Persistence and biodegradation of selected organophosphorus insecticides in flooded versus non-flooded soils

Summary The persistence of parathion, methyl parathion and fenitrothion in five tropical soils of varying physicochemical characteristics was compared under flooded and non-flooded conditions. The degradation of all the three insecticides was more rapid under flooded conditions than under non-flooded conditions in four out of five soils. Degradation of these insecticides proceeded by hydrolysis under non-flooded conditions and essentially by nitro group reduction and to a minor extent by hydrolysis under flooded conditions. Kinetic analysis indicated that degradation of the three insecticides followed a first-order reaction irrespective of the soil and water regime. The degradation of these organophosphorus insecticides was accelerated after repeated applications to flooded alluvial soil. Nitro group reduction was the major pathway of degradation for all the three insecticides after the first addition while the rate of hydrolysis increased after each successive addition.     

Tuning the properties of PVDF or PVDF-HFP fibrous materials decorated with ZnO nanoparticles by applying electrospinning alone or in conjunction with electrospraying

Novel composite nanofibrous materials of poly(vinylidene fluoride) (PVDF) or poly(vinylidene fluoride-cohexafluoropropylene) (PVDF-HFP) and ZnO nanoparticles were prepared by conjunction of electrospinning and electrospraying techniques. Simultaneous electrospinning of concentrated solution of PVDF or PVDF-HFP and electrospraying of suspension of ZnO in diluted PVDF or PVDF-HFP solution enable the preparation of materials consisting of fibers on which ZnO was deposited on the fibers’ surface (design type “on”). These fibrous materials were compared with materials consisting of PVDF or PVDF-HFP fibers in which ZnO was incorporated in the fibers (design type “in”) and which were obtained by one-pot electrospinning of a suspension of ZnO nanoparticles in concentrated PVDF or PVDF-HFP solution. The fiber morphology and the presence of ZnO “in” or “on” the fibers were observed by scanning electron microscopy (SEM) and by transmission electron microscopy (TEM). The effect of the used technique on the type, size and shape of the obtained structures was discussed. The fibrous mats were studied by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), X-ray diffraction (XRD), contact angle measurements and mechanical tests as well. It was found that the decoration of fibers with ZnO resulted in increase of their thermal stability and hydrophobicity. The microbiological tests showed that the materials of design type “on” possessed strong antibacterial activity against the pathogenic microorganism Staphylococcus aureus. The results suggest that, due to their antibacterial activity, the obtained composite materials are suitable for wound dressing applications.     

Foliar feeding of boron improves the productivity of cotton cultivars with enhanced boll retention percentage

Abstract

Cotton (Gossypium hirsutum L.) is of prime importance because of its quality fiber and edible oil production. Boron (B) is among essential micronutrients for plant growth; it aids in the transfer of sugars and nutrients from leaves to fruit that are involved directly or indirectly in many plant functions. Cotton growth, yield and quality are strongly affected with boron application. A two-year study was conducted to evaluate the impact of foliar applied B (0, 2, 4, 6, 8 and 10?g of B L^?1 of water) on the performance of cotton cultivars (FH-113, MNH-786 and CIM-496). The results indicated that growth, yield and quality traits of cotton were significantly influenced by different levels of foliar applied boron as well as cultivars of cotton. Among cotton cultivars, the yield and quality parameters were superior in cultivar “FH-113.” Foliar application of boron at 6?g L^?1 of water improved leaf area index and leaf area duration and eventually improved the number of bolls per plant, boll retention percentage, average boll weight, lint yield, ginning out turn, fiber length and uniformity ratio of cotton. Foliar application of B at 6?g per liter of water, showed promising results by improving growth and quality parameters and is recommend to enhance the economical yield production of cotton cultivar “FH-113” with improved quality.     

Impacts of Air Pollutants on Vegetation in Developing Countries

The predicted increases in emissions of primary pollutants in many rapidly industrializing countries may have severe consequences for the health and productivity of forest trees and agricultural crops. This paper presents a review of air pollution impacts on vegetation in developing countries by summarising information describing the direct impacts to vegetation caused by a number of air pollutants (sulphur dioxide (SO₂), nitrogen oxides (NOx), ozone (O₃) and Suspended Particulate Matter (SPM)). This information has been collected by experts from a number of rapidly industrializing countries in Asia, Latin America and Africa and includes observations of visible injury in the field and the use of transect studies and controlled experimental investigations to ascribe damage to different pollutant concentrations. The ability to synthesise this information to define exposure-response relationships and subsequent air quality guidelines similar to those established in North America and Europe is assessed. In addition, the use of regional and global models describing pollution concentrations is discussed with reference to assessing the extent of adverse impacts and identifying regions likely to be most at risk from air pollution, both for the present day and in the future. The evidence summarised in the paper clearly shows that current pollutant concentrations experienced in many developing countries, particularly Asia, can result in severe damage to vegetation and that without appropriate control measures such damage is likely to worsen in the future as pollutant emissions increase.     

Improving the Drought Tolerance in Rice (Oryza sativa L.) by Exogenous Application of Salicylic Acid

Drought stress encumbers the rice growth predominantly by oxidative damage to biological membranes and disturbed tissue water status. In this study, the role of salicylic acid (SA) to induce drought tolerance in aromatic fine grain rice cultivar Basmati 2000 was evaluated. SA was applied as seed and foliar treatments. For seed treatment, rice seeds were soaked in 50, 100 and 150 mg l⁻¹ aerated solution of SA for 48 h and then dried back. Treated and untreated seeds were sown in plastic pots in a phytotron. At four leaf stage, one set of plants was subjected to drought stress, while the other remained well watered. Drought was maintained at 50 % of field capacity by watering every alternate day. For exogenous application, SA was applied 50, 100 and 150 mg l⁻¹ at five leaf stage. In the control, SA was neither applied exogenously nor as seed treatment. Drought stress severely affected the seedling fresh and dry weight, photosynthesis, stomatal conductance, plant water relations and starch metabolism; however, SA application improved the performance of rice under both normal and stress conditions. Drought tolerance in rice was well associated with the accumulation of compatible solutes, maintenance of tissue water potential and enhanced potency of antioxidant system, which improved the integrity of cellular membranes and facilitated the rice plant to sustain photosynthesis and general metabolism. Foliar treatments were more effective than the seed treatments. Foliar application with 100 mg l⁻¹ (FA 100) was the best treatment to induce the drought tolerance and improve the performance under normal and stress conditions compared with the control or other treatments used in this study.     

Improving the Performance of Wheat by Seed Priming Under Saline Conditions

Salinity is one of a major threat in harvesting good wheat stand on sustained basis. In this study, potential of seed priming techniques to improve the performance of wheat varieties (SARC‐1 and MH‐97) in a saline field was tested. For priming, wheat seeds were soaked in aerated solution of ascorbate (50 mg l^?1; ascorbate priming), salicylic acid (50 mg l^?1; salicylicate priming), kinetin (50 mg l^?1; kinetin priming) and CaCl₂ (50 mg l^?1; osmopriming) for 12 h. For comparison, seeds were also soaked in simple water (hydropriming); in addition, untreated seeds were also taken as control. Seed priming treatments substantially improved the stand establishment; osmopriming (with CaCl₂) was at the top however. Likewise maximum fertile tillers, grains per spike, 1000‐grain weight, grain yield and harvest index were observed in plants raised from seeds osmoprimed (with CaCl₂) followed by ascorbate priming in both the varieties tested. As an index of salinity tolerance, seed priming treatments also improved the leaf K⁺ contents with simultaneous decrease in Na⁺ concentration, osmopriming being the best treatment. Similarly, maximum total phenolic contents, total soluble proteins (TSP), α‐amylase and protease activities were observed in osmoprimed (with CaCl₂) seeds followed by ascorbate priming. Economic analysis also indicated that osmopriming is more viable with maximum net return and benefit‐to‐cost ratio. In conclusion, different seed priming treatments in wheat seeds improved the salinity tolerance nonetheless osmopriming (with CaCl₂) was the most effective treatments to get higher grain yield and net return in both wheat varieties whereas kinetin was the least effective.     

The role of allelopathy in agricultural pest management

Allelopathy is a naturally occurring ecological phenomenon of interference among organisms that may be employed for managing weeds, insect pests and diseases in field crops. In field crops, allelopathy can be used following rotation, using cover crops, mulching and plant extracts for natural pest management. Application of allelopathic plant extracts can effectively control weeds and insect pests. However, mixtures of allelopathic water extracts are more effective than the application of single-plant extract in this regard. Combined application of allelopathic extract and reduced herbicide dose (up to half the standard dose) give as much weed control as the standard herbicide dose in several field crops. Lower doses of herbicides may help to reduce the development of herbicide resistance in weed ecotypes. Allelopathy thus offers an attractive environmentally friendly alternative to pesticides in agricultural pest management. In this review, application of allelopathy for natural pest management, particularly in small-farm intensive agricultural systems, is discussed.     

Iron isotope fractionation and the oxygen fugacity of the mantle

The oxygen fugacity of the mantle exerts a fundamental influence on mantle melting, volatile speciation, and the development of the atmosphere. However, its evolution through time is poorly understood. Changes in mantle oxidation state should be reflected in the Fe3+/Fe2+ of mantle minerals, and hence in stable iron isotope fractionation. Here it is shown that there are substantial (1.7 per mil) systematic variations in the iron isotope compositions (delta57/54Fe) of mantle spinels. Spinel delta57/54Fe values correlate with relative oxygen fugacity, Fe3+/sigmaFe, and chromium number, and provide a proxy of changes in mantle oxidation state, melting, and volatile recycling.     

Effect of rare earth elements on growth and nutrition of coconut palm and root competition for these elements between the palm and calotropis gigantea

Absorption of rare earth elements (REEs) namely lanthanum (La), cerium (Ce), praseodymium (Pr), and neodymium (Nd) by coconut, competition between coconut and Calotropis gigantea L. for these elements in mixed culture and the effects of the REEs on growth and nutrition of the palm were studied in a pot culture. At a low rate of application, REEs promoted root growth in coconut, but at a higher level, absorption of phosphorus (P) and zinc (Zn) by the palm was reduced significantly. Absorption of REEs by the palm tended to increase with increasing application rates, but the increases were not statistically significant. Although Calostropis gigantea accumulated more REEs per unit dry matter than coconut, it failed to compete effectively for REEs in mixed culture with coconut. However, in mixed culture, coconut depressed the absorption of REEs by Calostropis gigantea.     

Bacteriolytic activity and growth of marine isolates of labyrinthulids on dead bacterial cells

ABSTRACT:   Thirteen strains of labyrinthulids were isolated from the coastal area of Kagoshima Bay, Kagoshima Prefecture, Japan and from Batan Bay, Panay Island, the Philippines by using diatom double-layer agar plates. The cells of labyrinthulid isolates grew axenically on the dead bacterial cells and extract plus egg yolk agar medium (NSBEY agar). Three representative isolates were demonstrated to belong to the labyrinthulid phylogenetic group (LPG) based on 18S  rDNA sequence analysis. As bacteriolytic activity of labyrinthulid isolates was examined, it was found that they could lyze only the dead cells of gram-negative bacteria and not those of gram-positive bacteria during incubation in both agar and liquid media. The optimum temperature range for bacteriolysis was 25–31°C. Orange carotenoid pigment was accumulated during the stationary growth phase of strain 00-Bat-05, Philippine isolate, cultured in an L-shaped tube containing a bacterial dead cell suspension. Concomitant rapid cell movement of developing zoospores was observed.