Diurnal variations in two shallow ponds in Delhi,India

Summary Observations on the diurnal variations in water chemistry and plankton in two shallow ponds, show large fluctuations in oxygen, pH and correlated changes in carbonate concentrations. A dissolved oxygen concentration of 28.2 p.p.m. was recorded in one pond. Plankton counts suggest that the diurnal migration pattern is not similar to that often found in temperate waters. Nocturnal depletion of oxygen killed fish in one pond.Department of Zoology, University of Delhi.     

Diurnal variation of the delta 13C of pine needle respired CO2 evolved in darkness

The delta 13C of pine needle CO2 evolved in darkness (delta 13Cr) for slash pine trees (Pinus elliottii) was determined by placing recently collected pine needles in darkness and collecting respired CO2 over a short time period (<15 min). Delta 13Cr measurements were made over several 24 h periods to test the hypothesis that significant variation in delta 13Cr would be observed during a diurnal cycle. The delta 13Cr measurements from the 24 h time series trials showed a consistent midday 13C-enrichment (5-10 per thousand) relative to bulk biomass. The delta 13Cr values became more 13C-depleted at night and following shading, and approached bulk-biomass delta 13C values by dawn. The effect of night-time respired 13C-enriched CO2 on the delta 13C value of the remaining assimilate is shown to be minimal (13C depleted by 0.22 per thousand) under field conditions for P. elliottii needles.     

Diurnal variations in cycling kinematics

Physiological and biomechanical constraints as well as their fluctuations throughout the day must be considered when studying determinant factors in the preferred pedaling rate of elite cyclists. The aim of this study was to monitor the diurnal variation of spontaneous pedaling rate and movement kinematics over the crank cycle. Twelve male competitive cyclists performed a submaximal exercise on a cycle ergometer for 15 min at 50% of their W(max). Two test sessions were performed at 06:00 and 18:00 h on two separate days to assess diurnal variation in the study variables. For each test session, the exercise bout was divided into three equivalent 5-min periods during which subjects were requested to use different pedal rates (spontaneous cadence, 70 and 90 rev min(-1)). Pedal rate and kinematics data (instantaneous pedal velocity and angle of the ankle) were collected. The results show a higher spontaneous pedal rate in the late afternoon than in the early morning (p < 0.001). For a given pedal rate condition, there was a less variation in pedal velocity during a crank cycle in the morning than in the late afternoon. Moreover, diurnal variations were observed in ankle mobility across the crank cycle, the mean plantar flexion observed throughout the crank cycle being greater in the 18:00 h test session (p < 0.001). These results suggest that muscular activation patterns during a cyclical movement could be under the influence of circadian fluctuations.     

Diurnal variations in the carbon chemistry of two acidic peatland streams in north-east Scotland

1. Two acidic peatland upland streams in north‐east Scotland draining catchments of 1.3 and 41.4 km² were sampled each season for 2 years to investigate diurnal variations in dissolved and gaseous forms of carbon. Stream metabolism, alkalinity, discharge, pH, air and water temperatures were measured to aid data interpretation. 2. Free CO₂ showed marked diurnal variation with lowest concentrations during the period from late morning to early afternoon and highest during the hours of darkness. Although alkalinity and pH also showed some diurnal fluctuations, in comparison with other more productive alkaline systems, variation was small. Dissolved organic carbon (DOC) showed no significant diurnal pattern. However, significant changes in stream discharge influenced DOC concentrations, as well as over‐riding diurnal patterns of free CO₂, alkalinity and pH. 3. The highest diurnal ratios (maximum concentration/minimum concentration) in CO₂, gross primary productivity (GPP) and community respiration (CR) occurred in spring and summer and the lowest in autumn and winter. Variation in biotic in‐stream processes caused changes in CO₂ concentrations and temperature affected both the solubility of CO₂ and changes in up‐stream CO₂ inputs. There was no significant difference in diurnal fluctuations between the two orders of stream studied. 4. The mean GPP (as CO₂) was 0.81 g CO₂ m^?2 day^?1 and mean CR 2.67 g CO₂ m^?2 day^?1. The mean primary production/respiration (P/R) ratio was 0.26 ± 0.09 and 0.33 ± 0.15 in the first and second order streams, respectively. These values are low compared with published data because these heterotrophic headwater streams are dominated by benthic respiration and upstream allochthonous inputs with little autotrophic metabolism, particularly during the colder autumn and winter months. 5. The results have implications for the calculation of dissolved inorganic carbon (DIC) fluxes in streamwater. Samples taken during daylight hours tend to have lower concentrations of free CO₂ and HCO₃^? than samples taken during darkness. During spring, concentrations of free CO₂ were measured up to 2.4 (annual mean 1.8) times higher at night than during the day at a similar discharge. It is suggested that fluxes based on daytime measurements alone will under‐estimate the annual flux of these determinands in streamwater by as much as 40%.     

Effects of water stress on oxygen, hydrogen and carbon isotope ratios in two species of cotton plants

Abstract. Two cotton species ( Gossypium hirsutum L. cv. SJ-2 and Gossypium barbadence cv. S-5) were grown under irrigated (wet) and non-irrigated (dry) conditions in the same field. Leaf water was enriched in ¹⁸O and deuterium in the dry treatment relative to the wet treatment for both species. Only in plants of S-5 was a similar enrichment observed in leaf cellulose. In both species, the isotopic composition of leaf cellulose must reflect the isotopic composition of the actual water pool involved in cellulose synthesis. Therefore, our observations indicate that one species (SJ-2) can maintain a relative isolation of this water pool from direct evapotranspirational effects. Such plant species will more faithfully record, in the isotopic composition of organic matter, the isotopic composition of ground water. In contrast, the isotopic composition of organic matter in plants such as S-5 could be used as an integrated signal reflecting humidity conditions during growth. Water use efficiency, based on seed-cotton yield and total water applied, correlated linearly with differences in carbon isotopic ratios between species in both the wet and dry treatments and between treatments in each species.     

Diurnal variations in lipids of bracken fronds

The galactolipids, sulpholipid and phosphatidyl glycerol in the fronds of bracken show diurnal variations of 50–100%, with a maximum at about 1600 hr.     

Diurnal and seasonal trends of water relations in five co-occurring chasmophytic species

The present study examines the seasonal and diurnal patterns of water management by plant species inhabiting the wall fissures of the ancient castle of Patras. Their water status (water potential), stomatal behaviour (leaf resistance and transpiration rate) as well as tissue water relations (turgor loss point, osmoregulation capability and cell wall elasticity) were recorded in relation to season, daytime and respective environmental conditions. Despite some minor deviations, all five species exhibited a water spending strategy with high diurnal transpiration rates through seasons, limited only by the generally low light intensities prevailing at the northwest-facing vertical walls. Progressive shortage of water during summer resulted in the reduction of transpiration in four species. Diurnal water losses caused a reduction of water potential until midday or dusk, which further decreased with the progress of the dry period. However, predawn water potential remained high through all seasons. The above finding, together with the high transpiration, was unexpected for species growing in a very hostile environment as far as water supply is regarded. It could be partly explained by the recently found ability of all five species to absorb dew from leaf surfaces. However, such plants should also possess mechanisms to take up water efficiently from a rather dry substrate. Indeed, pressure–volume analysis revealed substantial seasonal changes in osmoregulatory capacity and minor changes in cell wall elasticity of leaf tissue. Both changes facilitate (the mechanism differs) water uptake from the wall-fissure substrate during the dry period. Although the relative contribution of the two mechanisms was different, they both allowed plants to maintain turgor and thus growth throughout their growing season.     

Diurnal variations of plasma testosterone in men

Plasma testosterone (T) levels were assayed by a Competitive Protein Binding (CPB) technique in a group of 31 healthy males. In 22 subjects a single blood sample was taken between 8:00 and 9:00 A.M. and the mean T concentration was 6.84 ± 2.11 ng/ml. In the other 9 normal men, blood samples were taken every 4 hours. The existence of temporal variations for testosterone was confirmed by finding the highest mean plasma levels at 4:00 A.M. (9.28 ± 1.17 ng/ml) and lowest mean levels at 8:00 P.M. (2.66 ± 0.52 ng/ml).     

Diurnal and seasonal variations in the photosynthetic performance and water relations of two co-occurring Mediterranean shrubs,Erica multiflora and Globularia alypum

Diurnal and seasonal fluctuations in the photosynthetic performance and water relations of two co-occurring Mediterranean shrubs, Erica multiflora and Globularia alypum were monitored throughout two consecutive years at Garraf Natural Park in north-east Spain. Leaf gas exchange rates, chlorophyll fluorescence and shoot water potentials were measured once each season. Leaf nitrogen and carbon concentrations, leaf delta13C and delta15N and specific leaf area (SLA) were also measured once a year (August) on well developed mature leaves. Globularia alypum experienced seasonal fluctuations in their water potential, with the lowest values recorded in summer, whereas E. multiflora did not show significant differences in water potential among seasons. Moreover, lower water potentials were found in G. alypum than in E. multiflora throughout the entire study, suggesting that the latter behaved as a drought-avoiding species, whereas the former tolerated lower water potentials. In both species, maximum leaf gas exchange rates were observed in autumn and secondarily in spring; in contrast, photosynthetic and transpiration rates reached absolute minima in summer. The stronger fluctuations in water potential and leaf gas exchange rates found in G. alypum compared to E. multiflora, suggest that G. alypum is, sensu Levitt (1980), a water spender, whereas E. multiflora is a water conservative. This hypothesis is further supported by a higher integrated water-use efficiency (higher delta13C values) and a higher degree of sclerophylly (lower SLA) in E. multiflora in comparison with G. alypum. Globularia alypum showed higher leaf gas exchange rates and higher predawn potential photochemical efficiency (Fv/Fm) than E. multiflora during most of the study. In spring and autumn, predawn Fv/Fm values were within the optimal range, whereas chronic photoinhibition in summer and winter was detected in both species. However, whereas both species could maintain positive photosynthetic rates in winter, frequent negative values were found in summer, suggesting higher levels of stress during the drought period. These results together with the high correlations that were found between the net photosynthetic rates and several parameters of water availability (accumulated rainfall, soil moisture or midday water potential) provided further evidence of the key role of water availability in the regulation of the photosynthetic rates in these Mediterranean species. Warmer and drier conditions in future decades, as a consequence of climate change, may alter the present, slight competitive advantage of G. alypum and the fitness of both shrub species within semi-arid Mediterranean environments.     

Diurnal variations in learning performance in chickens

Diurnal variations in the learning performance of young chicks were investigated using a visual discrimination task which requires birds to discrminate grains from a background of pebbles. Chicks accustomed to receiving fresh food daily in the morning were found to learn well during the day, in that they pecked almost exclusively at grains; but during the night they pecked indiscriminately at grains and pebbles. This occurred even though food was available ad libitum. Chicks accustomed to receiving fresh food daily in the evening learnt the task during the day, and also late at night. Thus the shape of the performance cycle depends in part on environmental factors. Other factors, such as activity, which may contribute to, or co-vary with, this variation in learning performance were investigated.     

Nucleotide variation in genes involved in wood formation in two pine species

Nucleotide diversity in eight genes related to wood formation was investigated in two pine species, Pinus pinaster and P. radiata. The nucleotide diversity patterns observed and their properties were compared between the two species according to the specific characteristics of the samples analysed. A lower diversity was observed in P. radiata compared with P. pinaster. In particular, for two genes (Pp1, a glycin-rich protein homolog and CesA3, a cellulose synthase) the magnitude of the reduction of diversity potentially indicates the action of nonneutral factors. For both, particular patterns of nucleotide diversity were observed in P. pinaster (high genetic differentiation for Pp1 and close to zero differentiation associated with positive Tajima's D-value for CesA3). In addition, KORRIGAN, a gene involved in cellulose-hemicellulose assembly, demonstrated a negative Tajima's D-value in P. radiata accompanied by a high genetic differentiation in P. pinaster. The consistency of the results obtained at the nucleotide level, together with the physiological roles of the genes analysed, indicate their potential susceptibility to artificial and/or natural selection.     

两种乳牛肝菌属菌根食用菌与马尾松的共生特征

菌根食用菌（edible mycorrhizal fungi,EMF）是兼具生态价值和经济价值的大型真菌,其对林木健康、森林生态系统的稳定性及林下经济的发展至关重要。本研究以贵州地区马尾松Pinus massoniana林2种乳牛肝菌属Suillus EMF为研究对象,研究了其子实体及其与马尾松形成的菌根的形态特征,调查了其子实体的发生规律及其与温度和降雨的关系。研究结果表明：粘盖乳牛肝菌S. bovinus和褐环乳牛肝菌S. luteus可同时在马尾松林发生。粘盖乳牛肝菌和褐环乳牛肝菌与马尾松形成的菌根均呈珊瑚状,其中粘盖乳牛肝菌形成的菌根表面光滑无根外菌丝但具有根外菌索,褐环乳牛肝菌形成的菌根具有密集的根外菌丝但无根外菌索。粘盖乳牛肝菌和褐环乳牛肝菌子实体具有较长的发生期、产量较大,且具有错峰发生的特点。相对于降雨,温度是这2种乳牛肝菌子实体发生的主要限制因素。     

Diurnal variations of serum GM-CSF levels

We aimed to investigate the daily variations of serum granulocyte-macrophage colony-stimulating factor (GM-CSF) levels and to correlate them with peripheral blood cells counts. Venous blood samples from eleven healthy volunteers were taken four times a day, being at 08:00, 14:00, 20:00 and 02:00h and serum GM-CSF levels measured by ELISA. We could not find a significant overall difference among GM-CSF levels at four different times of the day using the Friedman test. On the other hand, serum GM-CSF levels at night (20:00h) were found to be significantly increased when compared to the morning levels (08:00h) using the Wilcoxon test (P=0. 022). The levels of lymphocytes and white blood cells (WBCs) at 20:00h were also higher than the morning levels (08:00h) as expected. While there was a strong relationship between the morning levels of GM-CSF (08:00h) and all measurements of peripheral blood cells during the day, the levels of GM-CSF measured at 02:00, 14:00 and 20:00h were found to be significantly correlated with only the WBC levels. It was concluded that there may be a significant difference between morning and night levels of GM-CSF and morning levels of GM-CSF may be more important in the regulation of WBC counts during the day. These variations warrant further studies about diurnal rhythms of haematopoiesis chronotherapy with CSFs.     

Diurnal temperature-related variations in photosynthetic enzyme activities of two C<Subscript>4</Subscript> species of Chenopodiaceae grown in natural environment

The effects of the diurnal variations in ambient temperature on some C₃ and C₄ enzymes in the Salsola dendroides and Suaeda altissima species of Chenopodiaceae family were studied during the intensive vegetation period. Activities of phosphoenolpyruvate carboxylase (PEPC) and cytosolic aspartate aminotransferase (AsAT) were shown to decrease in both species in the afternoon and evening. The activity of the mitochondrial AsAT decreased in S. altissima, remained relatively constant in S. dendroides during the day. The activity of alanine aminotransferase was high in the S. dendroides species in the morning and evening and decreased in the S. altissima species by the evening. Glucose-6-phosphate activated PEPC in both species throughout the day. The study of the redox status-regulated C₃ enzymes showed temperature-related increases in NADP-glyceraldehyde 3-phosphate dehydrogenase activity in both plants, in fructose-2,6-bisphosphatase activity in the S. altissima species, and in NADP-MDH activity in the S. dendroides species in the afternoon.     

Diurnal variations of potassium content in lucerne plants

Diurnal changes in K content in leaf blades, petioles, stems and roots of eleven lucerne genotypes were followed. Significant positive correlations between changes in K content in petioles and upper half of stems and significant negative correlations between changes of K content in leaf blades and lower half of stems reflected rapid K movement. The velocity — up to 60 μmol g−1 (f.m.)h−1 — of changes in K content from leaf blades to lower part of stems and the other way round showed that long distance phloem transport occurred. Only moderate increase of K content contemporarily took place in roots. When total K amount in the whole plant was calculated then K uptake alternatively with K release were noticed during the day. Average K release reached 1.48 μmol g−1 (f.m.) h−1. The rate of K movement correlated with irradiance and physiological activity of plants. The time course of K movement was uniform in plants of the same strain and it differed partially in different strains.     

Acetylated tubulin is found in all microtubule arrays of two species of pine

Summary The distribution of acetylated tubulin in microtubule arrays of conifer cells was investigated by immunofluorescence techniques with 6-11B-1, a monoclonal antibody specific for posttranslationally acetylated -tubulins. In methacrylate sections ofPinus radiata andPinus conforta root tip cells, acetylated tubulin was detected in mitotic spindles, phragmoplasts, and cortical microtubules. Furthermore, staining of isolated, intact cells ofP. radiata andP. contorta indicated that all microtubule structures, including preprophase bands, prophase, metaphase and anaphase spindles, and phragmoplasts, contained some acetylated tubulin, and that the intensity of staining with 6-11B-1 was variable. For example, preprophase bands were lightly labelled, kinetochore fibres of anaphase spindles and phragmoplasts were heavily stained, and metaphase spindles had a granular appearance suggesting discontinuous acetylation of their constituent microtubules. This first report of the presence of acetylated tubulin in conifer cells is in contrast to our results with two species of angiosperms where no acetylated tubulin was detected. The significance of this and the variability of the intensity of staining in conifer arrays is discussed in terms of microtubule dynamics.