Zeitschrift für Pflanzenphysiologie最新文献

Labelled zeatin applied to the primary leaves of fruiting Phaseolus vulgaris plants was metabolized rapidly and extensively. After ten days the major metabolite detected in the leaves co-chromatographed with glucosylzeatin. No evidence could be found that this metabolite was exported to the developing fruits. From the available evidence it would appear that when compounds were exported from the primary leaves they were converted to a polar compound which was retained on Dowex 50 cation exchange resin and which co-eluted with N-(purin-6-yl)glycine. This was the only metabolite detected in the developing fruits. In all cases it represented less than 1% of the total radioactivity recovered from the plants. The results obtained suggest that cytokinin glucosides are stable metabolites which are not readily exported from the mature primary leaves of bean plants.

Nitrite reductase was isolated from nine day old rose cells cultured in NO₃^- and NH₄⁺ medium. The purification procedure involved extraction with Tris-HCl buffer containing EDTA, absorption on DEAE-Cellulose, ammonium sulfate fractionation, ion-exchange chromatography on DEAE-Cellulose and DEAE-Sephadex A-50, gel filtration on Sephacryl S-200 and followed by ferredoxin-Sepharose affinity chromatography. The purified preparation was apparently homogeneous as shown by non-denaturing and denaturing polyacrylamide gel electrophoresis. The sub-unit molecular weight of the purified preparation was found to be 66,000. The K_m value for nitrite was determined to be 0.79 mM. The enzyme activity from rose cells was precipitated by antiserum prepared against nitrite reductase from pea leaves and formed immunoprecipitin bands during immunodiffusion and rocket immunoelectrophoresis.

This work was done to see whether the general metabolism of roots of flood-tolerant Glyceria maxima showed any marked adaptation to lack of oxygen that distinguished them from roots of flood-intolerant Pisum sativum. We determined the effects of 14, 11, 8, 6, 4, 2 and 1% oxygen, and anoxia, on the metabolism of [U-¹⁴C]sucrose, and of that of ¹⁴CO₂ in the dark, by excised roots. No significant differences were found between the two species. The proportion of the metabolized label that was incorporated into polymers began to fall at 6% oxygen to reach in anoxia values that were only 10–30% of those in air. Glyceria roots formed aerenchyma. Glyceria plants, with shoots in air and roots in [U-¹⁴C]sucrose that lacked oxygen, readily incorporated ¹⁴C into polymers. This incorporation was greatly reduced when the shoots were cut off and the end of the stem sealed. We concluded that Glyceria roots show no major metabolic adaptation to hypoxia, and that their flood-tolerance is due mainly to aerenchyma. We related these conclusions to the metabolic theory of flood-tolerance.

Cell suspension cultures derived from Papaver bracteatum Lindl var. Arya II P. somniferum L. var. Hallé and var. Berlin, P. setigerum D. C., and P. nudicaule L. were found to contain protopine, sanguinarine, isothebaine and orientalidine. Growth of P. bracteatum suspensions at 36°C followed by 5°C caused release of thebaine into the media.

The accumulation of abscisic acid (ABA) in wheat seedlings in response to drought stress was studied following treatment with cycloheximide, an inhibitor of protein synthesis on cytosol ribosomes, and with chloramphenicol, lincomycin and spectinomycin, inhibitors of protein synthesis on plastid ribosomes. Cycloheximide treatment for 2 h completely inhibited subsequent ABA accumulation, but treatment for 5 h with the three inhibitors of protein synthesis on plastid ribosomes had no effect. It seems likely, therefore, that stress-induced ABA synthesis requires rapid enzyme production in the cytosol but not in the plastid.

Labelled zeatin applied to either the xylem or phloem regions of the stems of developing Phaseolus vulgaris L. plants was transported in a pattern which was in accordance with what appears to be the distribution of endogenous cytokinins in this plant. Available cytokinins seem to be transported to preferential sites which shift within the plants as they progress from a vegetative to a reproductive phase of growth. In the flowering and fruiting plants there was increased transport of phloem applied radioactivity to the reproductive organs. Metabolism of applied radioactive zeatin was considerably advanced in reproductive plants. Most of the recovered metabolites were of a polar nature suggesting either side-chain glucosylation and/or side-chain cleavage as the metabolic pathways.

The respiration of cotyledons from light-grown soybean seedlings (Glycine max L., Amsoy) showed a sharp peak of activity after two weeks of growth, followed by a slighter increase during senescence. Cotyledon respiration was found to be strongly cyanide-resistant. Mitochondria isolated from cotyledons at various stages of development displayed a progressive improvement in structure. The rate of succinate oxidation closely paralleled that of respiration, being also highly cyanide-resistant. Cotyledon mitochondria also oxidized glycine. However this oxidation was remarkably cyanide- and antimycin-resistant.