Influence of Nitrogen Availability on Aminotransferases in Lemna minor L

Protein contents and glutamate: glyoxylate, serine: glyoxylate, alanine: glyoxylate and glutamate: pyruvate aminotransferase activities per gram fresh weight declined sharply when Lemna minor L., previously grown on nitrate medium, was starved of nitrogen. Nitrogen replenishment after 5 d caused complete recovery of these parameters with higher values in ammonium-fed than nitrate-fed plants 7 d after transfer of plants from nitrogen-free medium. Glutamate: glyoxylate and alanine: glyoxylate aminotransferase specific activities (based on total extracted protein) showed little change with nitrogen availability. Serine: glyoxylate aminotransferase increased slowly during nitrogen starvation and decreased following nitrogen replenishment whether with ammonium or nitrate. After 1 d of nitrogen starvation the specific activity of glutamate: pyruvate aminotransferase declined; it increased following nitrogen replenishment and ammonium gave rise to agreater activity than nitrate. The results are discussed in relation to the differences in stability of the various enzymes relative to the overall protein turnover rat

Uptake of NO2 by plants grown at different salinity levels

It is demonstrated that the uptake of nitrogen dioxide (NO2) byPhaseolus vulgaris L. is decreased by the addition of sodium chloride (NaCl) to the root medium, as a result of increased diffusive resistance of the leaves. The NO2-uptake rate constant measured kinetically was in agreement with the nitrite content of the leaves after the fumigation

Die Veränderung des Stärke-, Protein- und RNS-Gehaltes vonLemna minor L. unter dem Einfluss von Kinetin (6-Furfurylaminopurin)

Kinetin (6-furfurylaminopurine) is rapidly absorbed byLemna minor L. 3 · 10−8 M/ml medium cause an immediate but temporary stimulation of RNA and protein synthesis during the first hour of the treatment. The following excessive accumulation of starch is considered to be more or less a direct consequence of a disturbed RNA and protein metabolism

Effect of Nitrate and Ammonium Nutrition of Nonnodulated Phaseolus vulgaris L. on Phosphoenolpyruvate Carboxylase and Pyruvate Kinase Activity

Young bean plants (Phaseolus vulgaris L. var Saxa) were fed with 3.5 or 10 millimolar N in either the form of NO(3)(−) or NH(4)(+), after being grown on N-free nutrient solution for 8 days. The pH of the nutrient solutions was either 6 or 4. The cell sap pH and the extractable activities of phosphoenolpyruvate carboxylase and of pyruvate kinase from roots and primary leaves were measured over several days. The extractable activity of phosphoenolpyruvate carboxylase (based on soluble protein) from primary leaves increased with NO(3)(−) nutrition, whereas with NH(4)(+) nutrition and on N-free nutrient solution the activity remained at a low level. Phosphoenopyruvate carboxylase activity from the roots of NH(4)(+)-fed plants at pH 4 was finally somewhat higher than from the roots of plants grown on NO(3)(−) at the same pH. There was no difference in activity from the root between the N treatments when pH in the nutrient solutions was 6. The extractable activity of pyruvate kinase from roots and primary leaves seemed not to be influenced by the N nutrition of the plants. The results are discussed in relation to the physiological function of both enzymes with special regard to the postulated functions of phosphoenolpyruvate carboxylase in C3 plants as an anaplerotic enzyme and as part of a cellular pH stat

The effect of kinetin on protein, amino acid, and RNA metabolism in Lemna minor L.

Lemna minor L. was cultivated on nutrient medium with kinetin (10-5 m) for 3 hours at 28°C and ca. 5,000 lux. Samples were taken at different times and their amino acid, protein and RNA content was determined. The amino acid content in the cultures with kinetin corresponds to that in the cultures without kinetin. The amino acid concentration seems to be regulated by mechanisms independent of kinetin. On the other hand, kinetin increases the quantity of protein immediately i.e., within the first two minutes. This increase stops after ca. 30 minutes, but the excess of protein remains for a long time. In the first 30 minutes the RNA concentration also rises. This increase is not as strong as that of the protein nor does it remain. After 30 minutes, when the rise of protein content stops, the RNA concentration begins to drop within 1 hour to that of the control cultures without kinetin. The extent of the protein and RNA increase induced by kinetin depends strongly upon the physiological state of the plants. This may be because the plants produce different quantities of endogenous cytokinins under different conditions. The protein induced by kinetin was then examined after centrifugation at 100,000 x g. In samples taken during the first 5 minutes, the quantity of protein in the supernatant and in the sediment is increased. In samples taken after this period, the increase of protein in the supernatant disappears and only that in the sediment remains. After some time, therefore, all the excess protein consists of structural protein, which is found in the sediment. The findings are compared with those of other authors and an unspecific stimulation of RNA is suggested

Zum Vorkommen von Thiothreonin im Pflanzenmaterial

In extracts of H2 35S gased pea seedlings, a radioactive substance has been revealed by thin layer chromatography which showed the same chromatographic properties as thiotheronine

On the use of a field exposure system to estimate air pollution levels

The paper describes a field exposure system involving the application of growing chambers, ventilated with filtered or nonfiltered ambient air. The diffusive resistance of primary leaves of beans (Phaseolus vulgaris L.), growing in medium with ammonium or nitrate as nitrogen source, has been used as indicator for low level air pollution, which does not produce visible leaf injury. In severely polluted atmosphere an addition of sodium chloride affected inversely the degree of injury

Tolerance of Aesculus hippocastanum L. to foliar accumulation of chloride affected by air pollution

The influence of air pollution, caused by emissions from motor vehicles, on the tolerance of Aesculus hippocastanum L. to foliar accumulation of chloride was investigated. Foliar accumulations of chloride reflect accumulation in soil as a result of successive winter applications of deicing salt (sodium chloride). Leaves of horse chestnut were sampled at different sites within the city of Berne, Switzerland, and analysed for chloride content and leaf necrosis. Areas of leaf necrosis were directly proportional to accumulations of chloride in the range 10 to 16 mg/g dry weight. As a measure of tolerance to accumulated chloride the concentration leading to a 25% necrosis of the total leaf area was determined. An ‘Air Quality Index’, calculated from the concentrations of carbon monoxide (CO) and nitrogen dioxide (NO2), was used to describe air pollution levels. Foliar accumulations of chloride were less damaging in more severely polluted atmospheres

Untersuchungen über die Biosynthese der Vitamine der Folsäuregruppe bei grünen Pflanzen

Des plantules de Pisum sont cultivées aseptiquement en milieu synthétique. A la lumière, elles synthétisent plus de facteurs du groupe de l'acide folique, déterminés par voie microbiologique, et plus d'acide ascorbique qu'à l'obscurité. L'adjonction d'acide ascorbique au milieu des plantes cultivées à l'obscurité compense partiellement l'absence de lumière

The influence of the nitrogen supply on the structure and activity of glycolate oxidase in Lemna minor L.

Glycolate oxidase, a key photorespiratory enzyme, appears to be influenced by the form of nitrogen supplied to sterile cultures of Lemna minor L. Both its specific activity and molecular weight were doubled in extracts of tissue grown with an ammonium nitrogen source as compared with the enzyme from Lemna grown on nitrate. A study of glycolate oxidase during growth of Lemna on ammonium nitrate revealed a transition from a high-molecular-weight (HMW)- to a low-molecular-weight (LMW)-form apparently correlated with depletion of ammonium ions from the culture-medium and the onset of nitrate uptake. The results are discussed in relation to the possible control of the glycolate pathway