Biochemie und Physiologie der Pflanzen最新文献

Metabolic effects caused by 3,5-diisopropylsalicylate (DIPS) and light were observed in etiolated maize coleoptiles using in vivo³¹P NMR spectroscopy. A decrease in the nucleotide triphosphate (NTP) resonances and an increase in nucleotide diphosphate hexose (NDP-hexose) signals were induced by 200 μM DIPS, with an acidification of the cytoplasm occurring in a fraction of the cells. Increased hexose phosphate and NDP-hexose signals, accompanied by a decreased cytoplasmic Pi resonance, were observed under intermittent blue light, while in red light only the increase of the hexose-P and decrease in cytoplasmic Pi signals occurred. These results provide evidence for an analogy between the action of DIPS and light at the molecular level, while the similar effects of red and blue light are compatible with phytochrome as the principal photoreceptor responsible for the metabolic changes.

The effect of varying nitrate levels (0—20 mM) was studied on the relative growth rate (RGR), acetylene reduction activity (ARA), nitrate uptake and nitrate reductase (NR) activity of A. caroliniana and A. pinnata. In both Azolla species, RGR was higher with 5 mM nitrate as compared to N-free medium whereas higher concentration of nitrate reduced the RGR. The significant inhibition of ARA was observed on 16th day after incubation with 5 mM nitrate, 12th day with 10 mM, 8th day with 15 mM and 4th day with 20 mM. The increasing nitrate levels resulted in increased nitrate uptake and NR activity in both the species. A. caroliniana recorded higher RGR and ARA whereas nitrate uptake and NR activity were higher in A. pinnata.

The chloroplasts in the parenchyma tissue of the galls on Zelkova serrata 'Aurea' leaves do not react to variations of light intensity by any remarkable ultrastructural changes, like those of the neighbouring leaf tissue. Both chloroplasts of the galls on green leaves, grown in the shade, as well as those on the yellow, sun-exposed leaves, contain a well developed thylakoid system with a high stacking degree of its membranes. The content of chloroplast pigments corresponds well to these facts. The possible cause for such behaviour of the gall parenchyma chloroplasts is discussed.

Cell-free extracts from cell suspension cultures of Lycopersicon peruvianum were found to catalyze the glucosylation of [U-³H]DJA and [2-¹⁴C]ABA in the presence of UDP-glucose. The products of enzymatic reactions were identified as glucosyl esters of DJA and ABA by means of TLC, HPLC and hydrolysis with cellulase. The two activities were not separated by ammonium sulfate fractionation and gel filtration, but the transferase activity of the enzyme was enriched toward radioactive DJA about 60-fold and toward radioactive ABA nearly 2-fold. A DJA metabolyzing enzyme was described for the first time and can be classified as UDP-glucose: DJA glucosyltransferase. In addition to the glucosyl esters of DJA and ABA the formation of further labelled products with still unknown structure were observed during the incubation.

The effect of nitrogen source on the cellular activity level of urease has been examined in the cyanobacteria Anacystis nidulans and Nostoc muscorum. In both, the N₂-fixing N. muscorum as well as non N₂-fixing A. nidulans, urea did not behave as an nutritional inducer of urease. NH₄⁺ promoted repression of urease was evident in both the cyanobacteria which was freed by Lmethionine, dl-sulphoximine (MSX), an irreversible inhibitor of glutamine synthetase. NH4, must therefore, be metabolised through glutamine synthetase before repressing the urease activity.