?kologische untersuchungen an aphiden

Zusammenfassung In Temperaturkabinen wird die Fortpflanzungspotenz von Myzus persicae (Sulzer) (Herkunft Groß-Lüsewitz) bei Dauertemperaturen von 15 bis 30° auf Kohlrüben (Brassica napus subspec. rapifera) untersucht.Eine Populationsanalyse nach Birch (1948) (intrinsic rate of increase) ergab den höchsten Wachstumsfaktor bei Dauertemperaturen zwischen 20 und 23°.Dauertemperaturen >25° führten zu einer starken Minderung der. Fortpflanzungspotenz. 30° ist die obere Grenze der Fortpflanzung der untersuchten Myzus persicae-Population.

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The reproductive potential of the peach-potato aphid (origin Gross-Lüsewitz) was studied at temperatures between 15° and 30° in constant temperature chambers. They were cultivated on Swede (Brassica napus spp. rapifera) which stood in Knop's nutrient under gauze cloches in petri dishes. The production of juvenile larvae and the mortality of the mothers was measured daily. The total of all larvae (including those which were dropped) and the total of larvae on the leaf were separately enumerated. The larvae on the leaf were designated as viable larvae. A population analysis using Birch's method showed a maximum value for the growth factor k (difference between birth and mortality rates) of 23° for the total of all larvae, and of 20° for the viable larvae (Fig. 6). The daily relative growth-ratio was at the same temperatures respectively 1.36 and 1.34 (Table IV). Optimum development of M. persicae on swedes occurs thus between 20° and 23°. The percentages of viable larvae which add to the net production of total larvae are 53, 61, 30, and 24 (Table III) at temperatures of 15, 20, 25, and 30° respectively. The average length of a generation was 18.5 days at 15° and less than 13 days at 28 to 30° (Fig. 5). The multiplication rate per generation was 38 at 15°, 48 at 20°, but only 5.5 at 30° (Fig. 4). The time of development from first-stage larva to adult was 12.5 days at 15°, 5 days at 28° and 6 days at 30° (Table VII). The upper limit, where a weak multiplication was still possible, was at 30°. It is concluded that in regions where such limiting temperatures occur during some part of the day, the temperature can be the major regulating factor of the insect populations.

     

Effect of low winter temperatures on milk production of dairy cows grazed on farms in a warm temperate climate (Australia)

Two-day milk production figures for dairymen at Armidale (31° S Lat.) and Goulburn (35° S Lat.), Australia, were compared with minimum daily temperatures. Comparisons were made between production levels on days with temperatures above and below 0°C, and between days with varying intensities of cold: differences in production were minor. The infrequent, more prolonged periods of cold weather (cold being days on which the minimum temperature was below 0°C) were also associated with only very slight reductions in milk output; and the most pronounced decline in production was not attributable to low temperatures. Although short-term fluctuations in output were not related to low temperature events or low temperatures in combination with rain, thermal stress on plant growth during winter contributed to a seasonal downturn in production and below-average annual milk yields in areas with low winter temperatures.     

Improvement of Kefir yeast by mutation with N-methyl-N- nitrosoguanidine

A commercial culture of Kefir grew well at 30°C and 37°C with NaCl up to 4% (w/v) but at 42°C and 4% (w/v) NaCl it grew very slowly. These conditions were selected for the mutation with N-methyl-N-nitrosoguanidine in order to improve cell yield at high temperatures and salt concentration. The mutated cells had higher biomass and growth rate compared with the original culture. The improvement of Kefir at high temperatures and salt concentrations offers advantages for uses in single cell protein production and alcohol production from whey containing high salt.     

Effects of high ambient temperatures on the metabolism of West African dwarf goats. I

Thirty-two West African dwarf goats were exposed to temperature treatments: 20, 25, 30, 35, 35, 35, 30, 25, 20°C each lasting three days.Sixteen goats were kept in individual pens (I), the others in two group pens (G). Heat production (HP) and activity were recorded during 48 hours in each temperature treatment.Mean HP and ME intake were similar for G and I animals, but I animals had lower values than G animals at low chamber temperatures and higher values than G animals at high temperatures. Upper critical temperature was between 25°C and 30°C under an increasing T and between 30 and 35°C under a decreasing T. Adaptation of heat production and ME intake to a change in temperature of 5°C required at least six and possibly more than nine days.Diurnal variation in HP was large, up to 44% between extremes. This was largely due to variation in activity.     

Production of β-mannosidase and β-mannanase by an alkalophilic Bacillus sp.

Summary An alkalophilic bacterium producing high amounts of the cell-associated -mannosidase and extracellular -mannanase was isolated from soil. The isolate (AM-001) that grew well in alkaline pH media was identified as a strain of Bacillus sp. The optimal cultivation temperature for enzyme production was 31° C for -mannosidase and 37° C for -mannanase with the optimum production medium composed of 1% konjac powder, 0.2% yeast extract, 2% Polypepton, 0.1% K₂HPO₄, 0.02% MgSO₄ · 7H₂O and 0.5% Na₂CO₃. Optimum pH and temperature for -mannosidase were 7.0 and 55° C, and for -mannanase were 9.0 and 65° C.     

Effects of high ambient temperatures on the metabolism of West African dwarf goats. II

32 West African dwarf goats were exposed in respiration chambers to temperature treatments of 20, 25, 30, 35, 35, 35, 30, 25, 20°C. Each treatment lasted three days. 16 goats were kept in individual pens (I); the others in two group pens of eight animals each (G). During each treatment, heat production and activity were recorded continuously over 48 hours. In addition, feed and water intake, rectal temperature, skin temperature and respiratory rate were measured during each treatment.Compared to 20°C, at 35°C rectal temperature increased from 39.0°C to 39.9°C, respiratory rate from 30 to 260 times. min^–1 and skin temperature from 37.1°C to 39.5°C. Hay intake decreased by 40%; concentrates (30 g. kg^–0.75. d^–1) were always completely consumed. Heat production was higher for the G animals at 20°C and higher for the I animals at 35°C. These differences in heat production between the two groups were reflected in differences in rectal and skin temperature and in respiratory rate but only very slightly in differences in hay intake.Tissue insulation was 0.014 K. m². W^–1 at 30°C and 35°C and 0.022 K. m². W^–1 at 20°C.It is concluded that the reactions of these dwarf goats to high ambient temperatures are not different in principle from those of other domestic ruminants and that they do not exhibit a specific suitability or unsuitability for ambient temperatures as prevailing in West Africa.     

Influence of temperature on bionomics of cotton aphid, Aphis gossypii, on cotton

Life table parameters of Aphis gossypii Glover (Homoptera: Aphididae) on Gossypium hirsutum L. were determined at six temperatures (10, 15, 20, 25, 30, and 35 ± 0.5°C) in the laboratory. Relationships of life table parameters with temperature were described with mathematical equations. Development was fastest at 30°C, with a pre-larviposition period of 4.6 d. Survival to adult was greatest at 25°C (81%). Fecundity was highest at 25°C, with a total fecundity of 28.3 nymphs per female and a mean reproductive rate of 3.1 nymphs per female per day. Threshold temperatures for development in the first through fourth instar and the adult were 8.2, 8.0, 7.2, 6.2 and 7.9°C, respectively. The durations of these stages, expressed as temperature sums above these thresholds, were 24.2, 23.7, 23.0, 25.5 and 168.8 degree-days (D°), respectively. A. gossypii achieved its maximum net reproductive number (24.4 nymphs per female) and greatest intrinsic rate of increase (0.386 d–1) at 25°C. The high relative rate of population increase at 25°C results in a daily population increase of 47% and a doubling time of only 1.8 d, illustrating the tremendous growth capacity of A. gossypii populations under favourable conditions. Compared to literature sources, our source of A. gossypii, fed on cotton, showed a comparatively great heat tolerance.     

Distribution of benthic algae and macroinvertebrates along a thermal stream gradient

The distribution and abundance of benthic algae and macroinvertebrates were examined along a natural thermal gradient formed by hot springs in Little Geysers Creek, Sonoma Co., California, USA. Maximum water temperatures ranged from 52 °C at the uppermost station to 23 °C at a station 400 m downstream. Benthic chlorophyll a decreased exponentially from 2.5 g m^–2 at 52 °C to less than 0.1 g m^–2 at 23 °C, a pattern of decline also exhibited by algal phaeophytin. Blue-green algae dominated at higher temperatures but were replaced by filamentous green algae and diatoms at lower temperatures.Macroinvertebrates were absent at temperatures 45 °C; the highest density (> 150 000 m^–2, mainly Chironomidae) occurred at 34 °C, whereas biomass was highest (4.6 g m^–2, as dry weight) at 23 °C and species richness (15 species) was highest at 27 °C. The two predominant macroinvertebrate populations (the midge Tanytarsus sp. and the caddisfly Helicopsyche borealis) occurred at sites that were several degrees below their lethal thermal threshold, suggesting that a temperature buffer is maintained.     

Optimization of cryopreservation of Artemisia annua L. callus

Cryopreservation of callus tissue of Artimisia annua L. was optimized. Two lines of calli were precultured on MS medium with 5% (v/v) dimethyl sulfoxide, and protected by a cryoprotectant containing 15% (v/v) ethylene glycol, 15% (v/v) dimethyl sulfoxide, 30% (v/v) glycerol and 13.6% (w/v) sucrose. The highest survival rate of callus A201 reached 87% after it was pretreated at 25°C, cryopreserved by liquid nitrogen, recovered in water bath at 25°C and reloaded at 25°C with 34% (w/v) sucrose solution, and that of callus A202 reached 78% after it was treated as callus A201, except pretreated at 35°C, recovered at 35°C and reloaded with 47.8% (w/v) sucrose solution.     

Characterization of a new Bacillus stearothermophilus isolate: a highly thermostable α-amylase-producing strain

A novel strain of Bacillus stearothermophilus was isolated from samples of a potato-processing industry. Compared to known -amylases from other B. stearothermophilus strains, the isolate was found to produce a highly thermostable -amylase. The half-time of inactivation of this -amylase was 5.1 h at 80°C and 2.4 h at 90°C. The temperature optimum for activity of the -amylase was 70°C; the pH optimum for activity was relatively low, in the range 5.5–6.0. -Amylase synthesis was regulated by induction and repression mechanisms. An inverse relationship was found between growth rate and -amylase production. Low starch concentrations and low growth temperatures were favourable for enzyme production by the organism. At the optimal temperature for growth, 65°C, the -amylase was a growth-associated enzyme. The optimal temperature for -amylase production, however, was 40°C, with -amylase increasing from 3.9 units (U)/ml to 143 U/ml when lowering the growth temperature from 65°C to 40°C. Maximal -amylase production in a batch fermentor run at 65°C was 102 U/ml, which was 26-fold higher than in erlenmeyer flasks at 65°C. The dissolved O₂ concentration was found to be a critical factor in production of the -amylase.     

Stability of xylanases in the presence of methanol and its evaluation on the bleaching capacity

A commercial (Cartazyme) and non-commercial (Asperzyme) xylanases were studied. Cartazyme stability in a 0–70% (v/v) methanol at 50°C and 65°C was carried out. No deactivation was found for Cartazyme in the presence of 15% methanol at 50°C. Half-life activity decay (t1/2) of Cartazyme at 50°C in 30%, 50% and 70% methanol solutions were 4.0 h, 2.3 h and 1.2 h, respectively. At 65°C, which is the ozone-alkali-peroxide (ZEP) bleaching temperature, only significant results on Kappa number reduction and selectivity were only observed in 15% methanol (t1/2 30 min) at the Z stage. For the Asperzyme, a t1/2 of 36.5 min at 50°C was found. In the Z stage with Asperzyme in the presence of 25% of methanol, a 20% Kappa number reduction and an improvement of the ZEP sequence of the brightness of 3.1 points were obtained. These results were correlated with the xylanase stability.     

Development, survival and reproduction of Euseius finlandicus (Acari: Phytoseiidae) at different constant temperatures

Development, survival and reproduction of Euseius finlandicus Oudemans were studied at seven constant temperatures (15, 20, 25, 27, 30, 32 and 34°C) in the laboratory. Within the temperature range tested, developmental period from egg to adult varied from 148 to 360.5h and 133.7 to 336.5h for females and males, respectively. The lower thermal threshold for immature development for females and males was 8.9 and 6.4°C, respectively. Survival during immature development exceeded 90% at all the temperatures from 15 to 32°C, but at 34°C an abrupt decline was recorded. Female longevity decreased gradually from 82.7d at 15°C to 12.2 d at 34°C. The mean generation time ranged from 44.3d at 15°C to 15.9d at 32°C. The highest r _m value (0.2817) was obtained at 30°C and the lowest at 15°C (0.0976). Temperatures above 30°C had an adverse effect on population increase.     

Photoperiodism and thermoperiodism in the predatory mite Amblyseius potentillae are probably based on the same mechanism

Summary A comparative study was made of the photoperiodic and thermoperiodic induction of diapause in the phytoseiid mite Amblyseius potentillae. Sensitivity to thermoperiod was found to be highest during the protonymphal and deutonymphal stages, with some sensitivity still being present in the young adult. Summation of both photoperiodic and thermoperiodic cycles was shown to take place, which demonstrated the presence of a photoperiodic counter as well as a thermoperiodic counter in these mites. Vitamin A appeared to be necessary for some early step in the physiological mechanism of diapause induction and not just for the expression of the diapause response. The light sensitivity threshold for photoperiodic induction of diapause was found to be extremely low, viz. less than 0.02 W/cm². Moreover, the light sensitivity threshold appeared to be strongly temperature dependent in A. potentillae. Experiments in which the mites experienced various sequences of short-day photoperiods and short-day thermoperiods, applied either concurrently or in succession, showed that the information collected by the photoperiodic counter and the thermoperiodic counter is integrated into one induction sum. These results strongly suggest that photoperiodic and thermoperiodic induction of diapause in these mites is based on the same physiological mechanism.Abbreviations DD continuous darkness - LL continuous light - LD light-dark cycle (e.g. LD 16:8 is a cycle of 16 h of light and 8 h of darkness) - TC thermoperiodic cycle (e.g. TC 16:8 (27°: 15°) is a thermoperiod with a 16 h thermophase of 27 °C and an 18 h cryophase of 15°C)     

The temperature-dependent duration of development and parasitism of three cereal aphid parasitoids, Aphidius ervi, A. rhopalosiphi, and Praon volucre

Temperature dependencies were established for the egg-to-mummy and mummy-to-adult phases, for mummy mortality, and for parasitism of Aphidius ervi Haliday, Aphidius rhopalosiphi De Stefani-Perez, and Praon volucre (Haliday) (Hymenoptera, Aphidiidae), three parasitoids of Sitobion avenae (Fabricius) (Homoptera, Aphididae), at 8°C, 12°C, 16°C, 20°C, and 25°C on winter wheat (cv. Haven). A physiological model described temperature-dependent development over the full temperature range, whereas a linear model was fitted for data above 8°C and used to estimate the lower temperature thresholds and day-degrees (° D) required for development. The thresholds for A. ervi were 2.2°C for egg-mummy development and 6.6°C for mummy-adult development, those for A. rhopalosiphi were 4.5°C and 7.2°C, and those for P. volucre were 3.8°C and 5.5°C. The time to develop into mummies and adults differed significantly between the three species: A. ervi development into mummies required an average of 159 ° D, while development into adults took an average of 73 ° D. The corresponding average times required for A. rhopalosiphi and P. volucre to develop mummies were 124° D and 126° D, while their development into adults required an average of 70° D and 150° D, respectively. Mummy mortality was 25–35% at 8°C and less at the higher temperatures tested, but began to increase again at 25°C, showing a quadratic relationship between mortality and temperature. Parasitization was very low or, in the case of P. volucre, absent up to 12°C and thereafter increased with increasing temperature. The relationship between parasitization, recorded as percent aphids mummified, and temperature was linear at the temperatures tested and depended on species. A. ervisuperparasitized 11.1% aphids at 20°C and 16.6% aphids at 25°C, whereas superparasitism was low in A. rhopalosiphi and absent in P. volucre. From 16°C to 25°C the P. volucre sex ratio increased. For A. ervi and A. rhopalosiphi there was no trend with temperature, but at 20°C and 25°C it was close to even. Field data for 1996 and 1997 allowed for a comparison of actual and expected emergence of overwintering mummies. In both years, parasitoids were predicted to have emerged from overwintering mummies well in advance of the onset of aphid infestation, and more than a month earlier than the first parasitized aphids were found in winter wheat. Observations from trap plants in other crops supported the predictions of the models. Other factors that can affect biological control by cereal aphid parasitoids are discussed.     

Oxygen isotope fractionation during respiration for different temperatures ofT. utilis andE. coli K12

Summary The temperature dependence of the oxygen isotope fractionation factor during respiration has been examined for two different microorganisms, namelyTorulopsis utilis andEscherichia coli K12 representing a yeast and a bacterium, respectively. The investigation covered a temperature range of 18° C, that is from 16° C to 34° C forT. utilis and from 19° C to 37° C forE. coli K12. Within this temperature range the fractionation factor ofT. utilis increases by 0.18; an insignificant change ( _{10° C} = 0.063;r = 0.067), whereas withE. coli K 12 an increase of 1.12; has been observed ( _{10° C} = 0.6;r = 0.55).     

Response of Hawaiian and other Indo-Pacific reef corals to elevated temperature

Loss of symbiotic zooxanthellae, or bleaching is one of the first visible signs of thermal stress. Critical threshold temperatures for coral bleaching vary geographically, but can be expressed universally as fixed increments relative to the historical mean local summer maximum. Bleaching can be induced by short-term exposure (i.e. 1–2 days) at temperature elevations of 3°C to 4°C above normal summer ambient or by long-term exposure (i.e. several weeks) at elevations of 1°C to 2°C. Corals in both tropical and subtropical locations live at temperatures close to their lethal limits during the summer months. Temperature elevations above summer ambient, but still below the bleaching threshold, can impair growth and reproduction. Temperature and light interact synergistically; high light accelerates bleaching caused by elevated temperature. Bleaching susceptibility is correlated with respiration rate. Any factor that increases respiration (such as high incident light) accelerates bleaching at higher temperatures. Ultraviolet (UV) radiation is a detrimental factor associated with solar radiation. Increased UV due to thinning of the earth's protective ozone layer may aggravate bleaching and mortality caused by global warming. A warming trend in Hawaiian waters has been observed over the past decade. In 1986, 1987 and 1988 Hawaiian corals were perilously close to their bleaching threshold during the summer months, and localized bleachings did occur. In some cases, local warming of surface water on shallow reef flats exceeded this threshold temperature and caused localized coral bleaching. In other cases, heating of large mesoscale eddies in the lee of the larger islands apparently caused wide-scale bleaching of the most sensitive coral species (Pocillopora meandrina) to depths of 20 m. A continuation of the warming trend in Hawaii would lead to mass bleachings similar to those observed recently in other geographic locations.     

Stability of fungal α-amylase in sodium dodecylsulfate

Unfolding of a fungal -amylase in aqueous sodium dodecylsulfate (SDS) solution was examined by SDS-polyacrylamide gel electrophoresis (PAGE). When the -amylase was incubated with 1% SDS at room temperature and subjected to SDS-PAGE, it showed a much higher mobility than expected from the molecular weight. Circular dichroic and gel filtration analyses indicated that the protein is apparently in the native conformation upon incubation with 1% SDS. When the protein was heated in the presence of 1% SDS at 90°C for 10 min, it had a lower mobility in SDS-PAGE and showed characteristics of an unfolded protein by circular dichroism and gel filtration. The melting temperatures of the protein were determined in the absence and presence of SDS by incubating it for 10 min at various temperatures. The melting temperatures were 70, 55, and 49°C in the presence of 0, 1, and 2% SDS, respectively. The observed small shift of the melting temperatures by SDS suggests that the destabilizing action of SDS on the -amylase is weak. However, the unfolding in SDS is not reversible process, since prolonged incubation of the protein with 1% SDS at 50°C gradually increased the amount of unfolded protein. This indicates that the SDS-induced unfolding of the -amylase is a slow process.     

Temperature induced variation in the distribution of different types of muscle fibre in the goldfish (Carassius auratus)

Summary Goldfish (Carassius auratus L.) were acclimated to environmental temperatures of 3 °C, 18 °C and 31 °C for a period of three months. Cytochemical techniques were used to study the metabolism and myofibrillar ATPase activities of individual muscle fibres. Fish muscle is composed of three basic fibre types each with distinct contractile and metabolic characteristics. Cold acclimation resulted in a shift to a more aerobic type of metabolism, particularly in the red and pink fibres. In addition, environmental temperature was found to affect the size and relative distribution of the different fibre types in the myotome. The total number of pink and red fibres increased significantly with cold acclimation. Mechanisms of environmentally-induced adaptation of muscle fibre phenotype are discussed.In addition to changes in the metabolism and distribution of muscle-fibre types, biochemical studies have provided evidence for different kinetic forms of Mg²⁺Ca²⁺ myofibrillar ATPase at different environmental temperatures. Activities of myofibrillar ATPase assayed at 31 °C were 2–3 times higher in fish acclimated to the higher environmental temperature. Activation enthalpy (H ) of the ATPase was also signficantly reduced in the cold adapted enzyme. Reduction of H in the cold acclimated ATPase is thought to reduce the temperature sensitivity of the activation process thus partly compensating for the reduced cell temperature.     

The control by atmospheric factors and water stress of midday stomatal closure in Arbutus unedo growing in a natural macchia

Summary Midday closure of stomata of well-watered ( between-10 and-25 bar) or moderately stressed ( between-25 and-35 bar) Arbutus unedo plants occurs when midday leaf temperatures increase above 30°C and vapor pressure difference between leaf air spaces and the external air increases above approximately 30 mbar/bar. Moderate water stress decreases maximum conductance and may result in greater sensitivity to high leaf temperature and vapor pressure dificit, which results in earlier closure and later reopening of stomata. Severe water stress ( of-50 bar) changes the form of the daily pattern observed for leaf conductance. A single morning peak in conductance occurs followed by decrease in conductance over the remainder of the day. Morning fog in Portugal during the dry season may facilitate stomatal opening and may allow improvement of carbon balances of the leaves for short periods, but contributes little to improvement of plant water balances over the longer term.