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1.
Picea asperata is a dominant species in the subalpine coniferous forests distributed in eastern edges of Tibetan Plateau and upper reaches of the Yangtze River. The paper mainly identified the short-term influences of experimental warming, nitrogen fertilization, and their combination on growth and physiological performances of Picea asperata seedlings. These seedlings were subjected to two levels of temperature (ambient; infrared heater warming) and two nitrogen levels (0; 25 g m−2 a−1 N) for 6 months. We used a free air temperature increase of overhead infrared heater to raise both air and soil temperature by 2.1 and 2.6°C, respectively. The temperature increment induced an obvious enhancement in biomass accumulation and the maximum net photosynthetic rate, and decreased AOS and MDA level under ambient nitrogen conditions. Whereas, negative effects of experimental warming on growth and physiology was observed under nitrogen fertilization condition. On the other hand, nitrogen fertilization significantly improved plant growth in unwarmed plots, by stimulating total biomass, maximum net photosynthetic rate (A max), antioxidant compounds, as well as reducing the content of AOS and MDA. However, in warmed plots, nitrogen addition clearly decreased A max, antioxidant compounds, and induced higher accumulation of AOS and MDA. Obviously, the beneficial effects of sole nitrogen on growth and physiology of Picea asperata seedlings could not be magnified by artificial warming.  相似文献   

2.
The impacts of global climatic change on belowground ecological processes of terrestrial ecosystems are still not clear. We therefore conducted an experiment in the subalpine coniferous forest ecosystem of the eastern edges of the Tibetan Plateau to study roots of Picea asperata seedlings and rhizosphere soil responses to soil warming and nitrogen availability from April 2007 to December 2008. The seedlings were subjected to two levels of temperature (ambient; infrared heater warming) and two nitrogen levels (0 or 25 g m−2year−1 N). We used a free air temperature increase from an overhead infrared heater to raise both air and soil temperature by 2.1 and 2.6°C, respectively. The results showed that warming alone significantly increased total biomass, coarse root biomass and fine root biomass of P. asperata seedlings. Both total biomass and fine root biomass were increased, but coarse root biomass was significantly decreased by nitrogen fertilization and warming combined with nitrogen fertilization. Warming induced a prominent increase in soil organic carbon (SOC) and NO3 -N of rhizosphere soil, while nitrogen fertilization significantly decreased SOC and NH4 +-N of rhizosphere soil. The warming, fertilization and warming × N fertilization interaction decreased soil microbial C significantly, but substantially increased soil microbial N. These results suggest that nitrogen deposition combined with warmer temperatures under future climatic change possibly will have no effect on fine root production of P. asperata seedlings, but could enhance the nitrification process of their rhizosphere soils in subalpine coniferous forests.  相似文献   

3.
The response and adaption mechanisms of seedlings under long-term warming have remained largely unknown. In this study, we investigated the effects of warming for 6 years on growth, and needle carbon, nitrogen, chlorophyll, and carbohydrate levels in a coniferous tree species, Abies faxoniana. Seedlings were grown in even-aged monospecific stands under ambient and warming (ambient +2.2°C) temperature in climate control chambers. Warming caused statistically significant increases in the specific leaf area, leaf area ratio, root biomass, leaf biomass, branch biomass, stem biomass, and total mass of the seedlings, and reduced the root/shoot ratio. Warming also increased total chlorophyll concentrations, specific chlorophyll pigments, and Chlorophyll a/b ratios in both studied needle age classes. In addition, C/N ratios of current-year and 1-year-old needles increased by warming. In contrast, warming decreased the levels of N, sugar, cellulose, and starch in needles, while warming had no effect on the height, stem diameter, needle mass ratio, root mass ratio, and root/needle ratio. We conclude that warming increases branch growth and changes needle chemistry, which enhances the light capture potential of seedlings.  相似文献   

4.
Summary The effect of 3-indoleacetic acid (IAA), 6-furfurylaminopurine (kinetin), and gibberellic acid (GA3) on germination of the orchid Comparettia falcata was evaluated in a factorial experiment (4×4×4) with Murashige and Skoog (1962) basal medium. It was established that seeds of this orchid could be maintained under aseptic conditions as long as the necessary nutrients and appropriate concentrations of growth regulators were provided. Of the three growth regulators used, IAA significantly decreased seed germination of Comparettia falcata. There was a synergistic effect in the kinetin:GA3 combination that produced a positive response in both percentage seed germination and development of seedlings. This study describes a single medium-based protocol able to achieve more than 160000 seedlings within 21 wk, starting from a single capsule, sufficient for both large-scale propagation and in vitro conservation of this threatened orchid.  相似文献   

5.
The seedlings of Acer mono Maxim. were exposed to two watering regimes (well watered (100% of field capacity) and drought (30% of field capacity)) and two light levels (high light (100% of full sunlight) and low light (15% of full sunlight)) in a greenhouse to assess growth, photosynthesis, and foliar nutrient traits of woody plants under drought and low light. Drought significantly reduced growth and gas exchange characteristics of A. mono, including net photosynthetic rate (P N), stomatal conductance (g s), intercellular CO2 concentration (Ci), and photosynthetic nitrogen use efficiency (PNUE). Also, drought reduced relative water content (RWC) and foliar C and N concentrations, but increased the C/N ratio. P N and C concentration were lower under drought and low light than in any other treatment, indicating that deep shade might seriously decrease C assimilation. However, the negative effect induced by drought was alleviated by improving RWC and maintaining C balance, and therefore low-light seedlings accumulated more biomass than those under high light when they were exposed to drought. Our results showed that trade-off and facilitation effects of drought and low light might be complementary and alter in different species.  相似文献   

6.
Twenty-three isolates of Metarhizium anisopliae (Metschnikoff) Sokorin and three isolates of Beauveria bassiana (Balsamo) Vuillemin (Ascomycota: Hypocreales: Clavicipitaceae) were assessed for their virulence against the two-spotted spider mite, Tetranychus urticae Koch (Acari: Tetranychidae). Based on the screening results, nine isolates of M. anisopliae and two isolates of B. bassiana were tested for their virulence against young adult (1- to 2-day-old) female T. urticae at constant temperatures of 20, 25, 30 and 35°C. At all temperatures tested, all the fungal isolates were pathogenic to T. urticae but mortality varied with isolates and temperatures. Fungal isolates were more virulent at 25, 30 and 35°C than at 20°C. The lethal time to 50% mortality (LT50) and lethal time to 90% mortality (LT90) values decreased with increased temperature. There were no significant differences in virulence between fungal isolates at 30 and 35°C; however, significant differences were observed at 20 and 25°C.  相似文献   

7.
Selecting entomopathogenic fungal isolates for use as biocontrol agents requires an assessment of their growth and virulence characteristics as affected by environmental conditions. Here we demonstrate a wide temperature and moisture range for colony growth, effective conidial germination and virulence against Pissodes strobi Peck (white pine weevil) of several isolates of Lecanicillium Gams and Zare, an entomopathogenic fungus distributed worldwide and indigenous to forests on Vancouver Island, British Columbia, Canada. In order to examine the potential Lecanicillium as a biological control agent, the pathogenicity of isolates collected from different geographical locations on P. strobi cadavers was assessed, and colony growth at different temperatures was evaluated. Colony growth was evident between 5 and 30°C, with optimal growth occurring at 25°C. Various combinations of water activity (0.55, 0.76, 0.85 and 0.99 a w) and temperature (10, 15, 20, and 25°C) were also used to evaluate environmental impacts on conidial germination and cumulative mycosis of adult P. strobi. Certain Lecanicillium isolates displayed xerophilic (0.85 a w) or psychrophilic (10°C) growth optima. Ultimately, identifying the abiotic limits of this entomopathogenic fungus will be used to determine which isolates have potential for future in situ biocontrol trials.  相似文献   

8.
Fecundity and feeding of two introduced sibling biological control species, Galerucella calmariensis and G. pusilla (Coleoptera: Chrysomelidae) on purple loosestrife, Lythrum salicaria L. (Lythraceae) were compared at constant temperatures of 12.5, 15, 20, 25, and 27.5 °C. Larval feeding was also carried out at 30 °C, but at this temperature, larvae developed only to the L2 stage and none pupated. Thus, data for this temperature were not used in the analysis. There were significant species × temperature interactions in fecundity. Of the two species, Galerucella pusilla laid more eggs. Although egg production of both species was lowest at 12.5 °C and increased to 20 °C, at higher temperatures, the two species reacted differently. From 25 to 27.5 °C, egg production decreased for G. pusilla, but G. calmariensis fecundity peaked at 27.5 °C. Significant temperature × species × life-stage interactions were also observed in feeding. For each species, the amount of feeding varied with temperature and stage of development. Galerucella pusilla adults consumed more foliage at 15, 20, and 27.5 °C. However, at 12.5 °C G. calmariensis adults fed more than G. pusilla. G. pusilla larvae consumed an average of 25% less foliage than G. calmariensis. The lower larval consumption of G. pusilla suggests that when food is limited, G. pusilla larvae may have a higher survival rate because of its ability to complete larval development with less food and produce more progeny due to its greater fecundity. When food is not limited neither species would have a competitive advantage and both species could coexist temporally and spatially. However, since G. calmariensis larvae consumed more leaf material, the larval stage of this species would have a greater impact on purple loosestrife than G. pusilla.  相似文献   

9.
In vitro culture is an important aid for ex situ conservation of rare, endemic or threatened plants. In this work, we establish an efficient method for the seed germination, seedling development, and axillary shoot propagation of Centaurea zeybekii Wagenitz. The seeds, collected from a wild population, were surface sterilised and cultured on various in vitro germination media. The effects of photoperiod and temperature on seed germination were also investigated. Germinations were obtained after 6 weeks in culture and the radicle emergence was evaluated as a main indicator. A high frequency of germination was obtained on distilled water supplemented with vitamines and 1 mg/L GA3. Although the seed germination frequencies were not affected by photoperiod, the highest germination frequency was obtained at 24 ± 2°C. A high frequency of axillary shoot proliferation was produced on MS medium supplemented with 1 mg/L BA. Then, the axillary shoots were separated and transferred to MS medium with or without plant growth regulators for rooting. Rhizogenezis was promoted after 6 weeks only in MS and 1/2 MS media containing 0.5 mg/L IBA. The rooting process was very slow and the percentage of shoot rooting was also very low (15%). The present study not only enables reinforcement of wild plant populations using ex situ growth of individuals, but it also helps to large number of aseptic seedling to use it in clonaly micropropagation studies.  相似文献   

10.
We conducted a night-time warming and drought field experiment for 7 years (1999–2005) in a Mediterranean shrubland. We focused on the two dominant shrub species, Erica multiflora L. and Globularia alypum L. and the tree Pinus halepensis L. and the final years to study the effects of the experimental night-time warming and drought on Fv/Fm, photosynthesis, and stomatal conductance. Warming treatment increased mean air temperature and mean soil temperature through the years by an average of 0.7 and 0.9°C respectively, and drought treatment reduced soil moisture through the years by an average of 19%. Warming tended to increase photosynthetic rates in E. multiflora, G. alypum and P. halepensis mostly in the cold seasons, when plants were more limited by temperature, as shown by the lowest values of Fv/Fm being detected in winter in the three studied species. A negative effect of warming was only detected for E. multiflora in summer 2003. Drought treatment generated different responses of net photosynthetic rates depending on the species, season and year. Stomatal conductance showed the same pattern as photosynthesis for the three studied species, displaying seasonal and inter-annual variability, although with an overall negative effect of drought for P. halepensis. Photosynthetic rates decreased significantly in the dry winter 2005 and spring 2005 in comparison to the same seasons of 2003 and 2004. There were positive correlations between the photosynthetic rates in different seasons for E. multiflora, G. alypum and P. halepensis and the soil moisture of the week prior to measurements. The great variation in the photosynthetic rates was thus explained in a significant part by soil moisture levels. The lowest Fv/Fm values usually corresponded with lowest stomatal conductances suggesting that drought stress could be associated to stress by low temperatures in winter.  相似文献   

11.
Tetranychus evansi Baker and Pritchard and Tetranychus urticae Koch (Acari: Tetranychidae) are important pests of Solanaceae in many countries. Several studies have demonstrated that T. urticae is an acceptable prey to many predatory mites, although the suitability of this prey depends on the host plant. T. evansi, has been shown to be an unfavorable prey to most predatory mites that have been tested against it. The predator Phytoseiulus fragariae Denmark and Schicha (Acari: Phytoseiidae) has been found in association with the two species in Brazil. The objective of this work was to compare biological parameters of P. fragariae on T. evansi and on T. urticae as prey. The study was conducted under laboratory conditions at 10, 15, 20, 25 and 30°C. At all temperatures, survivorship was lower on T. evansi than on T. urticae. No predator reached adulthood at 10°C on the former species; even on the latter species, only about 36% of the predators reached adulthood at 10°C. For both prey, in general, duration of each life stage was shorter, total fecundity was lower and intrinsic rate of population increase (r m ) was higher with increasing temperatures. The slower rate of development of P. fragariae on T. evansi resulted in a slightly higher thermal requirement (103.9 degree-days) on that prey than on T. urticae (97.1 degree-days). The values of net reproduction rate (R 0), intrinsic rate of increase (r m ) and finite rate of increase (λ) were significantly higher on T. urticae, indicating faster population increase of the predator on this prey species. The highest value of r m of the predator was 0.154 and 0.337 female per female per day on T. evansi and on T. urticae, respectively. The results suggested that P. fragariae cannot be considered a good predator of T. evansi.  相似文献   

12.
The species Trichoderma harzianum was analyzed as possible biocontrol agent of Alternaria alternata under different environmental conditions (water activity and temperature). The strains were analyzed macroscopically to obtain the Index of Dominance. The analysis was completed using two microscopic techniques. T. harzianum showed dominance on contact over A. alternata at all testing temperatures and water activities tested except at 0.95 a w and 15 °C, at which T. harzianum inhibited A. alternata at a distance. Biocontrol was governed by different mechanisms such as competition for space and nutrients, mycoparasitism, and possible antibiosis. Temperature and water activity significantly influenced fungal growth rate.  相似文献   

13.
14.
Eretmocerus sp. nr. furuhashii (Hymenoptera: Aphelinidae) is an indigenous parasitoid of Bemisia tabaci (Gennadius)(Hemiptera: Aleyrodidae) from southern China; the effects of constant temperatures on the life history of E. sp. nr. furuhashii were examined in the laboratory. The developmental period ranged from 39.2 days at 20°C to 12.40 days at 32°C. A total of 263.4 degree-days were required to complete development with a lower developmental threshold temperature of 11.1°C. Of the eggs produced, 59.3% completed development at 20°C with completion increasing to 71.5% at 26°C. Adult female longevity was 10.8 days at 20°C and 5.2 days at 32°C while the mean daily offspring reproduced per female was highest at 29°C with 5.9 offspring. Adult oviposition peaked three days after emergence at 26, 29 and 32°C, and four days post-emergence at 20°C and 23°C. The total numbers of offspring produced per female ranged from 25.7 individuals at 32°C to 41.1 individuals at 20°C. The sex ratio had a female bias and ranged from 0.72 at 17°C to 0.51 at 35°C. The intrinsic rate of increase was 0.1727 at 29°C followed with 0.1606 at 32°C. Results indicated that E. sp. nr. furuhashii reaches its maximum biological potential at temperatures ranging from 26°C to 32°C.  相似文献   

15.
Axenically germinated seedlings of two species of Southern beech (Nothofagus obliqua, N. glauca) from Chile were inoculated with spores of the Périgord black truffle (Tuber melanosporum). Ectomycorrhizal development was monitored for 6 months in the greenhouse and compared to the performance of the natural host species Quercus ilex and Quercus robur. Seedling survival and mycorrhization showed major differences in both Nothofagus species: T. melanosporum readily formed ectomycorrhizae with seedlings of N. obliqua, although at a lower rate than with Q. ilex but at a proportion very similar to Q. robur; survival and colonization rates were high, and seedling growth was not visibly affected by the high soil pH required by T. melanosporum. In contrast, more than 50% of N. glauca seedlings died after inoculation, and mycorrhiza formation was very sparse. In both species, no colonization by adventive ectomycorrhizal fungi could be observed, whereas both species of Quercus showed minor colonization by another fungus, probably Inocybe or Hebeloma. Our results show that it is possible to infect N. obliqua with the Périgord black truffle under greenhouse conditions, which opens up the possibility of cultivating this truffle as a secondary crop during reforestation with N. obliqua in Chile.  相似文献   

16.
Although resistance of microorganisms to Hg(II) salts has been widely investigated and resistant strains have been reported from many eubacterial genera, there are few reports of mercuric ion resistance in extremophilic microorganisms. Moderately thermophilic mercury resistant bacteria were selected by growth at 62 °C on Luria agar containing HgCl2. Sequence analysis of 16S rRNA genes of two isolates showed the closest matches to be with Bacillus pallidus and Ureibacillus thermosphaericus. Minimum inhibitory concentration (MIC) values for HgCl2 were 80 μg/ml and 30 μg/ml for these isolates, respectively, compared to 10 μg/ml for B. pallidus H12 DSM3670, a mercury-sensitive control. The best-characterised mercury-resistant Bacillus strain, B. cereus RC607, had an MIC of 60 μg/ml. The new isolates had negligible mercuric reductase activity but removed Hg from the medium by the formation of a black precipitate, identified as HgS by X-ray powder diffraction analysis. No volatile H2S was detected in the headspace of cultures in the absence or presence of Hg2+, and it is suggested that a new mechanism of Hg tolerance, based on the production of non-volatile thiol species, may have potential for decontamination of solutions containing Hg2+ without production of toxic volatile H2S.  相似文献   

17.
Biochemical parameters of the angiotensin converting enzyme-like activity (ACELA) in the gills of two Antarctic teleosts, Chionodraco hamatus and Trematomus bernacchii were characterized. Enzymatic activity was revealed following hydrolysis of a specific substrate of angiotensin-converting enzyme N-[3-(2-furyl)acryloyl]l-phenylalanyl-glycyl-glycine (FAPGG) and metabolites were separated by reverse phase HPLC analysis. The results showed similar Km values for the substrate FAPGG at 5°C for the two species with an increase of Km value for T. bernacchii at 25°C. The optimum pH value was 8.5 at 25°C and optimum chloride concentrations were about 300 mM. In T. bernacchii the optimum temperature for maximum enzyme activity was 50°C, while maximum activity in C. hamatus occurred at 35°C. Lisinopril was more efficient in inhibiting ACELA in C. hamatus with an I 50 value of 16.83 ± 5.11 nM, compared to an I 50 value of 30.66 ± 5.19 nM in T. bernacchii. In conclusion, it appears that some biochemical parameters of ACELA in C. hamatus differ from those in T. bernacchii, probably due to different ways that the enzyme adapts to the constantly cold temperatures of the animal’s environment.  相似文献   

18.
Extracellular exoinulinase from Kluyveromyces marxianus YS-1, which hydrolyzes inulin into fructose, was immobilized on Duolite A568 after partial purification by ethanol precipitation and gel exclusion chromatography on Sephadex G-100. Optimum temperature of immobilized enzyme was 55 °C, which was 5 °C higher than the free enzyme and optimal pH was 5.5. Immobilized biocatalyst retained more than 90% of its original activity after incubation at 60 °C for 3 h, whereas in free form its activity was reduced to 10% under same conditions, showing a significant improvement in the thermal stability of the biocatalyst after immobilization. Apparent K m values for inulin, raffinose and sucrose were found to be 3.75, 28.5 and 30.7 mM, respectively. Activation energy (E a) of the immobilized biocatalyst was found to be 46.8 kJ/mol. Metal ions like Co2+ and Mn2+ enhanced the activity, whereas Hg2+ and Ag2+ were found to be potent inhibitors even at lower concentrations of 1 mM. Immobilized biocatalyst was effectively used in batch preparation of high fructose syrup from Asparagus racemosus raw inulin and pure inulin, which yielded 39.2 and 40.2 g/L of fructose in 4 h; it was 85.5 and 92.6% of total reducing sugars produced, respectively.  相似文献   

19.
Sporulation in Bacillus megaterium var phosphaticum (PB — 1) was induced using modified nutrient media. This modified medium induced sporulation within 36 h. After spore induction the spores were kept under refrigerated (5°C) and room temperature (32°C) for five months and survival of spores was studied at 15 days intervals by plating them in nutrient agar medium. It was observed that there was not much variation in the storage temperature (5°C & 32°C). The spore cells of Bacillus megaterium var phosphaticum (PB — 1) were observed up to five months of storage under refrigerated (5°C) and room temperature (32°C). Regeneration of spore cells into vegetative cells was studied in tap water, rice gruel, nutrient broth, sterile lignite and sterile water at different concentrations of spore inoculum. The multiplication of sporulated Bacillus megaterium var phosphaticum culture was fast and reached its maximum (29.5 × 108 cfu ml−1) in nutrient broth containing 5 per cent inoculum level.  相似文献   

20.
Summary We describe an in vitro propagation protocol for Zingiber petiolatum (Holttum), I. Theilade, a rare species from the southern part of Thailand. Fruits were surface-sterilized and seeds germinated on Murashige and Skoog medium (MS) medium supplemented with 3% sucrose. Three-month-old seedlings were used as initial plant material for in vitro propagation. Terminal buds of the plants were inoculated on MS medium containing 6-benzylaminopurine (BA; 2.2–35.5 μM) alone or in combination with 1-naphthaleneacetic acid (0.5 μM). Eight weeks after inoculation, the cultures were transferred to MS medium without plant growth regulators for 4wk. The cultures transferred from MS medium with 17.8 μM BA revealed the highest shoot induction rate of 6.1±0.7 shoots per explant. Rooting was spontaneously achieved in MS medium without plant growth regulators. Rooted plants were successfully transplanted to soil.  相似文献   

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