PHOSPHORUS DEFICIENCY IN PELARGONIUM: EFFECTS ON NITRATE AND AMMONIUM UPTAKE AND ACIDITY GENERATION

A sudden pH decline (SPD) of the substrate is an increasing problem in geranium growth systems, and the cause is unknown. In this study, we investigate whether a phosphorus (P) deficiency can cause SPD, and whether the effect is related to inhibition of ammonium (NH₄ ⁺) and nitrate (NO₃ ^?) uptake and a corresponding shift in the cation to anion uptake balance. Geraniums (Pelargonium x hortorum Bailey ‘Designer Dark Red’) were grown in hydroponic solutions with or without P, and the hydroponics systems were located in a growth chamber programmed for light/dark temperatures of 22/18 or 26/22°C. Acidification potential was measured by the amount of base required to maintain pH at 5.8. The results indicated that much greater amounts of base were required to maintain a stable pH with P-limited plants. Using periodic exposures to ¹⁵NH₄ ⁺ or ¹⁵NO₃ ^?, it was found that NO₃ ^? uptake was strongly inhibited as plants became P stressed. Tissue nutrient profiles showed that the NO₃ ^? uptake inhibition was accompanied by an increase in the cation to anion uptake ratio. Rhizosphere acidification was greater at higher temperature even though the cation and anion responses were unchanged in control plants, suggesting the involvement of carbon dioxide (CO₂) generated by root respiration. The results indicate that changes in cation and anion uptake and the associated increase in net H+ extrusion that occur under P-stress conditions can contribute to SPD in geranium culture systems.     

Genetic fingerprinting identifies apple (Malus domestica Borkh.) fruit cultivars in historic orchards on public lands

Genetic Resources and Crop Evolution - The National Historic Preservation Act of 1966 mandates that historic resources, including orchards, on federal lands be evaluated for potential significance....     

A climatological basis for conserving groundwater and reducing overflow in aquaculture ponds in the Southeast United States

Drop-fill water management schemes for aquacultural ponds reduce both groundwater use and effluent release. A drop-fill scheme assumes that pond water level will be allowed to decrease to the “drop” depth before makeup water is used to return it to the “fill” depth, which is typically some fraction (e.g., 1/2) of the drop depth. This paper compares predicted performance of drop-fill schemes at five sites in the Southeast U.S. (Thompsons, TX, Stuttgart, AR, Stoneville, MS, Clemson, SC, and Fairhope, AL). The locations were chosen to assess the effect of the east–west precipitation gradient and the south–north change from maritime to continental characteristics on the drop-fill approach in this region.

Performance of the drop-fill schemes was based on calculated daily water balances for ponds using 40-year (1961–2000) precipitation (P) and evaporation (E) records at the sites. Pond evaporation is assumed to be 0.8 × pan evaporation. Since performance differences based on regional P minus E (P−E) records was the subject of this work, ponds were assumed identical in other respects (i.e., all ponds were assumed to be levee-type and to have zero infiltration).

Simulated drop-fill schemes tested included (in cm): 0/0, 5/2.5, 10/5, 15/7.5, 20/10, 25/12.5, 30/15, 45/22.5, 60/30, 90/45, and 120/60. Each scheme was simulated using daily time steps for 40 years at each site. Results suggested that rigorous adherence to even a modest drop-fill scheme results in substantial reductions in both groundwater use and effluent release. It also appears that P−E conditions at all sites allow implementation of more aggressive drop-fill schemes in properly designed ponds that will require no supplemental groundwater for most years. This was also true with respect to effluent release at three of five sites. At two sites, precipitation was sufficiently large that zero effluent years were either not predicted (Fairhope) or relatively uncommon (Clemson) for any drop-fill scheme.     

A comparison of the heart and muscle total lipid and fatty acid profiles of nine large shark species from the east coast of South Africa

We have assessed the fatty acid profiles of the hearts and different muscle tissues from nine large shark species (Carcharhinus limbatus (blacktip), Carcharhinus obscurus (dusky), Carcharhinus brevipinna (spinner), Carcharhinus leucas (Zambezi/bull), Galeocerdo cuvier (tiger), Sphyrna lewini (scalloped hammerhead), Sphyrna zygaena (smooth hammerhead), Carcharodon carcharias (great white) and Carcharias taurus (raggedtooth/grey nurse/sand tiger)) found off the east coast of South Africa. While there was generally little variation between the species, all species showed profiles rich in both n6 and n3 polyunsaturated fatty acids compared to terrestrial commercial meats that have low n3. Thus, utilizing skeletal muscle tissues from sharks caught as part of the bycatch when fishing for teleosts would avoid unnecessary wastage of a potentially valuable resource, with all the possible health benefits of high quality protein combined with balanced polyunsaturates, although contamination with high levels of metabolic wastes, such as urea, may be a negative consideration.     

Early detection of triploidy in the larvae of Pacific oysters,Crassostrea gigas,by flow cytometry

Triploidy may provide a means to neuter the Pacific oyster, C. gigas, genetically thereby increasing survival and marketability during periods of reproduction. Pressure treatments administered 10 min after fertilization for 10 min duration at 6000–8000 psi consistently produced triploids. The highest proportion obtained was 57%. Triploidy was assayed in all experiments at the larval stage and again as spat (metamorphosed larvae) using flow cytometry. A technique to assay larvae as small as 250 μm is described. Results obtained by flow cytometry were verified by chromosome counts. Analysis of triploidy at the larval stage provides reliable estimates of the proportion of triploids, eliminating several weeks of culture time.     

Genetic diversity in a Tasmanian hatchery population of Atlantic salmon (Salmo salar L.) compared with its Canadian progenitor population

The level of genetic diversity in a cultured Atlantic salmon (Salmo salar) population from Tasmania, Australia was examined at 11 microsatellite loci and compared with that in its progenitor population from the River Philip in Nova Scotia, Canada. The reference progenitor population consisted of archived scales collected from wild River Philip salmon in 1971 and 1972, not long after salmon from this river were imported into Australia in the mid‐1960s. The Tasmanian hatchery stock had a significant reduction in the mean number of alleles (31–43%) and mean allelic richness (28–39%) across all microsatellite loci compared with the wild Canadian population. Mean heterozygosity levels remained unchanged. Estimates of per‐generation effective population sizes for the Tasmanian population, based on allele frequency temporal variance with the wild progenitor population, ranged from 102–207 individuals and reflected hatchery records.     

Modelling temperatures and salinities of mixed seawater fish ponds

Modelling of fish pond temperatures and salinities requires application of fundamental energy and mass balance equations. Temperatures and salinities can then be simulated, given the hydrological characteristics and simple weather data. Results of several temperature estimation experiments of 1 and 5 days duration are discussed. The results indicate that pond temperatures can be accurately estimated if the transfer coefficients are known. While salinity estimation is discussed, experiments were not performed, since the temperature experiment indirectly used the salinity data.     

Cumulative impacts of habitat fragmentation and the environmental factors affecting upstream migration in the threatened sea lamprey,Petromyzon marinus

1. River ecosystems are often fragmented by artificial structures, such as weirs. For anadromous species, these structures can impede access to upstream spawning sites and ultimately lead to severe population declines.
2. This study focused on the freshwater spawning migration of the sea lamprey, Petromyzon marinus, an anadromous species threatened by habitat fragmentation across its native range. To quantify the cumulative impacts of multiple weirs on upstream-migrating adults, and to explore the environmental factors affecting migratory movements, passive acoustic telemetry was applied to 56 individuals during their spawning migration in the heavily fragmented River Severn basin, UK.
3. While 89% of tagged sea lamprey passed the first weir upstream of the release site on the main river, only 4% passed the fifth weir. For 85% of migrants, the upstream extent of migration was immediately downstream of a weir. Individuals that passed weirs upstream of the release site (n = 50) took 21.6 ± 2.8 days to reach their most upstream location, experiencing cumulative passage times at weirs of 15.7 ± 2.8 days; these delays constituted a median of 84% of total upstream movement times.
4. Multistate models showed that the weir passage rates of sea lamprey in tidal and non-tidal areas increased significantly when downstream river level and discharge were elevated. Upstream-to-downstream changes in direction were frequent downstream of weirs, but rare in unobstructed river sections.
5. The results provided evidence for a cumulative effect of multiple weirs on sea lamprey movements, substantially delaying upstream migrants and limiting their spawning to atypical habitat. The results also demonstrated the crucial roles of high tides and elevated discharge events in enabling weir passage. Although the Severn Estuary features conservation designations for sea lamprey, this study reveals that barriers are inhibiting their upstream migration, a problem that should be addressed to assist sea lamprey conservation.

     

Using bioacoustic tools to clarify species delimitation within the Blakiston's Fish Owl(Bubo blakistoni)complex

Although Blakiston's Fish Owl(Bubo blakistoni)is widely treated as a single species,marked differences in the structure of pair duets between continental and in...