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.
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
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)