Determination of organic acids in tissues and exudates of maize, lupin, and chickpea by high-performance liquid chromatography-tandem mass spectrometry

This article describes a fast and simple methodology for the extraction and determination of organic acids in tissues and root exudates of maize, lupin, and chickpea by LC/MS/MS. Its main advantage is that it does not require sample prepurification before HPLC analysis or sample derivatization to improve sensibility. The results obtained showed good precision and accuracy, a recovery close to 100%, and no significant matrix effect. Moreover, the sensibility of the method is in general better than that of previously described methodologies, with detection limits between 15 and 900 pg injected.     

Histopathological Changes in Third-Instar and Adult Anastrepha ludens (Diptera: Tephritidae) After in vitro Heat Treatment

The Mexican fruit fly, Anastrepha ludens Loew (Diptera: Tephritidae), is one of the most harmful pests of mango causing direct damage by oviposition on the fruit pulp. Mango for export is subjected to hydrothermal treatment as a quarantine method for the control of this pest, but exposure to heat for long periods of time reduces considerably the quality and shelf-life of treated fruit. The aim of this work was to study morphological changes of third-instar larvae and adults of A. ludens after in vitro exposure to high temperature at sublethal times. A heating block system was used to expose larvae at 46.1°C for 19.6 and 12.9 min, producing 94.6 and 70% mortality, respectively. Treated larvae were processed for optical microscopy. A fraction of surviving treated larvae was separated into containers with artificial diet to allow development into adults. Adult sexual organs were dissected and processed for transmission electron microscopy analysis. Results showed that 94.6% of the treated larvae died at 46.1°C for 19.6 min and none of the surviving larvae eclosed to adulthood, as they developed as malformed puparia. For the in vitro treatment at 46.1°C during 12.9 min, 70% of the treated larvae died and only 3.75% reached the adult stage, but ultrastructural damage in the male testes and in the female ovaries was observed. Additionally, 11.1% of the adult flies from the in vitro treatment also showed wing malformation and were incapable of flying. The analysis showed that surviving flies were unable to reproduce.     

Regeneration patterns of Eastern white pine (Pinus strobus L.) in hardwood-dominated forests in Virginia, USA

Eastern white pine (Pinus strobus L.) is a moderately shade-tolerant species that co-occurs with hardwood tree species in many forests of the eastern United States, as well as in pure stands. The species is valued for its timber, as well as for wildlife and recreation. Regeneration of this species is somewhat unpredictable and often occurs in patches of similarly-aged cohorts. We described the regeneration patterns of this species and examined their relation to environmental variables within hardwood forests of southwestern Virginia, USA. An average of 5.3 white pine patches per ha were observed in this study. The majority of patches consisted of saplings (85%), with 9% of patches in pole size classes, and 6% in seedling size classes. The average density of patches was 43.5 stems with an average age of 20 years. The size of patches averaged 80.6 m². The total density of seedlings and the number of regeneration patches of all sizes of regeneration (seedlings, saplings, and poles) in plots was related to the surrounding density of large white pine trees (potential seed trees). The density of seedlings or patches was not significantly related to current vegetation cover or soil surface cover variables, but more than half of regeneration patches were located in or adjacent to old canopy gaps, most of which were old logging gaps. While seedling regeneration may occur within the understory of these forests near seed trees, advancement to the sapling and pole stage appears to be associated with canopy gap formation.     

Simple estimation of available water capacity in soils of semiarid and subhumid environments

Soil available water capacity (AWC) is an important factor affecting soil productivity in semiarid and subhumid environments and is mainly determined by the soil textural composition. As the soils of these environments usually present fairly uniform textures across depth, we hypothesized that it would be possible to accurately estimate the whole-profile AWC using surface information. Our objective was to test this hypothesis in the Argentine Semiarid Pampas. Information was collected from 152 sites where AWC was measured in 20?cm layers up to a depth of 140?cm or up to the upper limit of the petrocalcic horizon, when present. In each case, whole profile AWC was estimated using a one-step and a two-step approach, comparing multiple regression and artificial neural networks as modeling techniques. Both modeling methods were effective (R²?>?0.76, P?相似文献   

Determinants of income-earning strategies and adoption of conservation practices in hillside communities in rural Honduras

Based on the results of participatory diagnostic surveys conducted in 95 rural communities in the hillsides of Honduras, we determine income earning strategies at the community level; identify their main determinants; and analyze the adoption of of conservation practices. Eight income-earning strategies were distinguished that reflect differences in comparative advantage between communities. We explain the choice of income earning strategy using a multinomial logit model that includes biophysical, economic, social and institutional variables. We use a probit model to show that adoption of conservation practices is determined by the type of income earning strategy, population density, market access, and organizational variables.     

Blackberry anthocyanins are mainly recovered from urine as methylated and glucuronidated conjugates in humans

The consumption of anthocyanins has been shown to prevent certain chronic diseases. However, anthocyanin metabolism has not yet been fully elucidated. The aim of this study was to evaluate anthocyanin urinary excretion in humans receiving a meal containing blackberries and to identify possible metabolites in urine. Five healthy volunteers were fed 200 g of blackberries (960 mumol of anthocyanins). Urine samples were collected and rapidly treated by solid-phase extraction. Anthocyanin metabolites were identified and quantified by HPLC-ESI-MS-MS and HPLC with UV-vis detection, respectively. In addition to native cyanidin 3-glucoside, several other anthocyanin metabolites were identified in the urine: methylated glycosides, glucuronides of anthocyanidins and anthocyanins, a sulfoconjugate of cyanidin, and anthocyanidins. Total urinary excretion of blackberry anthocyanin metabolites was 0.160 +/- 0.020% (n = 5) of the amount of anthocyanins ingested. Monoglucuronides of anthocyanidins represented >60% of this excretion. Urinary excretion of anthocyanins was maximal between 2 and 4 h after the meal, but continued during the 24 h of the experiment. This study highlighted the influence of aglycon structure on anthocyanin urinary excretion. It demonstrated that anthocyanins are not only methylated but also glucuroconjugated and sulfoconjugated in humans and that the main metabolites of blackberry anthocyanins in human urine were anthocyanidin monoglucuronides.