Two weeks-old maize (Zea mays cv. XL-72.3) plants were exposed to Al concentrations 0 (Al0), 9 (Al9), 27 (Al27) or 81 (Al81) g m-3 for 20 d in a growth medium with low ionic strength. Thereafter, the Al concentration-dependent interactions on root nitrate uptake, and its subsequent reduction to ammonia in the leaves were investigated. Al concentrations in the roots sharply increased with increasing Al concentrations while root elongation correspondingly decreased. Root fresh and dry masses, acidification capacity, and nitrate and nitrogen contents decreased from Al27 onwards, whereas leaf nitrogen, nitrate, nitrite, and ammonia concentrations decreased starting with Al9. Electrolytic conductance increased by 60 % in root tissues from Al0 to Al81 but it did not increase significantly in the leaves. In Al9, Al27, and Al81 plants a decrease in shoot fresh and dry masses was observed. Al concentrations between 0 and 27 g m-3 increased net photosynthetic rate, stomatal conductance, and the quantum yield of photosynthetic electron transport, whereas the intercellular CO2 concentration was minimum in Al27 plants. In the leaves, nitrate reductase (E.C. 1.6.6.1) activity increased until Al27, and nitrite reductase (E.C. 1.6.6.4) activity until Al81. Hence there may be an Al mediated extracellular and intracellular regulation of root net nitrate uptake. Nitrate accumulation in the roots affects the translocation rates and, therefore, the nitrate concentration in the leaves. The in vivo reducing power generated by the photosynthetic electron flow does not limit nitrate to ammonia reduction, and the increase of maximum nitrate and nitrite reductase activities parallels the decreasing nitrate, nitrite, and ammonia concentrations. and F. C. Lidon, J. C. Ramalho, M. G. Barreiro.
When spectators see a baroque play staged with use of period means of expression, they often appreciate fine form, but lack emotions. Dealing with Jesuit school plays from the first half of the 18th century, whose theme is true friendship, this article illustrates that baroque drama actually combines stylized form and strong emotions. It was also the main aim of baroque theatre: to transfer the emotions through this form., Magdaléna Jacková., and Obsahuje bibliografické odkazy
The spectroscopic monitoring programs carried out by the Spectroscopy Group of the German "Vereinigung der Sternfreunde" are reviewed in light of current research. Potential benefits for the professional community in collaborating and obtain long-term monitoring data otherwise unaccessible due to telescope time restrictions are summarized. The contribution highlights results on specific objects of wide interest, such as the well investigated Be stars ≥ Tauri or the S Doradus type variable P Cygni.