Ongoing challenges in the management of malaria

Background

Mosquitoes transmit serious human diseases, causing millions of deaths every year. Use of synthetic insecticides to control vector mosquitoes has caused physiological resistance and adverse environmental effects in addition to high operational cost. Insecticides of botanical origin have been reported as useful for control of mosquitoes. Azadirachta indica (Meliaceae) and its derived products have shown a variety of insecticidal properties. The present paper discusses the larvicidal activity of neem-based biopesticide for the control of mosquitoes.

Methods

Larvicidal efficacy of an emulsified concentrate of neem oil formulation (neem oil with polyoxyethylene ether, sorbitan dioleate and epichlorohydrin) developed by BMR & Company, Pune, India, was evaluated against late 3^rd and early 4^th instar larvae of different genera of mosquitoes. The larvae were exposed to different concentrations (0.5–5.0 ppm) of the formulation along with untreated control. Larvicidal activity of the formulation was also evaluated in field against Anopheles, Culex, and Aedes mosquitoes. The formulation was diluted with equal volumes of water and applied @ 140 mg a.i./m² to different mosquito breeding sites with the help of pre calibrated knapsack sprayer. Larval density was determined at pre and post application of the formulation using a standard dipper.

Results

Median lethal concentration (LC₅₀) of the formulation against Anopheles stephensi, Culex quinquefasciatus and Aedes aegypti was found to be 1.6, 1.8 and 1.7 ppm respectively. LC₅₀ values of the formulation stored at 26°C, 40°C and 45°C for 48 hours against Ae. aegypti were 1.7, 1.7, 1.8 ppm while LC₉₀ values were 3.7, 3.7 and 3.8 ppm respectively. Further no significant difference in LC₅₀ and LC₉₀ values of the formulation was observed against Ae. aegypti during 18 months storage period at room temperature. An application of the formulation at the rate of 140 mg a.i./m² in different breeding sites under natural field conditions provided 98.1% reduction of Anopheles larvae on day 1; thereafter 100% reduction was recorded up to week 1 and more than 80% reduction up to week 3, while percent reduction against Culex larvae was 95.5% on day 1, and thereafter 80% reduction was achieved up to week 3. The formulation also showed 95.1% and, 99.7% reduction of Aedes larvae on day 1 and day 2 respectively; thereafter 100% larval control was observed up to day 7.

Conclusion

The neem oil formulation was found effective in controlling mosquito larvae in different breeding sites under natural field conditions. As neem trees are widely distributed in India, their formulations may prove to be an effective and eco-friendly larvicide, which could be used as an alternative for malaria control.     

Removal of heavy metals from industrial wastewater using microbial fuel cell

Removal efficiency of gold from a solution of pure tetrachloroaurate ions was investigated using microbial fuel cell (MFC) technology. The effects of type of catholyte solution and initial gold concentration on the removal efficiency were considered. Due to its presence at high levels in the gold wastewater, the effect of copper ions on the removal efficiency of the gold ions was also studied. The effects of pH and initial biomass concentration on the gold removal efficiency was also determined. The results showed that after 5 h contact time, 95% of gold removal efficiency from a wastewater containing 250 ppm of initial gold ions at ambient temperature using 80 g/L yeast concentration was achieved. After 48 h of the cell''s operation under the same condition, 98.86% of AuCl₄ ^– ions were successfully removed from the solution. At initial gold concentration in the waste solution of 250 ppm, pH 2, and initial yeast concentration of 80 g/L, 100% removal efficiency of the gold was achieved. On the other hand, the most suitable condition for copper removal was found at a pH of 5.2, where 53% removal efficiency from the waste solution was accomplished.     

Bacillus thuringiensis and neem seed oil (Azadirachta indica) effects on the potato tuber moth Phthorimaea operculella zeller in the field and stores

A comparative evaluation for the efficacy of Bacillus thuringiensis and neem seed oil on Phthorimaea operculella has been carried out in the field and store. These two preparations were almost equally effective on the potato tuber moth infestation. The percentage of infestation was reduced through successive application of either preparations in the field up to harvest. No synergism was observed upon using combination of the two preparations. In the store, neem seed oil (500 ppm) was highly protective and was as effective as sevin. A combination of both neem and B.t. (Delfin) significantly protects the tubers. This suggests the possible use of either neem seed oil or B.t. in combating the insect pest in the field or during storage.     

Evaluation of neemAzadirachta indica seed extracts and oils as oviposition deterrents to noctuid moths

Applications of three concentrations of oil-free neem seed extracts (Azadirachta indica A. Juss; Meliaceae) to cabbage plants in cages did not deter oviposition by individuals of three species of noctuid moths,Trichoplusia ni, Peridroma saucia, andSpodoptera litura. The concentrations used corresponded to 10, 50, and 100 ppm of the main active ingredient, azadirachtin. The total number of eggs laid per female, female longevity, and median day of oviposition were not affected. Sprays of the neem oil-based insecticide Margosan-O ^R , and a 1% aqueous emulsion of a refined neem seed oil similarly had no effect on any of the parameters studied. However, a 1% crude oil emulsion significantly reduced the proportion of eggs laid byS. litura on treated plants. Our results suggest that literature reports of significant neem-based oviposition deterrence toS. litura are the result of compounds that are removed by higher levels of processing and thus not likely to be found in most commercial neem seed formulations. Sprays consisting of highly processed neem seed extracts, used at concentrations that provide larval control, are unlikely to be generally effective as oviposition deterrents to noctuid pests.     

Mouse sperm-egg interaction in vitro in the presence of neem oil

In vitro evidence is presented showing toxicity of neem oil on sperm-egg interaction in mouse. Cumulus oophorus-enclosed ova, inseminated with capacitated spermatozoa, were cultured in 1 ml of in vitro fertilization (IVF) medium and overlayered by 1 ml of different concentrations of neem oil (1, 5, 10, 25, 50 and 100%) for IVF duration of 4h. At the end of incubation, ova were allowed to grow in neem oil-free culture medium and assessed for fertilization, first cleavage (2-cell formation) and blastocyst formation in vitro at 4–14h, 24h and 108h post-insemination respectively. The study showed that the presence of neem oil at concentrations of 10, 25 and 50% caused inhibition of IVF in a dose-dependent manner. The toxic effect of exposure of 25 and 50% neem oil was further carried over to the first cleavage of the resulting fertilized ova and the toxic effect of 5, 10, 25, and 50% was carried over to the blastocyst formation from the resulting fertilized ova when grown in neem-oil free culture medium. A total of 94.1% inhibition of 2-cell formation and 100% inhibition of blastocyst formation from the inseminated ova was observed in 50 and 25% neem oil-treated groups respectively. Neem oil at 100% concentration caused 100% degeneration of ova at 1h of sperm-ova coculture. The study showed a direct toxic effect of neem oil on sperm-egg interaction in vitro and encourages research investigations of this herbal product as a pre-coital contraceptive.     

植物光合结构与非光合结构的功能平衡：来自三种亚热带乔木树种的实验证据

植物的地上部分和地下部分存在功能性平衡现已十分清楚,但植物的地上部分是否在其光合结构（叶组织）和非光合结构（枝和茎）之间也存在功能性平衡尚不明晰,本文提出两个研究假设并检验之：1）植物地上部分在其光合与非光合结构之间存在功能性平衡;2）此功能性平衡的维持依赖于对光合和非光合结构生物量分配的调节,为验证此假设,采用枝叶修剪的方式（连续两年修剪,四个修剪强度：0,20%,50%,70%）对3种亚热带乔木树种榕（Ficus microcarpa),黄桷树（Ficus virens)和樟（Cinnamomum camphora)进行了研究。结果表明,修剪使所有树种地上部分的光合与非光合结构生物量比率（P/NP）立即下降,下降程度随修剪强度的程式高而增大,但不论是首次修剪还是第二次修剪,修剪处理一年后,修剪株地上部分的光合与非光合结构生物量比率升高,且此生物量比率不低于非修剪株的光合与非光合结构生物量比率。此研究结果证实了植物地上部分光合与非光合结构间存在功能性平衡的假设,与假设一致。植株的生物量分配在修剪后发生了改变;修剪株加大了对光合结构（叶组织）的生物量分配（大量的新生产地上部分生物量被分配到光合结构）,同时却减少了对非光合结构（枝和茎）的分配,此分析格局的改变保证了光合与非光合结构功能性平衡的恢复与维持,可以认为,通过改变生物量分配格局以维持光合与非光合结构功能平衡是植物低御外来干扰和/或损伤的一种有效策略。     

The effect of neem (Azadirachta indica A. Juss) oil on oviposition, development and reproductive potentials of Sesamia calamistis Hampson (Lepidoptera: Noctuidae) and Eldana saccharina Walker (Lepidoptera: Pyralidae)

Abstract 1 The effect of different treatments of neem oil (0, 0.075, 0.1 and 0.15 mL/plant) and their persistence (0, 5 and 10 days after application; DAA) on the oviposition behaviour and the bionomics of the noctuid Sesamia calamistis and the pyralid Eldana saccharina were tested in laboratory and greenhouse experiments. 2 For most variables, no difference was found between DAA, showing that the treatments had a long‐term effect, and pooled analyses across DAA were performed. Compared with the control (0 mL/plant), mean reductions due to neem in numbers of egg batch and eggs laid were 70 and 88% for S. calamistis and 50 and 49% for E. saccharina, respectively, but no differences were found among neem concentrations. 3 For both species, larval and pupal development time was shortest in the control and longest with the highest oil concentration. Immature survival, larval weight and fecundity were highest in the control and similar in the neem treatments. 4 No differences were found in sex ratios. Egg viability was highest in the control (approximately 87%) and lowest (72%) with the highest oil concentration. As a result of lower fecundity and longer developmental time, on average, the intrinsic rates of increase in the neem treatments were 30% lower than in the control. 5 In view of the low oviposition rates, immature survival, fecundity and egg viability in the neem treatments, and the relatively high persistence of neem oil, it can be expected that the reduction in densities of the two borers species in the field will be considerable.     

S-SI,a New Alkaline Protease Inhibitor from Streptomyces albogriseolus S-3253

This study investigated the production of ethanol from unutilized branches pruned from pear trees by steam explosion pretreatment. Steam pressures of 25, 35, and 45?atm were applied for 5?min, followed by enzymatic saccharification of the extracted residues with cellulase (Cellic CTec2). High glucose recoveries, of 93.3, 99.7, and 87.1%, of the total sugar derived from the cellulose were obtained from water- and methanol-extracted residues after steam explosion at 25, 35, and 45?atm, respectively. These values corresponded to 34.9, 34.3, and 27.1?g of glucose per 100?g of dry steam-exploded branches. Simultaneous saccharification and fermentation experiments were done on water-extracted residues and water- and methanol-extracted residues by Kluyveromyces marxianus NBRC 1777. An overall highest theoretical ethanol yield of 76% of the total sugar derived from cellulose was achieved when 100?g/L of water- and methanol-washed residues from 35?atm-exploded pear branches was used as substrate.     

Use of plant products and copepods for control of the dengue vector, <Emphasis Type="Italic">Aedes aegypti</Emphasis>

The efficacy of plant extracts (neem tree, Azadirachta indica A. Juss.; Meliaceae) and copepods [Mesocyclops aspericornis (Daday)] for the control of the dengue vector Aedes aegypti L. was tested in the laboratory. Neem Seed Kernel Extract (NSKE) at 25, 50, 100, 200 and 400 ppm caused significant mortality of Ae. aegypti larvae. Lethal concentrations (LC₅₀ and LC₉₀) were worked out. The LC₅₀ and LC₉₀ values for I to IV larval instars were 111.98, 138.34, 158.93, 185.22 ppm and for pupae was 146.13 ppm, respectively. The LC₉₀ value of I instar was 372.95 ppm, II instar was 422.77 ppm, III instar was 440.63 ppm, IV instar was 456.96 ppm, and pupae was 476.92 ppm, respectively. A study was conducted to test the whether the predatory efficiency of copepods on first instars changed in the presence of NSKE. The percentage of predatory efficiency of copepod was 6.80% in treatments without NSKE and the percentage of predatory efficiency increased up to 8.40% when copepods were combined with NSKE. This increase in predation efficiency may caused by detrimental effects of the neem active principle compound (Azadirachtin) on the mosquito larvae. Our results suggest that the combined application of copepods and neem extract to control Aedes populations is feasible. Repeated application of neem does not cause changes in copepod populations, because neem is highly degradable in the environment.     

Effect of Neem and Selected Fungicides on Viability and Virulence of the Entomopathogenic Nematode Steinernema feltiae

Entomopathogenic nematodes are often used in conjunction with other pest management tactics and the lack of compatibility information is a major impediment in further expansion of their use. We evaluated the effects of different formulations of neem and selected fungicides commonly used in greenhouses on Steinernema feltiae which is used for the control of fungus gnats. Neem as pure oil at the field recommended concentrations (5- 10 mL L -1 ) had no effect on the viability and virulence of S. feltiae up to 120 h incubation. However the neem formulation, Nimbecidine and neem oil when mixed with a bactericidal soap (commonly used as a surfactant with neem oil) caused 13- 25% mortality of S. feltiae. This toxic effect was entirely due to the soap that alone caused about 24% mortality. Neither neem oil, Nimbecidine or soap had any effect on nematode virulence. The fungicide cinnamaldehyde (Cinnamate) was highly toxic, resulting in 100% nematode mortality after 4 h of incubation, followed by hydrogen dioxide/peroxyacetic acid mixture (ZeroTol) that caused 100% mortality after 120 h of incubation. Another fungicide, azoxystrobin (Abound) caused no nematode mortality. This investigation concludes that neem and the fungicide azoxystrobin (Abound) can be safely tank mixed at the field recommended concentrations with the infective juveniles of S. feltiae for application, but cinnamaldehyde (Cinnamate) and hydrogen dioxide/peroxyacetic mixture (ZeroTol), are incompatible. Also the surfactants that are usually recommended as 'tank-mix' applications can be toxic to the nematodes and should therefore be evaluated for compatibility prior to use.     

Biological response of S. littoralis larvae to feeding on diet mixed with neem product at different concentrations

Studies were carried out to determine the effect of the neem product, suneem oil, at two concentrations 10 and 100 ppm, on the second instar larvae of S. littoralis in the laboratory. Two sets of experiments were carried out, choice and no choice. Results showed that suneem oil has anti-feeding and repellency effects on the test insects and it markedly affects the longevity of larvae and pupae, impairs the normal development of larvae and has an effect on the weight of pupae, depending on the concentration used (100 or 10 ppm).     

Evaluation of various parts of the paw paw tree, Asimina triloba (Annonaceae), as commercial sources of the pesticidal annonaceous acetogenins.

Various plant parts of the paw paw tree (Asimina triloba Dunal, Annonaceae) were extracted and partitioned to concentrate the mixture of acetogenins into a standardized pesticidal extract (F005). A bioassay with brine shrimp larvae (Artemia salina Leach) was used to determine the relative potencies of the various extracts. The small twigs (0-0.5 cm diameter) yielded the most potent extract (LC50 = 0.04 ppm); the stem wood (LC50 = 4.9 ppm) and leaves (LC50 = 53.7 ppm) yielded the poorest activities. The unripe fruits, seeds, root wood, root bark, and stem bark were notably potent and, generally, yielded > 2% of their dry weight as F005. The smaller diameter stems were more potent than the larger stems. We conclude that, by pollarding the trees, the entire twigs and small branches of paw paw could be processed to produce a potent acetogenin mixture; this biomass could be made available in quantities needed for commercialization of the pesticidal product and could be renewable through regrowth from the parent trunk and larger branches.     

Stem canker (Rhizoctonia solani) of maincrop potatoes.

In two years, potato plants were sampled at 1- or 2- weekly intervals from plots planted with seed tubers bearing sclerotia of Rhizoctonia solani (black scurf) and with seed without sclerotia either infested or not with cultures of R. solani at planting. Sprouted King Edward seed was used in 1981 and sprouted and non-sprouted King Edward and Pentland Crown seed in 1982. In both years 60–80% of shoots from seed with sclerotia and 90% of shoots from seed inoculated at planting were affected with stem canker. Most disease developed before shoots emerged although it gradually increased later when new shoots arising both from seed tubers or as branches on shoots with damaged apices (pruned shoots) became infected before they emerged. Sprouting seed tubers bearing sclerotia decreased the disease on both cultivars but with soil-applied inoculum the disease was more severe on plants from sprouted than non-sprouted seed. Some stolons were infected by R. solani soon after they developed and incidence of infection later increased. Thirty to 50% of stolons were infected on plants from infected seed tubers and 60% on plants with soil-applied inoculum. With both cultivars and sources of inoculum about 70% of the infected stolons had their apices killed (pruned).     

Dendritic Branch Intersections Are Structurally Regulated Targets for Efficient Axonal Wiring and Synaptic Clustering

Synaptic clustering on dendritic branches enhances plasticity, input integration and neuronal firing. However, the mechanisms guiding axons to cluster synapses at appropriate sites along dendritic branches are poorly understood. We searched for such a mechanism by investigating the structural overlap between dendritic branches and axons in a simplified model of neuronal networks - the hippocampal cell culture. Using newly developed software, we converted images of meshes of overlapping axonal and dendrites into topological maps of intersections, enabling quantitative study of overlapping neuritic geometry at the resolution of single dendritic branch-to-branch and axon-to-branch crossings. Among dendro-dendritic crossing configurations, it was revealed that the orientations through which dendritic branches cross is a regulated attribute. While crossing angle distribution among branches thinner than 1 µm appeared to be random, dendritic branches 1 µm or wider showed a preference for crossing each other at angle ranges of either 50°–70° or 80°–90°. It was then found that the dendro-dendritic crossings themselves, as well as their selective angles, both affected the path of axonal growth. Axons displayed 4 fold stronger tendency to traverse within 2 µm of dendro-dendritic intersections than at farther distances, probably to minimize wiring length. Moreover, almost 70% of the 50°–70° dendro-denritic crossings were traversed by axons from the obtuse angle’s zone, whereas only 15% traversed through the acute angle’s zone. By contrast, axons showed no orientation restriction when traversing 80°–90° crossings. When such traverse behavior was repeated by many axons, they converged in the vicinity of dendro-dendritic intersections, thereby clustering their synaptic connections. Thus, the vicinity of dendritic branch-to-branch crossings appears to be a regulated structure used by axons as a target for efficient wiring and as a preferred site for synaptic clustering. This synaptic clustering mechanism may enhance synaptic co-activity and plasticity.     

Repellent effects of certain plant essential oil,plant extracts and inorganic salts to granary weevil,Sitophilus granarius (L.)

Repellency of six materials, two plant essential oil (clove and flax seed oils), two plant extracts (neem and harmal seed extracts) and two inorganic salts (silica dust and tri-calcium phosphate), to Sitophilus granarius L. were evaluated. Per cent repellency (PR) was determined for each material. Repellent effects of tested materials were proportional to concentration and higher concentration has stronger effect. Neem and flax seed oils had the strongest repellence effect (100%) after 2, 4 and 6?h of treatment at concentrations of 20, 10 and 5?mL/kg grains. Repellency activity of both oils was gradually decreased with the passage of time to reach its lowest level after 12?h of treatment. Their repellency tended to class IV or stronger during the whole exposure period. Neem and harmal seed extracts had maximum repellency (98.7 and 86.5%, respectively) at highest concentration (1000?ppm), while the lowest concentration (250?ppm) had minimum repellency effects (62.9 and 71.6%, respectively). Both extracts showed potent repellent activity against the pest and repellency values ranged between class IV and class V. The repellency action of silica dust and tri-calcium phosphate followed nearly the same trend as shown in case of oil and extracts. High repellent activities of silica dust and tri-calcium phosphate (87.3 and 97.4%, respectively) were observed at concentration of 5?g/kg, whereas the lowest mean of repellency (56.4 and 41.0%) was recorded at concentration of 1.29?g/kg. Thus, both salts exhibited high repellency activity against the weevil and repellency values ranged between class III and class IV.     

Cytotoxic and genotoxic effects of dioxacarb by human peripheral blood lymphocytes CAs and Allium test

Dioxacarb (Elecron, Famid) is a phenyl methylcarbamate insecticide and in vitro cytotoxic and genotoxic effects of this pesticide on human peripheral blood lymphocytes and Allium root meristematic cells were investigated by chromosomal aberrations (CAs) and Allium test. Human lymphocytes were treated with 62.5, 125, 250 and 500 ppm doses of dioxacarb for CAs. CA/cell, abnormal cell % and mitotic index % (MI %) data were obtained from these concentrations in 24 and 48 h treatment periods. Dioxacarb did not increase the CA/cell frequency significantly, so this insecticide was not identified as genotoxic. But it was found cytotoxic especially at 250 and 500 ppm concentrations because of the reduced the MI % and increased the abnormal cell %. In Allium test, 25 ppm (EC50/2), 50 ppm (EC50) and 100 ppm (EC50 × 2) concentrations were used for root growth inhibition (EC50 determination) and Allium mitotic index (MI) determination tests. The used concentrations of dioxacarb induced dose-dependent inhibition of MI and root growth on root meristems. Mitotic inhibition of dioxacarb was found significantly higher than for the positive control. These Allium results indicated the high cytotoxicity of dioxacarb. The present study is the first research on cytotoxicity and genotoxicity of dioxacarb by human lymphocyte CAs and Allium test.     

Evaluation of neem, Azadirachta indica, with and without water management, for the control of culicine mosquito larvae in rice-fields

Applications of neem, Azadirachta indica (Meliaceae), to rice-fields were evaluated with the dual objective of controlling the culicine mosquito vectors of Japanese encephalitis virus (JEV) and enhancing the grain yield. Since crude neem products deteriorate under improper storage conditions, a laboratory bioassay was developed to screen neem cake powder against mosquito larvae, Culex quinquefasciatus. Only samples of neem giving over 90% bioassay mortality were used in field trials. When good quality neem cake powder was applied at the dose of 500 kg/ha, either alone or coated over urea, there was a striking reduction in the abundance of late instar culicine larvae and pupae. Only fourteen pupae were obtained over a period of 13 weeks in neem cake powder treated plots, and four in those treated with neem coated urea, compared with 101 in control plots. Both treatments were significantly less than the control, but on par with one another. In another field trial, neem cake coated urea was tested at 500 and 250 kg neem/ha in combination with water management practices. No reduction in efficacy was noted at the lower dose. Larval abundance in plots under water management alone did not differ significantly from the controls, but was significantly reduced when water management was combined with neem products. Two stable formulations, 'Neemrich-I' (lipid rich) and 'Neemrich-II' (azadirachtin rich), also gave good suppression of immature culicines. All the treatments with neem also gave higher grain yield than the control.(ABSTRACT TRUNCATED AT 250 WORDS)     

Selection of suitable propagation method for consistent plantlets production in Stevia rebaudiana (Bertoni)

Stevia rebaudiana (Bert.) is an emerging sugar alternative and anti-diabetic plant in Pakistan. That is why people did not know the exact time of propagation. The main objective of the present study was to establish feasible propagation methods for healthy biomass production. In the present study, seed germination, stem cuttings and micropropagation were investigated for higher productivity. Fresh seeds showed better germination (25.51–40%) but lost viability after a few days of storage. In order to improve the germination percentage, seeds were irradiated with 2.5, 5.0, 7.5 and 10 Gy gamma doses. But gamma irradiation did not show any significant change in seed germination. A great variation in survival of stem cutting was observed in each month of 2012. October and November were found the most suitable months for stem cutting survival (60%). In order to enhance survival, stem cuttings were also dipped in different plant growth regulators (PGRs) solution. Only indole butyric acid (IBA; 1000 ppm) treated cutting showed a higher survival (33%) than control (11.1%). Furthermore, simple and feasible indirect regeneration system was established from leaf explants. Best callus induction (84.6%) was observed on MS-medium augmented with 6-benzyladenine (BA) and 2,4-dichlorophenoxyacetic acid (2,4-D; 2.0 mg l⁻¹). For the first time, we obtained the highest number of shoots (106) on a medium containing BA (1.5 mg l⁻¹) and gibberellic acid (GA₃; 0.5 mg l⁻¹). Plantlets were successfully acclimatized in plastic pots. The current results preferred micropropagation (85%) over seed germination (25.51–40%) and stem cutting (60%).     

Effect of pollutants on the ergosterol content as indicator of fungal biomass

Ergosterol content was determined in 20 white-rot fungi isolates and the values ranged from 2380 to 13 060 μg g⁻¹ fungal biomass. Significant changes of ergosterol content according the physiological stage for Bjerkandera adusta 4312 and Coriolopsis gallica 8260 were found, showing the highest values during the stationary phase. However, in the case of Phanerochaete chrysosporium 3642, no changes were detected during growth. The effect of pollutants, such as heavy metals and fungicides, on the ergosterol content of C. gallica was determined. Heavy metals (Cu 80 ppm, Zn 50 ppm or Cd 10 ppm) and fungicides (thiram 3 ppm or pentachlorophenol 1.5 ppm) at concentrations that reduce the metabolic activity between 18% and 53% (pollutant-stressed cultures) did not affect the ergosterol content. Only the fungicide zineb (25 ppm) reduced significantly the ergosterol content in biomass basis. In soil experiments with Cu (80 ppm) or thiram (10 ppm) after 15 and 30 days of incubation, the ergosterol content in soil was linearly correlated to the fungal biomass C in both polluted and control soil cultures. The ergosterol content was independent of the presence or the absence of pollutants. Thus, these results indicate that ergosterol can be a useful indicator for fungal biomass in polluted soils, and can be applied for monitoring bioremediation processes.     

Effects of sand burial on survival, growth, gas exchange and biomass allocation of Ulmus pumila seedlings in the Hunshandak Sandland, China

BACKGROUND AND AIMS: In the last decade, the number of young plants of Ulmus pumila in the Hunshandak Sandland has decreased sharply because of severe sand burial, and their ecological protective function has been weakened. In order to develop an understanding of the tolerance of U. pumila to sand burial and to suggest reasonable measures to protect the sparse-elm-grassland ecosystem, the effects of burial on the survival, growth, photosynthesis and biomass allocation in U. pumila were studied. METHODS: Seedlings were buried at five different depths in pot experiments: no burial (control), partial burial (33 % and 67 % stem height), and complete burial (100 % and 133 % stem height). Growth analyses and measurements of photosynthesis were carried after the plants had been uncovered. KEY RESULTS: All the plants survived partial burial, but about 30 % and 80 % of the seedlings died as a result of the 100 % and 133 % sand burial treatments, respectively. The numbers of newly produced leaves and branches, and the height of the stems of the seedlings in the 33 % and 67 % burial treatments during the period of the experiment were significantly greater than those in the control. Furthermore, net photosynthetic rate, transpiration rate and water use efficiency were also elevated by the partial burial, but not affected by burial time. This might be attributed to the increased root length, which improved water acquisition. The biomass and biomass allocation of the seedlings were significantly changed by the burial treatments and burial times. The biomass was enhanced by partial burial but was reduced by complete burial at each burial time. However, the biomass allocation was not significantly changed by the 33 % and 67 % sand burial treatments 2 or 4 weeks following the burial. CONCLUSIONS: Ulmus pumila was shown to be tolerant to partial sand burial, but must be protected from complete burial.