Ethylene: Response of Fruit Dehiscence to CO(2) and Reduced Pressure

These studies were conducted to determine whether ethylene serves as a natural regulator of fruit wall dehiscence, a major visible feature of ripening in some fruits. We employed treatments to inhibit ethylene action or remove ethylene and observed their effect on fruit dehiscence. CO₂ (13%), a competitive inhibitor of ethylene action in many systems, readily delayed dehiscence of detached fruits of cotton (Gossypium hirsutum L.), pecan (Carya illinoensis [Wang.] K. Koch), and okra (Hibiscus esculentus L.). The CO₂ effect was duplicated by placing fruits under reduced pressure (200 millimeters mercury), to promote the escape of ethylene from the tissue. Dehiscence of detached fruits of these species as well as attached cotton fruits was delayed. The delay of dehiscence of cotton and okra by both treatments was achieved with fruit harvested at intervals from shortly after anthesis until shortly before natural dehiscence. Pecan fruits would not dehisce until approximately 1 month before natural dehiscence, and during that time, CO₂ and reduced pressure delayed dehiscence. CO₂ and ethylene were competitive in their effects on cotton fruit dehiscence. All of the results are compatible with a hypothetical role of ethylene as a natural regulator of dehiscence, a dominant aspect of ripening of cotton, pecan, and some other fruits.     

Tellurium tetrahalides in rubber chemistry: Some new tellurium(IV) complexes with an S2X4 (X = halogen) ligand environment

The reaction of tellurium tetrahalides with natural rubber parallels closely reactions with model compounds such as cyclohexene and 2-methyl- pent-2-ene carried out under similar conditions. In both cases an α-elimination reaction of an ‘organic halide’ with deposition of elemental tellurium is a dominant process, but some evidence for cross- linking of natural rubber is obtained. If methyl cyanide is the solvent for cyclohexene, or if a nitrile rubber is used, elimination of tellurium is inhibited.Tellurium tetrachloride enhances the rate and density of cross-link formation when added to tetramethylthiuram disulphide (TMTD) based natural rubber vulcanisates, but this effect is negated in the presence of triphenylphosphine. TeCl₄ reacts with TMTD to eliminate an atom of sulphur and to form a complex of tetramethylthiuram monosulphide (TMTM) viz. [Te(TMTM)Cl₄]. Corresponding bromo- and iodo-complexes have been prepared, the iodo- complex is a 1:1 electrolyte. ¹²⁵Te Mössbauer data for the complexes are briefly discussed.Further reactions of the complexes are described which lead to the formation of: [Te(TMTM)Cl₂(O)(pyridine)], [Te(TMTM)X₂(O)] (X=Br, I), and [Cu(TMTM)₂] [TeCl₅]₂. Organyltellurium(IV) trihalides also react with TMTD to release sulphur and give complexes of TMTM, i.e. [(p-EtO·C₆H₄)Te- X₃]₂(TMTM) (X=Cl, Br, I).     

Selective attraction and reproductive performance of a harpacticoid copepod in a response to biofilms

The relationship between monobacterial films and the preference of harpacticoid copepods for such films was investigated using still water multiple-choice assays with natural biofilm and sterile conditions as controls. Adult Schizopera sp. were most attracted by a heterogeneous natural biofilm, followed by monospecies-biofilms of Rhodovulum sp., Vibrio proteolyticus, and Flexibacter sp. The preferred bacterial films stemmed from different phylogenetic and physiological groups. The results indicated that the harpacticoid Schizopera sp. was effectively and differentially attracted by bacterial films. Since bacteria constitute a substantial portion of the organic carbon available at the sea bottom as nutritive sources for harpacticoid copepods, we subsequently examined the influence of 9 bacterial strains and a natural biofilm as a nutrient source on the growth and reproductive performance of ontogenetic stages (nauplii and copepodids) of Schizopera sp. The food value of bacterial strains was assayed in terms of life table data that provided growth parameters. All variables were affected by the type of food offered. A diet on Rhodovulum sp. resulted in optimal growth performance of nauplii and copepodids demonstrating that bacteria can be used as a sole diet to support postembryonic development. The present study is the first to link behavioral preferences to bacterial biofilms with life history parameters when cultivating harpacticoid copepods on the same bacterial strains as the only diet. This study revealed a discrepancy between the biofilm favored (natural biofilm) and the one leading to maximal reproductive performance (monobacterial film of Rhodovulum sp. MB253) as indicated by major life table data as net reproductive rate (R_o), mean generation time (T_m), and capacity for increase (r_c).     

A family of general production curves for exploited populations

A form for the growth term in the differential equation for biomass change with time is proposed, which is based on a versatile new family of stock-recruitment curves. The resultant yield curves of a general production model are investigated. The form of the curves is more variable than is usual in such models, but depends systematically on the values adopted for biologically well-defined parameters such as natural mortality and natural rate of increase. The consequences for management are explored by examining the magnitude of the maximum sustainable yield (MSY) and suitable values for the yield?biomass ratio.It is concluded that the MSY is of the order of but usually somewhat less than 0.5 MB₀, although variation by a factor of three either way is possible. MSY is usually attained at a yield?biomass ratio no more than a few times M (the natural mortality), and at biomasses less than half the pristine biomass (B₀). However, exploitation of stocks having domed stock-recruitment curves at MSY is dangerous, because the ability of the population to recover from perturbations is impaired. This is associated with an increase in the return time for the population.     

Short- and long-term conditioning of a temperate marine diatom community to acidification and warming

Ocean acidification and greenhouse warming will interactively influence competitive success of key phytoplankton groups such as diatoms, but how long-term responses to global change will affect community structure is unknown. We incubated a mixed natural diatom community from coastal New Zealand waters in a short-term (two-week) incubation experiment using a factorial matrix of warming and/or elevated pCO₂ and measured effects on community structure. We then isolated the dominant diatoms in clonal cultures and conditioned them for 1 year under the same temperature and pCO₂ conditions from which they were isolated, in order to allow for extended selection or acclimation by these abiotic environmental change factors in the absence of interspecific interactions. These conditioned isolates were then recombined into ‘artificial’ communities modelled after the original natural assemblage and allowed to compete under conditions identical to those in the short-term natural community experiment. In general, the resulting structure of both the unconditioned natural community and conditioned ‘artificial’ community experiments was similar, despite differences such as the loss of two species in the latter. pCO₂ and temperature had both individual and interactive effects on community structure, but temperature was more influential, as warming significantly reduced species richness. In this case, our short-term manipulative experiment with a mixed natural assemblage spanning weeks served as a reasonable proxy to predict the effects of global change forcing on diatom community structure after the component species were conditioned in isolation over an extended timescale. Future studies will be required to assess whether or not this is also the case for other types of algal communities from other marine regimes.     

Genetic Coadaptation in the Chromosomal Polymorphism of DROSOPHILA SUBOBSCURA. I. Seasonal Changes of Gametic Disequilibrium in a Natural Population

Seasonal changes in gene arrangement and allozyme frequencies have been investigated in Drosophila subobscura for several years. Some arrangements (O_st and O₃₊₄₊₇) show seasonal variation, which suggests that chromosomal polymorphism is flexible in this species. Seasonal changes in allozyme frequencies for Lap and Pept-1 loci, both located within the same inversions of chromosome O, are significant only inside the O_st arrangement, but not inside O₃₊₄ arrangement. This arrangement-dependent response of allozyme generates variation in arrangement-allozyme disequilibrium. The historical hypothesis on the maintenance of disequilibria cannot explain these seasonal changes, and some kind of natural selection must be invoked. Association between Lap and Pept-1 is also seasonal inside O_st but not inside O₃₊₄. We propose that O_st probably consists of a finite array of supergenes that are differentially favored in each season by natural selection. The present evidence on this supergene selection and other genetic, biogeographic and phylogenetic data points to O₃₊₄ as the most primitive gene order among the present arrangements.     

Responses of Two Scleractinian Corals to Cobalt Pollution and Ocean Acidification

The effects of ocean acidification alone or in combination with warming on coral metabolism have been extensively investigated, whereas none of these studies consider that most coral reefs near shore are already impacted by other natural anthropogenic inputs such as metal pollution. It is likely that projected ocean acidification levels will aggravate coral reef health. We first investigated how ocean acidification interacts with one near shore locally abundant metal on the physiology of two major reef-building corals: Stylophora pistillata and Acropora muricata. Two pH levels (pH_T 8.02; pCO₂ 366 μatm and pH_T 7.75; pCO₂ 1140 μatm) and two cobalt concentrations (natural, 0.03 μg L^-1 and polluted, 0.2 μg L^-1) were tested during five weeks in aquaria. We found that, for both species, cobalt input decreased significantly their growth rates by 28% while it stimulated their photosystem II, with higher values of rETR_max (relative Electron Transport Rate). Elevated pCO₂ levels acted differently on the coral rETR_max values and did not affect their growth rates. No consistent interaction was found between pCO₂ levels and cobalt concentrations. We also measured in situ the effect of higher cobalt concentrations (1.06 ± 0.16 μg L^-1) on A. muricata using benthic chamber experiments. At this elevated concentration, cobalt decreased simultaneously coral growth and photosynthetic rates, indicating that the toxic threshold for this pollutant has been reached for both host cells and zooxanthellae. Our results from both aquaria and in situ experiments, suggest that these coral species are not particularly sensitive to high pCO₂ conditions but they are to ecologically relevant cobalt concentrations. Our study reveals that some reefs may be yet subjected to deleterious pollution levels, and even if no interaction between pCO₂ levels and cobalt concentration has been found, it is likely that coral metabolism will be weakened if they are subjected to additional threats such as temperature increase, other heavy metals, and eutrophication.     

Ocean Acidification and Increased Temperature Have Both Positive and Negative Effects on Early Ontogenetic Traits of a Rocky Shore Keystone Predator Species

The combined effect of ocean acidification and warming is expected to have significant effects on several traits of marine organisms. The gastropod Concholepas concholepas is a rocky shore keystone predator characteristic of the south-eastern Pacific coast of South America and an important natural resource exploited by small-scale artisanal fishermen along the coast of Chile and Peru. In this study, we used small juveniles of C. concholepas collected from the rocky intertidal habitats of southern Chile (39°S) to evaluate under laboratory conditions the potential consequences of projected near-future levels of ocean acidification and warming for important early ontogenetic traits. The individuals were exposed long-term (5.8 months) to contrasting pCO₂ (ca. 500 and 1400 μatm) and temperature (15 and 19°C) levels. After this period we compared body growth traits, dislodgement resistance, predator-escape response, self-righting and metabolic rates. With respect to these traits there was no evidence of a synergistic interaction between pCO₂ and temperature. Shell growth was negatively affected by high pCO₂ levels only at 15°C. High pCO₂ levels also had a negative effect on the predator-escape response. Conversely, dislodgement resistance and self-righting were positively affected by high pCO₂ levels at both temperatures. High tenacity and fast self-righting would reduce predation risk in nature and might compensate for the negative effects of high pCO₂ levels on other important defensive traits such as shell size and escape behaviour. We conclude that climate change might produce in C. concholepas positive and negative effects in physiology and behaviour. In fact, some of the behavioural responses might be a consequence of physiological effects, such as changes in chemosensory capacity (e.g. predator-escape response) or secretion of adhesive mucous (e.g. dislodgement resistance). Moreover, we conclude that positive behavioural responses may assist in the adaptation to negative physiological impacts, and that this may also be the case for other benthic organisms.     

Identification of two acetylcholinesterases in Pardosa pseudoannulata and the sensitivity to insecticides

Pardosa pseudoannulata is an important predatory enemy against insect pests, such as rice planthoppers and leafhoppers. In order to understand the insecticide selectivity between P. pseudoannulata and insect pests, two acetylcholinesterase genes, Pp-ace1 and Pp-ace2, were cloned from this natural enemy. The putative proteins encoded by Pp-ace1 and Pp-ace2 showed high similarities to insect AChE1 (63% to Liposcelis entomophila AChE1) and AChE2 (36% to Culex quinquefasciatus AChE2) with specific functional motifs, which indicated that two genes might encode AChE1 and AChE2 proteins respectively. The recombinant proteins by expressing Pp-ace1 and Pp-ace2 genes in insect sf9 cells showed high AChE activities. The kinetic parameters, V_max and K_m, of two recombinant AChE proteins were significantly different. The sensitivities to six insecticides were determined in two recombinant AChEs. Pp-AChE1 was more sensitive to all tested insecticides than Pp-AChE2, such as fenobucarb (54 times in K_i ratios), isoprocarb (31 times), carbaryl (13 times) and omethoate (6 times). These results indicated that Pp-AChE1 might be the major synaptic enzyme in the spider. By sequence comparison of P. pseudoannulata and insect AChEs, the key amino acid differences at or close to the functional sites were found. The locations of some key amino acid differences were consistent with the point mutation sites in insect AChEs that were associated with insecticide resistance, such as Phe331 in Pp-AChE2 corresponding to Ser331Phe mutation in Myzus persicae and Aphis gossypii AChE2, which might play important roles in insecticide selectivity between P. pseudoannulata and insect pests. Of course, the direct evidences are needed through further studies.     

Chilean euphorbiaceae species as sources of fuels and raw chemicals

The potential of some species of Chilean Euphorbiaceae as sources of hydrocarbon-like materials was evaluated. Samples of plants excluding roots, were analyzed for CH₂Cl₂ extractives, resins and hydrocarbons. The presence of waxes and natural rubber (cis-1,4-polyisoprene) was confirmed using spectroscopic and chromatographic methods. C/H values for representative fractions were calculated and extracted samples from selected species analyzed for apparent protein contents. Results suggested that at least two species, Euphorbia lactiflua and Euphorbia copiapina might have an industrial potential.     

The water content/water activity relationship of cured tobacco and water relations of associated spoilage fungi

The relationship between moisture content and water activity (a_w) in cured tobacco was significantly influenced by sugar content. Overall, high sugar tobaccos such as Oriental and Virginia had a higher moisture content at any given water activity compared to low sugar tobaccos such as Burley. Virginia and Burley were both predominantly colonised by Aspergillus and Penicillium spp. Of these, about 80% of isolates could germinate at between 0·75 and 0·85 a_w, equivalent to moisture contents of between 18% and 24% in Burley and between 22% and 31% in Virginia. Growth of the dominant Aspergillus and Penicillium spp. was much slower on Virginia and Burley tobacco extract than on malt extract agars over the range 0.85 to 0.98 a_w. For some species the optimum a_w for growth on tobacco extract medium was altered from that on the richer malt extract agar and for some there was also a significant difference in growth between Virginia and Burley extract agars. The mould-free storage periods for five different tobacco types was influenced by a_w. Visible moulding occurred within 7–14 days at 0.85–0.90 a_w but only after about six months at 0.70–0.75 a_w. There were some differences in rate of moulding between tobacco types as well as in the range of fungi isolated at different a_w storage levels.     

Dihydroactinidiolide,a natural product against Aβ25-35 induced toxicity in Neuro2a cells: Synthesis,in silico and in vitro studies

Synthesis of natural products has speeded up drug discovery process by minimizing the time for their purification from natural source. Several diseases like Alzheimer's disease (AD) demand exploring multi targeted drug candidates, and for the first time we report the multi AD target inhibitory potential of synthesized dihydroactinidiolide (DA). Though the activity of DA in several solvent extracts have been proved to possess free radical scavenging, anti bacterial and anti cancer activities, its neuroprotective efficacy has not been evidenced yet. Hence DA was successfully synthesized from β-ionone using facile two-step oxidation method. It showed potent acetylcholinesterase (AChE) inhibition with half maximal inhibitory concentration (IC₅₀) 34.03 nM, which was further supported by molecular docking results showing strong H bonding with some of the active site residues such as GLY117, GLY119 and SER200 of AChE. Further it displayed DPPH and (.NO) scavenging activity with IC₅₀ value 50 nM and metal chelating activity with IC₅₀ >270 nM. Besides, it significantly prevented amyloid β_25-35 self-aggregation and promoted its disaggregation at 270 nM. It did not show cytotoxic effect towards Neuro2a (N2a) cells up to 24 h at 50 and 270 nM while it significantly increased viability of amyloid β_25-35 treated N2a cells through ROS generation at both the concentrations. Cytotoxicity profile of DA against human PBMC was quite impressive. Hemolysis studies also revealed very low hemolysis i.e. minimum 2.35 to maximum 5.61%. It also had suitable ADME properties which proved its druglikeness. The current findings demand for further in vitro and in vivo studies to develop DA as a multi target lead against AD.     

Inhibitors of secreted phospholipase A2 suppress the release of PGE2 in renal mesangial cells

The upregulation of PGE₂ by mesangial cells has been observed under chronic inflammation condition. In the present work, renal mesangial cells were stimulated to trigger a huge increase of PGE₂ synthesis and were treated in the absence or presence of known PLA₂ inhibitors. A variety of synthetic inhibitors, mainly developed in our labs, which are known to selectively inhibit each of GIVA cPLA₂, GVIA iPLA₂, and GIIA/GV sPLA₂, were used as tools in this study. Synthetic sPLA₂ inhibitors, such as GK115 (an amide derivative based on the non-natural amino acid (R)-γ-norleucine) as well as GK126 and GK241 (2-oxoamides based on the natural (S)-α-amino acid leucine and valine, respectively) presented an interesting effect on the suppression of PGE₂ formation.     

Effects of Animal Husbandry on Secondary Production and Trophic Efficiency at a Regional Scale

Agricultural systems are expected to have higher net secondary production (NSP) than natural systems as a result of higher trophic efficiency and lower interannual variability. These differences, however, have not been quantified across regional gradients. We compiled a dataset of herbivore biomass, consumption, NSP, annual precipitation, and aboveground net primary production (ANPP) for extensive livestock farms across a wide precipitation gradient in Argentina. We compared these data with worldwide published studies of natural systems. In a double-logarithmic scale, NSP of agricultural systems increased with ANPP from semiarid to subhumid systems and decreased from subhumid to humid systems, a response that contrasted with the linear positive increase of natural systems. Compared to natural systems dominated by homeotherms, E _troph (NSP:ANPP) in agricultural systems in semiarid areas was 8 times higher, due to a 2 times higher E _consump (Consumption:ANPP) and a 4 times higher E _prod (NSP:Consumption). In subhumid areas, E _troph was 46 times higher, due to a 13.7 times higher E _consump and a 3.3 times higher E _prod. In humid areas, E _troph was 5 times higher, due to a 2.5 times higher E _consump and a 2 times higher E _prod. The interannual variation of herbivore biomass, a major determinant of NSP, was 60 % lower in agricultural than in natural systems dominated by homeotherms, and was decoupled from the variability of precipitation. Agricultural systems reach higher NSP by (1) diverting a major proportion of ANPP from the detritus to the grazing chain, (2) converting more efficiently consumption into NSP, and (3) stabilizing herbivore biomass across years.     

THE INFLUENCE OF AMMONIUM SALTS ON CELL REACTION

1. It may be shown by means of cells of the flowers of a hybrid Rhododendron which contain a natural indicator, by means of starfish eggs stained with neutral red, and by means of an "artificial cell" in which living frog''s skin is employed that increased intracellular alkalinity may be brought about by solutions of a decidedly acid reaction which contain ammonium salts. 2. These results are analogous to those previously obtained with the CO₂-bicarbonate system, and depend on the facts: (a) that NH₄OH is sufficiently weak as a base to permit a certain degree of hydrolysis of its salts; and (b) that living cells are freely permeable to NH₄OH (or NH₃?) and not to mineral and many organic acids, and presumably not at least to the same extent to ammonium salts as such.     

Genic Variation in Male Haploids under Deterministic Selection

Genic variation in male haploids and male diploids was compared assuming constant fitnesses (derived from computer-generated random numbers) and infinite population size. Several models were studied, differing by the fitness correlation between the sexes (r_s) and genotypes (r_g), and by the intensity of selection as measured by the coefficient of variation (CV) of the fitness distribution. Genic variation was quantified using the proportion of polymorphic loci, P, the gene diversity at polymorphic loci, H_p, and the gene diversity over all loci, H_a. The two genetic systems were compared via variation ratios: variation in male haploidy/variation in male diploidy.—P and H_a were markedly lower for male-haploids than for male diploids, the variation ratios declining with increasing r_s, r_g and CV, but the two genetic systems were similar for H_p. Except for male diploids with r_s = 1, the two sexes had different equilibrium gene frequencies but the sample sizes required to detect such differences reliably were larger than usually possible in surveys of natural populations.—Data from natural populations fit the above trends qualitatively, but the variation ratios are much lower than those from our analyses, except that for H_p, which is higher when Drosophila is excluded. Also, the frequency distribution of most common alleles from electrophoretic data has a deficiency of intermediate frequencies compared to that from the computer-generated sets of fitnesses, possibly reflecting either the influence of stochastic processes shifting frequencies away from equilibrium or the involvement of alleles under selection-mutation balance.——While electrophoretic data suggest that Drosophila has unusually high levels of genic variation, unusually low levels of genic variation in male haploids compared with male diploids are not strongly indicated. However, if further data confirm male haploids as having low levels of genic variation, likely explanations are that the bulk of electrophoretically detected variation involves fixed-fitness balancing selection, selection-mutation balance involving slightly deleterious recessive alleles, new favorable male haploid alleles moving more rapidly to fixation than under male diploidy and thus carrying linked loci to fixation faster, or some combination of these possible factors.     

Evidence for plant traits driving specific drought resistance. A community field experiment

Drought is known to be a major bottleneck for woody-community recruitment. The species-specific resistance to drought and factors involved in its variation are of special interest to forecast community fate. We performed an experiment under natural field conditions from winter 2006 to end summer 2008 to investigate the structural responses of woody saplings to nine combinations of light (three habitats differing in plant cover: forest, shrubland, and open) and water (three climate scenarios: drier, current and wetter summers). Our working hypothesis is that plant strategies to cope with drought are determined by habitat characteristics and/or variation of plant traits, and that these different strategies may determine community composition and dynamics. Eight woody species with different life forms and successional stages (trees, mid-successional shrubs, and pioneer shrubs) were selected for the comparison, including therefore species representative of the entire woody community. We explored drought resistance at the population level (D_S), the relations of the different morphological traits to D_S, and the potential importance for plants of inter-specific trade-offs. D_S ranged from 0% to 99% for the different species, depending on the habitat. Some structural traits were found to be related to D_S: positively with total biomass and leaf mass ratio (LMR) and negatively with leaf area-root mass ratio (LARMR). Contrary to previous studies, the present work revealed no evidence of trade-offs, such as survival in forest vs. growth in open, or growth in forest vs. growth in open. Accordingly, some species with low D_S values (Acer opalus and Pinus sylvestris) would be threatened under the future climate conditions, while species having structural characteristics to increase their resistance under expected dry years in coming decades (i.e., high LMR and total biomass or low LARMR, such as Quercus ilex and the shrub Cytisus scoparius) might enhance their recruitment probabilities. Thus, species-specific plant traits, and their effect on D_S, may filter future community assemblages.     

Morphological variability of Arthrospira (Spirulina) fusiformis (Cyanophyta) in relation to environmental variables in the tropical soda lake Chitu,Ethiopia

Although variability of Arthrospira morphology, widely used in taxonomy and other valuable aspects, as a response to changes in environmental variables has been studied in laboratory cultures, little is known about such responses in the natural habitats. In this study, Arthrospira fusiformis was characterized morphologically in relation to selected environmental variables in the natural ecosystem. Three distinct morphotypes, tightly coiled (H-type), spiral or loosely coiled (S-type), and intermediately coiled (C-type) were observed and described. They varied largely in the degree of coiling, trichome and helix dimensions, coils, shape of trichome end and trichome abundance. The H-type was the most dominant (50%) followed by the S-type (40%). The dominance of H-type and tightening of helix pitch were strongly associated with NO₃ ^? and HCO₃ ^? deficiencies, and high levels of photosynthetically active radiation (PAR) and temperature of the lake. The abundance of S-type was more strongly but negatively related to the high salinity of the lake, probably indicating that decreasing salinity may favor the S-type. In conclusion, the variability in abundance and morphology seem to suggest that A. fusiformis could show morphological modifications in response to environmental stresses in their natural soda lakes, resulting in occurrence of various morphotypes of the same species.