Search results for "otos"
showing 10 items of 857 documents
Synthesis and radical polymerization of novel methacrylates with mesoionic 6-oxo-1,6-dihydropyrimidin-3-ium-4-olates as photosensitive components
2001
New polymerizable mesoionic 6-oxo-1,6-dihydropyrimidin-3-ium-4-olates 5a-f have been synthesized using tosylated 2-hydroxymethyl methacrylate and various thioureas and malonic acids. Radical polymerization of the mesoionic derivatives 5a, c, d, e with AIBN as initiator resulted in soluble polymers, which were used for the preparation of photosensitive films.
Photosensitization of DNA by β-carbolines: Kinetic analysis and photoproduct characterization
2012
β-Carbolines (βCs) are a group of alkaloids present in many plants and animals. It has been suggested that these alkaloids participate in a variety of significant photosensitized processes. Despite their well-established natural occurrence, the main biological role of these alkaloids and the mechanisms involved are, to date, poorly understood. In the present work, we examined the capability of three important βCs (norharmane, harmane and harmine) and two of its derivatives (N-methyl-norharmane and N-methyl-harmane) to induce DNA damage upon UV-A excitation, correlating the type and extent of the damage with the photophysical characteristics and DNA binding properties of the compounds. The r…
Effect of Glufosinate (Phosphinothricin) and Inhibitors of Photorespiration on Photosynthesis and Ribulose-1,5-Bisphosphate Carboxylase Activity
1992
Summary Glufosinate (phosphinothricin) irreversibly inhibits glutamine synthetase and leads to a great decrease in the amino acids glutamine, glutamate, aspartate, serine, glycine and alanine. Due to the lack of glutamate and serine, the transamination of glyoxylate into glycine in the course of photorespiration cannot take place. The inhibition of this part of the photorespiratory process plays the essential role with respect to the photosynthesis inhibition caused by PPT under atmospheric conditions. After addition of different photorespiration or Calvin cycle intermediates to phosphinothricin no decrease in photosynthesis inhibition can be measured. This suggests that photosynthesis inhi…
Modulation of Fatty Acid Patterns During Protoplast Isolation
1983
Protoplast isolation and regeneration is known from numerous plant species (Binding et al. 1). But there are plant species which show very unconstant regeneration or no reaction at all, even if the isolation showed high viability of the protoplasts. Does this lacking response only depend on medium composition and effectors or are there other unknown conditions? The procedure of protoplast isolation and the use of strong hypertonic media is a dramatic disturbance of cell metabolism and might be a stress situation, which cannot be overcome by the cell. Fleck et al. (2) reported “osmotic-stress proteins” in Nicotiana sylvestris protoplasts and Kaiser et al. (3) showed a remarkable influence of…
The Influence of (2-Chloroethyl)trimethylammoniumchloride (CCC) on Growth and Photosynthetic Metabolism of Young Wheat Plants (Triticum aestivum L.)
1984
Summary The influence of (2-chloroethyl)trimethylammoniumchloride on growth and cell metabolism of Triticum aestivum var. Kolibri was investigated. CCC was added to the nutrient solution on the 11th day of development with a final concentration of 10 −2 mol·1 −1 . It immediately stopped root growth and showed a strong inhibitory influence on the growth of the leaves. Smaller and fewer cells accounted for the reduction in final leaf size of about 40 %. The content of soluble proteins and soluble reducing sugars were significantly increased in the treated leaves. CCC also exhibited a stimulating effect on the synthesis of RubPc-ase protein and the in vitro activity of this enzyme. In contrast…
Demonstration and study of characters of foliar « compensatory growth» phenomenon in grapevine (<em>Vitis vinifera</em> L.)
1996
<p style="text-align: justify;">Defoliation and decapitation experiments showed that the growth of a grapevine leaf was inhibited by both the terminal bud and the younger higher leaves. There is a phenomenon of synergy between these two influences. A young leaf freed of these two influences showed a higher growth rate than the norm ; this is « compensatory growth ». It is when a leaf is in its phase of maximal growth that it is most able to realize this &amp;laquo compensatory growth ». This is not due to a longer growth time, but more to a faster growth rate. This « compensatory growth » is not the consequence of competition between leaf growth and internodal elongation. Exogenou…
Carotenoids and the Assembly of Light-harvesting Complexes
2006
Carotenoids are constitutive components of all light-harvesting complexes in plants and many such complexes in bacteria. In the crystal structures of several light-harvesting complexes, carotenoids are seen to span the lipid bilayer and connect components of the complex on both membrane surfaces and/or to mediate the interaction of transmembrane protein helices. This important stabilizing function suggests that these pigments are also actively involved in the assembly of light-harvesting complexes. Verification of this notion appears too ambitious a goal at present, as the question of how the pigment-protein complexes of the photosynthetic apparatus are assembled is still open. However, inf…
Inhibitory Action of Glufosinate on Photosynthesis
1993
Glufosinate (phosphinothricin) irreversibly blocks the glutamine synthetase which subsequently gives rise to an accumulation of ammonium and to a strong decrease in some amino acids, especially glutamine and glutamate. Under atmospheric conditions (400 ppm CO2, 21% O2) glufosinate causes a rapid inhibition of photosynthesis, too. H ow ever, under non-photo respiratory conditions (1000 ppm CO2, 2% O2) only a slight inhibition of photosynthesis occurs with glufosinate. Since under both conditions an accumulation of ammonium occurs, it is concluded that inhibition of photosynthesis is not induced by the higher concentrations of ammonium. The results rather suggest that the absence of amino don…
The Effect of Light on the Growth of Pea Plants and the Subsequent Influence in Shikimate Oxidoreductase (EC 1.1.1.25) Activity
1981
Summary Pea plants were cultured in white light, red and far red light, and in the dark during a period of three weeks. At several states of development we investigated the activity of the enzyme shikimate oxidoreductase, the amount of fresh and dry matter, and the contents of protein in stem, leaves, cotyledons, and roots. The enzyme activity was found to be distributed organ-specifically and uninfluenced by the phytochrome system, but it was significantly depressed in plants grown in the dark compared to plants grown in white light. Enzyme activity occurred also in non photosynthetic plants. Regarding the different light conditions the activity of shikimate oxidoreductase was found to cor…
Cardenolides of Digitalis obscura: The effect of phosphate and manganese on growth and productivity of shoot-tip cultures
1997
Abstract Cardenolide composition of leaves from wild and micropropagated elite plants of Digitalis obscura (genotype T4) has been investigated and no qualitative differences were found among their major cardenolides (series A). All of the detected glycosides belong to the digitoxose-type cardenolides. Genins represented less than 2% of the overall content, while lanatoside A was the predominant cardenolide ( ca. 65%) in all samples. The cardenolide yield of micropropagated D. obscura plants depended on the age and development of the cultures, but productivity of long-term cultures (2 years) was quite similar to that of the parent plant. Changes in the concentrations of phosphate or manganes…