Phytochemical and morphological characterization of hop (Humulus lupulus L.) cones over five developmental stages using high performance liquid chromatography coupled to time-of-flight mass spectrometry, ultrahigh performance liquid chromatography photodiode array detection, and light microscopy techniques

Hop (Humulus lupulus L.) inflorescences, commonly known as "hop cones", are prized for their terpenophenolic contents, used in beer production and, more recently, in biomedical applications. In this study we investigated morphological and phytochemical characteristics of hop cones over five developmental stages, using liquid chromatography coupled to time-of-flight mass spectrometry (LC-TOF-MS), and ultrahigh performance liquid chromatography photodiode array detection (UHPLC-PDA) methods to quantitate 21 polyphenolics and seven terpenophenolics. Additionally, we used light microscopy to correlate phytochemical quantities with changes in the morphology of the cones. Significant increases in terpenophenolics, concomitant with glandular trichome development and associated gross morphological changes, were mapped over development to fluctuations in contents of polyphenolic constituents and their metabolic precursor compounds. The methods reported here can be used for targeted metabolic profiling of flavonoids, phenolic acids, and terpenophenolics in hops, and are applicable to quantitation in other crops.     

Local management and landscape drivers of pollination and biological control services in a Kenyan agro-ecosystem

Arthropods that have a direct impact on crop production (i.e. pests, natural enemies and pollinators) can be influenced by both local farm management and the context within which the fields occur in the wider landscape. However, the contributions and spatial scales at which these drivers operate and interact are not fully understood, particularly in the developing world. The impact of both local management and landscape context on insect pollinators and natural enemy communities and on their capacity to deliver related ecosystem services to an economically important tropical crop, pigeonpea was investigated. The study was conducted in nine paired farms across a gradient of increasing distance to semi-native vegetation in Kibwezi, Kenya. Results show that proximity of fields to semi-native habitats negatively affected pollinator and chewing insect abundance. Within fields, pesticide use was a key negative predictor of pollinator, pest and foliar active predator abundance. On the contrary, fertilizer application significantly enhanced pollinator and both chewing and sucking insect pest abundance. At a 1 km spatial scale of fields, there were significant negative effects of the number of semi-native habitat patches within fields dominated by mass flowering pigeonpea on pollinators abundance. For service provision, a significant decline in fruit set when insects were excluded from flowers was recorded. This study reveals the interconnections of pollinators, predators and pests with pigeonpea crop. For sustainable yields and to conserve high densities of both pollinators and predators of pests within pigeonpea landscapes, it is crucial to target the adoption of less disruptive farm management practices such as reducing pesticide and fertilizer inputs.     

Impact of fatty acyl composition and quantity of triglycerides on bioaccessibility of dietary carotenoids

A carotenoid-rich salad meal with varying amounts and types of triglycerides (TG) was digested using simulated gastric and small intestinal conditions. Xanthophylls (lutein and zeaxanthin) and carotenes (alpha-carotene, beta-carotene, and lycopene) in chyme and micelle fraction were quantified to determine digestive stability and efficiency of micellarization (bioaccessibility). Micellarization of lutein (+zeaxanthin) exceeded that of alpha- and beta-carotenes, which was greater than that of lycopene for all test conditions. Micellarization of carotenes, but not lutein (+zeaxanthin), was enhanced (P < 0.05) by addition of TG (2.5% v/w) to the meal and was dependent on fatty acyl chain length in structured TG (c18:1 > c8:0 > c4:0). The degree of unsaturation of c18 fatty acyl chains in TG added to the salad purée did not significantly alter the efficiency of micellarization of carotenoids. Relatively low amounts of triolein and canola oil (0.5-1%) were required for maximum micellarization of carotenes, but more oil (approximately 2.5%) was required when TG with medium chain saturated fatty acyl groups (e.g., trioctanoin and coconut oil) was added to the salad. Uptake of lutein and beta-carotene by Caco-2 cells also was examined by exposing cells to micelles generated during the simulated digestion of salad purée with either triolein or trioctanoin. Cell accumulation of beta-carotene was independent of fatty acyl composition of micelles, whereas lutein uptake was slightly, but significantly, increased from samples with digested triolein compared to trioctanoin. The results show that the in vitro transfer of alpha-carotene, beta-carotene, and lycopene from chyme to mixed micelles during digestion requires minimal (0.5-1%) lipid content in the meal and is affected by the length of fatty acyl chains but not the degree of unsaturation in TG. In contrast, fatty acyl chain length has limited if any impact on carotenoid uptake by small intestinal epithelial cells. These data suggest that the amount of TG in a typical meal does not limit the bioaccessibility of carotenoids.     

Plant growth responses to biochar addition: an Australian soils perspective

The use of biochar as an agricultural amendment has attracted much attention owing to its potential to improve soil condition and plant growth; however, production outcomes are often uncertain. Although soil type is a major driver of plant productivity, there are relatively few biochar studies that directly compare plant growth responses across a range of soil types. We tested the wheat growth response to biochar derived from poultry litter and from wheat straw applied at 1, 5 and 10 t ha^?1 (approximately 0.13, 0.67 and 1.33 % w/w) in four soils representing major agricultural regions in Australia: an acidic arenosol (Western Australian cereal belt), an acidic rhodic ferralsol (Northern New South Wales), a neutral vertisol (Queensland cropping) and an alkaline haplic calcisol (Eyre Peninsula in South Australia). In the neutral vertisol, where plant growth was vigorous in the control treatments, biochar had little impact, whereas in the alkaline calcisol, there was a small significant increase in shoot biomass at high (10 t ha^?1) application rates. Plant growth responses in the acidic soils were most evident but demonstrated a strong contrast to one another. In the acidic arenosol, negative growth impact correlated with increasing electrical conductivity, while in the acidic ferralsol a small rate-dependent increase in pH correlated with relatively large gains in biomass, possibly due to improved phosphorus nutrition and alleviated Al toxicity. Moving towards effective integration of biochar as a management tool will not only require stratification based on soil types, but wider consideration of the main plant production constraints, such as pH, pertinent to a particular system.     

Ascorbic acid concentration in Cv. conference pears during fruit development and postharvest storage

L-ascorbic acid (L-AA) concentration changes during the development of cv. Conference pears and the influence of postharvest handlings (gas condition, cooling rate, cooling duration) on L-AA breakdown were studied. L-AA concentration fluctuates in young fruits, remains stable during fruit maturation, and starts to decline 1 week before commercial harvest. The most rapid decrease in L-AA concentration was found during immediate controlled atmosphere. During short-term storage, only the gas condition was found to influence L-AA breakdown; no significant difference between gradually or immediately cooled pears was determined. Under air conditions, both cooling strategies did not differ from the L-AA breakdown in pears allowed to ripen on the tree up until 3 weeks after the optimal harvest date. During long-term storage, the cooling duration (1-3 weeks) had no effect whereas both O2 and CO2 had a significant effect on L-AA retention. After 7 months of storage, no difference was found in dehydroascorbic acid concentration; the L-AA and total L-AA concentrations, in contrast, were significantly lower in the 5% CO2 conditions.     

Developing a magnetic tracer to study soil erosion

Soil erosion is commonly measured as the quantity of sediment leaving a plot or watershed. The techniques for measuring soil erosion patterns and sediment redistribution within plots or watersheds by direct monitoring are very limited. The objective of this study was to develop a direct and non-intrusive tracer method to study the sources, patterns and rates of erosion and deposition of sediments in erosion plots. The magnetic tracer developed in this study consisted of polystyrene plastic beads embedded with a magnetic powder (magnetite). The “magnetized” beads, with a mean weight diameter of 3.2 mm and particle density of about 1.2 g cm⁻³, were uniformly mixed with soil and tested in the laboratory using simulated rainfall and inflow studies to simulate the interrill and rill components of soil erosion, respectively. In the interrill and rill experiments, the tracer was transported in the same proportion it was initially mixed with the soil. Given this fact, a magnetometer, which measures the soil's magnetic susceptibility, could be used to identify areas of deposition or detachment. The magnetic susceptibility would be increased or reduced depending on whether deposition or detachment occurs. To simulate detachment and deposition, a magnetometer was tested for different tracer concentrations and different thickness of soil containing the tracer. The magnetometer promises to be a sensitive, accurate, and useful tool to study the spatial variation of soil erosion when magnetic tracers are used.     

Anthropogenic Mercury Deposition to Arctic Lake Sediments

The history of atmosheric mercury inputs to remote arctic regions can be measured in lake sediment cores using lead-210 chronology. In this investigation, total mercury deposition is measured in sediments from Imitavik and Annak Lakes on the Belcher Islands in southeastern Hudson Bay, an area in the southern Canadian Arctic with no history of local industrial or agricultural sources of contamination. Both lakes received background and atmospheric inputs of mercury while Annak also received mercury from raw domestic sewage from the Hamlet of Sanikiluaq, a growing Inuit community of about 550 established in the late 1960's. Results from Imitavik show that anthropogenic mercury inputs, apparently transported through the atmosphere, began to appear in the mid-eighteenth century, and continued to the 1990's. Annak had a similar mercury history until the late 1960's when disposal of domestic sewage led to increased sediment and contaminant accumulation. The high input of mercury to Annak confirms that Sanikiluaq residents are exposed to mercury through native food sources.     

Landscape cover type and pattern dynamics in fragmented southern Great Plains grasslands,USA

We documented land cover and landscape pattern changes in an area of northwestern Oklahoma, USA using aerial photography from 1965, 1981, and 1995. This region of the southern Great Plains is fragmented by agricultural activity, and in recent years many remnant native grasslands have experienced extensive invasion by woody juniper (Juniperus virginiana L.). Concurrently, many cropland areas are being planted into perennial forage grasses and converted to intensively managed introduced grasslands as part of the U.S. Conservation Reserve Program (CRP). Our objectives were to document land cover and landscape pattern changes in the region relative to the expansion of juniper and CRP activity. We then examined how local landscape dominance by either anthropogenic or woody vegetation patches affected landscape pattern indices. Land cover changes from 1965 to 1995 included substantial increases in juniper woodlands and mixed woodlands that resulted from juniper encroachment into deciduous woodlands. Introduced grasslands also increased in many areas as a result of CRP implementation. Changes in landscape pattern generally reflected the influx of juniper into many areas. Landscapes dominated by woody vegetation had significantly more patches, smaller patches and patch core areas, more total edge, and higher patch diversity than landscapes dominated by anthropogenic cover types. Results indicate that expanding juniper is exacerbating the fragmentation process initiated by previous human activity, and represents a serious threat to the continued integrity and conservation of remaining southern Great Plains grasslands.This revised version was published online in May 2005 with corrections to the Cover Date.