Studies of the Involvement of an Endogenous Rhythm in the Photoperiodic Response of Hyoscyamus niger

An attempt was made to determine the involvement of an endogenous circadian rhythm in the flowering response of the long-day plant Hyoscyamus niger L. grown in a modified White's medium. Both variable-cycle-length and light interruption experiments were employed in this attempt. In the variable-cycle experiments, plants were subjected to light periods of 6, 12, or 18 hours followed by varying lengths of darkness. The total lengths of the cycles varied from 12 to 72 hours. In experiments utilizing a 6-hour photoperiod, a high level of flowering occurred in cycle lengths of 12, 36, and 60 hours. Flowering was suppressed in the 24-, 48-, and 72-hour cycles. When a 12-hour photoperiod was used the flowering response was low between 24 and 36 hours and flowering did not indicate a rhythmic response. When an 18-hour photoperiod was used, the flowering response was suppressed in the 36- and 60-hour cycles.

Light-break experiments were conducted to study further the flowering response in Hyoscyamus. These experiments consisted of a 6-hour main photoperiod followed by varying lengths of darkness to make cycles of 24, 48, and 72 hours. At given intervals the dark period was interrupted by 2-hour light breaks. In a 24-hour cycle, flowering was promoted when a light break was given at either the twelfth or eighteenth hour of the cycle. In a 48-hour cycle, flowering was strongly promoted by light breaks given near the beginning or at the end of the dark period. In a 72-hour cycle, light breaks given at the eighteenth, forty-second, and sixty-sixth hour of the cycle stimulated flowering as compared with light breaks given at the thirtieth and fifty-fourth hour. These results are indicative of the involvement of an endogenous rhythm in the flowering response of Hyoscyamus niger.

     

The effects of prolonged emersion and submersion by tidal manipulation on marine macrobenthos

Effects of tidal manipulation, resulting in prolonged periods of emersion and submersion or in protracted tidal cycles, on estuarine benthic animals are reviewed.Prolonged submersion periods did not show effects on mortality of most benthic animals tested, with the exception of the crumb-of-bread sponge Halichondrea panicea, which, at low water-flow rates, was covered with a layer of bacteria and subsequently died.Protracted low-water periods of 18 hours during several weeks hardly caused any mortality. However, protracted low-water periods of 30 hours during some weeks or emersion during several days caused a strong increase in mortality, depending on: the duration of emersion, temperature, condition of the animals, species and age. At temperatures below –1 °C and above 24 °C mortality was generally high. Animals with a low glycogen content were more sensitive to emersion than those with a high content. Species with a shell and those that are relatively big were less sensitive than those without a shell or of small size.The reproductive cycle of benthic animals could be delayed or accelerated by both emersion and submersion.     

Changes in respiration, photosynthesis, adenosine 5'-triphosphate, and total adenylate content of ozonated pinto bean foliage as they relate to symptom expression

The effect of 0.25 to 0.30 microliter per liter ozone on photosynthesis and respiration and on the ATP and total adenylate content of the primary leaves of pinto beans (Phaseolus vulgaris L.) was examined. Changes in these parameters over a 72-hour time period were correlated with the development of symptoms of ozone toxicity. Toxicity symptoms normally appeared within 24 hours. The content of ATP and total adenylates increased immediately following a 3-hour exposure to ozone. Photosynthesis was depressed initially, but returned to normal within 24 hours. Respiration was not always altered initially, but it was significantly stimulated within 24 hours. We interpret the results to mean that the changes in adenylate content and photosynthesis are early events in the initiation of ozone damage and that the change in respiration is a consequence rather than a cause of cellular injury.     

Circadian variations in plasma LH and FSH in juvenile and adult male mice

Experiments were performed to ascertain circadian fluctuations in plasma levels of LH and FSH in juvenile and adult male mice. Animals under natural lighting (11 h day/13 h night) were killed at 1-hour intervals over a 24-hour period. There were large variations in plasma LH concentrations between animals sacrificed within each killing period. Baseline LH levels (values lower than 60 ng/ml) showed a significant 24-hour periodicity in adult males. FSH concentrations exhibited significant diurnal variations in juvenile and adult males. There was significant influence of age on the temporal pattern and 24-hour mean plasma hormone levels.     

Preliminary observations on the collection of baboon oviducal fluid

Five sexually mature and regularly ovulating baboons (Papio cyanocephalus) were subjected to bilateral oviducal cannulation. Prior to failure of the primary cannulation, peri-ovulatory fluids were collected during three menstrual cycles from one animal, during two cycles from a second animal, and during a single cycle from each of two additional animals. These four animals were subsequently recannulated and oviducal fluids obtained during six additional cycles, but tubal fluid collection after the second procedure was generally less satisfactory than following the initial manipulation. Two attempted cannulations in the fifth animal did not result in oviducal fluid collection. Of the 13 menstrual cycles during which tubal fluid was collected, four were apparently anovulatory. Collections from two of these as well as from three ovulatory cycles were characterized by erratic flow and mucous-blood contamination. Tubal fluids were collected without apparent technical interference or serum contamination from six ovulatory and two anovulatory cycles. Maximum volumes (1.77±.34 ml/oviduct/24 hours) of tubal fluids were collected during the 48 hours following the midcycle LH peak. Thereafter, the rate of oviducal fluid collection declined rapidly.     

Further studies on the involvement of the circadian system in photoperiodic control of antifreeze protein production in the beetle Dendroides canadensis

The role of circadian rhythmicity in the photoperiodic time measuring processes regulating antifreeze protein production in the beetle Dendroides canadensis was further investigated. Using “T” experiments larvae were exposed to environmental light cycle periods close to the period length of the endogenous circadian oscillator. The following light cycles were employed: light/dark 8/13, 8/14, 8/16, 8/18 and 8/19 corresponding to period lengths of 21, 22, 24, 26 and 27 h. Larvae maintained in cycles equal to or less than 24 h displayed a characteristic short-day response, showing significantly (P < 0.01) greater antifreeze protein activity than did those measured on the day of collection in late summer. In contrast, a long-day response was observed in larvae maintained under a 26- or 27-h light cycle in that antifreeze protein activity did not differ from that measured on the initial collection date.

The role of photoperiod and temperature in influencing the photoperiodic timing processes were examined with a series of resonance experiments. The first group consisted of a 24, 36, 48, 60 or 72-h light cycle, each with an 8-h photophase at temperatures of 20 or 17°C. Rhythmic increases in antifreeze protein levels at intervals of 24 h occurred under both temperatures. However, the lower temperature displaced the resonance curve in the vertical direction (i.e. increasing % population response) and reduced the difference between peaks and troughs on the resonance curve. Resonance experiments incorporating a 14-h photophase resulted in low antifreeze protein activity under all conditions except a 36-h light cycle in which a 67% induction was observed.

Eight hour resonance experiments were also conducted with D. canadensis collected in early spring to determine whether the circadian system participates in the photoperiodic timing processes influencing the spring termination of antifreeze protein production. Positive resonance results were obtained in that only larvae maintained in cycles of 36 and 60 h displayed significantly (P < 0.01) lower antifreeze activity when compared to animals on the initial collection date.

The combined results emphasize the involvement of the circadian system in the photoperiodic control of antifreeze protein production by D. canadensis during the fall and spring. Furthermore, the induction of antifreeze protein production is a function of light cycle and its waveform (photoperiod). Temperature appears to modify the photoperiodic response in some manner involving the photoperiodic time measuring processes. It is concluded that the photoperiodic response of antifreeze protein production by D. canadensis is dependent upon the entrainment of the circadian system by the light cycle.     

Effects of cycling temperatures on fiber metabolism in cultured cotton ovules

The effects of temperature on rates of cellulose synthesis, respiration, and long-term glucose uptake were investigated using cultured cotton ovules (Gossypium hirsutum L. cv Acala SJ1). Ovules were cultured either at constant 34°C or under cycling temperatures (12 h at 34°C/12 h at 15-40°C). Rates of respiration and cellulose synthesis at various temperatures were determined on day 21 during the stage of secondary wall synthesis by feeding cultured ovules with [¹⁴C]glucose. Respiration increased between 18 and approximately 34°C, then remained constant up to 40°C. In contrast, the rate of cellulose synthesis increased above 18°C, reached a plateau between about 28 and 37°C, and then decreased at 40°C. Therefore, the optimum temperature for rapid and metabolically efficient cellulose synthesis in Acala SJ1 is near 28°C. In ovules cycled to 15°C, respiration recovered to the control rate immediately upon rewarming to 34°C, but the rate of cellulose synthesis did not fully recover for several hours. These data indicate that cellulose synthesis and respiration respond differently to cool temperatures. The long-term uptake of glucose, which is the carbon source in the culture medium, increased as the low temperature in the cycle increased between 15 and 28°C. However, glucose uptake did not increase in cultures grown constantly at 34°C compared to those cycled at 34/28°C. These observations are consistent with previous observations on the responses of fiber elongation and weight gain to cycling temperatures in vitro and in the field.     

Diel variation in diet composition of a riverine fish community

Although diel food habit studies have been undertaken on a number of individual species, few studies have examined diel variation in the diets of fish communities. We examined the diel diet variation and feeding periodicity of a fish community in the Juniata River, Pennsylvania. Nine species, totalling 1,098 fish, were collected at 4-h intervals over a 24-h period in October 1989, in numbers sufficient to describe their diel variation in diet composition. Diel variation in diet composition was evident in all species, as no single prey taxon was dominant in the diet of any species during any 4-h interval. Ephemeropterans were the most important prey taxa for four species of centrarchids, whereas chironomids were the main prey of banded killifish, mimic shiners, and spotfin shiners. Algae was the major component in the diet of spottail shiners, whereas bluntnose minnows contained mostly detritus. Feeding activities of rock bass, redbreast sunfish, and pumpkinseed occurred at low levels throughout the day; peak feeding occurred from 2000 to 0400 hours. Food consumption of smallmouth bass increased throughout the day with peak consumption occurring at 2000 hours. Non-centrarchids fed little during daylight hours and showed peak activity at 2000–2400 h. Construction of a 24-hour diet from six 4-h interval estimates and feeding periodicity data provided a comprehensive representation of the diel feeding ecology of all species collected.     

Ontogeny of the Locomotor Activity Rhythm in the Common Marmoset (Callithrix jacchus)

The ontogeny of locomotor activity rhythm in the common marmoset was studied in three animals, observed during infant and juvenile stages, and in adult age. Animals were kept with their families in outdoor cages under natural temperature, humidity and light cycles. Data were collected from sunrise to sunset, three consecutive days a week, at 5 min intervals randomly distributed in the clock hours, and were recorded as the total of arbitrary cage sections traveled by the animal each interval. Animal 3 was observed continuously one day a week in order to detect less than 2 h period harmonic components. Animals' weekly data series were analyzed by Fourier analysis and Siegel's test to detect significant harmonic components. Results showed a main 24 h period com ponent for all records and a secondary 8 h period component in at least 34% of animal's week data series. The power content of the 24 h component showed an increase with age, reaching some stability near the 16th week of life suggesting that this component is mature at the end of the animal's infant stage. However, for the 8 h component an oscillating pattern was observed following the environmental annual temperature cycle; this may indicate a seasonal modulation of daily locomotor activity profiles.     

Effect of stage of the estrous cycle on interval to estrus after PGF(2alpha) in beef cattle

Effect of stage of the estrous cycle at the time of prostaglandin F(2alpha) (PGF(2alpha)) injection on subsequent reproductive events in beef females was studied in four trials involving 194 animals. Cycling animals were given two injections of 25 mg PGF(2alpha) 11 days apart or, in some cases, the interval was altered to allow the second injection to fall on a specific day of the cycle. Day of estrous cycle at time of the second injection was determined by estrous detection. Interval from the second PGF(2alpha) injection to the onset of estrus (interval to estrus) was shorter (P<.01) in heifers than in cows. Both cows and heifers injected on days 5 to 9 (early cycle) had a shorter (P<.01) interval to estrus (estrus = day 0) than did those injected on days 10 to 15 (late cycle). Conception rate was lower (P<.05) for early-cycle heifers than for late-cycle heifers inseminated by appointment at 80 hours. There was no significant difference in conception rate of early-or late-cycle heifers or cows inseminated according to estrous detection or early- or late-cycle cows inseminated at 80 hours. Progesterone concentrations in blood samples collected in heifers at 4-hour intervals after the second PGF(2alpha) injection on either day 7 or day 14 declined linearly (P<.05) through 36 hours. Day of the estrous cycle at PGF(2alpha) injection had no effect on rate of progesterone decline, even though heifers injected on day 7 had a shorter (P<.05) interval to estrus. All animals whose cycle length was not affected by the second PGF(2alpha) injection were treated on days 5 through 8 of the cycle, indicating that PGF(2alpha) was less effective in regressing the corpus luteum between days 4 and 9 of the cycle than later in the cycle.     

Thermal acclimation of leaf respiration of tropical trees and lianas: response to experimental canopy warming,and consequences for tropical forest carbon balance

Climate warming is expected to increase respiration rates of tropical forest trees and lianas, which may negatively affect the carbon balance of tropical forests. Thermal acclimation could mitigate the expected respiration increase, but the thermal acclimation potential of tropical forests remains largely unknown. In a tropical forest in Panama, we experimentally increased nighttime temperatures of upper canopy leaves of three tree and two liana species by on average 3  ° C for 1 week, and quantified temperature responses of leaf dark respiration. Respiration at 25  ° C (R₂₅) decreased with increasing leaf temperature, but acclimation did not result in perfect homeostasis of respiration across temperatures. In contrast, Q₁₀ of treatment and control leaves exhibited similarly high values (range 2.5–3.0) without evidence of acclimation. The decrease in R₂₅ was not caused by respiratory substrate depletion, as warming did not reduce leaf carbohydrate concentration. To evaluate the wider implications of our experimental results, we simulated the carbon cycle of tropical latitudes (24 ° S–24 ° N) from 2000 to 2100 using a dynamic global vegetation model (LM3VN) modified to account for acclimation. Acclimation reduced the degree to which respiration increases with climate warming in the model relative to a no‐acclimation scenario, leading to 21% greater increase in net primary productivity and 18% greater increase in biomass carbon storage over the 21st century. We conclude that leaf respiration of tropical forest plants can acclimate to nighttime warming, thereby reducing the magnitude of the positive feedback between climate change and the carbon cycle.     

Ontogeny of the Locomotor Activity Rhythm in the Common Marmoset (Callithrix jacchus)

The ontogeny of locomotor activity rhythm in the common marmoset was studied in three animals, observed during infant and juvenile stages, and in adult age. Animals were kept with their families in outdoor cages under natural temperature, humidity and light cycles. Data were collected from sunrise to sunset, three consecutive days a week, at 5 min intervals randomly distributed in the clock hours, and were recorded as the total of arbitrary cage sections traveled by the animal each interval. Animal 3 was observed continuously one day a week in order to detect less than 2 h period harmonic components. Animals' weekly data series were analyzed by Fourier analysis and Siegel's test to detect significant harmonic components. Results showed a main 24 h period com ponent for all records and a secondary 8 h period component in at least 34% of animal's week data series. The power content of the 24 h component showed an increase with age, reaching some stability near the 16th week of life suggesting that this component is mature at the end of the animal's infant stage. However, for the 8 h component an oscillating pattern was observed following the environmental annual temperature cycle; this may indicate a seasonal modulation of daily locomotor activity profiles.     

Influence of low temperature on respiration and contents of phosphorylated intermediates in darkened barley leaves

The aim of this work was to examine the effect of exposure of leaves to low temperatures (5°C) upon the contents of phosphorylated intermediates and respiration in darkened barley (Hordeum vulgare L.) plants which differed in their carbohydrate status. In leaves that had previously been illuminated for 24 hours, there was a large increase in amounts of phosphorylated metabolites at 5°C during the first 3 hours of darkness, compared with control plants kept at 30°C. Hexose phosphates accounted for about two-thirds of this increase, which reached a peak after about 3 hours. At higher temperatures, there was a peak in the amount of fructose 2,6-bisphosphate and the rate of respiration which accompanied the transient increase in phosphorylated intermediates. At 5°C the increase in phosphorylated intermediates was not accompanied by appreciable changes in fructose 2,6-bisphosphate, and there was a rapid decline in the rate of respiration. Leaves that had previously been darkened for 24 hours and that were low in carbohydrate failed to accumulate phosphorylated intermediates when exposed to low temperatures. The results are discussed with respect to the acclimation of carbohydrate metabolism to low temperatures. The results suggest that respiratory carbohydrate metabolism is strictly controlled even when the carbohydrate supply and glycolytic intermediates are abundant. The possibility that accumulation of hexose phosphates may be involved in acclimation of metabolism to low temperature is discussed.     

Effects of light on the cell cycle in the shoot apex ofSilene coeli-rosa L. on the first day of floral induction

Summary 28-day-old plants ofSilene coeli-rosa were exposed, at 1,700 hours, to 5 minutes far-red light, 5 minutes red, 5 minutes far-red followed by 5 minutes red light, or maintained in darkness (short day controls). All plants were exposed to tritiated (methyl-³H-)thymidine for 2 hours (1645–1845) and subsequently sampled at 2-hour intervals for 24 hours. The length of the cell cycle (pulse-label mitoses (PLM) method) and changes in cell number were measured in the shoot apical meristems. The cell cycle in the short day controls was 16–17 hours compared with a mean cell generation time of 18 hours. Exposing plants to far-red light resulted in a shortening of the cell cycle to 11 hours, red light resulted in a shortened cycle of 12 hours whilst far-red, red gave a value of 9 hours. Mean cell generation times following each light treatment were approximetely 2–5 hours longer than the corresponding cell cycle times, suggesting that the shortened cell cycles reverted to longer cycles over the experimental period. Measurements of the proportions of cells with the 2C and 4C amounts of DNA in the apical meristems of unlabeled plants indicated that G1 shortened but G2 lengthened in response to far-red light. A measurement of the labeling index also indicated that S-phase shortened in response to far-red. These data also suggested that red light caused G1 to shorten and G2 to lengthen although the corresponding PLM curve was consistent with a dramatic shortening of G2. Far-red followed by red resulted in decreases in the durations of both G2 and G1.     

Respiration Rate of Steinernema feltiae Infective Juveniles at Several Constant Temperatures

Respiration was measured in dauer stages of the insect-parasitic nematode Steinernema feltiae (= Neoaplectana carpocapsae) at 7, 17, and 27 C. Respiration, Q₁₀, and nematode viability were temperature dependent. Mean O₂ consumption for 5 × 10⁵ nematodes the first 24 hours was 0.27 ml at 7 C, 0.83 ml at 17 C, and 2.68 ml at 27 C. The Q₁₀ was 3.10 for 7-17 C and 3.24 for 17-27 C. Some nematodes died during 2, 14, and 21 days at 27, 17, and 7 C, respectively. The respiratory quotient was below 1 at all temperatures tested. A standard asymptotic model is expressed as oxygen consumed = 2.77 * {1 - exponent[-time * exponent(-B + C * temperature)]}; where 2.77 is the maximum response at 27 C. This model estimates nematode O₂ consumption and viability at storage temperatures between 7 and 27 C. The nematodes died when the O₂ concentration reached 0.5 ml/5 × 10⁵ nematodes. This model may be used to predict O₂ requirements of S. feltiae infective juveniles when stored as a waterless concentrate.     

The effect of viral concentrate addition on the respiration rate of Chaetoceros gracilis cultures and microplankton from a shallow bay (Coliumo, Chile)

Experiments were conducted to test the possible effects of viralconcentrate additions on the respiration rates of both Chaetocerosgracilis and a natural microplankton community (<200 µm)from a shallow bay located in central-south Chile (Coliumo Bay,36°32'S, 72°57'W). Each experiment was started by adding2 ml of viral concentrate to a C. gracilis culture, microplanktoncommunity or bacterioplankton community (nominal size 0.2–1.0µm) contained in a 125 ml borosilicate bottle. The incubationslasted 24 h at in situ temperatures and included a minimum offive replicates and five controls. Respiration was measuredas oxygen consumption using a semi-automatic photometric Winklermethod. Samples were taken from the experimental bottles toassess chlorophyll a, ATP concentration and bacterioplanktonabundance throughout the incubation period. Our results showthat the addition of viral concentrates can affect the respirationrates of both natural microplankton communities and C. graciliscultures. When subjected to a viral concentrate addition, therespiration rates of the natural microplankton community decreasedby 12–50% or increased by 29%, depending on the experiment,whereas bacterioplankton respiration rates increased by 92%and decreased by 78%, and C. gracilis rates increased by ~4%and decreased by ~7%.     

The effect of temperature on flight initiation in the cockroach Periplaneta americana

The effect of temperature during development of the flight system of the American cockroach was tested. Animals were raised at three different temperatures from egg cases to adulthood then various parameters of flight were tested. Animals raised at cooler temperatures were found to require significantly stronger wind puffs to initiate flight than did animals raised in warmer temperatures. Some animals were raised at one temperature during embryonic development (i.e. while the animals were still in egg cases) and then switched to a different temperature for nymphal development. In these cases only the temperature experienced during embryonic development had a significant permanent effect on flight. Parameters associated with pattern generation such as interburst interval were not affected by temperature during either developmental period.     

Nitrogen fixation and respiration by root nodules ofAlnus rubra Bong.: Effects of temperature and oxygen concentration

Summary Using a root nodule cuvette and a continuous flow gas exchange system, we simultaneously measured the rates of carbon dioxide evolution, oxygen uptake and acetylene reduction by nodules ofAlnus rubra. This system allowed us to measure the respiration rates of single nodules and to determine the effects of oxygen concentration and temperature on the energy cost of nitrogen fixation. Energy cost was virtually unchanged (2.8–3.5 moles of carbon dioxide or oxygen per mole of ethylene) from 16 to 26°C (pO₂=20 kPa) while respiration and nitrogenase activity were highly temperature dependent. At temperatures below 16°C, nitrogenase activity decreased more than did respiration and as a result, energy cost rose sharply. Acetylene reduction ceased below 8°C. Inhibition of nitrogenase activity at low temperatures was rapidly reversed upon return to higher temperatures. At high temperatures (above 30°C) nitrogenase activity declined irreversibly, while respiration and energy cost increased.Energy cost was nearly unchanged at oxygen partial pressures of 5 to 20 kPa (temperature of 20°C). Respiration and nitrogenase activity were strongly correlated with oxygen tension. Below 5 kPa, acetylene reduction and oxygen uptake decreased sharply while production of carbon dioxide increased, indicating fermentation. Fermentation alone was unable to support nitrogenase activity. Acetylene reduction was independent of oxygen concentration from 15 to 30 kPa. Nitrogenase activity decreased and energy cost rose above 30 kPa until nearly complete inactivation of nitrogenase at 70–80 kPa. Activity declined gradually, such that acetylene reduction at a constant oxygen concentration was stable, but showed further inactivation when oxygen concentration was once again increased. Alder nodules appear to consist of a large number of compartments that differ in the degree to which nitrogenase is protected from excess oxygen.Supported by United States Department of Agriculture Grant 78-59-2252-0-1-005-1     

Phosphoenolpyruvate carboxylase from spinach leaf tissue: inhibition by sulfite ion

Respiration and gas exchange in the light were studied manometrically with tissue slices from stem material of Opuntia basilaris Engelm. and Bigel. Dark respiration rates were greater in young stems than in mature stems. The timing of the experiment in the day/night cycle influences the magnitude and pattern of respiration and gas exchange in the light. Net dark respiration has a temperature optimum between 35 and 40 C, and is maintained at 60% of the control rate in tissue equilibrated with experimental osmotic potentials of −25 bars. Net gas exchange in the light is regulated by the titratable acidity of the tissue and by the tissue temperature. Increased rates of net CO₂ evolution and net O₂ consumption occur in the light with high levels of titratable acidity and high temperatures. An efflux of CO₂ and influx of O₂ occur following light/dark transitions. These patterns are reversed following dark/light transitions. Similar results were demonstrated at 15, 25, and 35 C, and are interpreted as a mechanism of adaptation to desert environments.     

Circadian rhythm of serum and tissue lipids in fed and fasted rats

The oscillations of the free fatty acid concentration in the serum and white (epididymal) adipose tissue, of triglycerides in the serum and liver, of total serum, liver and adrenal cholesterol and of serum phospholipids were studied at 3-hour intervals for a period of 24 hours in fed male Wistar rats and in animals fasted for 24 hours (both adapted to an illumination regimen of 12 hours' light and 12 hours' darkness. The rhythm--studied by means of the cosinor analysis--was present in most of the given parameters; it was not recorded in the liver triglycerides and serum phospholipids of fasted rats and in the adrenal cholesterol of fed animals. Apart from the circadian rhythm, many parameters distinctly displayed an ultradian rhythm, mainly an approximately 12-hour period. In general, one day's starvation did not significantly affect the course of the circadian oscillations of the given indicators of rat lipid metabolism.