Hydroprene prolongs developmental time and increases mortality of Indianmeal moth (Lepidoptera: Pyralidae) eggs

Eggs of the Indianmeal moth, Plodia interpunctella (Hübner), were exposed to the labeled rate of hydroprene (1.9 x 10(-3) mg [AI]/cm2) sprayed on concreted petri dishes. These eggs were exposed for 1, 3, 6, 12, and 18 h and until hatching (continuous exposure) at temperatures of 16, 20, 24, 28, and 32 degrees C and 57% RH until the emergence of first instars. The developmental time and egg mortality were significantly influenced by temperature and exposure periods. At 16 degrees C, hydroprene did not cause differences in developmental time when eggs were exposed for different periods. At temperatures >16 degrees C, both exposure period and temperature influenced developmental time. The maximum developmental time (15.0 +/- 0.2 d) occurred at 16 degrees C, and the minimum developmental time (3.2 +/- 0.3 d) occurred at 32 degrees C. Mortality increased when eggs were exposed to hydroprene for longer periods at all of the five tested temperatures. The greatest mortality (81.6 +/- 2.1%) occurred when eggs were continuously exposed on treated surfaces at 32 degrees C. We used developmental time instead of rate (1/ developmental time) to fit simple linear or polynomial regression models to the development data. Appropriate models for developmental time and mortality were chosen based upon lack-of-fit tests. The regression models can be used in predictive simulation models for the population dynamics of Indianmeal moth to aid in optimizing use of hydroprene for insect management.     

Effects of fluctuating moisture and temperature regimes on the infection potential of Beauveria bassiana for Rhodnius prolixus

The effect of both moisture and temperature on the infective potential of Beauveria bassiana to the Chagas' disease vector, Rhodnius prolixus, was studied under fluctuating regimes. At constant 25 degrees C, contaminated first-instar nymphs exposed to increasing daily periods of initial exposure to 97% RH, followed by transfer to reduced humidity (43, 53, 75, and 86% RH), showed a significant reduction in mortality when the 97% RH exposure time declined from 12 to 8 h per day. The duration of disease incubation depended on the daily 97% RH exposure time. Under fluctuating regimes of both humidity (97% RH versus 75% RH) and temperature (15/28, 20/25, 25/28, and 25/35 degrees C), first-instar mortality was affected by weather conditions, daily 97% RH exposure time (8, 12, and 16 h per day), and number of temperature and humidity fluctuations before transferring tested insects to constant unfavorable conditions. In most cases, at 12/12 h alternating cycles, high and rapid mortality required five cycles. Under these fluctuating regimes, fungus-induced mortality and mortality time were similarly affected in third- and fifth-instar nymphs by the daily 97% RH exposure time. Despite a lower susceptibility of older larval stages, mortality rates in insects exposed for at least 12 h per day at 97% RH remained very high except at 15 degrees C. Moisture and temperature regimes at 12/12 h cycling significantly affected the dose-mortality response in first-instar nymphs. The most favorable conditions consisted of 97%-20 degrees C combined with either 75%-25 degrees C or 43%-25 degrees C. Under less favorable alternating conditions (lower and higher temperatures) the amounts of inoculum required for killing 50% of first-instar nymphs were 10 or 20 times higher. From a vector control standpoint, daily high humidity appears to be the most crucial climatic constraint. B. bassiana has the potential to control R. prolixus populations with applications made during the rainy seasons when humidity is high.     

Fruit Number in Relation to Pollen Production and Viability in Groundnut Exposed to Short Episodes of Heat Stress

Hot days and warm nights are important environmental factorslimiting fruit yields of groundnuts in the semi-arid tropics.The objective of the present research was to quantify the effectsof short episodes of heat stress on pollen production and viability,and fruit yield. Plants of cultivar ‘ICGV 86015’were grown at a day/night temperature of 28/22 °C from sowinguntil 9 d after flowering. Cohorts of plants were then exposedto a factorial combination of four day (28, 34, 42 and 48 °C)and two night (22 and 28 °C) temperatures for 6 d. Thereafter,all plants were maintained at 28/22 °C until final harvest9 d later. Number of flowers per plant (FN), the proportionof flowers setting pegs (fruit-set), the number of pegs andpods per plant (reproductive number, RN_t), pollen productionper flower and pollen viability were determined during the 6d stress period. There were strong negative linear relationsbetween day temperature over the range of 28 to 48 °C andFN (slope, -1.1 °C^-1), fruit-set (-2.8% °C^-1), RN_t(-0.90°C^-1), and pollen production (-390 °C^-1) and viability(-1.9% °C^-1). Warmer night temperature (28 vs. 22 °C)had no effect on FN, but reduced fruit-set (31 to 19%), RN_t(8to 5), and pollen production (4389 to 2800) and viability (49to 40%). There were no significant interactions between dayand night temperature. Reduced fruit-set was a consequence offewer pollen grains and reduced pollen viability. The thresholdday temperature for pollen production and viability was 34 °Cand there were strong negative linear relations between bothpollen production and pollen viability and accumulated temperature>34 °C. Copyright 1999 Annals of Botany Company Arachis hypogaea L., fruit-set, groundnut, heat-stress, peanut, pollen viability, pollen production, temperature.     

Effects in mice of high and low environmental temperature on the maternal and fetal toxicity of 2-sec-butyl-4,6-dinitrophenol (dinoseb) and on disposition of [14C]-dinoseb(12).

Swiss-Webster female mice were treated with 2-sec-butyl-4,6-dinitrophenol (dinoseb) and maintained in an increased environmental temperature (32 degrees C) for 24 h or a decreased temperature (0-6 degrees C) for 1.5-4 h. In two experiemtns animals maintained at low temperature were kept wet during the cold exposure, to enhance the reduction in body temperature, by rinsing them with water at approximately 30 min intervals. Results from nonpregnant females indicated that increased temperature lowered the LD50 for single injections of dinoseb from 20.2 to 14.1 mg/kg and that reduced temperature for 4 h had no effect on the LD50. A 24 h exposure to 32 degrees C enhanced the effect of 3 daily dinoseb treatments of pregnant mice; it increased maternal mortality, decreased fetal body weight, and increased frequency of fetal anomalies. Fetal body weight and the frequency of malformations were the same in groups exposed to low temperature and maintained at room temperature. Disposition of [14 C] dinoseb was also determined in nonpregnant mice exposed to temperatures of 0, 24, and 32 degrees C. The periods of environmental temperature studied (3-24 h) had no effect on the rate of disappearance of dinoseb from plasma or other tissues examined.     

Liver and brain mitochondrial ATPase activities in rats exposed to high ambient temperature

Liver and brain mitochondrial ATPase activities in rats exposed to high ambient temperature. Acta physiol. pol., 1985, 36 (3): 185-192. Rat liver and brain mitochondrial ATPase activities were investigated after a single exposure (6 h) of the animals to temperatures of 21 degrees, 28 degrees and 37 degrees C. An increase of ATPase activity stimulated by Ca++ ions was noted in the mitochondrial fractions of the liver at 28 degrees C and of the brain at 28 degrees and 37 degrees C. Only in liver mitochondria of rats exposed to 28 degrees C a depression of Mg++-ATPase activity was found.     

Floral Initiation of Upland Cotton Gossypium hirsutum L. in Response to Temperatures

The effect of germination temperature, duration of high-intensitylight, and day temperature in modifying the influence of nighttemperature on the flowering process of the M-8 strain of Uplandcotton was examined. In general, night temperatures above 28°C caused the first floral branch to be formed at a higher node.The magnitude of the reaction was conditioned by the other environmentalfactors studied. Germination temperature had a slight but significanteffect on subsequent floral responses to night temperature.Plants given eight-hour periods of high-intensity light eachday were delayed more by high night temperature than those exposedto 14 or 24 hours of high light. At high day temperatures (28–32°C) the inhibiting influence of the high night temperature wasgreatly increased. High day temperatures delayed floral initiationif the night temperature was high (28–32°C) but causeda lowering of position of first floral branch when the nighttemperature was low (20–22°C). The enhancement offlowering by 32°C days and 22°C nights was expressednot only in the low node of first floral branch, but also inthe shorter time from planting to floral initiation.     

Thermoregulatory responses of the immature rat following repeated postnatal exposures to 2,450-MHz microwaves

This study was designed to determine the changes that occur in the thermoregulatory ability of the immature rat repeatedly exposed to low-level microwave radiation. Beginning at 6-7 days of age, previously untreated rats were exposed to 2,450-MHz continuous-wave microwaves at a power density of 5 mW/cm2 for 10 days (4 h/day). Microwave and sham (control) exposures were conducted at ambient temperatures (Ta) which represent different levels of cold stress for the immature rat (ie, "exposure" Ta = 20 and 30 degrees C). Physiological tests were conducted at 5-6 and 16-17 days of age, in the absence of microwaves, to determine pre- and postexposure responses, respectively. Measurements of metabolic rate, colonic temperature, and tail skin temperature were made at "test" Ta = 25.0, 30.0, 32.5, and 35.0 degrees C. Mean growth rates were lower for rats exposed to Ta = 20 degrees C than for those exposed to Ta = 30 degrees C, but microwave exposure exerted no effect at either exposure Ta. Metabolic rates and body temperatures of all exposure groups were similar to values for untreated animals at test Ta of 32.5 degrees C and 35.0 degrees C. Colonic temperatures of rats repeatedly exposed to sham or microwave conditions at exposure Ta = 20 degrees C or to sham conditions at exposure Ta = 30 degrees C were approximately 1 degrees C below the level for untreated animals at test Ta of 25.0 degrees C and 30.0 degrees C. However, when the exposure Ta was warmer, rats exhibited a higher colonic temperature at these cold test Ta, indicating that the effectiveness of low-level microwave treatment to alter thermoregulatory responses depends on the magnitude of the cold stress.     

Growth performance and concentrations of thyroid hormones and growth hormone in plasma of broilers at high temperatures

Responses of broiler chickens to a high ambient temperature (35 degrees C) were measured in two experiments. In one experiment temperatures were increased abruptly from 21 degrees C to a daily range of 21-35 degrees C whereas, in the other, temperatures were increased more gradually over 6 days. The high temperatures were maintained for 5 h/day. In both experiments, birds exposed to the high temperatures ate less food and gained less liveweight than birds maintained at 21 degrees C. Efficiency of food conversion to liveweight gain and body composition were not affected by high temperature but there was a tendency for thyroid weight to decrease. Overall, the plasma concentration of triiodothyronine (T3) decreased and the plasma concentration of thyroxine (T4) increased, resulting in a decreased T3/T4 molar ratio, during exposure to high temperature. The concentration of plasma growth hormone, but not plasma reverse T3, was increased by high temperature. The initial responses to increased temperature were variable, with birds exposed more gradually adjusting relatively well until the maximum temperature was increased to 35 degrees C. All heated birds readjusted quickly to the daily reduction in temperature to 21 degrees C.     

Effects on fetal and maternal body temperatures of exposure of pregnant ewes to heat, cold, and exercise.

We exposed Dorper-cross ewes at approximately 120-135 days of gestation to a hot (40 degrees C, 60% relative humidity) and a cold (4 degrees C, 90% relative humidity) environment and to treadmill exercise (2.1 km/h, 5 degrees gradient) and measured fetal lamb and ewe body temperatures using previously implanted abdominal radiotelemeters. When ewes were exposed to 2 h of heat or 30 min of exercise, body temperature rose less in the fetus than in the mother, such that the difference between fetal and maternal body temperature, on average 0.6 degrees C before the thermal stress, fell significantly by 0.54 +/- 0.06 degrees C (SE, n = 8) during heat exposure and by 0.21 +/- 0.08 degrees C (n = 7) during exercise. During 6 h of maternal exposure to cold, temperature fell significantly less in the fetus than in the ewe, and the difference between fetal and maternal body temperature rose to 1.16 +/- 0.26 degrees C (n = 9). Thermoregulatory strategies used by the pregnant ewe for thermoregulation during heat or cold exposure appear to protect the fetus from changes in its thermal environment.     

Hypothermia: teratogenic and protective effects on the development of mouse embryos in vitro

Hypothermia often occurs in association with clinical conditions involving severe hypoglycemia, but its effect on embryonic development has not been well evaluated. Thus, the whole embryo culture method was used to expose day 9 (neurulating) and day 10 (early limb bud stage) mouse embryos to physiologic levels of hypothermia (35 degrees C and 32 degrees C) for 4 and 24 hr. Embryos were evaluated after 24 hours for growth and malformations and compared with controls grown at 37 degrees C. Lactate production was measured in embryos cultured for 4 hr at 32 degrees C and compared with those cultured at 37 degrees C. A 4-hr exposure to hypothermia produced little effect morphologically but reduced the rate of lactate production at both embryonic stages. A 24-hr exposure to hypothermia at 35 degrees C or 32 degrees C produced growth retardation and dysmorphogenesis in embryos undergoing neurulation. Early limb bud stage embryos were less sensitive to this treatment, with growth retardation produced only at the lower temperature. Since hypothermia is commonly associated with severe hypoglycemia in cases of diabetic insulin overdose, day 9 (neurulating) mouse embryos were exposed concurrently to short periods of hypothermia and hypoglycemia and compared with embryos cultured in hypoglycemic medium at normal temperature. The results demonstrate that hypothermia partially protects embryos against the dysmorphogenic effects of hypoglycemia. A balance of metabolic rate and available substrate is discussed as a possible mechanism for this protective effect.     

Naturally occurring variation in high temperature induced floral bud abortion across Arabidopsis thaliana accessions

A system to study the basis of high temperature-induced floral bud abortion using naturally occurring variation for heat-tolerance of floral development among Arabidopsis thaliana (L.) Heynh. wild-collected accessions is described. High temperature-induced floral bud abortion was dependent on both temperature and duration of exposure. Normalizing high temperature exposures to degree-hours (°C-h) above 33 °C indicated that abortion of flower buds increased as exposure increased between 200 and 300 °C-h above 33 °C and exposures > 300 °C-h above 33 °C resulted in abortion of the entire primary inflorescence. Thirteen wild-collected Arabidopsis accessions representing a latitudinal gradient were screened for variation in high temperature-induced floral bud abortion, and Col-0 and No-0 were selected as models for heat-tolerance and -sensitivity for flower development, respectively. No-0 flower buds were heat-sensitive across a wider range of developmental stages (stages 9–12, compared to stage 12 for Col-0 flower buds). Exposing the inflorescence alone to high temperature was sufficient to induce floral bud abortion, and Col-0 and No-0 photosynthetic rates were similar during high temperature exposure and recovery, indicating that high temperature induced floral abortion is not simply due to reductions in carbon assimilation under high temperatures. Determining that exposing floral buds alone to high temperature is sufficient to induce abortion and identifying the stages of floral development sensitive to high temperature-induced abortion will aid in identifying the developmental events subject to disruption under high temperatures.     

The Influence of Temperature on Floral Initiation in the Olive

Floral initiation is completely inhibited when the olive is grown in a glasshouse at a minimum temperature of 16°C and a maximum temperature of 27°–30°C but occurs when it is grown at natural winter conditions in California. This study was undertaken to determine more specifically the temperature requirements for flowering and to show the relation of temperature treatment to hud development and floral initiation. Results of experiments performed with trees in containers grown at constant temperatures in controlled environment growth rooms show that the optimum temperature for flowering is 10°–13°C. Either higher (18°C) or lower (4°C) temperatures inhibit flowering completely. Morphological studies show that axis elongation and floral initiation occur in buds during temperature treatment at 10°C and 13°C but fail to occur during 4°C or 18°C treatments, or following these treatments when the temperature is raised to 21°C. When plants were exposed to 13°C for varying durations, it was found that no inflorescences formed after a 7.5 week exposure but that many formed after an 11-week exposure. A subsequent experiment showed that many more inflorescences formed after a 10-week exposure at 13°C than after 9 weeks exposure. Morphological changes in the bud seem to be associated with this increase in flowering affected by duration of treatment.     

Changes in body temperature of rats acclimated to heat with different acclimation schedules

Male Wistar rats, initially maintained at an ambient temperature (Ta) of 23.8 degrees C, were subjected to one of seven different heat acclimation schedules under a 12:12-h light-dark cycle (lights on at 0600 h). Two groups of rats were exposed to Ta of 32.4 degrees C all day for 5 (HC5) or 10 (HC10) days. The other four groups were exposed to Ta of 32.8 degrees C for 5 h/day during the last half of the dark phase for 5 (NI5) or 10 (NI10) consecutive days or during the last half of the light phase for 5 (DI5) or 10 (DI10) consecutive days. Control rats (C) were kept at 23.8 degrees C throughout the experiment. Hypothalamic temperature (Thy) was measured every 5 min with a chronically implanted thermocouple from 1 day before the beginning to 2 days after the end of the heat acclimation periods. During the heat acclimation periods, daily mean Thy rose significantly in HC5 and HC10 rats but decreased significantly in NI5 and NI10 rats. Daily mean Thy did not change in C, DI5, and DI10 rats. Thy in HC10 rats sharply decreased at the end of the heat acclimation periods and remained at low levels for approximately 3 h. On the 2nd postacclimation day, however, mean Thy returned and remained at a significantly higher level. In NI10 rats, the mean Thy in the postacclimation period was significantly lower than the preacclimation values. No such changes in mean Thy were observed in DI10 rats. Five-days of heat exposure had little effect on the postacclimation Thy.(ABSTRACT TRUNCATED AT 250 WORDS)     

Determining critical pre- and post-anthesis periods and physiological processes in Lycopersicon esculentum Mill. exposed to moderately elevated temperatures

To determine the thermosensitive periods and physiological processes in tomato flowers exposed to moderately elevated temperatures, tomato plants (Lycopersicon esculentum Mill., cv. NC 8288) were grown at 28/22 degrees C or 32/26 degrees C day/night temperature regimes and then transferred to the opposite regime for 0-15 d before or 0-24 h after anthesis. For plants initially grown at 28/22 degrees C, moderate temperature stress before anthesis decreased the percentage of fruit set per plant, but did not clarify the thermosensitive period. The same level of stress did not significantly reduce fruit set when applied immediately after anthesis. For plants initially grown at 32/26 degrees C, fruit set was completely prevented unless a relief period of more than 5 d was provided before anthesis. The same level of stress relief for 3-24 h after anthesis also increased fruit set. Plants were most sensitive to 32/26 degrees C temperatures 7-15 d before anthesis. Microscopic investigation of anthers in plants grown continuously at high temperature indicated disruption of development in the pollen, endothecium, epidermis, and stomium. This disruption was reduced, but still observable in plants relieved from high temperature for 10 d before anthesis.     

Dehydration increases the magnitude of selective brain cooling independently of core temperature in sheep

By cooling the hypothalamus during hyperthermia, selective brain cooling reduces the drive on evaporative heat loss effectors, in so doing saving body water. To investigate whether selective brain cooling was increased in dehydrated sheep, we measured brain and carotid arterial blood temperatures at 5-min intervals in nine female Dorper sheep (41 +/- 3 kg, means +/- SD). The animals, housed in a climatic chamber at 23 degrees C, were exposed for nine days to a cyclic protocol with daytime heat (40 degrees C for 6 h). Drinking water was removed on the 3rd day and returned 5 days later. After 4 days of water deprivation, sheep had lost 16 +/- 4% of body mass, and plasma osmolality had increased from 290 +/- 8 to 323 +/- 9 mmol/kg (P < 0.0001). Although carotid blood temperature increased during heat exposure to similar levels during euhydration and dehydration, selective brain cooling was significantly greater in dehydration (0.38 +/- 0.18 degrees C) than in euhydration (-0.05 +/- 0.14 degrees C, P = 0.0008). The threshold temperature for selective brain cooling was not significantly different during euhydration (39.27 degrees C) and dehydration (39.14 degrees C, P = 0.62). However, the mean slope of lines of regression of brain temperature on carotid blood temperature above the threshold was significantly lower in dehydrated animals (0.40 +/- 0.31) than in euhydrated animals (0.87 +/- 0.11, P = 0.003). Return of drinking water at 39 degrees C led to rapid cessation of selective brain cooling, and brain temperature exceeded carotid blood temperature throughout heat exposure on the following day. We conclude that for any given carotid blood temperature, dehydrated sheep exposed to heat exhibit selective brain cooling up to threefold greater than that when euhydrated.     

Cytogenetic effects of microwave irradiation on male germ cells of the mouse

Hybrid male mice were exposed to 2.45 GHz microwaves for 30 min/day, 6 days a week for two consecutive weeks at power densities of 1.0, 100 or 400 W m-2, with sham-exposed controls. Rectal temperatures before and after exposure were measured on days 1, 6 and 12. Measurements made on day 1 were treated with caution because of heterogeneity in rectal temperatures taken before exposure between the groups of mice given different treatments. On days 6 and 12, rectal temperatures rose by approximately 1 degree C in mice sham exposed, or exposed to 1 W m-2 or 100 W m-2. Only in the group of mice exposed to 400 W m-2 was the mean rise in rectal temperature during exposure (about 3 degrees C) significantly increased above the sham value. In groups killed 2-3 days after treatment (mainly meiotic exposure) frequencies of chromosome aberrations in spermatocytes showed no significant heterogeneity although the highest frequency of 1.5 per cent was at the highest (400 W m-2) power density. Another group killed 30 days after 100 W m-2 exposures (spermatogonial sampling) showed no significant increase over controls in chromosome aberration frequency. There was a small but significant increase in sperm count with increasing power density in mice killed 12-13 days after exposure, but a non-significant one in those exposed as spermatogonia (killed 41 days later). Thus effects were markedly less severe than those reported previously by Manikowska-Czerska et al. (1985) with a very similar radiation regime and were probably caused by the temperature enhancement.     

Hydroprene prolongs developmental time and increases mortality in wandering-phase Indianmeal moth (Lepidoptera: Pyralidae) larvae

Wandering phase Indianmeal moth, Plodia interpunctella (Hübner), larvae were exposed to the label rate of hydroprene (1.9 x 10(-3) mg [AI] /cm2) sprayed on concreted petri dishes. Larvae were exposed for 1, 3, 6, 12, 18, 24, and 30 h and maintained at 16, 20, 24, 28, and 32 degrees C and 57% RH until adult emergence. Larval developmental time and mortality were significantly influenced by temperature and exposure intervals. Maximum developmental time (47.2 +/- 1.3 d) occurred at 16 degrees C, and the minimum developmental time (7.0 +/- 0.5 d) occurred at 32 degrees C. Larval mortality generally increased at all of the five tested temperatures as exposure period increased. The greatest mortality (82.0 +/- 0.1%) occurred when larvae were exposed for 30 h at 28 degrees C, and minimum mortality (0.0 +/- 0.5%) occurred at 16 degrees C when larvae were exposed for 1 h. The relationships between temperature, exposure period, and developmental time were described by polynomial models, based on lack-of-fit tests. Hydroprene has potential to be an effective alternative to conventional insecticides in surface treatments for Indianmeal moth management. Response-surface models derived from this study can be used in simulation models to estimate the potential consequences of hydroprene on Indianmeal moth population dynamics.     

Acclimation of rats following stepwise or direct exposure to heat

The physiological changes in male rats during acclimation were studied following direct or stepwise exposure to heat (32.5 degrees C) in a controlled-environment room. The animals were exposed to each temperature for 10 days beginning at 24.5 degrees C and returning to 24.5 degrees C in the reverse order of initial exposure. Relative humidity of 50 +/- 2% and a 12-h light-dark photoperiod (light from 0900 to 2100 h) were maintained. Physiological changes in metabolic rate (MR), evaporative water loss (EWL), plasma corticosterone, body water turnover, and food and water intake were measured. The results indicate a significantly (P less than 0.001) elevated plasma corticosterone and MR in rats exposed directly to heat from control temperature (24.5 degrees C) but not in those animals exposed stepwise via 29.0 degrees C. All kinetic parameters of water pool changed (P less than 0.01) on direct exposure to heat, whereas rats exposed in a stepwise manner increased only pool turnover. In addition, exposure to experimental temperatures resulted in reduced (P less than 0.05) relative food intake and increased (P less than 0.05) water intake. Compared with the control condition of 24.5 degrees C, EWL was significantly (P less than 0.05) elevated when the animals were exposed either directly or in a stepwise fashion to 32.5 degrees C. These data suggest that the response to elevated temperatures is influenced by the temperature to which the rat is acclimated.     

Histochemical Study of Photoperiodic and Low Temperature Effects on Floral Induction of Spinacia oleracea

Shoot apices of Spinacia oleracea plants have been induced toflower either by: (a) subjecting leaves to 24 h long day, or(b) exposure to a short photoperiod but displaced by 8 h (displacedshort day) in the usual 24 h short-day cycle, or (c) exposureto low temperature (5 °C) during the dark period of thenormal short day. A quantitative cytochemical assay of pentosephosphate pathway activity during floral induction indicatesan approximate doubling of the rate of activity when comparedto that of vegetative apices (short day) (21 °C). Exposure to either low temperature, or a displaced short photoperiodstimulates pentose phosphate pathway activity in the shoot apexin a manner similar to that seen by long-day induction. Thischange in metabolic activity is accompanied by changes in theshape of the shoot apex which resembles that seen at an earlystage during floral induction. Spinacia oleracea, pentose phosphate pathway, shoot apex, glucose-6-phosphate dehydrogenase, floral induction, chilling, displaced short day     

Acclimation to constant and variable temperatures in plethodontid salamanders--I. Rates of oxygen consumption

In preliminary experiments, salamanders of three species (Desmognathus ochrophaeus, Plethodon cinereus and Plethodon jordani) required 5-11 days to complete metabolic acclimation to a constant warm temperature; the rate of oxygen consumption (VO2) decreased 16-28% during acclimation. Unfed animals of each species underwent cyclic exposure to 5 and 21 degrees C at three different cycle periods (12 hr, 4-5 days, 51 days), or constant exposure to 14 degrees C for 102 days. The experimental treatments significantly affected the VO2 measured at 5, 14, 17.5 and 21 degrees C. The direction and magnitude of the acclimatory effects upon VO2 were inconsistent among species and among experimental temperatures, and resulted in little energy saving. The VO2 during exposure to cyclic temperatures averaged only 83% of that during preliminary experiments, perhaps as a response to starvation.