flowers that are morphologically intermediate between male and female flowers as is the case in other genera of Aroideae (e.g., Cercestis, Philodendron, Schismatoglottis). The structure of the bristles in the inflorescences of Arum does not correspond to any type of atypical flower (unisexual or bisexual) that has been analysed previously in the Araceae. From a developmental point of view, it is not possible to determine if the bristles correspond to aborted or modified female or male flowers. In the early stages of development, the stamens, staminodes, and appendix are covered by globular masses of extracellular calcium oxalate crystals. [PUBLICATION ABSTRACT] Key words: development, unisexual flowers, gradient, calcium oxalate crystals.Source type: Electronic(1
Quantitative developmental analysis of two phenotypes of Hibiscus rosa-sinensis in the context of homeosis
No full textGermination potential, updated population surveys and floral, seed and seedling morphology of Symphyotrichum laurentianum, the Gulf of St. Lawrence Aster, in the Prince Edward Island National Park
No full textS. laurentianum, the Gulf of St. Lawrence Aster, is an endemic aster of Prince Edward Island, New Brunswick, and the Magdalene Islands. It is considered by the Committee on the Status of Endangered Wildlife in Canada to be of special concern in Canada and to be critically imperiled in Prince Edward Island. One goal of this study was to conduct test germination to clarify the relationship between dormancy and germination in this species. Seeds germinated in culture media had an overall mean germination of 68.37%, whereas seeds germinated in soil had an overall mean germination of 17.38%. Kinetin supplements positively affected germination rates. However, these kinetin supplements eventually led to abnormal morphological development in S. laurentianum seedlings. Cold treatments had no significant effects on the germination of S. laurentianum seeds. Micropropagation of this type of explant and reintroduction should therefore be considered by Prince Edward Island as potential techniques for the conservation of S. laurentianum on Prince Edward Island. A complementary goal of this study was to survey the Blooming Point and Covehead sites to update the population status of S. laurentianum within the Prince Edward Island National Park. The size of the S. laurentianum population at Covehead Pond during 1999 was very similar to the population size at this site in 1993. Population sizes showed more fluctuation at Blooming Point between 1993 and 1999. No asters were found in the East Marsh in 1999, however, there was a large increase in population numbers at the Dune Slack site. Seeds of S. laurentianum appear to respond well to tissue culture. Annual monitoring of S. laurentianum populations should also occur to ensure appropriate management of this species on Prince Edward Island..RN: 525-79-1; SC: 0C; 7G; 0W; 7W; 7Q; 6C; CA; PE; EC; HO; PL; 7BSource type: Electronic(1
Estimation of seed bank and seed viability of the Gulf of Saint Lawrence Aster, Symphyotrichum laurentianum, (Fernald) Nesom
No full textThe Gulf of St. Lawrence Aster, Symphyotrichum laurentianum, is a member of the family Asteraceae and is listed as "threatened" by COSEWIC (Committee on the Status of Endangered Wildlife in Canada). This rare and vulnerable halophyte grows in only a few locations in New Brunswick, Prince Edward Island, and the Magdalen Islands, Quebec. As an annual, S. laurentianum relies exclusively on its seeds to survive to the next generation. The goal of this study was to estimate the quantity of viable S. laurentianum seeds in the persistent and transient seed banks at selected sites in Prince Edward Island. Overall, the number of seeds in the transient and persistent seed banks is low. The greatest concentration of seeds was found near the surface of the soil. In addition, only a small proportion of those seeds tested positive for viability based on Tetrazolium staining. Of the seeds in the persistent and transient seed banks combined, 53% were viable whereas only 2% of the seeds in the persistent seed bank were viable. Population surveys were also completed at the five known sites (both extinct and extant) in Prince Edward Island National Park. All sites showed signs of decline based on population estimates dating back to 1993. The Covehead Pond site showed the greatest decline: from 250-300 individuals in 1993 to only 10 individuals in 2002. The population at Dune Slack also showed a dramatic decrease from approximately 65 000 in 1999, to 2 200 individuals in 2002. Monitoring of this plant and the development of a management plan for the species are critical to its survival.PT: J; CR: *COMM STAT END WIL, 2004, COSEWIC ASS UPD STAT BASKIN CC, 1998, SEEDS ECOLOGY BIOGEO FENNER M, 2000, SEEDS ECOLOGY REGENE GILBERT H, 1999, SITUATION ASTER SAIN GRABE DF, 1970, HDB SEED TESTING, V29 HOULE F, 1990, CAN FIELD NAT, V104, P455 STEWART SE, 2000, THESIS U PRINCE EDWA STEWART SE, 2001, CAN FIELD NAT, V115, P287; NR: 8; TC: 0; J9: CAN FIELD-NATUR; PG: 6; GA: 887SMSource type: Electronic(1
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