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5792. Daily irradiance and feedback inhibition of photosynthesis at elevated carbon dioxide concentration in Brassica oleracea

Creator:
Bunce, J. A. and Sicher, R. C.
Format:
bez média and svazek
Type:
model:article and TEXT
Subject:
collard, irradiance, kohlrabi, saccharides, stomatal conductance, and variety differences
Language:
Multiple languages
Description:
The fundamental cause of down-regulation of photosynthesis at elevated carbon dioxide concentration (EC) is thought to be a slower rate of utilization of saccharides than their stimulated rate of production, but there are few studies directly supporting this idea under field conditions. We hypothesized that within Brassica oleracea, down-regulation would not occur in kohlrabi because it has a large sink for saccharides in an enlarged stem, but would occur in collards, which lack this sink. Field tests were consistent with this hypothesis. In collards, the degree of down-regulation of photosynthesis in plants grown at EC varied depending on the daily integral of photosynthetically active radiation (PAR) of the day prior to the measurement of photosynthetic capacity, as did leaf saccharide content. However, EC did not result in lower leaf contents of chlorophyll, soluble protein, ribulose-1,5-bisphosphate carboxylase, or nitrate in collards, nor was there any evidence of a triose phosphate utilization rate limiting photosynthesis. Experiments in controlled environment chambers confirmed that there was a threshold response for the down-regulation of photosynthesis in collards at EC to the PAR of the previous day, with down-regulation only occurring above a minimum daily integral of PAR. Down-regulation of photosynthesis could be induced in plants grown at ambient carbon dioxide by a single night at low temperature or by a single day with high PAR and EC. In the controlled environment study, the degree of down-regulation of photosynthesis was highly correlated with leaf glucose, fructose, and sucrose contents, and less well correlated with starch content. Hence down-regulation of photosynthesis at EC in collards in the field represented feedback inhibition from the accumulation of soluble saccharides and day-to-day variation in its occurrence was predictable from the weather. and J. A. Bunce, R. C. Sicher.
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public

5793. Daily profiles of steroid hormones and their metabolites related to food intake

Creator:
Rácz, B., Michaela Dušková, Karel Vondra, Šrámková, M., Hill, M., and Luboslav Stárka
Format:
print, bez média, and svazek
Type:
article, články, model:article, and TEXT
Subject:
Fyziologie člověka a srovnávací fyziologie, steroidní hormony, steroid hormons, daily pattern, food intake, ghrelin, orexin, SHBG, 14, and 612
Language:
English
Description:
The aim of this study was to look for changes in the daily profile of steroid hormones after standardized food intake. Eight young women not taking contraceptives were followed from 5:30 a.m. till 9:30 p.m. before and 1 and 2 h after eating breakfast, snack, lunch, the second snack and dinner. The differences in steroid levels before and after meals were evaluated. As expected, glucose, C-peptide and ghrelin levels changed postprandially. The steroid hormones cortisol, progesterone, pregnenolone and dehydroepiandrosterone showed a decrease after main meals, whereas testosterone and dihydrotestosterone showed no significant dependence on food intake. Estrogen levels did not exhibit a significant nycthemeral rhythm, but estradiol decreased after main meals. In our study the known nycthemeral rhythm of LH, FSH, cortisol, progesterone and pregnenolone after food intake were confirmed, but significant changes after meals were also observed in the levels of cortisol, dehydroepiandrosterone, estradiol and SHBG., B. Rácz, M. Dušková, K. Vondra, M. Šrámková, M. Hill, L. Stárka., and Obsahuje bibliografii
Rights:
http://creativecommons.org/publicdomain/mark/1.0/ and policy:public

5794. Daily relative sunspot numbers 1749 - 1818: reconstruction of missing observations

Creator:
Letfus, Vojtěch
Format:
bez média and svazek
Type:
model:article and TEXT
Subject:
daily observations of the Sun, sunspots, and method of interpolation
Language:
Czech
Description:
In the time interval 1749-1818 a great part of missing daily relative sunspot numbers was reconstructed by nonlinear two-step method of interpolation. In the first step directly interpolated were gaps not longer than five days. In the second step the data were sorted in the so called Bartels scheme, i.e. in rows of a length of 27 days subsequently ranged in a matrix. In thís step the missing data of longer gaps were interpolated columnwise, i.e. missing value at any position was interpolated from the data at same column positions of preceeding and folloving rows. The interpolation was limited to sequences of no more than four missing data. The procedure enables interpolate long gaps and simultaneously respect the 27-day variation of solar activity. A part of missing data in the intervals, where the frequency of observations was very low and has not fullfilled the limitations of the interpolation method. was not interpolated. Annual tables of daily data are given in Appendix A, monthly and annual means in Appendix B, and annual plots of daily data in Appendix C. The differences between monthly and annual means of the primary observations and of the data completed by interpolation fluctuate around zero. The amplitude of fluctuations depends inversely on the frequency of observations. Most conspicuous are the deviations in the time interval 1776-1795, when the frequency of observations was wery low or almost zero. The dispersion of monthly differences σ is ±13.7 R and of annual differences ±9.3 R. The results give insight on the reliability of relative sunspot numbers in the investigated time interval. and Součástí článku jsou 2 apendixy: - Appendix A Daily relative sunspot numbers 1749-1818 (s. 7-42) - Appendix B Monthly and annual means of relative sunspot numbers 1749-1818 (s. 43-66)
Rights:
http://creativecommons.org/publicdomain/mark/1.0/ and policy:public

5795. Daily relative sunspot numbers 1818-1848: reconstruction of missing observations

Creator:
Letfus, Vojtěch
Format:
bez média and svazek
Type:
model:article and TEXT
Subject:
observations, sunspots, and method of interpolation
Language:
Czech
Description:
The missing daily relative sunspot numbers in the time interval 1818-1848 were reconstructed by the nonlinear two-step method of interpolation. In the first step directly interpolated gaps were not longer than five days. In the second step, the data were sorted in the so called Bartels scheme, i.e. in rows of the length of 27 days subsequently ranged in a matrix. The missing data of longer gaps were interpolated columnwise, i.e. the missing value at any position was interpolated from the data at the same positions of preceeding and following rows. The procedure enables to interpolate long gaps and simultaneously respect the 27-day data variation. The Appendix A contains annual tables of daily data, Appendix B gives monthly and annual means and Appendix C presents simutaneously annual plots of primary data and of those reconstructed by interpolation. The differences between the monthly and annual means of primary data and of data completed by interpolation are small and fluctuate around zero. Only in the time interval 1835-1842, when the frequency of observations was lowered, the amplitude of fluctuations is enhanced. The dispersion of monthly differences σ is ±4.3 R and of annual means ±1,1 R. The two-step method of interpolation was tested on the daily data series in the time interval 1918-1948. The sequence of missing daily data in the years 1818-1848 represents a masking function. The differences between the monthly and annual means of primary and modified data are small with fluctuations around zero and with dispersion σ for monthly differences ±2.7 R and for annual differences ±0.6 R. The small dispersion gives evidence about a high reliability of relative sunspot numbers derived from observations in the years 1818-1848 and also about the effectivity of the two-step method of interpolation. and Materiál obsahuje 3 (nestránkované) apendixy: - Appendix A Daily relative sunspot numbers 1818-1848 [s. 6-22] - Appendix B Monthly and annual means of relative sunsppot numbers 1818-1848 [s. 23-24] - Appendix C Plots of daily relative sunspot numbers 1818-1848 [s. 25-56]
Rights:
http://creativecommons.org/publicdomain/mark/1.0/ and policy:public

5796. Daily rhythm in rat pineal catecholamines

Creator:
Ivan Ahlers, Bernadetta Pástorová, Peter Solár, and Eva Ahlersová
Format:
print, bez média, and svazek
Type:
article, články, model:article, and TEXT
Subject:
Fyziologie člověka a srovnávací fyziologie, fyziologie, physiology, rat pineal, catecholamines, daily oscillations, 14, and 612
Language:
English
Description:
A daily rhythm in the oscillations of pineal dopamine, norepinephrine and epinephrine content was found in male Wistar:Han rats. The acrophases of the oscillations were localized in the first half of the dark period and generally higher values were found in the dark part of the day., I. Ahlers, B. Pástorová, P. Solár, E. Ahlersová., and Obsahuje bibliografii
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public

5797. Daily temperature drop prevents inhibition of photosynthesis in tomato plants under continuous light

Creator:
Ikkonen, E. N., Shibaeva, T. G., Rosenqvist, E., and Ottosen, C.-O.
Format:
print, bez média, and svazek
Type:
model:article and TEXT
Subject:
fotosyntéza, photosynthesis, chlorophyll fluorescence, gas exchange, leaf area, photodamage, stomatal conductance, 2, and 581
Language:
Multiple languages
Description:
The negative effects of continuous light (CL) seen in tomato plants are often claimed to be linked to effects of offsetting the diurnal rhythm. In this study we tested whether a short-term daily temperature drop prevents the decreased photosynthetic performance seen in tomato plants grown under CL. Tomato (Lycopersicon esculentum Mill.) plantlets were grown at constant temperature of 26°C under 16-h day (16D) or 24-h day (24D) at 150 μmol m-2 s-1 PPFD. Some 24D plants were treated daily by 2 h temperature drop from 26 to 10°C (24D+DROP). Physiological disorder, such as severe leaf chlorosis, a large decrease in net photosynthetic rate, maximal quantum yield of PSII photochemistry, and the effective quantum yield of PSII photochemistry were observed in 24D, but not in 16D and 24D+DROP plants. The daily 2-h drop in temperature eliminated a negative effect of CL on photosynthesis and prevented the development of leaf chlorosis in tomato plants. This could be due to a change in carbohydrate metabolism as the short drop in temperature might allow maintenance of the diurnal rhythms., E. N. Ikkonen, T. G. Shibaeva, E. Rosenqvist, C.-O. Ottosen., and Obsahuje seznam literatury
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public

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