Balancing photosynthetic light-harvesting and light-utilization capacities in potato leaf tissue during acclimation to different growth temperatures

We investigated the effect of temperature during growth and development on the relationship between light-harvesting capacity, indicated by chlorophyll concentration, and light-utilization potential, indicated by light- and bicarbonate-saturated photosynthetic oxygen evolution, in Solanum tuberosum L. cv. Norland. Conal plantles were transplanted and grown at 20°C for 2 weeks before transfer to 12, 16, 20, 24 and 28°C for 6 weeks. After 4 weeks of the temperature treatments, leaf tissue fresh weights per area were one-third higher in plants grown at 12°C vs those grown at 28°C. Conversely, chlorophyll content per area in tissue grown at 12°C was less than one-half of that of tissue grown at 28°C at 4 weeks. Photosynthetic capacity measured at a common temperature of 20°C and expressed on a chlorophyll basis was inversely proportional to growth temperature. Leaf tissue from plants grown at 12°C for 4 weeks had photosynthetic rates that were 3-fold higher on a chlorophyll basis than comparable tissue from plants grown at 28°C. These results suggest that the relationship between light-harvesting capacity and light-utilization potential varies 3-fold in response to the growth temperatures examined. The role of this response in avoidance of photoinhibition is discussed.     

Incidence of Enterotoxigenic Clostridium perfringens in Healthy Humans in relation to the Enhancement of Enterotoxin Production by Heat Treatment

Enterotoxin production was greatly enhanced in two of five food poisoning strains of Clostridium perfringens subjected to heat treatment prior to incubation in Duncan and Strong sporulation medium. Heating was carried out on three successive cultures of each strain, the optimum temperature for treatment being 85 °C for one strain and 95 °C for another: on each occasion cultures were heated for 20 min. The triple heat treatment procedure was used in testing strains of Cl. perfringens isolated from faeces of healthy human subjects for production of enterotoxin. Eleven of 35 (31%) individuals were found to be carriers of enterotoxigenic strains, the isolates producing more than 0·1 μ/ml of enterotoxin. Six of the 11 enterotoxigenic strains were killed by heating at 95 °C but one isolate produced more enterotoxin following treatment at this temperature than after heating at 75 °C.     

Influence of growth temperature on the production of extracellular virulence factors and pathogenicity of environmental and human strains of Aeromonas hydrophila

The biochemical properties, virulence for mice and trout, and the extracellular virulence factors at 28° and 37°C of 11 environmental and nine human strains of Aeromonas hydrophila were compared. All the environmental isolates and four of the human group were virulent for trout at 3 x 10⁷ cfu, but only human strains were able to cause death or lesions in mice by the intramuscular route. Extracellular virulence factors such as haemolysins, cytotoxins and proteases were also investigated in supernatant fluids of cultures grown at 28°C and 37°C. The production of haemolysins, caseinases, elastases and growth yields of environmental strains decreased sharply during cultivation at 37°C but cytotoxins were produced to the same extent, or slightly less, than at 28°C. The human strains differed from the environmental strains in response to growth temperatures: protease activity decreased at 37°C, although growth yield was not affected, but more haemolysins and cytotoxins were produced by the virulent strains at this temperature than at 28°C. Sodium caseinate SDS-PAGE of culture supernatant fluids of selected human strains revealed that temperature selectively inhibited the production of certain proteases.     

Is thermal time adequate for expressing the effects of temperature on sunflower leaf development?

We have tested whether the effects of temperature on sunflower leaf growth could be documented by using thermal time. The rates of leaf expansion and of cell division were analysed in leaves located at two positions on the stem, and a spatial analysis of expansion rate was carried out. Experiments were performed in growth chamber (stable conditions), in the field or in a greenhouse (fluctuating conditions). We compared three methods for characterizing the rate and the duration of expansion. Responses to leaf temperature were consistent only when expansion was characterized as a two-phase process — a period of exponential expansion (constant relative expansion rate, RER ) followed by a decrease in RER . RER and relative cell division rate ( RDR ) responded linearly to temperature with a common response curve for all studied conditions. This response curve was also common to all studied zones within a leaf and to leaves at two positions on the stem. The reciprocals of the durations of the periods of exponential expansion, non-zero expansion and non-zero division were also linearly related to leaf temperature with common response curves in a given leaf zone. The x -intercepts of all these response curves and of the response curve of leaf initiation rate to temperature did not significantly differ in an analysis of covariance, with a common value of 4·8 °C. The expression of time in cumulative degree days, with a base temperature of 4·8 °C, resulted in a unique time course of RER and cell division rate regardless of temperature. These results suggest that a powerful 'program' of leaf development exists in a sunflower plant.     

Prediction of the shelf-life of pasteurized milk at different storage temperatures

Initial psychrotroph counts determined by a Most Probable Number technique were correlated with shelf-lives of pasteurized milk determined at a number of storage temperatures. The initial psychrotroph count was also correlated with a bacterial count carried out on milk agar containing crystal violet penicillin and nisin after previous incubation of the milk at 15°C for 25 h.
Pre-incubation counts carried out at a variety of temperatures and on a variety of media were examined for their relation to shelf-life. Shelf-lives at four pre-set temperatures (2, 6, 10 and 14°C) could best be predicted by pre-incubation of pasteurized milk at 15°C before inoculation on milk agar.
An equation which allows prediction of shelf-life of pasteurized milk at any storage temperature is described.     

STUDIES ON THE EFFECT OF TEMPERATURE ON VIRUS MULTIPLICATION IN INOCULATED LEAVES

The rate at which the Rothamsted tobacco necrosis virus (RTNV) accumulates in inoculated French bean leaves increases with rising temperature to 22°C. and then decreases. Three days after inoculation, leaves at 22°C. contain 4000 times as much virus as at 10°C. and 1000 times as much as at 30°C. At all temperatures the rate of accumulation may depend on the balance between synthesis and inactivation of RTNV, but inactivation becomes increasingly important with rise of temperature above 22° C. and as the virus content of the leaves increases. Above 22°C. the rate of multiplication may increase but less rapidly than the rate of inactivation, and exposing inoculated leaves to ultra-violet radiation at various intervals after inoculation suggests that at 30°C. RTNV multiplies in and moves from the initially infected epidermal cells in slightly less than the 6 hr. needed at 22°C. Thirty hr. are needed at 10°C. Newly formed virus is rapidly inactivated at 30°C. Raising the ambient temperature also decreases the numbers of local lesions produced by RTNV, possibly by increasing the chances that the introduced virus particles will become inactivated. Increasing the virus content of the inoculum above the level giving one lesion per sq.cm. does not increase the subsequent virus content of inoculated leaves.
At temperatures of 30°C. and below, tomato aucuba mosaic virus produces necrotic lesions in leaves of tobacco and Nicotiana glutinosa whereas above 30°C. the lesions are chlorotic. In both hosts this virus multiplies more rapidly when the infected cells are killed.     

Germination and emergence characteristics of triazine-susceptible and triazine-resistant biotypes of Solanum nigrum

1. Seedling emergence patterns of triazine-susceptible and triazine-resistant Solanum nigrum in the field were studied in Wageningen, the Netherlands. Emergence patterns were similar in the first year, but in the second year resistant seedlings emerged faster and the number of resistant seedlings was higher. To explain emergence patterns, a germination experiment was carried out.
2. Seeds from two populations with triazine-susceptible and -resistant biotypes were buried in late autumn and exhumed monthly during spring. Germination was assessed in incubators at different constant temperatures.
3. The lowest temperatures for germination of seeds from the Achterberg population ranged from 20°C on 1 February to 10°C on 1 May for the susceptible biotype, and from 15°C on 1 February to 10°C on 1 May for the resistant biotype. The lowest temperatures for germination of seeds from the Zelhem population ranged from 25°C on 1 February to 10°C on 1 May for the susceptible biotype, and from 15°C on 1 February to 10°C on 1 May for the resistant biotype. The minimum germination temperature of seeds from the resistant biotype appeared to be lower than that of the susceptible biotype.
4. Emergence patterns in the field could be explained by soil temperature and different minimum germination temperature requirements of seeds from the triazine-susceptible and -resistant biotype. This knowledge can be used to manage triazine-resistant biotypes of S. nigrum by the timing of soil cultivation.     

Hypometabolism in torpid goldsinny wrasse subjected to rapid reductions in seawater temperature

Goldsinny Ctenolabrus rupestris were subjected to rapid, environmentally realistic, reductions in temperature at 2° C increments from 10 to 4° C over a 3-day period in full-strength sea water. In separate experiments, oxygen uptake measurements and ultrasound recordings of heart rate and opercular motion were carried out at regular intervals over the same temperature regime. Mean oxygen uptake rates fell from 0.042 to 0.028 ml O₂ g⁻¹ h⁻¹ between 10 and 6° C respectively (Q₁₀=2.71). Between 6 and 4° C mean rates decreased from 0.028 to 0.008 ml O₂ g⁻¹ h⁻¹ (Q₁₀=542). Mean opercular motion and heart beat rates decreased from 49.5 and 60.3 beats min⁻¹ respectively at 10° C to 18.7 and 18.0 beats min⁻¹ respectively at 4° C. Most goldsinny subjected to 4° C were observed in a torpid state and would not react to external stimulation. Opercular motion was erratic at 4° C and would at times cease altogether for periods up to 1.3 min duration. Heart movement was diffcult to detect at 4° C and may also have ceased for prolonged periods. Q₁₀ values for opercular motion and heart beat rates recorded between 6 and 4° C were 6.39 and 24.52 respectively compared with values of 2.42 and 2.93 respectively recorded between 10 and 8° C. Such large depressions in metabolism appear not to have been reported previously for a marine fish species. No goldsinny mortalities were recorded at any temperature. The possibility that hypometabolic torpor is an adaptive strategy for goldsinny survival at low environmental temperatures is discussed.     

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.     

Effect of temperature on the demography of Galerucella birmanica (Coleoptera: Chrysomelidae)

Studies on the effect of temperature on the development of the water chestnut beetle, Galerucella birmanica Jacoby were carried out in the laboratory at seven different temperatures: 16 °C, 19 °C, 22 °C, 25 °C, 28 °C, 31 °C and 34 °C. The developmental time decreased with increase in temperature. The developmental time at 16 °C, 19 °C, 22 °C, 25 °C, 28 °C, 31 °C and 34 °C was 96.60, 80.68, 58.96, 43.48, 35.03, 30.08 and 28.02 days for the period from egg hatching to adult emergence, respectively. The developmental threshold estimated for a generation by linear regression was 10.36 °C. The fecundity per female at 22 °C, 25 °C, 28 °C, 31 °C and 34 °C was 102.3, 134.5, 141.2, 130.1 and 116.2 eggs, respectively. Oviposition period ranged from 15.6 days at 22 °C to 8.6 days at 34 °C. Hatchability of eggs was highest at 31 °C with 76.9% and lowest at 34 °C with 57.1%. The highest generation survival rate was 65.3% at 31 °C, and the intrinsic rate of natural increase ( r _m) for G. birmanica was the highest at 34 °C.     

Characteristics of alternating temperatures which stimulate loss of dormancy in seeds of Rumex obtusifolius L. and Rumex crispus L.

Abstract. Alternating temperatures stimulate the germination of Rumex crispus L. and Rumex obtusifolius L. The optimum period spent at the lower temperature in a diurnal cycle is greater than that spent at the higher temperature. Under most conditions the optimum period at the upper temperatures is about 8 h but, as the upper temperature of a cycle is increased, the optimum period at the upper temperature becomes shorter and more critical. Thus when it is 35°C the optimum period is 2.5–4 h in the light, or about 1 h in the dark. The effect of alternating temperatures is much less in the dark than in the light and in general only extreme alternations with short periods at the higher temperature are effective in the dark. In the light any temperature alternation within the range 1–35°C is effective to at least some extent, providing the temperature difference is 5°C or more and providing the alternation includes one temperature which is above approximately 15°C and one which is below approximately 25°C. The optimum temperature difference is about 15°C. In the light, 4 to 10 cycles saturate the response, but in the dark, where the effect is much less, the response may not be saturated even by 16 cycles. KNO₃ at 10⁻³ M has little effect on the response to alternating temperatures either in the light or the dark. The response to alternating temperature regimes does not appear to vary in quality, i.e., in terms of which particular treatments are best, but it varies in magnitude with site and year of seed collection; and it increases slowly during dry storage, even when stored at a temperature as low as 1.5°C.     

Temperature-induced changes of early development and yolk utilization in the African catfish Clarias gariepinus

Artificially fertilized eggs and yolk-sac larvae of a freshwater tropical/subtropical fish Clarias gariepinus receiving no external food were incubated at 22, 25 and 28° C until full yolk resorption. Developmental time, size and matter composition (CHNS-O Analyzer and ashing) were assessed at egg fertilization, hatching and yolk resorption; respiration was measured every 4–5 h. The course of acceleration of C. gariepinus embryonic developmental rate with temperature ( Q_{10 dev}) was compared over the temperature range to those of Cyprinus carpio and Oncorhynchus mykiss ; they differed greatly, but were similar when compared on the basis of effective temperatures specific to each fish. Specific growth rates for energy (88, 150 and 183% per day at 22,25 and 28° C, respectively) as well as the conversion efficiencies of egg energy (64, 71 and 68%, respectively) and protein (71, 78 and 76%, respectively) in C. gariepinus larval tissues were higher than those known for the endogenous feeding period of coldwater and temperate fish species. In C. gariepinus at the end of yolk resorption, the carbon percentage and caloric values of dry weight, size (in terms of dry matter, minerals, protein and energy per larva) and transformation efficiencies were lowest at 22° C, highest at 25° C and had slightly decreased at 28° C. A tentative mechanism which leads to the positive or negative response of body size to temperature over the viable temperature range is defined.     

Cytoplasmic microtubules of normal and tumor cells of the leopard frog

Abstract. The cytoplasmic microtubule complex (CMTC) was examined in monolayer cultures of normal tadpole mesonephros, primary renal adenocarcinoma, and an established cell line derived from a pronephric renal adenocarcinoma (PNKT-4B) of the leopard frog, Rana pipiens. Immunocytochemistry revealed typical arrays of microtubules extending from the cytocentrum to the cell periphery in all three cell types when cultured at 28° C; similar results were obtained at 20° C. However, the CMTC was disorganized in both tumor types, in contrast to the retention of a typical CMTC in normal tissue cultured at 7° C. The response of PNKT-4B cells differed from that of normal tadpole mesonephros when treated with the microtubule inhibitor drug nocodazole. At 28° C, PNKT-4B and tadpole mesonephros cells lost their CMTC with nocodazole treatment, and both were able to reconstitute CMTC when nocodazole was removed. Similarly, both lost CMTC organization with nocodazole and culture at 7° C. However, while normal cells could effect a recovery at 7° C after the removal of nocodazole, PNKT4B cells were unable to restructure CMTC under the same conditions. Metastasis in the frog renal adenocarcinoma is temperature-dependent, with an elevated prevalence of metastasis in tumor-bearing frogs maintained at 28° C. Few metastatic colonies are detected in tumor-bearing frogs maintained at a low temperature (7° C). Other studies have indicated that microtubules, which are essential for cell motility, play an important role in the invasion by tumor cells of normal tissue fragments in vitro. The effects of temperature on metastasis of the Lucke renal adenocarcinoma are consistent with temperature-mediated changes in tumor-cell CMTC.     

Geographical variation in Japan in egg development of the mayfly, Ephoron shigae (Ephemeroptera: Polymitarcyidae)

1. The effect of temperature on embryonic development was compared in four populations, two bisexual and two unisexual, of Ephoron shigae , including one each near the northern and southern periphery of the species range in Japan.
2. Eggs from every population were chilled at 4, 8 or 12 °C for diapause development after 50 days at 20 °C for pre-diapause development (experiment I). Some eggs hatched during chilling at 8 °C or 12 °C, whereas no eggs hatched at 4 °C. The rate of hatching in a given condition of chilling was higher for the eggs from warmer winter environments.
3. Chilling at 4 or 8 °C effectively facilitated diapause development. Chilling at 12 °C was, in general, not so effective, but relatively effective for the eggs from warmer winter environments.
4. Eggs were incubated at 8, 12, 15 or 20 °C after chilling at 4 °C to examine the effect of temperature on post-diapause development (experiment II). The eggs incubated at higher temperature after chilling hatched quicker and more synchronously and had higher hatching success.
5. The relationship between temperature and the days required for hatching after chilling was well described by the power function. There was no significant difference in the slope of the regression lines (i.e. temperature dependency) among local populations. However, a longer time was required for hatching at a given temperature for the population from the colder winter environment.
6. There was no detectable difference in the observed intraspecific variations between unisexual and bisexual populations.     

Gravitropic response of primary maize rootlets as influenced by light and temperature

Abstract. The gravitropic curvature of primary maize rootlets was measured as a function of temperature, both in the presence and absence of light. In two different cultivars, light strongly increased the downward curvature of roots developing from horizontally-oriented embryos. At 15–20°C, the bending angle was in the range of 70–80° in the light, and 25–50° in the dark, depending on the cultivar. When the temperature was increased above the 15–20°C range, marked differences were found between the two cultivars in their response to light. In one variety tested, JX180, the effect of light was relatively small at 30–35°C. Gravitropic curvature in another variety, Halamish, depended strongly on light throughout the temperature range tested. In both cultivars, gravitropic curvature was only slightly temperature dependent when germination and growth were in total darkness. In the dark, the extent of gravitropic curvature also depended on whether the kernels were oriented with their embryos facing upwards or downwards. Under continuous light, the gravitropic bending of roots of cultivar Halamish did not show a marked temperature dependence. When the seedlings were subjected to only a 15 min illumination, their gravitropic response was partial, and the dependence on temperature somewhat increased. In cultivar JX180, a combination of temperature and light modulates gravitropism. The gravitropic response of different maize cultivars thus differs considerably in its combined dependence on light and temperature.     

Germination Responses of Taraxacum platycarpum Seeds to Temperature

Abstract Germination responses of Taraxacum platycarpum seeds to temperature were examined under laboratory conditions to investigate the emergence-season choice mechanism of the seeds. Almost all the newly collected seeds were non-dormant. Under constant temperature conditions, maximum percentage germination (approximately 90%) was attained at temperatures 6–16°C, where simple linear relationships were observed between the temperature and the rates of germination, i.e. the reciprocals of the time taken to germinate by seed subpopulations with 10–80% germination. Thermal time required for germination of the subpopulations ranged from 600 Kh (degree Kelvin × hours) to 1500 Kh with a relatively constant base temperature of about 2.5°C. Lower limit temperature for germination was slightly below 6°C. Higher limit temperature for germination has the normal distribution with the mean ±SD of 19±2.5°C. Pre-exposure of imbibed seeds to temperatures higher than the higher limit temperature for germination, 25 and 30°C, had no effect on the germinability and the rate of germination at a circa-optimum temperature. Moist chilling treatment at 4°C caused an increase in the variation of germination rate within the seed population, but no evidence for dormancy-inducing or breaking effects was obtained.     

Photosynthetic characteristics of Lactuca serriola L.

Abstract. Gas exchange responses of intact leaves of Lactuca serriola serriola and L. serriola integrifolia were examined. The light, temperature and intercellular CO₂ dependence of photosynthesis of these two forms of L. serriola were indistinguishable. Dependence of photosynthesis on leaf temperature differed only slightly between plants grown at approximately 10/3°C and those grown at 33/25°C with the thermal optimum shifting 4°C. Transpiration was shown to increase exponentially with leaf temperature. The gas exchange characteristics of L. serriola are discussed in relation to water relations, carbon gain and compass leaf orientation under field conditions.     

Time required for temperature-induced changes in gonadal aromatase activity and related gonadal structure in turtle embryos

Abstract. In the turtle Emys orbicularis , sexual differentiation of gonads is temperature-dependent. Oestrogens have been shown to be involved in this phenomenon and temperature has been expected to act, directly or indirectly, on regulation of synthesis or activity of cytochrome P-450 aromatase (P-450 arom). We have studied the effects of temperature shifts and of exposure at female- or male-producing temperatures for different times on gonadal aromatase activity and gonadal structure. In a first series of experiments, eggs were incubated at 25°C (masculinizing temperature) up to stage 18 and then exposed for 1 to 8 days at 35°C, a highly feminizing temperature. The response was exponential: aromatase activity increased clearly only after 4 day exposure at 35°C, then it was considerably enhanced. After 1 and 2 days at 35°C, the structure of gonads was not modified. With longer exposures at 35°C, gonads were progressively feminized: medullary epithelial cords disappeared, whereas an ovarian cortex was forming. In another type of experiment, eggs incubated at 30°C (feminizing temperature) until stage 19 were transferred at 25°C for 6 days. In embryos of these shifted eggs, gonadal aromatase activity was about ninefold lower than that in control embryos (maintained at 30°C). However, this activity did not fall to the level measured in embryos of the same stage incubated at 25°C from egg-laying and was about twofold higher than that measured at the time of transfer. Gonads exhibited a cortex anlage but the medulla was more voluminous than that of controls and epithelial cords were beginning to form within. Together these results show that changes in gonadal aromatase activity and in gonadal structure are correlated, and that temperature acts on regulation of P-450 arom synthesis. Amplification of this synthesis during the thermosensitive period at higher temperatures could reflect amplification of expression of the P-450 arom gene.     

Enhanced biodegradation and emulsification of crude oil and hyperproduction of biosurfactants by a gamma ray-induced mutant of Pseudomonas aeruginosa

A gamma ray-induced mutant of Pseudomonas aeruginosa strain S8, capable of hyperproduction of biosurfactant from hydrocarbons, was isolated and named as EBN-8. The mutant showed 3–4 times more hydrocarbon emulsification/conversion as compared to the parent when grown on Khaskheli crude oil in minimal medium. Enhanced biosurfactant production and hydrocarbon utilization by the mutant was also observed during growth on heptadecane in minimal medium as indicated by emulsion index and surface tension of cell-free culture broth. Using heptadecane as carbon and energy source, time course for the growth (cfu ml^-1) and biosurfactant production were compared for both parent and mutant. These studies were carried out for 24 d at 30 ± 2°C and for 20 d at 37°C. Growth of EBN-8 was much faster compared to the parent as well as being 2–3 times more hyperproductive.     

Effect of rootstock on photoperiodic control of elongation growth in grafted ecotypes of Salix

Scions of a southern (59° 40'N Lat.) and a northern (69° 39'N Lat.) ecotype of Salix pentandra L. were grafted on clonal rootstocks of the same ecotypes. Effects of photoperiod on elongation growth of the 4 combinations (south/south, south/north, north/south and north/north) were studied in a phytotron at 18° and 15°C. The photoperiodic response was primarily dependent on the ecotype of the scion, but this response was significantly modified by the rootstock. Cessation of apical growth was advanced by a northern clone and delayed by a southern clone as a rootstock. The results indicate that the critical photoperiod for cessation of apical growth could be slightly decreased by a northern and increased by a southern rootstock.