Botany & plant ecology.
The Integrin-binding Peptide, RGD, Causes Cell Death in Suspension Culture Cells of Daucus carota. Emily Williams, Tristan Kemps ton, Robert Bradley, Mark Staves, and Sheila Blackman, Grand Valley State University, Biology Department
The aim of our work is to understand the processes controlling plant cell development, particularly the involvement of cues from neighboring cells. We have previously shown that an integrin inhibiting peptide (arginine-glycine-aspartic acid -abbreviated RGD) specifically disrupts somatic embryogenesis in carrot (Daucus carota). Integrin is a plasma membrane-spanning protein that links the extracellular matrix on the outside of the cell to the cytoskeleton inside the cell in animals. Here, we show that, regardless of the stage of embryo development at which RGD is applied, cellular disorganization, growth arrest, and cell death ensues within 24 h. The peptide also has toxic effects when applied to non-differentiating suspension culture cells. The emergence of this effect of RGD is accompanied by the peptide's uptake by the cells. In contrast to the rapid and dramatic toxic effects on whole carrot cells, we found that RGD was not toxic to plant cells from which the cell wall had been removed (protoplasts). We conclude that RGD may be promoting cell death via a signal passed through the cell wall, and arc investigating whether the effect of RGD is mediated through programmed-cell-death.
Interaction between Light and Gravity Signals in Single Plant Cells. Mark P. Staves, Grand Valley State University, Biology Department
The "shoots" of Chara corallina are composed of large internodal cells alternating with smaller, node-forming cells. We find that these shoots are both negatively gravitropic as well as positively phototropic. Differential growth in response to both gravity and light typically takes place in the two most apical internodal cells, however the plants can be manipulated so that all curvature takes place in a single cell. Experimental plants were allowed to develop to a stage where they had one or two visible internodal cells. In the absence of light, internodal cells are negatively gravitropic. If gravistimulated (horizontal) internodal cells are illuminated with white light from above, gravity and light act together and more rapid curvature ensues. If however, gravistimulated internodal cells arc illuminated from below, gravity and light act antagonistically and light can overcome the gravity signal. We find that gravistimulated cells illuminated from below will bend up (i.e. negatively gravitropic and negatively phototropic) at light intensities below ca. 1 ([micro]mol m-2 s-1, whereas they curve downward (positively gravitropic and positively phototropic) at higher light intensities. Chara thus provides a system in which a single, statolith-free cell responds to both light and gravity and in which the interactions of the light- and gravity-induced signal transduction pathways can be investigated.
Assessment of Phytoplankton Populations and Associated Toxins in West Michigan Lakes. Janel Hagar and Richard R. Rediske, Annis Water Resources Institute, Grand Valley State University
The increasing prevalence of algal blooms in freshwater arising from cultural euttophication and the. action of non-indigenous species is creating issues related to the use of water for drinking and recreational purposes. Cyanobacteria are well known for their ability to produce potent toxins that have been responsible for animal deaths and human health problems. An investigation of phytoplankton assemblages and their associated toxins was conducted in 7 western Michigan Lakes in 2006. Samples from three ambient water locations and three beaches were collected and analyzed from each lake in July and August. Cyanobacteria densities followed a total phosphorus dependent gradient with hypereutrophic lakes having the greatest number of potentially toxic-species. Toxin levels, measured by enzyme linked immunosorbent assay kits (EL1SA), were above the World Health Organization advisory levels for microcystin LR in three of the seven lakes.
Spatial and Temporal Variations of Phytoplankton Communities in Spring Lake, Michigan. Brent Kasza, Ying Hong, and Richard R. Rediske, Annis Water Resources Institute, Grand Valley State University
Bloom-firming, toxic cyanobacteria occur worldwide in nutrient-enriched freshwaters. Such blooms can have disastrous short- and long- term consequences for water quality and resource utilization. Spring Lake is part of the Grand River watershed and has a long history of algal blooms from cultural eutrophication. Water samples from three open water locations and three beaches were collected during the summer of 2006 and analyzed for phytoplankton species by light microscopy. Phytoplankton assemblages were dominated by diatoms in July. The community composition shifted to cyanobacteria in August. Toxin producing cyanobacteria species identified included Anahaena flos-aquae, Aphanizomenon flos-aquae, Cylindrospermopsis raciborskii. Microcystis aeruginosa, and Planktothrix sp. C. racihorskii is a toxic, subtropical species of cyanobactertia that is common in Florida. The data from Spring Lake represent the second reported occurrence of this organism in the Lake Michigan drainage basin. Similar abundances were found in the beach and open water samples.
Monthly Analyses of Nanoplankton Algal Communities of a Bog Dystrophic Lake. Jessica Neumann and Mark Oemke, Department of Biology, Alma College
The planktonic algal community was examined monthly during the summer and fall of 2006 at Davis Lake, a small dystrophic lake, in Montcalm County, Michigan. Water samples and plankton samples were collected at surface, 1.5 m, and 3.0 m depth. Quantitative samples were collected with a 2.2 liter Van Dorn sampler, and the water filtered through a 10 micron mesh, nanoplankton net. Identification of algae to genus or species was made through examination of qualitative plankton samples collected on the same date, examined using 1000X magnification. Algal communities showed significant changes in species dominance between the three water depths and frequently temporal changes in community composition or species dominance, between the monthly samples. Sphaerocystis schroeteri dominated with a peak abundance of 61,938 cells/liter in May. Aphanocapsa delicatissima was observed in June and July with a density of 25,268 cells/liter dominated all three water depths in June and July. Over a third of all algal species identified to date belong to the large group of algae known as Desmids. Chemical and physical measurements of pH, dissolved oxygen, water temperature and photometric readings (P.A.R.) were also recorded throughout the water column or at each sampling depth for each sampling date.
The Growth Rate of Microcystis aeruginosa in Saginaw Bay and Lake Erie (Poster). Michael Rediske, Gary Fahnenstiel, Great Lakes Environmental Research Laboratory, National Oceanic and Atmospheric Administration, Muskegon, MI 49441 and Ying Hong, Grand Valley State Univ., Annis Water Resources Institute, Muskegon, MI 49441
Microcystis aeruginosa has become the dominant organism in the phytoplankton of Saginaw Bay and Lake Erie. This species produces microcystin, a potent toxin that has been measure in the ambient water of both systems at levels that exceed World Health Organization guidelines. Toxin production has been linked to many factors including growth rate. The growth rate and frequency of dividing cells (I. DC) of M. aeruginosa in Saginaw Bay and Lake Erie were determined during the summer of 2006 using field measurements and laboratory studies. M. aeruginosa exhibited a strong diel pattern of cell division. The FDC peaked in the early afternoon and reached its minimum before sunrise. FDC values observed ranged from 5.5%--13.8%. Calculated growth rates ranged from 0.0432 day-1--0.222 day-1. Growth rates were influenced by a variety of factors including water temperature and light conditions.
Submersed Macrophyte Species Growth Responses to Varying Concentrations of Dissolved Inorganic Carbon in Adirondack Lakes. Jennifer L. Jermalowicz-Jones, ASI Environmental Technologies, Inc.
A randomized block design transplant experiment conducted in five Adirondack lakes (Herkimer and Hamilton Counties, NY, USA) measured the relative growth rate (RGR) response of Myriophyllum tenellum, Lobelia dortmanna, Eriocaulon septangulare, Vallisneria americana, Elodea canadensis, and Potamogeton robbinsii to a dissolved inorganic carbon (D1C) gradient over the summer of 1999. The hypothesis that species able to utilize bicarbonate (HCO3-) would show a greater growth response to elevated water column DIC concentrations than would species that assimilate free CO2 from lake sediments, was tested on homogenized, nutrient-poor sediment. In addition, a smaller study evaluated the growth of the HCO3-user, V. americana and the sediment CO2-user, L. dortmanna on a fertile sediment in two lakes of low and high DIC concentration. Comparisons of the two experiments may provide an explanation of the relative importance of sediments and water column carbon source for submersed macrophyte growth. A linear regression model is currently being developed to predict the concentration of DIC necessary for optimal growth of each of the six macrophyte species.
Plant Biomass in St. Mary's River Coastal Marshes. Gregory Zimmerman, Department of Biology, Lake Superior State University
Great Lakes coastal marshes are important for biodiversity, water quality, shoreline structure, aesthetics and other values. These marshes are at risk of declining ecological integrity due to mechanical disturbance, invasive species, pollution, and other stressors. In the summer of 2005, LSSU researchers examined plant, fish, and insect communities and water and sediment chemistry in St. Mary's River coastal marshes with the objective of assessing effects of pollution and ship traffic. This report concerns plant community biomass. Biomass data was collected at 11 Mile Marsh, Cook Island, Churchville Pt and from 0.25 m2 quadrats along a transect parallel to the shoreline in the region inundated during high-water but exposed during low-water periods. Vegetation was clipped to ground level, identified to species, oven dried and weighed. Data summaries included species and group composition, species and group richness and dominance, total live biomass and total detritus. Graminoids dominated in all marshes. Invasive species were rare. No consistent differences were seen between sites. The plant communities did not seem to be affected by urban influences or ship traffic in terms of these biomass-based metrics.
Coalition Building as a Model to Address Regional Environmental Issues in Restoration Ecology: A Case Study to Sustain Wild Rice. Scott Herron, The University of Michigan Biological Station & Ferris State University, Biology Department
Through an Environmental Leadership Program grant the momentum was gathered to organize citizens, scientists, agencies, homeowner & lake-owner associations, and Tribal communities to focus on wild rice in our Great Lakes watershed. My focus is to build sustainable wild rice communities, including the humans harvesting this food resource through the networking of people and organizations from across Michigan, Minnesota, and Wisconsin. Wild rice community meetings have empowered local citizens in become invested in this natural resource and better educated about wild rice also. Miscommunication has been the biggest road block to resource managers, landowners, and governments working together to ensure the health and sustainability of human and wild rice communities. A regional conference was utilized to create the momentum needed for wild rice management, restoration, harvest, and education to keep our regional Wild Rice Coalition functioning into the future. Data from the community meetings in Michigan will be discussed to stimulate dialog about a similar approach for use in other states to address other environmental issues. Discussion about building a regional network on an environmental issue where empowerment thru facilitation and education are the approach utilized. Suggestions for future Wild Rice Coalition projects, research, outreach, and publications will be covered.
The Effects of Seed Maturity on Seed Quality in Epidendrum tempense. Rachel Schwallier and Sheila Blackman, Grand Valley State University, Biology Department
Current orchid ex situ conservation efforts focus on refining long-term storage success. Prior research, though, has overlooked both the initial viability of the seed lot and consideration of the harvest time. Here, we evaluate the influence of maturity on aspects of seed quality for the epiphytic orchid Epidendrum tempense. To do so, we investigate the following features; capsule characteristics, seed weight and water content, and viability as measured by staining with fluorescein diacetate (FDA). We found that capsule diameter, but not length, correlated with maturity. Total seed weight and water content also varied with maturity. Seeds stained positively with FDA (that we showed previously correlated with germinability) indicating embryos were living, with no change detected through development. We conclude that capsule width may he a useful indicator of seed maturity, and that seeds undergo a drop in water content approximately midway through development. The impact of these results on orchid seed storage practices will be discussed.
Effects of Environmental Variables on Plant Communities in a Ravine System in Southwest Michigan. Eileen Fleischmann and Robert Keys, Cornerstone University, Science Department
Ravine systems in the temperate region of the Midwestern United States have not received the same level of scientific attention as those of tropical regions. Previous studies indicate that plants order themselves into distinct communities along the edges of a ravine, particularly the vertical axis. Research was conducted, using a ravine in southwest Michigan, to determine the make-up of herbaceous plant communities along the vertical axis. The goal was to determine if distinct plant communities existed along this axis and how these distinct communities were related to changes in the environmental gradient. Using a direct gradient analysis, it was shown that significant differences in environmental variables exist between vertical levels of the ravine. These differences correlate closely with noticeable changes in the plant communities, although it remains unclear which variable is the limiting factor in the determination of these distinct plant communities. However, it can be concluded that even relatively small changes in these environmental variables drive significant changes within these communities.
Light Characteristics of an Urban Forest Canopy. Gabriel DeJong and David L. Dornbos, Calvin College, Biology Department
Creating urban green spaces that function as carbon sinks and add to the aesthetic appeal of a city can also aid in reducing atmospheric carbon. Evaluation of light distribution characteristics within the plant community may inform optimum organization of native plantings in site restoration activities. Using hemispherical photographs and computer software, we measured effective LAI and light intensity to quantify and assess how leaf and plant distribution interacted in several plant communities on the Calvin College campus (Grand Rapids, MI). Measurements of photosynthetically active radiation (PAR) were recorded using a Licor LI-191SA line sensor. Our results indicate that LAI is a valuable measure of the dynamic light regime in a plant community, characterizing the amount of light (PAR) available for photosynthesis and enabling projection of carbon assimilation rate of a plant community as a function of its species composition. In particular, we determined that buckthorn (a non-native invasive plant species) significantly altered the light regime in infested communities, thereby jeopardizing the health and survivorship of several native plant species. LAI alone was insufficient to explain why buckthorn was present in some areas and not others, but did provide insight of how this invasive shrub alters the growth environment of infested areas.
Characterization of the Photosynthetic Competitiveness of Autumn Olive (Elaeagnus umbellata). Michele R. Ritsema and David L. Dornbos, Calvin College, Grand Rapids, MI
Elaeagnus umbellata (autumn olive), a non-native invasive shrub in the United States, threatens to decrease biodiversity in natural areas throughout Michigan. This study, conducted at the ecological preserve at Pierce Cedar Creek Institute in Barry County, Michigan, sought to characterize the photosynthetic competitiveness of E. umbellata in comparison with several established native species in both open meadow and forest under-story environments. E. umbellata fixed carbon faster than any of the native species in the meadow environment. In the forest environment, the climax community species (Quercus velutina and Acer saccharum) accumulated CO2 faster than E. umbellata at lower photosyntheticly active radiation (PAR) intensities (0-400 umol/m2/sec). E. umbellata's photosynthesis rate surpassed all native species evaluated at PAR intensities < 600 umol/m2/sec. Prunus serotina had photosynthesis rates similar to those of E. umbellata in both the under-story and meadow environments. Given that many heavily E. umbellata-infested areas exist, the efficacy of glyphosate herbicide as a function of concentration on freshly cut stumps was evaluated. I be highest concentration solution (41% glyphosate) was optimum. Knowledge of the physiological advantages of E. umbellata, will equip managers of natural areas to effectively control E. umbellata, preventing degradation of native biodiversity in areas of North America where E. umbellata is found.
CO2 Sequestration Potential of Understory Species in Western Michigan. Laura Holtrop and David L. Dornbos, Calvin College. Biology Department
Atmospheric CO2 level is increasing, likely driving global changes such as rising temperatures. The rate at which atmospheric CO2 is increasing may be counteracted by managing urban areas in such a way as to optimize carbon sequestration rate and plant biodiversity by augmenting turf with native woodland species. CO2 uptake rates of eight representative native and two non-native species, Rhamnus cathartica and Rhamnus frangula, were measured using a TPS-I (PP Systems) gas exchange sensor on the Calvin College campus (Grand Rapids, MI). Species rankings for carbon fixation rate, one estimate of competitiveness, depended on light levels to which their leaves were exposed. Significant polynomial relationships were obtained for each species describing the rate of carbon fixation as a function of light intensity. When compared with native species, both buckthorn species demonstrated a significant carbon sequestration advantage, especially in high radiation areas. At high light levels, eastern redbud and bladdernut were the only native species able to compete with buckthorn. Light and water use efficiency did not vary among species. These data suggest that a restoration project placing desired species in high light levels may optimize carbon sequestration and could inhibit invasive plant growth, optimizing aesthetic quality and carbon sequestration rare.
Plasticity in Phytotoxin Production by Ailanthus altissima Across a U.S. Megatransect. Gary K. Greer, Grand Valley State University, Biology Department, Allendale, MI, and Preston Aldrich, Bennedictine University, Department of Biological Sciences.
Ailanthus altissma is an invasive tree from China. Intentionally introduced to the eastern U.S. in the late I 700's and repeatedly (presumably) on the west coast during the 1800's, Ailanthus is now found in all 48 continental states. Ailanthus possesses a number of invasion promoting traits including production of at least one phytotoxin, ailanthone. We investigated: (1) large-scale patterns of Ailanthus phytotoxin production and plasticity in phytotoxin production in response to injury across an East-West U.S. transect that included WV, OH, IL, CO, UT and CA, and (2) regional scale-scale patterns throughout West Virginia. Ailanthus seed were collected from each site and seedlings grown in an OH greenhouse and half from each site were injured one week prior to harvest. Aqueous extracts were used in bioassays on commercial lettuce (Lactuca sativa buttercrunch), annual rye (Secale cereale), and Quercus alba, Q. prinus, and Q. rubra. Phytotoxin production was observed in all Ailanthus populations; however, effects varied considerably among assay species. Substantial variation was observed in: (1) levels of phytotoxin production and (2) the magnitude and direction of plasticity in phytotoxin production at both large and regional scales. These patterns reflect genetic differences among Ailanthus populations due to either drift or selection.
Integrated Management Strategies and Pathogen Detection in the Potato' Streptomyces Spp. Pathosystem. Elise C, Hollister, Grand Valley State University, Biology Department, Saginaw MI; R. Hammerschmidt, W.W. Kirk, Michigan State University, Department of Plant Pathology; and D.S. Douches, Michigan State University, Department of Crop and Soil Sciences, Lansing MI
The potato ranks fourth as the most important human food source. This research examined environmentally friendly disease management methods in reducing the severity of an important bacterial disease, common scab, as well as molecular detection methods of the causal agents (Streptomyces spp.). Controlled environment and field experiments were conducted to determine the effectiveness of cultivar resistance and soil moisture in reducing disease incidence and severity. Cultivar resistance against common scab appeared to be more effective. Resistance activators for elicitation of systemic acquired resistance (SAR) in potato to scab produced variable results. Analysis of a pathogenesis related protein found no differences between treatments, suggesting that SAR did not occur. PCR and real time PCR were used as methods of pathogen detection and quantification, respectively, A gene associated with pathogenicity in Streptomyces spp., was used to screen isolates obtained from Streptomyces spp. soil populations. Real time PCR was effective for pathogen population quantification between different fields. This research demonstrates that cultivar resistance is the primary method for managing potato scab. Detection of the pathogenic Streptomyces spp. was achieved more economically by PCR. Real time PCR was reliable for quantification, but is much less economic for use as a diagnostic tool.
A Multivariate Approach to Characterizing Insect Resistance in Willow and Poplar Biomass Production Clones. Erik E. Nordman, Daniel J. Robison, Lawrence P. Abrahamson, Timothy A. Volk. Grand Valley State University, Biology Department, Saginaw, MI
Short-rotation woody crops (SRWC) are being developed to meet a growing demand for renewable bioenergy and bioproduct feedstocks. SWRC also provide a suite of environmental and rural development benefits. However, damage from defoliating insects can significantly reduce the yield of SRWC and negatively affect their sustainability. Scores of different willow (Salix spp.) and poplar (Populus spp.) clones have shown potential for bioenergy applications but their insect resistance is relatively unknown. Nineteen willow and six poplar biomass production clones were subjected to feeding by seven common folivorous insects in no-choice laboratory feeding assays. Significant differences in resistance were found among clones. Multivariate cluster analysis was compared against univariate techniques (correlation and ANOVA) for ease of discriminating resistant clones. The multivariate approach proved effective in sorting clones into susceptibility classes and sorting folivores along a continuum of insect specialization. The multivariate cluster analysis technique shows promise for efficiently evaluating large numbers of clones to reveal insect-resistant candidates for field deployment.
These abstracts were edited by the Chair of this section, Gary K. Greer.
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|Author:||Greer, Gary K.|
|Date:||Jan 1, 2008|
|Previous Article:||Biochemistry/molecular Biology.|