Transformation products distribution of atrazine in corn plants treated with radiolabelled herbicide

Roots of whole plants at four leaf stage grown in specialized soil treatment vessels were treated with ¹⁴C-atrazine. Plant tissues were exhaustively extracted with methanol and extracts were separated by preparative thin layer chromatography (TLC). The extracted material was separated in two TLC bands at Rf0.00 and Rf0.18 containing 33% and 67% of plant ¹⁴C-residues, respectively. Methanol extracts of these bands subjected to derivatization, hydrolysis and analysis by TLC, revealed the presence of a number of transformation products consisting of hydroxy analogues of atrazine and their dealkylated metabolites. The transformation products had variable distribution patterns amongst leaf, stalk and root tissues. Diaminohydroxyatrazine, hydroxyatrazine, and deethylhydroxyatrazine were the main ¹⁴C-residues. Stalk tissue contained more ¹⁴C-residues which were largely located at and just below the ligule. The significance of ¹⁴C-residue accumulation at the ligule and the transformation product compartmentalization are discussed.     

Irrigation and collective action: A study in method with reference to the Shiwalik Hills, Haryana

In recent years decentralized development approaches have gained prominence in the agricultural sector. A host of community based watershed management projects have been implemented that encourage community organizations to undertake management of previously government controlled irrigation systems and forests. Community organizations have been given the responsibility of managing water distribution, collection of irrigation service fees and undertaking routine maintenance of irrigation infrastructure. In this context, analysis of irrigation management has concluded that groups that are relatively homogeneous may fare better than heterogeneous groups in facilitating collective action. However, this article argues that analysis of the influence of group heterogeneity on collective action is complicated because of its multi‐dimensional nature and the presence of non‐monotonic effects in mechanisms linking heterogeneity and collective outcomes. The article discusses the importance of context specification in analysis of group heterogeneity through a discussion of elements of a joint management contract in Haryana (India), identification of key variables with a potential to explain collective action in irrigation management and construction of household endowment and water interest scores to account for the influence of group heterogeneity in facilitating collective action. In the process of applying household endowment and water interest scores, the authors highlight the role of local ecological variation and non‐farm employment in influencing collective action. Proper specification of local context enables the researchers to rely on household endowment and water interest scores to predict conflicts and potential for irrigation service provision and compliance with irrigation service rules.     

Enzymatic degradation of low-rank coals by a cell-free enzymatic system from Coriolus versicolor

An extracellular fraction from the lignin degrading white-rot fungus, Coriolus versicolor, can biosolubilize leonardite and pretreated lignites in vitro. Leonardite is often found as an overburden to lignite deposits, and is related to humic acid, and is more oxidized than lignites. Extracts from certain fungi such as C. versicolor solubilize leonardite. The biosolubilization activity is at least in part enzymatic in nature. A protein which is at least partly responsible for the solubilization effect has been substantially purified and concentrated by ultrafiltration and ion-exchange chromatography from the broth of an agitated submerged culture of C. versicolor grown in a defined medium. An in vitro coal biosolubilization assay was used to establish the effects of various physical and chemical factors affecting enzyme activity, including temperature and the salt and buffer composition of the reaction mixture. Some initial studies on the mechanism of the enzymatic leonardite biosolubilization reaction are described.     

Reactive uptake of ozone at simulated leaf surfaces: Implications for ‘non-stomatal’ ozone flux

The reaction of ozone (O₃) with α-pinene has been studied as a function of temperature and relative humidity and in the presence of wax surfaces that simulate a leaf surface. The objective was to determine whether the presence of a wax surface, in which α-pinene could dissolve and form a high surface concentration, would lead to enhanced reaction with O₃. The reaction of O₃ itself with the empty stainless steel reactor and with aluminium and wax surfaces demonstrated an apparent activation energy of around 30 kJ mol^?1 for all the surfaces, similar to that observed in long-term field measurements of O₃ fluxes to vegetation. However, the absolute reaction rate was 14 times greater for aluminium foil and saturated hydrocarbon wax surfaces than for stainless steel, and a further 5 times greater for beeswax than hydrocarbon wax. There was no systematic dependence on either relative or absolute humidity for these surface reactions over the range studied (20–100% RH). Reaction of O₃ with α-pinene occurred at rates close to those predicted for the homogeneous gas-phase reaction, and was similar for both the empty reactor and in the presence of wax surfaces. The hypothesis of enhanced reaction at leaf surfaces caused by enhanced surface concentrations of α-pinene was therefore rejected. Comparison of surface decomposition reactions on different surfaces as reported in the literature with the results obtained here demonstrates that the loss of ozone at the earth's surface by decomposition to molecular oxygen (i.e. without oxidative reaction with a substrate) can account for measured ‘non-stomatal’ deposition velocities of a few mm s^?1. In order to quantify such removal, the effective molecular surface area of the vegetation/soil canopy must be known. Such knowledge, combined with the observed temperature-dependence, provides necessary input to global-scale models of O₃ removal from the troposphere at the earth's surface.     

Causes of habitat divergence in two species of agamid lizards in arid central Australia

The deserts of central Australia contain richer communities of lizards than any other arid regions, with the highest diversity occurring in sand dune habitats dominated by hummock-forming spinifex grasses. To investigate the mechanisms that permit coexistence, we studied two species of coexisting agamid lizards that exhibit striking divergence in their use of habitat in the Simpson Desert of central Australia. Here, the military dragon Ctenophorus isolepis is restricted primarily to sites providing > 30% cover of hard spinifex Triodia basedowii, whereas the central netted dragon C. nuchalis occurs in areas with much sparser (< 10%) cover. We constructed four mechanistic models to explain this pattern and then derived hypotheses to test them. One hypothesis, that competition restricts each species to its preferred habitat, was rejected after dyad encounters in field enclosures failed to elicit any habitat shift or any overt interactions between the species. Our next hypotheses were that each species exhibits preferences for different thermal environments or different prey types and that each selects the habitats that maximize access to them. Both were supported. C. isolepis preferred lower temperatures when active and specialized in eating ants < 5 mm long and selected spinifex-dominated areas where these requirements were met. In contrast, C. nuchalis preferred higher temperatures and a diversity of prey, both of which were available mostly in open areas. Finally, we used plasticine models to test the hypothesis that each species faced lower risk of predation in its selected habitat. This was partly supported, as models of both species were attacked more often in the open than under spinifex cover. The results show that habitat divergence occurs along several, probably covarying, niche axes. We suggest that different levels of spinifex cover provide the template for a broad range of ecological interactions, allowing lizard species to partition biotic and abiotic resources and achieve the extraordinarily high levels of local diversity that are observed.     

Sexual conflict in a polygynous primate: costs and benefits of a male-imposed mating system

Fundamental reproductive interests dictate that females generally benefit most from mate selectivity and males from mate quantity. This can create conflict between the sexes and result in sexual coercion: male use of aggression to garner mating success at a cost to females. Potential fitness costs of sexual coercion, however, can be difficult to measure. Here, we demonstrate benefits to males and costs to females of female defense polygyny in wild hamadryas baboons, cercopithecoid primates in which females are coercively transferred among social units by males, restricting both female choice and bonding among female kin. Of all coercive transfers (takeovers) of females with young infants, 67 % were followed by infant mortality, which was significantly more likely to occur after takeovers than at other times. As expected, infant mortality decreased time to subsequent conception but lengthened intervals between surviving infants. Following infant survival, whether a female had experienced a takeover after the previous birth was a significant predictor of subsequent interbirth interval, with interbirth intervals of females remaining with the same male between births being significantly shorter than those of females incurring takeovers between births. Together, these results reveal that takeovers increase the chance of infant mortality while delaying subsequent conception. Male-driven female defense polygyny in this species is thus costly to females in two ways. These results demonstrate that reproductive strategies benefitting males can evolve despite substantial costs to females. These costs may be mitigated over the long term, however, by female counterstrategies and protective behavior by males.     

Species dispersal rates alter diversity and ecosystem stability in pond metacommunities

Metacommunity theory suggests that relationships between diversity and ecosystem stability can be determined by the rate of species dispersal among local communities. The predicted relationships, however, may depend upon the relative strength of local environmental processes and disturbance. Here we evaluate the role of dispersal frequency and local predation perturbations in affecting patterns of diversity and stability in pond plankton metacommunities. Pond metacommunities were composed of three mesocosm communities: one of the three communities maintained constant "press" predation from a selective predator, bluegill sunfish (Lepomis macrochirus); the second community maintained "press" conditions without predation; and the third community experienced recurrent "pulsed" predation from bluegill sunfish. The triads of pond communities were connected at either no, low (0.7%/d), or high (20%/d) planktonic dispersal. Richness and composition of zooplankton and stability of plankton biomass and ecosystem productivity were measured at local and regional spatial scales. Dispersal significantly affected diversity such that local and regional biotas at the low dispersal rate maintained the greatest number of species. The unimodal local dispersal-diversity relationship was predator-dependent, however, as selective press predation excluded species regardless of dispersal. Further, there was no effect of dispersal on beta diversity because predation generated local conditions that selected for distinct community assemblages. Spatial and temporal ecosystem stability responded to dispersal frequency but not predation. Low dispersal destabilized the spatial stability of producer biomass but stabilized temporal ecosystem productivity. The results indicate that selective predation can prevent species augmentation from mass effects but has no apparent influence on stability. Dispersal rates, in contrast, can have significant effects on both species diversity and ecosystem stability at multiple spatial scales in metacommunities.     

Boundary impulse response functions in a century-long eddying global ocean simulation

Results are presented from a century-long 1/10° global ocean simulation that included a suite of age-related passive tracers. In particular, an ensemble of five global Boundary Impulse Response functions (BIRs, which are statistically related to the more fundamental Transit Time Distributions, TTDs) was included to quantify the character of the TTD when mesoscale eddies are explicitly simulated rather than parameterized. We also seek to characterize the level of variability in water mass ventilation timescales arising from eddy motions. The statistics of the BIR timeseries are described, and it is shown that the greatest variability occurs at early times, followed by a remarkable conformity between ensemble members at longer timescales. The statistics of the first moment of the BIRs are presented, and the upper-ocean spatial distribution of the standard deviation of the first moment of the BIRs discussed. It is shown that variations in the BIR first moment with respect to the ensemble average are typically only a few percent, and that the variability slightly decreases with increasing ensemble size, implying that only a few ensemble members may be necessary for a reasonable estimate of the TTD. The completeness of the estimated TTD, i.e., the degree to which the century long BIRs capture the range of global ocean ventilation timescales is discussed, and the potential for extrapolation of the BIR to longer times is briefly explored. Several regional BIRs were also simulated in order to quantify the relative abundance of fluid parcels that originate in specific geographical locations.     

Study on the gill of field crab,Paratelphusa hydrodromus (Herbst.) exposed to nickel

Paratelphusa hydrodromus (Herbst.) was exposed to 50 ppm nickel chloride solution for a period of 10 days under laboratory conditions. The gills of the treated and non-treated animals were sectioned, stained and examined under a compound microscope and noticed significant changes such as enlargement of gill lamellae, lifting up and rupture of epithelial cells, enlargement of mid rachis, hyperplasia and hypertrophy, appearance of pyknotic nuclei and a general necrosis in the treated gills. Results suggest that a comparatively low concentration of nickel (50 ppm) is enough to elicit pathological changes in Paratelphusa hydrodromus.