共查询到20条相似文献,搜索用时 15 毫秒
1.
G. Selvakumar S. Kundu Piyush Joshi Sehar Nazim A. D. Gupta H. S. Gupta 《Indian journal of microbiology》2010,50(1):50-56
Exiguobacterium acetylicum strain 1P (MTCC 8707) is a gram-positive, rod-shaped, yellow pigmented bacterium isolated from soil on nutrient agar plates
at 4°C. The identity of the bacterium was arrived on the basis of the biochemical characterization, BIOLOG sugar utilization
pattern and sequencing of the 16S rRNA gene. It grew at temperatures ranging from 4 to 42°C, with temperature optima at 30°C.
It expressed multiple plant growth promotion attributes such as phosphate solubilization, indole acetic acid (IAA), siderophore
and hydrogen cyanide (HCN) production, differentially at suboptimal growth temperatures (15 and 4°C). At 15°C it solubilized
phosphate (21.1 μg of P ml−1 day−1), and produced IAA (14.9 μg ml−1 day−1) in tryptophan amended media. Qualitative detection of siderophore production and HCN were possible at 15°C. At 4°C it retained
all the plant growth promotion attributes. Seed bacterization with the isolate, positively influenced the growth and nutrient
uptake parameters of wheat seedlings in glass house studies at suboptimal cold growing temperatures. 相似文献
2.
Crisp lettuce plants cv. Saladin were grown from the time they started flowering, at 20/10°C (16 h day, 8 h night), 25/15°C and 30/20°C in glasshouses on two occasions in 1985. Yields of seed increased from, on average, 15 g to 27 g and then fell to 20 g per plant with progressive increases in temperature. The number of mature florets per plant increased with temperature but the number of seeds per mature floret was lower at 20/10°C and 30/20°C than at 25/15°C. An increase in temperature reduced mean seed weight by up to 45%, seed volume by 15%, cell numerical volume density (Nv) by 27% and the number of cells per seed by 39%. Percentage seed germination reached a maximum early in seed development at the stage when the pappus appeared through the involucral bracts. Differences in percentage germination and vigour of seeds (slope test) from different temperatures were accounted for largely by the effects on mean seed weight. However, when germinated at 30°C seeds produced at 30/20°C germinated more readily than those produced at 25/15°C or 20/10°C. Seed vigour gradually increased with an increase in the length of storage after harvest, reaching a maximum after 260 days. In general, seeds produced at 25/15°C exhibited a greater variation in numbers of seeds per floret, Nv, seed weight, times of seedling emergence, seedling and mature head weight than seeds produced at lower or higher temperatures. 相似文献
3.
Filipa M. Lupi Helena M. L Fernandes Isabel Sá-Correia Júlio M. Novais 《Journal of applied phycology》1991,3(1):35-42
Temperature profiles (range 20–33 °C) were obtained for growth and exopolysaccharide (EPS) biosynthesis of the microalga Botryococcus braunii strain UC 58 under photoautotrophic conditions. The maximum temperature for growth was 32 °C and the temperature dependence
of the specific growth rate was described by the Hinshelwood equation based on the Arrhenius relationship. The optimal range
of temperatures for growth and extracellular EPS synthesis (25–30 °C) concurred and production of 4.5–5 g l−1 of EPS was obtained routinely, leading to high broth viscosities. Below 23 °C EPS biosynthesis was negligible, although the
specific growth rate maintained high values. At supraoptimal temperatures EPS biosynthesis decreased, accompanying the increase
in doubling time.
The polymers formed at temperatures within the optimal range for production, when dissolved in water, produced solutions (2
gl−1) with the highest viscosity, suggesting that their molecular weight showed the highest values. The degree of polymerization
of the EPS synthesized at suboptimal and supraoptimal temperatures was significantly below the values within the optimal range. 相似文献
4.
Booth DT Thompson MB Herring S 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》2000,170(4):269-276
Eggs of two small Australian lizards, Lampropholis guichenoti and Bassiana duperreyi, were incubated to hatching at 25 °C and 30 °C. Incubation periods were significantly longer at 25 °C in both species, and
temperature had a greater effect on the incubation period of B. duperreyi (41.0 days at 25 °C; 23.1 days at 30 °C) than L. guichenoti (40.1 days at 25 °C; 27.7 days at 30 °C). Patterns of oxygen consumption were similar in both species at both temperatures,
being sigmoidal in shape with a fall in the rate of oxygen consumption just prior to hatching. The higher incubation temperature
resulted in higher peak and higher pre-hatch rates of oxygen consumption in both species. Total amount of oxygen consumed
during incubation was independent of temperature in B. duperreyi, in which approximately 50 ml oxygen was consumed at both temperatures, but eggs of L. guichenoti incubated at 30 °C consumed significantly more (32.6 ml) than eggs incubated at 25 °C (28.5 ml). Hatchling mass was unaffected
by either incubation temperature or the amount of water absorbed by eggs during incubation in both species. The energetic
production cost of hatchling B. duperreyi (3.52 kJ · g−1) was independent of incubation temperature, whereas in L. guichenoti the production cost was greater at 30 °C (4.00 kJ · g−1) than at 25 °C (3.47 kJ · g−1). Snout-vent lengths and mass of hatchlings were unaffected by incubation temperature in both species, but hatchling B. duperreyi incubated at 30 °C had longer tails (29.3 mm) than those from eggs incubated at 25 °C (26.2 mm). These results indicate that
incubation temperature can affect the quality of hatchling lizards in terms of embryonic energy consumption and hatchling
morphology.
Accepted: 27 January 2000 相似文献
5.
J. T. Moraghan 《Plant and Soil》1987,104(1):121-127
The influence of FeEDDHA (0, 0.2 and 2 μg Fe g−1 soil) and NaH2PO4·H2O (0 and 120 μg Pg−1 soil) on the growth of two Fe-ineffective soybean (Glycine max L. Merr.) varieties (anoka and T203) on a calcareous soil at two soil temperatures (16 and 24°C) was compared under greenhouse
conditions. The two soybean varieties differed in the following respects: (a) T203 accumulated smaller concentrations of Fe
in washed tops than Anoka under comparable conditions; (b) T203 was more susceptible to Fe deficiency and its accentuation
by high levels of fertilizer P than Anoka; (c) T203 accumulated lower quantities of Mn in tops than Anoka under comparable
conditions; (d) T203, but not Anoka, developed Mn deficiency symptoms when treated with P and 2 μg Fe g−1 at 16°C. Fe deficiency was more severe in both varieties at the higher soil temperature due apparently to: (a) greater plant
concentration of P in tops at 24°C; and/or (b) an increased rate of plant growth and greater dilution of Fe in young tissue
at 24°C. Foliar P concentration was increased much more than foliar Fe concentration by an increase in soil temperature. Severely
Fe deficient T203 plants grown without FeEDDHA at 24°C accumulated less foliar Mn than their FeEDDHA counterparts. Comparisons
of Fe effectiveness of various soybean cultivars based on relative responses to FeEDDHA can be influenced by differential
effects on Mn nutrition. 相似文献
6.
Vogelaar JC Klapwijk B Temmink H van Lier JB 《Journal of industrial microbiology & biotechnology》2003,30(2):81-88
Kinetic parameters describing growth and decay of mesophilic (30°C) and thermophilic (55°C) aerobic biomass were determined
in continuous and batch experiments by using oxygen uptake rate measurements. Biomass was cultivated on a single soluble substrate
(acetate) in a mineral medium. The intrinsic maximum growth rate (μ
max) at 55°C was 0.71±0.09 h−1, which is 1.5 times higher than the μ
max at 30°C (0.48±0.11 h−1). The biomass decay rates increased from 0.004 h−1 at 30°C to 0.017 h−1 at 55°C. Monod constants were very low for both types of biomass: 9±2 mg chemical oxygen demand (COD) l−1at 30°C and 3±2 mg COD l−1at 55°C. Theoretical biomass yields were similar at 30 and 55°C: 0.5 g biomass COD (g acetate COD)−1. The observed biomass yields decreased under both temperature conditions as a function of the cell residence time. Under
thermophilic conditions, this effect was more pronounced due to the higher decay rates, resulting in lower biomass production
at 55°C compared to 30°C.
Electronic Publication 相似文献
7.
Jordi Urmeneta Óscar Alcoba Efrén Razquín Elena Tarroja Antoni Navarrete Ricardo Guerrero 《Current microbiology》1998,37(3):151-155
Photosynthetic and respiratory activities at low light intensities (300 μE m−2 s−1) in the microbial mats of the Ebro Delta were measured by the oxygen exchange method in the laboratory. The response to H2S concentration, a significant factor in the dynamics of that ecosystem, was assessed. Total photosynthesis reached 23.78–28.17
μg O2 cm−2 h−1. Photosynthetic activity was not significantly different at the two temperatures tested. Respiratory activity reached a consumption
of 6.95–8.56 μg O2 cm−2 h−1 at 25°C and 11.42–11.70 μg O2 cm−2 h−1 at 35°C. The Q10 value for respiration was 1.37–1.64. Oxygen production in Microcoleus chthonoplastes, the most abundant cyanobacterium in those microbial mats, was highly resistant to sulfide inhibition. Concentrations less
than 0.02 mM sulfide did not affect the rate of photosynthesis. Concentrations up to 0.1 mM sulfide caused different degrees
of partially reversible inhibition, with a maximum of 67% at 0.78 mM sulfide. Primary production (g C assimilated/m2/year) in those microbial mats was also assessed and compared with data from other ecosystems.
Received: 24 October 1997 / Accepted: 18 December 1997 相似文献
8.
Ziguo Zhao Fengjuan Zhao Jianting Yao Jingmei Lu Put. O. AngJr. Delin Duan 《Journal of applied phycology》2008,20(5):925-931
Morphology and culture studies on germlings of Sargassum thunbergii (Mertens et Roth) Kuntze were carried out under controlled laboratory conditions. Growth characteristics of these germlings
grown under different temperatures (from 10 to 25°C), irradiances (from 9 to 88 μmol photons m−2 s−1), and under blue and white light conditions are described. The development of embryonic germlings follows the classic “8
nuclei 1 egg” type described for Sargassaceae. Fertilized eggs spent 5–6 h developing into multicellular germlings with abundant
rhizoids after fertilization. Under conditions of 20°C, 44 μmol photons m−2 s−1 and photoperiod of 12 h, young germlings with one or two leaflets reached 2–3 mm in length after 8 weeks. Temperature variations
(10, 15, 20, 25°C) under 88 μmol photons m−2 s−1 significantly influenced the growth rate within the first week, although this effect became less obvious after 8 weeks, especially
at 15 and 20°C. Variation in germling growth was highly significant under different irradiances (9, 18, 44, 88 μmol photons
m−2 s−1) at 25°C. Low temperature (10°C) reduced germling growth. Growth of germlings cultured under blue light was lower than in
white light. Optimal growth of these germlings occurred at 25°C and 44 μmol photons m−2 s−1. 相似文献
9.
In this study, the kinetic behaviors between n-butyl acetate and composite bead were investigated. Both microbial growth rate and biochemical reaction rate would be inhibited with increasing average inlet concentration. The order of the inhibitive effect, which resulted from increased average inlet concentration for four operation temperatures, was 30>35>40>25 °C. Both microbial growth rate and biochemical reaction rate would be enhanced and inhibited with increasing operation temperature in the operation temperature ranges of 25 to 30 and 30 to 40 °C, respectively. The enhancing and inhibitive effects resulting from increased operation temperature were the most pronounced at the average inlet concentration of 200 ppm. The values of maximum reaction rate V
m and half-saturation constant K
s ranged from 0.011 to 0.047 g C h−1 kg−1 packed material and from 19.30 to 62.40 ppm, respectively. The zero-order kinetic with the diffusion rate limitation could be regarded as the most adequate biochemical reaction kinetic model. The values of maximum elimination capacity ranged from 0.51 to 0.20 g C h−1 kg−1 packed material, and the optimal maximum elimination capacity of biofilter occurred at the operation temperature of 30 °C. 相似文献
10.
G. Selvakumar S. Kundu Piyush Joshi Sehar Nazim A. D. Gupta P. K. Mishra H. S. Gupta 《World journal of microbiology & biotechnology》2008,24(7):955-960
Pantoea dispersa strain 1A is a Gram-negative rod-shaped, yellow-pigmented bacterium isolated on nutrient agar plates incubated at 4°C. The
identity of the bacterium was confirmed by sequencing of the 16 S rRNA gene. It was capable of growing at temperatures ranging
from 4 to 42°C, but maximum growth was observed at 30°C. It is endowed with multiple plant growth promotion attributes such
as phosphate solubilization, IAA production, siderophore production and HCN production, which are expressed differentially
at sub-optimal temperatures (15 and 4°C). It was able to solubilize phosphate (17.6 μg of P2O5 ml−1 day−1), and produce IAA (3.7 μg ml−1 day−1), at 15°C. Qualitative detection of siderophore production and HCN were also observed at 15°C. At 4°C it was found to express
all the plant growth promotion attributes. This bacterial isolate was able to positively influence and promote the growth
and nutrient uptake parameters of wheat (cv. VL.802) under glasshouse conditions. Hence in the context, of cold wheat-growing
environments, it is proposed that Pantoea dispersa 1A (MTCC 8706), could be deployed as an inoculant to attain the desired results of bacterization. 相似文献
11.
The effects of temperature and light on the growth and geosmin production of Lyngbya kuetzingii were determined. Of the three temperatures tested, 10, 25 and 35°C, the maximal geosmin concentration and geosmin productivity
were yielded at 10°C, while the highest chl a production was observed at 25°C. In the studies on light intensity, the maximal geosmin concentration and geosmin productivity
were observed at 10 μmol m−2 s−1, while the highest chl a production was at 20 μmol m−2 s−1. It was suggested that more geosmin was synthesized with lower chl a demand. Meanwhile, the relative amounts of extra- and intracellular geosmin were investigated. Under optimum growth conditions
(20 μmol m−2 s−1, 25°C; BG-11 medium), the amounts of extracellular geosmin increased as the growth progressed and reached the maximum in
the stationary phase, while the intracellular geosmin reached its maximum value in the late exponential phase, and then began
to decline. However, under the low temperature (10°C) or light (10 μmol m−2 s−1) conditions, more intracellular geosmin was synthesized and mainly accumulated in the cells. The proportions of extracellular
geosmin were high, to 33.33 and 32.27%, respectively, during the stationary phase at 35°C and 20 μmol m−2 s−1. It was indicated that low temperature or light could stimulate geosmin production and favor the accumulation of geosmin
in cells, while more intracellular geosmin may be released into the medium at higher temperatures or optimum light intensity. 相似文献
12.
Abstract Seed germination, seedling emergence and seed persistence in the soil were investigated for Dianthus morisianus (Caryophyllaceae), a psammophilous endemic species of Sardinia. Stored and freshly collected seeds were incubated in a range of constant temperatures (5–25°C) and an alternating temperature regime (25/10°C). The effect of seed burial depth on seedling emergence was investigated under controlled environmental conditions. Seed persistence in the soil was verified by in situ experimental seed burials. Seeds of this species were non-dormant, and all seed lots germinated both in the light and darkness, mainly at low temperatures (≤20°C), with a maximum at 15°C (≥95%). Optimal seedling emergence was obtained when seeds were buried at a depth of 1–2 cm, and a declining emergence with increasing depth was observed. D. morisianus was also unable to form a persistent soil seed bank. The fate of the seeds that, after dispersal, do not emerge from the soil in the spring is, therefore, presumably to die before the next favourable growing season. 相似文献
13.
Comparison of SHF and SSF processes for the bioconversion of steam-exploded wheat straw 总被引:6,自引:0,他引:6
F Alfani A Gallifuoco A Saporosi A Spera M Cantarella 《Journal of industrial microbiology & biotechnology》2000,25(4):184-192
Two processes for ethanol production from wheat straw have been evaluated — separate hydrolysis and fermentation (SHF) and
simultaneous saccharification and fermentation (SSF). The study compares the ethanol yield for biomass subjected to varying
steam explosion pretreatment conditions: temperature and time of pretreatment was 200°C or 217°C and at 3 or 10 min. A rinsing
procedure with water and NaOH solutions was employed for removing lignin residues and the products of hemicellulose degradation
from the biomass, resulting in a final structure that facilitated enzymatic hydrolysis. Biomass loading in the bioreactor
ranged from 25 to 100 g l−1 (dry weight). The enzyme-to-biomass mass ratio was 0.06. Ethanol yields close to 81% of theoretical were achieved in the
two-step process (SHF) at hydrolysis and fermentation temperatures of 45°C and 37°C, respectively. The broth required addition
of nutrients. Sterilisation of the biomass hydrolysate in SHF and of reaction medium in SSF can be avoided as can the use
of different buffers in the two stages. The optimum temperature for the single-step process (SSF) was found to be 37°C and
ethanol yields close to 68% of theoretical were achieved. The SSF process required a much shorter overall process time (≈30
h) than the SHF process (96 h) and resulted in a large increase in ethanol productivity (0.837 g l−1 h−1 for SSF compared to 0.313 g l−1 h−1 for SHF). Journal of Industrial Microbiology & Biotechnology (2000) 25, 184–192.
Received 02 December 1999/ Accepted in revised form 20 July 2000 相似文献
14.
Eastern Inner Mongolia of China is a typical ecotone between sandy forests and steppe. Little is known about the effect of
overgrazing on carbon loss from soil in semiarid steppe and sandy forests of the north of China. The soil carbon parameters
were measured in a 10,000 ha natural reserve in eastern Inner Mongolia of China (43°30′–43°36′N, 117°06′–117°16′E). Three
situations were compared: primary protected (PP), moderately protected (MP) and highly degraded (HD). Soil and litter samples
were recovered in spring and summer. Soil organic carbon (SOC) and CO2–C values decreased from the PP (9.23 kg m−2 and 157 g m−2) to the HD (1.69 kg m−2 and 57 g m−2) sites whereas the C mineralization rate increased toward the less restored sites (1.06–2.37). Surface-litter C was different
in both sites under protection (PP 648 and MP 408 g m−2), an was low at the HD site (17 g m−2). Leaves from woody species dominated the surface litter at the PP site, whereas grass material was predominant at the MP
site. During summer, both CO2–C and SOC decreased, whereas the C mineralization rate increased. We calculated that C loss since the introduction of cattle
into the forest was 77 M g ha−1, reaching a total of 1.1×1015 g for eastern Inner Mongolia. These values are higher than those caused by the conversion of steppe and other ecosystems into
agriculture or cultivated pastures. The amount of C fixed at the PP site (650 g ha−1year−1) indicates that the sandy soils have a significant potential as atmospheric carbon sinks.
Foundation item: The National Natural Science Foundation of China (No. 39900019, 30070129). 相似文献
15.
The butenolide, 3-methyl-2H-furo[2, 3-c]pyran-2-one, is an highly active compound isolated from plant-derived smoke. This compound is known to stimulate seed germination in a wide range of plants akin to smoke or aqueous extracts of smoke. The present study attempted to elucidate the role of the butenolide in overcoming detrimental effects of low and high temperatures on tomato seed germination and seedling growth. The germination percentage followed a parabolic curve for temperatures ranging from 10 to 40°C, with 25°C being the optimum for all treatments. Control seeds showed radicle emergence at two extreme temperatures (10 and 40°C) and seedlings failed to develop further, even upon prolonged incubation. By comparison the butenolide-treated seeds grew into phenotypically normal seedlings at these non-optimum temperatures. The smoke–water-treated seeds had an intermediate response as only a fraction of germinated seed developed into normal seedlings. Seedling vigour indices as well as seedling weight were significantly higher (p ≤ 0.05) for butenolide-treated seeds at all temperatures. Furthermore, seedlings developed in the presence of the butenolide had about a 1:1 correspondence between root and shoot length. Butenolide-treated seeds grew better than the control seeds in the temperature shift experiments. A gradual decline in the vigour index values was recorded with an increased duration of incubation at the extreme temperatures. Results of the present study are very important from an horticultural point of view as they indicate the potential use of the butenolide compound in restoring normal seed germination and seedling establishment in tomato below and above optimum temperatures. 相似文献
16.
Zilouei H Soares A Murto M Guieysse B Mattiasson B 《Applied microbiology and biotechnology》2006,72(3):591-599
Two reactors, initially operated at 14 and 23±1°C (RA and RB, respectively), were inoculated with a bacterial consortium enriched and acclimatized to the respective temperatures over 4 months. The biofilms, formed in the reactors, were studied using scanning electron microscopy, cultivation of the biofilm microflora, and physiological analysis of the isolates. Two bacteria able to mineralize chlorophenols under a large range of temperature (10–30°C) were isolated from the biofilm communities of reactors RA and RB and characterized as Alcaligenaceae bacterium R14C4 and Cupriavidus basilensis R25C6, respectively. When temperature was decreased by 10°C, the chlorophenols removal capacity was reduced from 51.6 to 22.8 mg l−1 h−1 in bioreactor RA (from 14 to 4°C) and from 59.3 to 34.7 mg l−1 h−1 in bioreactor RB (from 23±1 to 14°C). Fluorescence in situ hybridization (FISH) of the biofilm communities showed that, in all temperatures tested, the β-proteobacteria were the major bacterial community (35–47%) followed by the γ-proteobacteria (12.0–6.5%). When the temperature was decreased by 10°C, the proportions of γ-proteobacteria and Pseudomonas species increased significantly in both microbial communities. 相似文献
17.
Yun Hee Kang Jong Ahm Shin Myung Sook Kim Ik Kyo Chung 《Journal of applied phycology》2008,20(2):183-190
In integrated multi-trophic aquaculture (IMTA), seaweeds have the capacity to reduce the environmental impact of nitrogen-rich
effluents in coastal ecosystems. To establish such bioremediation systems, selection of suitable seaweed species is important.
The distribution and productivity of seaweeds vary seasonally based on water temperature and photoperiod. In Korea, candidate
genera such as Pophyra, Laminaria, and Undaria grow from autumn to spring. In contrast, Codium grows well at relatively high water temperatures in summer. Thus, aquaculture systems potentially could capitalize on Codium’s capacity for rapid growth in the warm temperatures of late summer and early fall. In this study, we investigated ammonium
uptake and removal efficiency by Codium fragile. In laboratory experiments, we grew C. fragile under various water temperatures (10, 15, 20, and 25°C), irradiances (dark, 10, and 100 μmol photons m−2 s−1), and initial ammonium concentrations (150 and 300 μM); in all cases, C. fragile exhausted the ammonium supply for 6 h. At 150 μM of , ammonium removal efficiency was greatest (99.5 ± 2.6%) when C. fragile was incubated at 20°C under 100 μmol photons m−2 s−1. At 300 μM of , removal efficiency was greatest (86.3 ± 2.1%) at 25°C under 100 μmol photons m−2 s−1. Ammonium removal efficiency was significantly greater at 20 and 25°C under irradiance of 100 μmol photons m−2 s−1 than under other conditions tested. 相似文献
18.
Amy E. Miller Joshua P. Schimel James O. Sickman Thomas Meixner Allen P. Doyle John M. Melack 《Biogeochemistry》2007,84(3):233-245
Cold-season processes are known to contribute substantially to annual carbon (C) and nitrogen (N) budgets in continental high
elevation and high-latitude soils, but their role in more temperate alpine ecosystems has seldom been characterized. We used
a 4-month lab incubation to describe temperature (−2, 0, 5°C) and moisture [50, 90% water-holding capacity (WHC)] effects
on soil C and N dynamics in two wet and one dry meadow soil from the Sierra Nevada, California. The soils varied in their
capacity to process N at and below 0°C. Only the dry meadow soil mineralized N at −2°C, but the wet meadow soils switched
from net N consumption at −2°C to net N mineralization at temperatures ≥0°C. When the latter soils were incubated at −2°C
at either moisture level (50 or 90% WHC), net NO3
− production decreased even as NH4
+ continued to accumulate. The same pattern occurred in saturated (90% WHC) soils at warmer temperatures (≥0°C), suggesting
that dissimilatory processes could control N cycling in these soils when they are frozen. 相似文献
19.
Cold tolerance and dehydration in Enchytraeidae from Svalbard 总被引:4,自引:1,他引:3
L. Sømme T. Birkemoe 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1997,167(4):264-269
When cooled in contact with moisture, eight species of arctic Enchytraeidae from Svalbard were killed by freezing within
minutes or hours at −3 and −5 °C; an exception was Enchytraeus kincaidi which survived for up to 2 days. When the temperature approached 0 °C the enchytraeids apparently tried to escape from the
moist soil. The supercooling capacity of the enchytraeids was relatively low, with mean supercooling points of −5 to −8 °C.
In contrast, specimens of several species were extracted from soil cores that had been frozen in their intact state at −15 °C
for up to 71 days. Compared to freezing in a moist environment, higher survival rates were obtained during cooling at freezing
temperatures in dry soil. Survival was recorded in species kept at −3 °C for up to 35 days, and in some species kept at −6 °C
for up to 17 days. Slow warming greatly increased survival rates at −6 °C . The results strongly suggest that arctic enchytraeids
avoid freezing by dehydration at subzero temperatures. In agreement with this, weight losses of up to ca. 42% of fresh weight
were recorded in Mesenchytraeus spp. and of up to 55% in Enchytraeus kincaidi at water vapour pressures above ice at −3 to −6 °C. All specimens survived dehydration under these conditions.
Accepted: 12 December 1997 相似文献
20.
M. Raeini-Sarjaz N. N. Barthakur N. P. Arnold 《International journal of biometeorology》1997,40(2):81-85
Leaf movements of bush bean plants were studied at the relatively low photon flux density of 0.2 mmol/m2 per s, and air temperatures of 25° and 35° C in a growth chamber. A beta-ray gauge system was used to monitor continuously
pulvinus water status and bending. Leaf angles were below the horizontal and were linearly related to the soil water content
(R≥−0.91 at 25° C and R≥−0.93 at 35° C). The beta-ray transmission maxima coincided with the stem temperature minima in darkness and vice versa when
brightness prevailed as the growth chamber temperature varied with the photoperiod. Leaf angle increased linearly with increased
beta-ray transmission. The Q10 temperature coefficient, a measure of the metabolic energy requirement for leaf movement between 25° and 35° C was estimated
at 1.8, and the corresponding mean Arrhenius constant at 423 kJ/mol for bush bean.
Received: 19 July 1996 / Accepted: 9 September 1996 相似文献