Academic literature on the topic 'Independent Fern Gametophytes'

SynopsisPerennial indendent gametophytes of Hymenophyllaceae, Vittariaceae and Grammitidaceae are a well-known phenomenon in the eastern United States. Their persistence is attributed to the ability of gametophytes of these fern families to reproduce themselves vegetatively via gemmae. This paper reviews the biology of independent gametophytes of these families as they exist in the eastern United States and presents new evidence from enzyme electrophoresis regarding their identity and origin.

Forest community assembly is usually framed in terms of sporophyte dynamics; however, the recruitment and maintenance of fern populations, frequently influential in forest composition and structure, are initially determined by gametophytes. Sporophytes of three Cyathea tree fern species show habitat partitioning along gradients of phosphorus and light; we asked whether gametophyte niche differences parallel this pattern. To compare niche characteristics among taxa we compared growth rates to a size threshold (≥3 mm) of gametophytes under controlled conditions using a multi-factorial, multi-level (3 × 4) experiment, varying irradiance (5.4 ± 4.4; 59.1 ± 44.3; 107 ± 74.1 µmol m −2 s −1 ) and orthophosphate concentrations (5, 10, 20, 40 mg kg −1 ). Gametophytes of the pioneer species C. medullaris developed to the size threshold across a broad range of phosphate and irradiance treatments (more than 20% of gametophytes in ≥ 7 of the 12 treatments), peaking at 20 mg kg −1 P and 60 µmol m −2 s −1 irradiance. The growth rates of the forest understorey species C. dealbata and C. smithii also peaked at 60 µmol m −2 s −1 but varied across treatments, suggesting niche differentiation along irradiance and orthophosphate gradients. Our analysis suggests that gametophyte development is strategically aligned to the ecological habits of sporophytes and that forest community assembly is likely strongly influenced by the independent gametophyte life-stage.

Ferns have conspicuous sporophytes as the dominant phase in their life cycle; however, the gametophytes are completely separated from the sporophytes and supply their own nutrition, unlike in bryophytes and seed plants. Among the gametophytes, some maintain their populations in the gametophyte phase without progressing to sporophyte production and are known as independent gametophytes. Independent gametophytes of Antrophyum obovatum Baker were recently reported in one population on Jeju Island, Korea. In the present study, we surveyed more places to find new independent gametophyte populations of A. obovatum using the rbcL gene sequence-based DNA barcoding technique. We identified two new sites inhabited by independent gametophytes. Archegonia and juvenile sporophytes were independently observed in each location under slightly different environmental conditions. Consequently, in the case of this species, functional sporophyte production is likely suppressed by prezygotic and postzygotic sterility, depending on microenvironmental factors.

Abstract The alternation of generations in land plants occurs between the sporophyte phase and the gametophyte phase. The sporophytes of seed plants develop self-maintained, multicellular meristems, and these meristems determine plant architecture. The gametophytes of seed plants lack meristems and are heterotrophic. In contrast, the gametophytes of seed-free vascular plants, including ferns, are autotrophic and free-living, developing meristems to sustain their independent growth and proliferation. Compared with meristems in the sporophytes of seed plants, the cellular mechanisms underlying meristem development in fern gametophytes remain largely unknown. Here, using confocal time-lapse live imaging and computational segmentation and quantification, we determined different patterns of cell divisions associated with the initiation and proliferation of two distinct types of meristems in gametophytes of two closely related Pteridaceae ferns, Pteris vittata and Ceratopteris richardii. Our results reveal how the simple timing of a switch between two meristems has considerable consequences for the divergent gametophyte morphologies of the two ferns. They further provide evolutionary insight into the function and regulation of gametophyte meristems in seed-free vascular plants.

The mission statements of Utah State University and the Department of Biology, as well as the requirements of funding agencies like the National Science Foundation encourage an integration of teaching and research. I have attempted to achieve that in my dissertation work by using tools I originally created to support and inform my biological research projects to teach science content and inquiry to middle school and undergraduate students. Chapter 2 of this dissertation reports the results of surveys for Hymenophyllum wrightii, a fern with independent gametophyte populations in the Pacific Northwest, which improved our understanding of the range, distribution, and habitat requirements of this species that was previously thought to be rare. The result of these surveys led to the removal of the species from the Forest Service's Alaska Region Sensitive Species List and provided a first report of the species in the contiguous United States. A preliminary genetic data analyses of gametophyte populations found during the surveys sets the stage for future work to determine the relationships between the independent gametophyte populations and sporophytes growing in Haidi Gwaii, British Columbia and East Asia, which is important for understanding their evolutionary and conservation potential. Chapter 3 describes an attempt to explore the population genetics of another fern with independent gametophyte populations, Crepidomanes intricatum in the Appalachian mountains of Eastern North America. This species apparently exists only as gametophytes, which raises interesting questions about how and when it was established, and its conservation and evolutionary potential. This population genetics analysis was not able to be completed, but led to an analysis of potential sources of error in genotyping-by-sequencing datasets and to the development of a set of software tools for evaluating the quality of these datasets. To help better visualize the evolutionary processes at work in populations of ferns with independent gametophytes, I developed an interactive software tool to simulate populations of ferns in a virtual 3-dimensional space. Chapter 4 describes that tool, an educational activity using it to teach population genetics and science inquiry to undergraduates, and the results of a study demonstrating its effects on student content learning and confidence in their ability to perform inquiry. This tool and the activity built around it have been used in undergraduate genetic laboratories at Utah State University since 2011. The apparent benefits of this simulation tool led to a collaboration with educators and the development of another 3-dimensional simulation tool to teach eight grade students about the effects of the environment and human impacts on living organisms. Chapter 4 presents an educational activity using this tool that has been used as part of a larger National Science Foundation funded project to train teachers to use technology in the classroom. The simulations are publicly available and have been used by hundreds of students in two Utah school districts. Together, these projects demonstrate on way that research to expand knowledge can lead to tools to impart knowledge to students.