Aluminum-induced oxidative stress in cucumber

Aluminum (Al) is one of the most abundant elements of the planet and exposure to this metal can cause oxidative stress and lead to various signs of toxicity in plants. Plants are essential organisms for the environment as well as food for humans and animals. The toxic effect of aluminum is the major cause of decreased crop productivity. Thus, the objective of the present study was to analyze the effects of aluminum on the activity of antioxidant enzymes such as catalase (CAT – E.C. 1.11.1.6), superoxide dismutase (SOD – E.C.1.15.1.1) and ascorbate peroxidase (APX – E.C. 1.11.1.11), and on lipid peroxidation, electrolyte leakage percentage (ELP) and chlorophyll and protein oxidation levels in Cucumis sativus L. (cv. Aodai). Seedlings were grown at different concentrations of aluminum ranging from 1 to 2000 μM for 10 days. The increase in ELP and H₂O₂ production observed in the seedlings may be related to the decreased efficiency of the antioxidant system at higher aluminum concentrations. The antioxidant system was unable to overcome toxicity resulting in negative effects such as lipid peroxidation, protein oxidation and a decrease in the growth of Cucumis seedlings. Aluminum toxicity triggered alterations in the antioxidant and physiological status of growing cucumber seedlings.     

Factors influencing adult female oviposition in the citrus leafminer Phyllocnistis citrella

1 The citrus leafminer (CLM) Phyllocnistis citrella Stainton (Lepidoptera: Gracillariidae) is a serious pest in most citrus‐growing regions of the world. The influence of leaf length, citrus species or variety, leaf colour tone and temperature on CLM oviposition was studied from field observations and laboratory experiments. The spatial distribution of eggs on leaves was also examined. Field data were obtained from 1100 samples collected in eastern Spain for 7 years. 2 Significant differences in oviposition rate were found among citrus species in ‘no choice’ laboratory experiments. This tendency was not apparent in the field due to the confounding effect of such factors as the intensity of new flushes and adult CLM abundance. Leaf colour tone and air temperature in the range studied (18–27°C) had no effect on CLM egg‐laying. 3 The distribution of eggs among leaves was random for population densities lower than four eggs per leaf, but became strongly aggregated above this, when not all eggs could survive and complete development. 4 The CLM developmental stage found on leaves depended on the leaf length, and most of the egg‐laying occurred only on leaves that were 10–25 mm long. These leaves had the highest CLM stages in the field and thus give the best estimate of CLM oviposition.     

Spatial analysis of the distribution of Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae) and losses in maize crop productivity using geostatistics

The fall armyworm, Spodoptera frugiperda (J.E. Smith), is one of the chief pests of maize in the Americas. The study of its spatial distribution is fundamental for designing correct control strategies, improving sampling methods, determining actual and potential crop losses, and adopting precise agricultural techniques. In S?o Paulo state, Brazil, a maize field was sampled at weekly intervals, from germination through harvest, for caterpillar densities, using quadrates. In each of 200 quadrates, 10 plants were sampled per week. Harvest weights were obtained in the field for each quadrate, and ear diameters and lengths were also sampled (15 ears per quadrate) and used to estimate potential productivity of the quadrate. Geostatistical analyses of caterpillar densities showed greatest ranges for small caterpillars when semivariograms were adjusted for a spherical model that showed greatest fit. As the caterpillars developed in the field, their spatial distribution became increasingly random, as shown by a model adjusted to a straight line, indicating a lack of spatial dependence among samples. Harvest weight and ear length followed the spherical model, indicating the existence of spatial variability of the production parameters in the maize field. Geostatistics shows promise for the application of precise methods in the integrated control of pests.     

Fast projection matching for cryo-electron microscopy image reconstruction

A new FFT-accelerated projection matching method is presented and tested. The electron microscopy images are represented by their Fourier-Bessel transforms and the 3D model by its expansion in spherical harmonics, or more specifically in terms of symmetry-adapted functions. The rotational and translational properties of these representations are used to quickly access all the possible 2D projections of the 3D model, which allow an exhaustive inspection of the whole five-dimensional domain of parameters associated to each particle.     

A preponderantly 4-sulfated, 3-linked galactan from the green alga Codium isthmocladum

The green algae of the genus Codium have recently been demonstrated to be an important source of sulfated galactans from the marine environment. Here, a sulfated galactan was isolated from the species Codium isthmocladum and its structure was studied by a combination of chemical analyses and NMR spectroscopy. Two fractions (SG 1, approximately 14 kDa, and SG 2, approximately 20 kDa) were derived from this highly polydisperse and heterogeneous polysaccharide. Both exhibited similar structures in (1)H 1D NMR spectra. The structural features of SG 2 and its desulfated derivative were analyzed by COSY, TOCSY, DEPT-HSQC, HSQC, and HMBC. This sulfated galactan is composed preponderantly of 4-sulfated, 3-linked beta-D-galactopyranosyl units. In minor amounts, it is sulfated and glycosylated at C-6. Pyruvate groups are also found, forming five-membered cyclic ketals as 3,4-O-(1'carboxy)-ethylidene-beta-D-galactose residues. A comparison of sulfated galactans from different marine taxonomic groups revealed similar backbones of 3-beta-D-Galp-1.     

A reassessment of the in vitro RBC haemolysis assay with defibrinated sheep blood for the determination of the ocular irritation potential of cosmetic products: comparison with the in vivo Draize rabbit test

We examined the correlation between results obtained from the in vivo Draize test for ocular irritation and in vitro results obtained from the sheep red blood cell (RBC) haemolytic assay, which assesses haemolysis and protein denaturation in erythrocytes, induced by cosmetic products. We sought to validate the haemolytic assay as a preliminary test for identifying highly-irritative products, and also to evaluate the in vitro test as alternative assay for replacement of the in vivo test. In vitro and in vivo analyses were carried out on 19 cosmetic products, in order to correlate the lesions in the ocular structures with three in vitro parameters: (i) the extent of haemolysis (H50); (ii) the protein denaturation index (DI); and (iii) the H50/DI ratio, which reflects the irritation potential (IP). There was significant correlation between maximum average scores (MAS) and the parameters determined in vitro (r = 0.752-0.764). These results indicate that the RBC assay is a useful and rapid test for use as a screening method to assess the IP of cosmetic products, and for predicting the IP value with a high level of concordance (94.7%). The assay showed high sensitivity and specificity rates of 91.6% and 100%, respectively.     

Relative importance of natural enemies and abiotic factors as sources of regulation of mealybugs (Hemiptera: Pseudococcidae) in Brazilian coffee plantations

In the present study, we determined the critical stages and the key factors of mortality for Planococcus citri (Hemiptera: Pseudococcidae) in Brazilian coffee plantations using a life table to understand the role of natural biological control on its population. Predators, parasitoids, rainfall, sunlight, physiological disturbances and fungal diseases were collectively responsible for 98.79% in the total mortality of P. citri. Predators belonging to the Chrysopidae, Syrphidae, Dolichopodidae and Coccinellidae families were the most important mortality factors in the early developmental stages of P. citri (i.e. eggs and 1st and 2nd instar nymphs), whereas predators belonging to the Coccinellidae and Chrysopidae families were the most important mortality factors for the last instars (i.e. 3rd instars and adults) for P. citri. The generalist predators Harmonia axyridis, Chrysoperla genanigra and Chrysoperla externa were the key mortality factors for P. citri. The third nymph stage was considered the critical life stage (i.e. the life stage that most influences population size). Our results show that generalist predators and climatic factors are important sources of natural mortality of P. citri governing the population dynamics of this pest in the field.