Influence of the sporulation temperature upon the heat resistance of Bacillus subtilis

The influence of different sporulation temperatures (30, 37, 44 and 52°C) upon heat resistance of Bacillus subtilis was investigated.
Heat resistance was greater after higher sporulation temperatures. Relation of heat resistance and temperature of sporulation was not linear over all the range of temperatures tested. Heat resistance increased about tenfold in the range of 30–44°C. Sporulation at 52°C did not show any further increase in heat resistance.
This effect was constant over all the range of heating temperatures tested (100–120°C). z value remained constant ( z = 9°C).
Greater heat resistances at higher temperatures of sporulation were not due to selection of more heat resistant cells by a higher sporulation temperature. Spores obtained from cells incubated at 32 or 52°C always possessed heat resistances that corresponded to the sporulation temperature regardless of the incubation temperature of their vegetative cells.     

Regulation of the loss of frost hardiness in Pinus radiata by photoperiod and temperature

Abstract. In controlled environments, the interactive effects of warm (16: 8°C, day: night) and cool (12: 4°C, day: night) temperatures and long (13.5 h) and short (10 h) photoperiods on the dehardening of seedlings of Pinus radiata D. Don were investigated. In another experiment, the effect of four photoperiods from 9 to 14 h was examined. In a third, dehardening at constant temperatures from 5 to 17°C was followed. There was no evidence for an interaction between photoperiod and temperature. Dehardening was temporarily delayed by photoperiods below about 10 h, but there was no other quantitative effect of photoperiod. At constant temperatures, the rate of dehardening was initially constant but declined as the minimum summer frost hardiness was reached. In the initial phase the rate of dehardening was a linear function of temperature, increasing from 0.05°C day⁻¹ at 8°C to 0.30 °C day⁻¹ at 17°C. Temperature controlled the loss of frost hardiness by regulating the rate of dehardening.     

Biochemical and stress responses of rohu Labeo rohita and mrigal Cirrhinus mrigala in relation to acclimation temperatures

The biochemical and stress responses of two Indian major carps, rohu Labeo rohita and mrigal Cirrhinus mrigala were studied after acclimating them to four preset temperatures (26, 31, 33 and 36° C) for 30 days. The blood glucose and liver glycogen levels showed an inverse trend in both the species and were significantly different in L. rohita at higher temperatures. The decrease in the liver glycogen level of C. mrigala , however, was not significant. Plasma cortisol levels increased significantly whereas the ascorbic acid content in the brain and kidney of both the species decreased significantly with increasing temperatures. Total lipid content in the liver of both the species decreased significantly with increasing acclimation temperatures. The phospholipid concentration decreased in L. rohita with increasing acclimation temperatures, and in C. mrigala the values decreased up to 33° C and increased at 36° C. In C. mrigala , the cholesterol level decreased up to 33° C and then increased at 36° C, but the absolute value was lower in comparison to L. rohita . The cholesterol levels, however, were not significantly different in L. rohita . Triglycerides and free fatty acids concentrations decreased significantly with increasing acclimation temperatures in both the species. The present study indicates species-specific metabolic responses of L. rohita and C. mrigala to thermal acclimation.     

Significance of temperature and preincubation temperature on survival of Listeriamonocytogenes at pH 4·8

Listeria monocytogenes is a food-borne pathogenic bacterium that can be found in softcheese. At the beginning of cheese ripening, the pH is about 4·85–4·90. The aimof this work was to study the influence of temperature, preincubation temperature (temperature atwhich the inoculum was cultivated) and initial bacterial concentration on the survival of L.monocytogenes (strain Scott A) at pH 4·8. It was demonstrated in an earlier study thatthese factors did influence growth kinetics. Survival studies of L. monocytogenes weredone in a laboratory broth simulating cheese composition. Four test temperatures (2, 6, 10 and14°C) and two preincubation temperatures were studied (30°C or the test temperature). Listeria monocytogenes (strain Scott A) was unable to grow at pH 4·8 under allconditions tested. The time for 10% survival was about 11 and 2 d, at 2°C with preincubationat 2°C and 30°C, respectively; 9 d at 6°C with preincubation at 6°C; 4 d at 6°Cwith preincubation at 30°C; and 1 d at 14°C with preincubation at 14°C or at 30°C.The results show that survival of L. monocytogenes (strain Scott A) at pH 4·8 is notdependent on initial bacterial concentration but on both the test and preincubation temperatures.     

Influence of photoperiod and temperature on testicular recrudescence and body growth in the lizards, Lacerta sicula and Lacerta muralis

Annual testicular cycles in the lizards Lacerta sicula and L. muralis appear to be regulated by the interaction between seasonal changes in body temperature and an endogenous rhythmicity in thermal responsiveness. Photoperiodism does not appear to be an important factor; i.e. testicular activity does not appear to be regulated by daylength.
Following testicular regression in July, the lizards are refractory to sexual stimulation by high temperatures (i.e. normal preferred levels) for about five months. High temperatures accelerate gonadal regression and prevent recrudescence during late summer. Reduced temperatures stimulate testicular enlargement and spermatid formation during the autumn; this recrudescence can be blocked by treatment with testosterone. Very low temperatures suppress gonadal activity during mid-winter.
Maintenance of lizards at constant high temperatures (33°C) starting in July suppresses testicular recrudescence until December. Also, testicular collapse occurs in lizards transferred to high temperatures after recrudescence has started. The gonads are stimulated by exogenous gonadotropins at 33°C during the fall indicating that high temperatures reduce circulating levels of gonadotropins.
The refractoriness to high temperatures is "spontaneously" terminated during midwinter (December) under a wide range of photo-thermal conditions. Low temperatures may accelerate the termination of refractoriness. Thereafter, high temperatures stimulate, and are required for the final development of the testes and accessory sexual structures. Thus, the increase in body temperature following hibernation times the onset of breeding in the spring.
Temperature also has a marked influence on appetite and growth, independent of photo-period. Weight gains are greater at 33° than at 20°C. At 33° there is a tendency for abdominal fat bodies to enlarge but with little hepatic growth; whereas, the reverse occurs at 20°C.     

Environmental control of flowering and morphology in the high-arctic Cerastium regelii, and the taxonomic status of C. jenisejense

Cerastium regelii has a distribution confined largely to regions north of 70° N but has retained a strong short-day (SD) response for primary flower induction despite the fact that it will hardly ever experience SD in a non-frozen condition in its natural environment. However, like many other high-latitude short-long-day plants it has also an alterntive long day (LD) pathway for floral initiation at low temperatures (<15°C). Floral primordia which are fully differentiated during SD have an absolute requirement for LD for flower development. The critical photoperiod for this LD response is about 16 h at 18°C and more than 20 h at 9°C. Plant morphology, including key characters for identification of the species, is greatly modified by environment and stage of plant development. At higher temperatures and LD C. regelii develops a striking resemblance to the sub-arctic C. jenisejense . Based on examination of authentic herbarium material it is concluded that the latter is merely a high-temperature morphotype of C. regelii .     

Some observations on the adenine nucleotide levels of rat tissues stored at low temperature

Evidence is presented which indicates that there is a significant breakdown of the adenine nucleotides of animal tissues which have been stored at low temperatures (−18 °C.) for periods of time ranging between 1 and 4 weeks. Rat brain and kidney appear to be most active in bringing about this effect, whereas liver and muscle are somewhat less active.     

Prolonged and daily torpor in the feathertail glider, Acrobates pygmaeus (Marsupialia: Acrobatidae)

Deep and prolonged torpor in marsupials is only known from the pygmy possums, family Burramyidae. We investigated the pattern of torpor in the feathertail glider Acrobates pygmaeus (Acrobatidae) to determine whether members of other marsupial families also possess the ability of remaining torpid for several days with body temperatures (T_b) approaching 0°C. At high air temperatures (T_a) of 15 and 20°C, A. pygmaeus usually exhibited daily torpor. Torpor bouts at T_a 12°C usually lasted for about 2˙5 days and at T_a 8°C up to 5˙5 days. The metabolic rate during torpor was reduced to about 1% of that in normothermic, resting individuals. The T_b during torpor was regulated at about 2°C when T_a fell below about 0˙8 °C. Arousal from torpor was rapid and the mean fastest rewarming rate was 0˙88°C/min. While A. pygmaeus exhibited deep and prolonged torpor, its pattern differed somewhat from deep hibernation. Acrobates pygmaeus did not show prehibernation fattening and a subsequent prolonged hibernation period and it appears that prolonged torpor is used only in emergency situations.     

Flowering requirements of Scandinavian Festuca pratensis

Flowering requirements of three Scandinavian cultivars of Festuca pratensis Huds, have been studied in controlled environments. At 3 and 6°C, primary induction was independent of photoperiod, while short days (8 h) were more effective than long days (24 h) at higher temperatures. The critical temperature for induction was about 15°C in short days and about 12°C in long days. Saturation of induction required 18–20 weeks of exposure to optimal conditions. At temperatures below 12°C both induction and initiation of inflorescence primordia took place in long days, while a transition to long days was required for inflorescence initiation after primary induction in short days. A minimum of 8 long-day cycles were required for flowering of plants primary induced in short days and saturation of flowering required more than 16 cycles. The critical photoperiod for secondary induction was about 13 h. High temperature (21°C) had some devernalization effect in primary induced plants, suppressing flowering compared with 15°C.     

Temperature control of germination and its possible role in the survival of a non-dormant population of Avena fatua

Germination of freshly harvested seeds of a non-dormant (ND) line (Stonehouse 319) of wild oats ( Avena fatua L.) was inhibited by incubation of the seeds at relatively high temperatures of 25 and 30°C. The germination inhibition in these seeds appeared to be a case of thermo-inhibition which was the direct effect of hightemperature treatment (HIT), since it did not persist after transferring the seeds to an optimum germination temperature of 20°C. Even a prolonged HTT of 30°C for over 5 weeks did not prevent germination of about 80% of the seeds transferred to 20°C. However, in a significant proportion of the seeds, thermo-dormancy was induced by 10 days of HTT at 30°C if the seeds were then incubated at sub-optimal temperatures of 5 to 15°C. This thermo-dormancy would appear to be 'restrictive' in form, since its expression was restricted to very specific conditions. Relatively low inclubation temperaturs of 5 and 10°C markedly slowed germination whether HTT was applied or not. The results suggest that thermo-inhibition and thermo-dormancy, induced during seasonal temperature fluctuations, may provide a survival mechanism for seeds of such ND lines as Stonehouse 319.     

THE EFFECTS OF TEMPERATURE AND HUMIDITY ON THE RATE OF DEVELOPMENT AND THE MORTALITY OF TRIBOLIUM CONFUSUM DUVAL (COLEOPTERA, TENEBRIONIDAE)

The speed of development and the developmental mortality of Tribolium confusum were studied over a series of constant temperatures between 15° and 40° C. at 10, 30, 70 and 90% R.H. using wheatfeed as food.
Eggs did not hatch at 15° or 40° C. at any humidity. At 37.5° C. about 60% of eggs hatched and at all other conditions about 90% hatched. The effect of temperature on the duration of the egg period is shown graphically, the shortest period being at 35° C. Humidity does not affect the egg period.
Larvae failed to develop to pupae at 17.5° C., at 10% R.H. at 20° C, and at 10 and 90% R.H. at 37.5° C. The rate of larval development was affected by both temperature and humidity being quickest at the higher humidities and at about 32.5° C. Larval mortality was less than 16% except at 37.5° C., at 10% R.H. or less, and at 20°C., 90% R.H.
The duration of the pupal period was not affected by humidity and was shortest at 37.5°C. The total developmental period is compared with that of T. castaneum over the range of temperature and humidity conditions in which both species can grow. The optimum for developmental speed and the maximum and the minimum temperatures at which development is possible were all about 2.5°C. lower for T. confusum than for T. castaneum. The developmental periods for the two species were equal at temperatures between 23 and 27°C., depending on humidity. At lower temperatures, T. confusum developed the more quickly and at higher temperatures the more slowly.     

A comparison of the effects of temperature on melanophore in vitro responses to noradrenalin in two teleost species adapted to cold ocean and tropical conditions

Melanosome-aggregating responses to noradrenalin in winter flounder, Pseudopleuronectes americanm Walbaum, manifest different in vitro temperature characteristics compared with such activity in sailfln molly, Poecilia velifera Regan. Winter flounder off St John's are adapted to cold ocean temperatures between − 1° C and + 15° C associated with the Labrador current, whilst sailfin molly is a tropical species adapted to temperatures up to about 30° C. The experimental data indicate that melanophores from these two species are physiologically adapted to function in contrasting thermal environments. Consequently, the optimum temperature for melanosome aggregation in winter flounder is approximately 20° C, and that of the tropical species approximately 40° C. Also, flounder melanophore In vitro responses are relatively uninfluenced by low temperatures, which drastically inhibit sailfin molly melanophore activity.     

Effect of Temperature on the Formation of Microsclerotia of Verticillium dahliae

Microsclerotium formation by six isolates of Verticillium dahliae was studied at different temperatures both in vitro and in Arabidopsis thaliana . In vitro mycelial growth was optimal at 25°C, but microsclerotium formation was greatest at 20°C (two isolates) or 15–20°C (one isolate). Seedlings of A. thaliana were root-dipped in a conidial suspension, planted, and either placed at 5, 10, 15, or 25°C, or left at 20°C until the onset of senescence, after which some of the plants were placed at 5, 10, 15, or 25°C. The amount of microsclerotia per unit of shoot weight was assessed in relation to isolate and temperature. The optimal temperature for production of microsclerotia was 15–25°C. Two isolates each produced about 10 times more microsclerotia than each of the other four isolates. For these isolates, high R ²_adj.-values of 0.77 and 0.66 were obtained, with temperature and its square as highly significant (P   < 0.001) independent variables. R ²_adj.-values for the other isolates varied between 0.28 and 0.39. Moving plants to different temperatures at the onset of senescence led to microsclerotial densities that were intermediate between densities on plants that had grown at constantly 20°C and plants grown at other temperatures. This suggests that vascular colonization rate and rate of microsclerotium formation are similarly affected by temperature. The senescence rate of plants appeared unimportant except for plants grown at 25°C, which showed the highest amounts of microsclerotia per unit of plant weight in the most rapidly senescing plants.     

Interannual variation in the reproductive cycle of the New Zealand snapper Pagrus auratus (Bloch & Schneider) (Sparidae)

Changes in reproductive condition in the New Zealand snapper Pagrus auratus (Bloch & Schneider) were monitored in a wild population over three successive years. Recrudescence occurred in spring with spawning beginning in October and continuing for 3 to 5 months. The initiation of spawning varied by up to 3 weeks and was associated with sea surface temperatures of 15–16° C. Theconclusion of spawning was associated with temperatures of 19–21° C but showed greater interannual variation than the onset of spawning. Changes in the gonadosomatic index were accompanied by parallel changes in hepatosomatic index in females but not males, reflecting the role of the liver in vitellogenesis in females.     

Temperature dependent reduction of protochlorophyllide in darkness followed by the assembly of active photosystems in pigment mutant C-2A' of Scenedesmus obliquus

In the wild type of Scenedesmus obliquus strain D3 grown heterotrophically, the chlorophyll biosynthesis and thus the reduction of protochlorophyllide to chlorophyllide takes place in darkness. However, in pigment mutant C-2A' of Scenedesmus obliquus only traces of protochlorophyllide are reduced under optimal growth conditions in darkness. By lowering the growth temperature from 33° to 15–25°C, protochlorophyllide can be reduced in darkness. At 20°C this process is about 10 times more active than at 33°C, but reaches only about 13% of the light-dependent chlorophyll biosynthesis. The chlorophylls synthesized at the lower temperatures are inserted into the pigment-protein complexes and photosystem I as well as photosys-tem II capacities are developed. The rate of light-independent protochlorophyllide reduction at lower temperatures is not limited by the enzyme PChlide-oxidoreductase itself, but rather by its substrate, being in turn limited by the amount of 5-amino levulinic acid (ALA) available.     

Low temperature acclimation of guard cell chloroplasts by the arctic plant Saxifraga cernua L.

Abstract. The potential for thermal acclimation of photosynthetic electron transport by guard cell chloropiasts (GC ch) was assessed in epidermal peels taken from the abaxial side of Saxifraga cernua leaves grown at 20°C and 10°C. Chlorophyll a fluorescence induction kinetics measured in pairs of guard cells in individual stomata from tissue grown at 10 °C demonstrated a rise in the fluorescence to a maximum and a larger amplitude in variable fluorescence when measured at temperatures below 18°C than was seen in GC ch from tissue grown at 20°C. The rates of fluorescence quenching in 10°C-grown tissue were also faster than in 20°C-grown tissue when measured at temperatures below 18°C. State 1-State 2 transitions by GC ch were measured at selected temperatures between 5 and 25 °C as changes in the magnitude of the fluorescence emission maxima at 685, 695 and 730nm (F685, F695 and F730) measured at 77K. At measuring temperatures of 5 and 10°C, GC ch in tissue grown at 10 °C showed a greater transition to State 2 (a larger F730/F695 ratio) than did GC ch in tissue grown at 20 °C. At measuring temperatures of 20 and 25 °C, there was no difference in either the kinetics or the magnitude of the State 1 to State 2 transition in the two tissues. The ultrastructure of GC ch from tissues grown at 10 and 20 °C was also examined using transmission electron microscopy. Less than half (48%) of the grana from the higher temperature grown tissue had more than nine thylakoids/grana. Grana in GC ch which had developed at 10 °C showed a dramatic reduction in stacking, such that 85% of the grana contained no more than two thylakoids. The reduction in grana stacking was also accompanied by a decrease in the degree of appression of thylakoid membranes. The results demonstrate a capacity for thermal acclimation of GC ch function to low temperatures. This acclimation is associated with alterations in the chloroplast ultrastructure.     

Diapause in a Glasgow strain of the flour moth, Ephestia kuehniella

ABSTRACT. The incidence of diapause in Ephestia kuehniella Zeller from an unhealed granary in Scotland was influenced by both photoperiod and temperature. At 25°C, nearly 50% of larvae entered diapause when reared in continuous darkness (DD) and up to 30% did so in short photoperiods. Little diapause was detected around LD 14:10 but a second, smaller peak of about 20% occurred at LD 16:8 and LD 18:6, falling away again to nearly zero in continuous light. More larvae entered diapause when reared continuously at 15 or 20°C than at 25 and 30°C. However, when larvae reared from hatch at 25°C in LD 16:8 were transferred after 1 week to 15°C in LD 9:15, almost twice as many entered diapause as did those reared at 15°C throughout. The sensitive phase for diapause induction occurred near the start of the final instar. The mean duration of diapause was between 2 and 3 months in most photoperiods at 20 and 25°C, and was shorter at 15°C. However, in DD at 25°C, it lasted about 7 months. Termination of diapause was hastened in larvae reared at 25°C in DD by transferring them to LD 14:10, and also by chilling them at 7.5°C for 6 weeks before returning to 25°C in DD. In an unhealed store in southern England, viable adults emerged from May to July and originated from larvae which terminated diapause relatively late. It would appear from the results of transferring larvae back to the laboratory at various times during the winter that some phases of diapause development were completed quite early after exposure to low temperatures, although no further development took place in the store until temperatures rose again in April.     

Thermal ecology of the mudskippers, Periophthalmus koelreuteri (Pallas) and Boleophthalmus boddarti (Pallas) of Kuwait Bay

The annual range of body temperatures (14–35°C) of emergent mudskippers are substantially less than that of air temperatures (10–42°C) as a result of behavioural thermoregulation. In winter, low surface temperatures are avoided by remaining in burrows. Newly emerged mudskippers then bask until body temperatures rise above 14°C before they move onto the mud. In summer, body temperatures are kept lower than ambient by selecting areas where evaporative cooling is high. Body temperatures generally match those of wet mud, which can be 7°C lower than air shade temperatures. The smaller, more terrestrial, Periophthalmus koelreuteri have body temperatures which are mainly lower in summer and higher in winter than Boleophthalmus boddarti .     

Dual induction control of flowering in Leucanthemum vulgare

The perennial herb Leucanthemum vulgare (oxeye daisy) has a dual induction requirement for flowering. The primary induction is a typical low temperature vemalization response. Temperatures up to 15°C are effective, and the optimum is 6–9°C. Short days (SD) during low temperature exposure enhanced primary induction, but SD could not fully substitute for low temperature in primary induction. At optimum temperatures about 6 weeks exposure were required for 100% flowering, but the flowering response increased with increasing exposure up to 12 weeks, especially at higher temperatures. Seedling have a short juvenile phase of about 4 weeks. Populations with origin ranging from 59 to 69°N in Norway did not vary in their primary induction requirements. Long days (LD) were required for inflorescence initiation and stem elongation at 9°C. At 21 and 15°C some plants initiated and developed inflorescences in SD, but the inflorescences were sessile and their development strongly delayed. More than 16 LD cycles were required for normal stem elongation (bolting).