摘要:

Glutamine‐synthetase (GS) fromBeta vulgarisseedlings, purified 150‐fold, was characterized with regard to its physiological substrate NH3. The data were compared to the unphysiological substrate NH2−OH frequently used in the assay (both synthetase and transferase reaction). The pH‐optimum was found at pH 7.5 for the synthetase and at pH 6.3 for the transferase reaction. Through plots of pKm vs pH, the pKe values for dissociable groups in the reaction center were found to be in the range from pH 7–8. Mg2+‐ion serves as an allosteric effector with a Hill coefficient of 4.2. The results are discussed in relation to the control of nitrogen metabo

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1981.tb05563.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

Lipoxygenase activity has been measured in various sections of the growing first leaf of wheat (Triticum aestivumL. cv. Florence Aurore). Weight, chlorophyll and lipoxygenase activity have been determined during the growth of the coleoptile and of the first and second leaf. Lipoxygenase activity variations are correlated with the growth of each organ. It seems that this enzyme has to do with chloroplast growth rather than with chloroplast division.

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1981.tb05564.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

The effect of different concentrations of salicylic acid on total Kjeldahl nitrogen and nitrate reductase activity in the maize (Zea maysL.) seedling was studied. The total nitrogen of the maize embryonic axis (root + shoot) from seedlings raised with 10 mMCa(NO3)2for 5 days was substantially higher than that from the control when 0.01 mMsalicylic acid was supplied. As supply of high (1 mM) concentrations of salicylic acid decreased the accumulation of organic nitrogen. Thein vivoactivity of nitrate reductase in the roots increased at low concentrations of salicylic acid, while high concentrations were inhibitory. The stimulative concentration of the acid protectedin vivoloss of nitrate reductase activity under non‐inducing conditions, whereas it had no effect onin vitroloss of enzyme. It is suggested that salicylic acid increasesin vivoenzyme activity indirectly, to some extent by protecting the natural inactivation of the enzym

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1981.tb05565.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

In extracts of the unicellular green algaEremosphaera viridisDeBary (Chlorococcales, Chlorophyceae) the average specific activity of α‐1,4‐glucan phosphorylase (E.C. 2.4.1.1) was 200 nmol glucose 1‐phosphate formed per min and mg protein. Using continuous and discontinuous electrophoresis on polyacrylamide gels, three phosphorylase forms were found. When the log of the relative mobility of the three enzyme forms was plotted versus the acrylamide gel concentration (Ferguson plot) parallel lines were obtained, indicating that the three enzymes were indiscernible with respect to molecular weight. Electrophoresis on density gradient gels resulted in three activity zones lying close to each other. The relative molecular mass (Mr) of the three enzymes was estimated to be around 180,000 with a difference of less than 7,000 between the small and the large

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1981.tb05566.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

Five‐week‐old seedlings of Norway spruce,Picea abies(L.) Karst., metabolized 1,2‐/3H/‐gibberellin A1into a single major compound chromatographically similar to gibberellin A8. The conversion rate exceeded 10% within the 24‐h incubati

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1981.tb05567.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

Changes in surface phosphatase activity of tomato root (Lycopersicon esculentumL. cv. Marmande) have been studied in relation to its P status. Experiments were performed either with excised roots culturedin vitroor with entire plants (split root method) grown in various conditions (P deficiency, renewal of P supply). In some experiments different parts of the root were separated according to their P status during their primary growth.The surface phosphatase in different root parts depends first of all on P status during their primary growth. Moreover the cell wall phosphatase of tomato root is stablein vivo. Thus the changes in the surface phosphatase of a root system result mainly from the growth of new roots, which bear an enzyme activity that is either high if they are P deficient or low if they are P provided. The control of the cell wall phosphatase synthesis appears to be a repression‐derepression process mediated by the root cell concentration in some P compound, probably orthophosphate. Cycloheximide stops or alters the growth of excised roots, so that this inhibitor was found unsuitable to study the synthesis of cell wall phosphatase underin vivoconditions. Split root experiment shows that the increase in surface phosphatase activity may occur locally,i.e.only in the parts of the root system which are P deficient. Agricultural and ecological aspects of these findings are pointed ou

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1981.tb05568.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

In leaf segments of barley (Hordeum vulgareL. cv. Mozoncillo), the cytokinin specificity for retarding the loss of phosphate is different from that of retarding the loss of chlorophyll. Some cytokinins require the simultaneous application of gibberellins to delay the loss of phosphate. Although both chlorophyll and phosphate losses occur in senescence, they are apparently controlled by cytokinins through different mechanisms.

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1981.tb05569.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

Extracts of cold stored chestnut cuttings (Castanea sativaMill.) were examined for the inhibitory effect on the stimulation of rooting by 1AA which has been detected previously in extracts from freshly collected cuttings. The extracts were fractionated by paper chromatography and the different zones of the chromatograms were bioassayed together with 1AA by the bean rooting test. The bean rooting test showed that the inhibitory effect decreased with the length of cold storage period, so that after 5 months of storage, the inhibitory effect had disappeared, and a root promoting zone was found on the chromatograms. A comparative study of phenolics in this zone, before and after cold storage, revealed the formation of vanillyl and salicyl alcohols in the chilled material. Vanillyl and salicyl alcohols are rooting stimulators and increase the effect of 1AA on rooting in bean cuttings.

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1981.tb05570.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

Light‐induced absorbance changes (LIAC), indicating the reversible reduction of a b‐type cytochrome, and with a possible connection to blue light photomorphogenesis, have been found in a presumptive plasma membrane rich centrifuge fraction from LIAC could be due to plasma membrane vesicles turned inside out or to cytochromes localized in other organelles. Phase partition proved to be a rapid method (results technique membrane particles are separated according to differences in surface properties rather than size and density. LIAC could be separated into two fractions: one partitioning into the polyethylene glycol rich upper phase and another preferring the dextram rich lower phase. Mitochondria (cytochrome c oxidase) were recovered in the lower phase. A dual distribution of LIAC was found with all materials tested: corn coleoptiles, corn shoots, barley shoots and cauliflower inflorescences. About 80–90% of the cytochromes in the upper phase were related to LIAC, whereas only 10–15% of those in the lower phase were of this kind. The LIAC preferring the upper phase was probably bound to the plasma membrane, since plasma membrane vesicles are known to have a high partition in these phase systems. The lower phase LIAC could be due to plasma membrane vesicles turned inside out or to cytochromes localized in other organelles. Phase partition proved to be a rapid method (results within one hour after the initial pelleting) for purification of presumptive plasma membranes, yielding a preparation which contained five times less mitochondrial contamination than the preparation obtained with sucrose gradient centrifugation (the 33/45% w/w sucrose interface fr

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1981.tb05571.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

Decapitation of the primary roots ofPisum sativumL. resulted in a significant increase in the initiation of lateral root primordia within 12 h of the surgical treatment. Although this increase occurred both in the light and in the dark, lateral root initiation and development was much more rapid in the dark. The formation of lateral root primordia was accompanied by increased levels of endogenous cytokinins suggesting that newly formed root primordia start producing cytokinins very soon after being initiated. The significance of the present results in terms of possible sites of synthesis in vegetative tissue is discussed.

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1981.tb05572.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY