Sarah A. White

Interactions of gold nanoparticles with freshwater aquatic macrophytes are size and species dependent

The partitioning of 4- and 18-nm gold nanoparticles (AuNPs) to aquatic macrophytes was investigated in vivo with exposure suspension in well water. Three morphologically distinct aquatic macrophytes were studied. Myriophyllum simulans Orch. and Egeria densa Planch. are submerged aquatic vascular plants, whereas Azolla caroliniana Willd. is a free-floating aquatic fern. Because aquatic plants absorb the majority of their nutrients from the water column, it is logical to hypothesize that they may absorb nanomaterials in suspension, potentially facilitating trophic transfer. Each plant was exposed to two different-sized gold nanospheres at a nominal concentration of 250 µg/L AuNPs for 24 h. Macrophytes were harvested at six time points (1, 3, 6, 12, 18, and 24 h), dried, and then analyzed for gold concentration via inductively coupled plasma-mass spectrometry. Concentrations were normalized to whole-plant dry tissue mass. The present study shows that absorption of AuNPs through root uptake was size and species dependent. Electron microscopy revealed that 4- and 18-nm AuNPs adsorbed to the roots of each species. Root tissue was sectioned, and transmission electron microscopy indicated that 4-nm and 18-nm AuNPs were absorbed by A. caroliniana, whereas only 4-nm AuNPs were absorbed by M. simulans. Egeria densa did not absorb AuNPs of either size. Gold nanoparticles were confirmed in tissue by using energy-dispersive X-ray spectroscopy. Absorption of AuNPs by plants may be a function of the salinity tolerance of each species.

Stakeholder Vision of Future Direction and Strategies for Southeastern U.S. Nursery Pest Research and Extension Programming

Extension and research professionals worked with a focus group of 10 nursery owners and managers across a five-state region (Georgia, Kentucky, North Carolina, South Carolina, Tennessee) in the southeastern United States to prioritize diverse nursery pests and production issues that are related to container and field production. A second focus group meeting, focused on technology, was followed by a survey that asked nursery growers to prioritize potential inputs and uses of information technology and the features they most valued, for example, that might be included within a nursery-specific mobile device application. The resulting prioritization highlights common challenges faced by growers across the southeastern United States in managing major plant diseases, arthropod pests, and weeds; as well as documenting emerging critical issues of nonpest related production issues, regulatory constraints, and technological needs. The focus group and survey format effectively identified grower needs that will help inform nursery producers and guide university Extension and research professionals, university administrators, industry associations, and state and federal government officials toward efficient resource allocation. These prioritizations explain the current state-of-need across a diverse agricultural industry segment and will help further refine future strategic action plans for nursery integrated pest management (IPM) and emerging critical nursery crop pest issues.

Assessing the integrated pest management practices of southeastern US ornamental nursery operations

BACKGROUND The Southern Nursery Integrated Pest Management (SNIPM) working group surveyed ornamental nursery crop growers in the southeastern United States to determine their pest management practices. Respondents answered questions about monitoring practices for insects, diseases and weeds, prevention techniques, intervention decisions, concerns about IPM and educational opportunities. Survey respondents were categorized into three groups based on IPM knowledge and pest management practices adopted. RESULTS The three groups differed in the use of standardized sampling plans for scouting pests, in monitoring techniques, e.g. sticky cards, phenology and growing degree days, in record-keeping, in the use of spot-spraying and in the number of samples sent to a diagnostic clinic for identification and management recommendation. CONCLUSIONS Stronger emphasis is needed on deliberate scouting techniques and tools to monitor pest populations to provide earlier pest detection and greater flexibility of management options. Most respondents thought that IPM was effective and beneficial for both the environment and employees, but had concerns about the ability of natural enemies to control insect pests, and about the availability and effectiveness of alternatives to chemical controls. Research and field demonstration is needed for selecting appropriate natural enemies for augmentative biological control. Two groups utilized cooperative extension almost exclusively, which would be an avenue for educating those respondents.

Floral Colonization of a Free-Water Surface Constructed Wetland System in Grady County, Georgia

ABSTRACT  A comprehensive survey of the vascular flora of a constructed wetland in Grady County, Georgia was conducted at monthly intervals between August 2004 and May 2006. The constructed wetland is used as a part of a nutrient remediation system to improve the sustainability of plant nursery water-handling practices. The survey evaluated vegetation in a 3.1 ha, two-stage constructed wetland consisting of two deep cells (Stage 1; mean depth 0.75 m) totaling 1.8 ha that drain into two shallow cells (Stage 2; mean depth 0.2 m) totaling 1.3 ha. Each cell was band planted in 1997 with seedlings or liners of six wetland plant species. During the 2-yr survey, 141 distinct species were collected from the 3.1 ha constructed wetland; of the taxa collected, there were 101 genera from 51 families. Native taxa made up 76.6% of the species recorded, and 24.1% of the taxa were introduced. Hydrophytic plants accounted for 68.1% of the plants collected and the remainder (31.9%) were classified as nonhydrophytes. Because 57.4% of the taxa surveyed were perennial, it is likely that plant propagules introduced by wildlife (waterfowl, reptiles, and amphibians) were the dominant method of plant introduction rather than primary succession. Vascular plant community diversity increased 24-fold during the 9-yr period after constructed wetland installation.

Water Use and Treatment in Container-Grown Specialty Crop Production: A Review

While governments and individuals strive to maintain the availability of high-quality water resources, many factors can “change the landscape” of water availability and quality, including drought, climate change, saltwater intrusion, aquifer depletion, population increases, and policy changes. Specialty crop producers, including nursery and greenhouse container operations, rely heavily on available high-quality water from surface and groundwater sources for crop production. Ideally, these growers should focus on increasing water application efficiency through proper construction and maintenance of irrigation systems, and timing of irrigation to minimize water and sediment runoff, which serve as the transport mechanism for agrichemical inputs and pathogens. Rainfall and irrigation runoff from specialty crop operations can contribute to impairment of groundwater and surface water resources both on-farm and into the surrounding environment. This review focuses on multiple facets of water use, reuse, and runoff in nursery and greenhouse production including current and future regulations, typical water contaminants in production runoff and available remediation technologies, and minimizing water loss and runoff (both on-site and off-site). Water filtration and treatment for the removal of sediment, pathogens, and agrichemicals are discussed, highlighting not only existing understanding but also knowledge gaps. Container-grown crop producers can either adopt research-based best management practices proactively to minimize the economic and environmental risk of limited access to high-quality water, be required to change by external factors such as regulations and fines, or adapt production practices over time as a result of changing climate conditions.

Photosynthetic Characteristics of Veratrum californicum in Varied Greenhouse Environments

Corn lily or California false hellebore (Veratrum californicum Durand), a perennial species native to the western United States, produces several alkaloid compounds. A derivative of these alkaloid compounds, primarily veratramine and cyclopamine, shows promise as a therapeutic agent for treatment of a variety of tumor types. Here we report the first study of corn lily cultivated in greenhouse. Growth response of corn lily was examined under two light levels (ambient and supplemental), two fertilization types (20 N-4.4 P16.6 K Peat-lite special and 15N-2.2P-12.5K CalMag special) at 100-mg·L total nitrogen, and three irrigation cycles [sub-irrigation every day (wet), every third day (dry), and hand watering]. Net CO2 assimilation rate (Pn) and transpiration rate (ET) of corn lily grown under supplemental light were 11.0% and 44.7%, respectively, higher than those under ambient light. The Pn and ET of corn lily grown with the wet irrigation cycle increased by 15.2% and 29.4%, respectively, when compared with the Pn and ET of plants grown under the dry irrigation cycle. Corn lily grown wet with supplemental light had the highest average Pn of 8.55 ± 0.36 μmol·m·s, while plants grown under ambient light with hand watering had the lower average Pn of 6.52 ± 0.48 μmol·m·s. The highest mean ET recorded for corn lily was 4.97 ± 0.17 mmol·m·s when plants were grown dry with supplemental light, while the lowest ET recorded was 2.51 ± 0.18 mmol ms when plants were grown under ambient light and hand with supplemental light and when volumetric water content remained above 44%. The water use efficiency of corn lily may be low, as water is not normally limiting in the natural environment where corn lily grows. INTRODUCTION Corn lily (Veratrum californicum Durand; Melanthiaceae family) is a poisonous, herbaceous perennial, facultative wetland species in its native habitat range within the Rocky Mountains and mountains of western North America (Niehaus et al., 1984; USDA, 2011). The Veratrum genus consists of 27 species (Ferguson, 2010; Liao et al., 2007; Zomlefer et al., 2003). The corn lily plant, also known as California false hellebore, can grow from 1 to 2 m in height with a cornstalk-like stem (Niehaus et al., 1984). The plant is attractive with large, broadly ovateelliptical leaves and with dense panicles of creamywhite flowers (James et al., 2004; Keeler and Binns, 1971). Corn lily has been used in herbal medicine for a relatively long time and has potential pharmaceutical uses (Boericke, 1927). The activity of the plant alkaloids, such as cyclopamine, manifests as birth defects, such as cyclopia and holoprosencephaly on grazing pregnant animals (James et al., 2004; Keeler and Binns, 1971). Recently, cyclopamine and its derivatives have been examined as promising therapeutic agents for the treatment of tumors arising from activation of the hedgehogsignaling pathway (Berman et al., 2002; Chen et al., 2002; James et al., 2004; Taipale and Beachy, 2001; Wang, 1990; Watkins et al., 2003). In particular, watered. In corn lily, photosynthesis was increased Sun et al.: Photosynthetic Characteristics of Veratrum californicum in Varied

In Situ Production of Zoospores by Five Species of Phytophthora in Aqueous Environments for Use as Inocula

The goal of this study was to develop a procedure that could be used to evaluate the potential susceptibility of aquatic plants used in constructed wetlands to species of Phytophthora commonly found in nurseries. V8 agar plugs from actively growing cultures of three or four isolates of Phytophthora cinnamomi, P. citrophthora, P. cryptogea, P. nicotianae, and P. palmivora were used to produce inocula. In a laboratory experiment, plugs were placed in plastic cups and covered with 1.5% nonsterile soil extract solution (SES) for 29 days, and zoospore presence and activity in the solution were monitored at 2- or 3-day intervals with a rhododendron leaf disk baiting bioassay. In a greenhouse experiment, plugs of each species of Phytophthora were placed in plastic pots and covered with either SES or Milli-Q water for 13 days during both summer and winter months, and zoospore presence in the solutions were monitored at 3-day intervals with the baiting bioassay and by filtration. Zoospores were present in solutions throughout the 29-day and 13-day experimental periods but consistency of zoospore release varied by species. In the laboratory experiment, colonization of leaf baits decreased over time for some species and often varied among isolates within a species. In the greenhouse experiment, bait colonization decreased over time in both summer and winter, varied among species of Phytophthora in the winter, and was better in Milli-Q water. Zoospore densities in solutions were greater in the summer than in the winter. Decreased zoospore activities for some species of Phytophthora were associated with prolonged temperatures below 13 or above 30°C in the greenhouse. Zoospores from plugs were released consistently in aqueous solutions for at least 13 days. This procedure can be used to provide in situ inocula for the five species of Phytophthora used in this study so that aquatic plant species can be evaluated for potential susceptibility.

Micropropagation, Acclimatization, and Greenhouse Culture of Veratrum californicum

Micropropagation and production of Veratrum californicum is most successful when using a premixed Murishage and Skoog basal medium with vitamins and a 5-week subculture cycle at 16 °C for multiplication. These culture conditions provide the best percent survival after acclimatization in the greenhouse. However, clone response to temperature and light quality within culture conditions varies. Micropropagated plants have mass and morphology similar to 2- or 3-year-old seedlings. Acclimatized plantlets can then be grown in the greenhouse using sub-irrigation (ebb and flood) to maintain substrate volumetric water content > 44 %. Growth cycle in the greenhouse must be about 100 days, followed by dormancy for 5 months at 5 °C.