Chloroplast thylakoid contains several membrane-bound protein kinases that phosphorylate thylakoid polypeptides for the regulation of photosynthesis. Thylakoid protein phosphorylation is activated when the plastoquinone pool is reduced either by light-dependent electron flow through photosystem 2 (PS2) or by adding exogenous reductants such as durohydroquinone in the dark. The major phosphorylated proteins on thylakoid are components of light-harvesting complex 2 (LHC2) and a PS2 associated 9 kDa phosphoprotein. Radiation inactivation technique was employed to determine the functional masses of various kinases for protein phosphorylation in thylakoids. Under the photosynthetically active radiation (PAR), the apparent functional masses of thylakoid protein kinase systems (TPKXs) for catalyzing phosphorylation of LHC2 27 and 25 kDa polypeptides were 540±50 and 454±35 kDa as well as it was 448±23 kDa for PS2 9 kDa protein phosphorylation. Furthermore, the functional sizes of dark-regulated TPKXs for 25 and 9 kDa proteins were 318±25 and 160±8 kDa. The 9 kDa protein phosphorylation was independent of LHC2 polypeptides phosphorylation with regard to its TPKX functional mass. Target size analysis of protein phosphorylation mentioned above indicates that thylakoid contains a group of distinct protein kinase systems. A working model is accordingly proposed to interpret the interaction between these protein kinase systems. and S. C. Lee ... [et al.].
Net photosynthetic rate, radiation use efficiency, chlorophyll (Chl) fluorescence, photochemical reflectance index (PRI), and leaf water potential were measured during a 25-d period of progressive water deficit in quinoa plants grown in a glasshouse in order to examine effects of water stress and ontogeny. All physiological parameters except Fv/Fm were sensitive to water stress. Ontogenic variations did not exist in Fv/Fm and leaf water potential, and were moderate to high in the other parameters. The complete recovery of photosynthetic parameters after re-irrigation was related with the stability in Fv/Fm. PRI showed significant correlation with predawn leaf water potential, Fm', and midday Fv/Fm. Thus PRI and Chl fluorescence may help in assessing physiological changes in quinoa plants across different developmental stages and water status. and T. Winkel, M. Méthy, F. Thénot.
Investigations conceming the deactivation of radiant energy absorbed by the pigments of photosynthetic organisms, either through emitting the fluorescence and delayed luminescence or converting into heat in slow or fast processes, are described. These paths of deactivation can be established by measurements of the absorption, fluorescence excitation, delayed emission and photoacoustic spectra in the same sample. The slow paths of radiative and non-radiative deactivation are of a speciál interest. Even with complex photosynthetic samples it is possible to evaluate slow and fast components of the thermal deactivation from photoacoustic spectra taken at various frequencies of the radiation modulation. In all samples containing reaction centres, anteima complexes or their models, at least a part of delayed deexcitation is due to ionization and delayed recombination of pigments. This is confirmed by photopotential generation for the same samples located in a photoelectrochemical cell. The methods of investigating slow processes of radiative and radiationless deexcitation of the photosynthetic pigments in organisms, their fragments and model Systems are described. Also the results of spectral measurements from some experiments are shown as examples of the described proceduře. These measurements were carried out predominantly as an attempt at explaining the interactions between chlorophylls and carotenoids.
This paper aims to present an informative overview of early modern Bohemical manuscripts ar Herzog August Bibliothek i Wolfenbüttel. Attention focuses primarily upot the Latin correspondence between Czech humanists and those abroad, though the overview also includes other genres and languages (Czech abd German). Of the previously unknown non-epistolary manuscripts, the discoveries of original manuscripts by Lutheran pastor Zacharias Theobald and Siegmund Schererz can be considered to be of interest.