摘要:

AbstractThe kinetics of prenyl chain formation (C20phytyl in chlorophylls, vitamin KIand α‐tocopherol; C40carotenoids and C45in plastoquinone‐9) in plastids of etiolatedHordeumseedlings was compared in continuous darkness and after far‐red and white light treatments:1Continuous far‐red (via phytochrome Pfr) enhances the synthesis rate of all prenyl chains, but does practically not change the dark pattern of prenyl chain accumulation. Free C20phytyl chains could not be detected by means of thin layer chromatography.2White light induces a much stronger enhancement of prenyl chain formation than does far‐red. It also changes the pattern of prenyl chain synthesis by a particularly strong promotion of the synthesis of phytyl chains, which get bound to chlorophylla. The rate of chlorophyllide formation seems to determine the rate of enhanced phytyl formation.3It is assumed that the enzyme, which esterifies chlorophyllideawith the phytyl chain, is formed or activated by far‐red treatment, but only starts working in white light, when the protochlorophyllide holochrome is re‐arranged to the chlorophyll

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1975.tb03161.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

摘要:

AbstractThe capacity for photosynthesis, measured as light enhanced14CO2uptake, was demonstrated in the wood of first and fourth year twigs ofBetula pendulaRoth,Populus tremuloidesMichx.,Syringa vulgarisL., andTilia AmericanaL, but not inGleditschia triacanthosL. In Betula and Syringa, but not in the others, photosynthesis occurred in the secondary xylem as well as in the primary xylem.

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1975.tb03162.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

摘要:

AbstractApple seedlings,Pyrus malusL., were grown in complete nutrient solutions containing nitrate, ammonium, or ammonium plus nitrate as the nitrogen source. Uptake of nitrogen was calculated from depletion measurements of the nutrient solutions and by using15N labelled nitrate and ammonium salts.If the plants received nitrogen as ammonium only or as nitrate only, the amounts of nitrogen taken up were similar. However, if the seedlings were supplied with ammonium nitrate, the amount of nitrate‐nitrogen assimilated was only half that of ammonium. Nevertheless, if ammonium and nitrate were supplied to a plant with a split‐root system, with each root half receiving a different ion, the uptakes were similar.The possibility of independent inhibition by ammonium of both nitrate uptake and reduction in the roots is discus

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1975.tb03163.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

摘要:

AbstractChanges in the synthetic activities of nucleic acids and protein and in the amount of adenine nucleotides inDaucus carotacells have been examined during a period of rapid cell division and during the stationary phase. Cell growth and the syntheses of those macromolecules in the logarithmic phase were significantly enhanced by increasing the concentration of phosphate in the medium. In a phosphate‐rich medium, RNA and protein rapidly degraded and the number of cells with denatured cytoplasm increased when the culture entered into a stationary phase because of exhaustion of glucose. On the other hand, when the growth ceased by exhaustions of phosphate and nitrogen, the cells slowly underwent physiological changes leading to cellular senescence. The value of adenylate energy charge during the growth period was about 0.8–0.9 irrespective of the growth rate. After cessation of growth the value declined to about

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1975.tb03164.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

摘要:

AbstractThe commercial polychlorinated biphenyl (PCB) mixture Aroclor 1242 was tested regarding its effects on the uni‐cellular green algaScenedesmus obtusiasculusChod. The algae were grown in liquid medium at PCB concentrations between 10 and 1000 ppb. Growth was inhibited at 300 ppb and above, viability was only affected at the highest concentration, 1000 ppb. Reduction of phosphate uptake was seen at 300 ppb and above. The inhibition of phosphate uptake had almost exactly the same appearance in light as in darkness. It is suggested that this inhibition is mainly caused by PCB action on the plasmalemma. At 800 ppb some experiments indicated an uncoupling of the oxidative phosphorylation. 1000 ppb inhibited both respiration and O2evolutio

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1975.tb03165.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

摘要:

AbstractExtracts prepared from resting seeds of Scots pine,Pinus sylvestrisL., rapidly hydrolysed two peptides, Leu–Tyr and Ala–Gly, at pH 8.6 and 7.8, respectively. In gel chromatography on Sephadex G‐100 the two activities were eluted as separate peaks, which indicates that they are due to two different peptidases.The seeds were allowed to germinate at 20°C, the activities of the two enzymes were assayed separately on extracts from the endosperm and seedling tissues at different stages of germination, and compared with corresponding changes in dry weight and total nitrogen. Both enzyme activities were relatively high in the endosperm of resting seeds, and they increased about 2‐ and 3‐fold during germination (expressed as enzyme units per seed), the increases coinciding with the time of rapid reserve protein mobilization. Both enzymes were also abundant in the embryos of resting seeds, and during germination their activities increased even more rapidly than those in the endosperm.The possible role of these two “alkaline peptidases” in reserve protein hydrolysi

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1975.tb03166.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

摘要:

AbstractBy use of surface electrodes electropotenlial measurements were carried out on hypocotyl hooks ofPhaseolus vulgarisseedlings. The hooks were illuminated with a small spot of white, blue, red or far red light.The potential changes in bean hypocotyl hooks do not show the red‐far red reversible characteristics of phytochrome‐mediated processes. By experimenting with inhibitors of photosynthesis we could demonstrate that the light‐triggered potential changes in green bean hooks are correlated to photosynthetic electron transport phenomena. The red‐light‐induced transient is a depolarization, whereas blue light induces a hyperpolarization. Etiolated beans exhibit no bioelectric potential changes when subjected to red or far red irradiations. Blue light and white light induce a strong hyperpolarization in etiolated hooks cells. This transient seems to be an action potential induced by light. The action potential is influenced by inhibitors of electron transport and oxidative phosphorylation. By comparing the action spectrum of the action potential induced by light with the absorption spectra of extracted carotenoids and xanthophylls from etiolated bean hypocotyl hooks, we observed sim

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1975.tb03167.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

摘要:

AbstractEffects of metabolic inhibitors and growth regulators on the course of abscission and on the activities of cell wall solubilizing enzymes were studied in pedicel explants ofBegoniaflower buds.Actinomycin D, chloramphenicol and 2,4‐dinitrophenol slightly retarded abscission, whereas cycloheximide exerted a strong inhibition if applied until 10.5 h after explant excision.Indoleacetic acid retarded and ethylene promoted abscission and cell wall solubilization. However, the activities of cell wall solubilizing enzymes did not correspond with the course of abscission. No polygalacturonase and pectic acid and pectin transeliminases could be detected in the abscission zone during abscission, whereas a low pectin methylesterase activity did not change. Endo‐ and exocellulase activities did not increase until about 10 h after the onset of abscission, indicating that they are the result rather than the cause of absciss

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1975.tb03168.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

摘要:

AbstractIn order to analyse the hormonal regulation of flower bud shedding inBegonia, levels of indoleacetic acid (IAA), abscisic acid (ABA) and ethylene were determined in buds and pedicels. The translocation and metabolism of14C‐labeled IAA in pedicel segments were also studied.In a monoeciousBegonia fuchsioideshybrid, abscising male flower buds contain about 1% of the IAA present in non‐abscising female flowers. In a maleBegonia davisiihybrid, the seasonal variation in bud drop coincides with changes in the IAA content of the buds, while also the release of IAA from the bud to the pedicel is hampered.Abscission zones of these pedicels always contain abscission promoting ethylene concentrations. The tissue is prevented from responding with abscission by IAA from the flower buds. The buds also contain ABA but without influencing abscission considerably.Pretreatment with ethylene or ABA does not affect IAA transport in pedicel segments. The rate of this transport is 4–6 mm × h–1:; the capacity increases with the transverse area. In young segments, IAA is decarboxylated and also otherwise met

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1975.tb03169.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

摘要:

AbstractThe frequency of glycolytic oscillations in yeast cells is only slightly modified by the consumption rate of either glucose or fructose, but it is reduced to 1 /2 to 2/3 if the ketohexose is the only substrate.Phase relations between NADH, adenine nucleotides and sugar phosphates (G‐6‐P, F‐6‐P, FDP, DAP) are independent of the hexose fermented.With fructose as a substrate the amplitudes of adenylates and hexose phosphates are distinctly smaller than with glucose. The maximum of G‐6‐P is higher with glucose and the minimum concentration of FDP is higher with fructose.In the transition to anaerobiosis FDP, adenosine 5′‐diphosphate and adenosine 5′‐phosphate are extremely high, whereas G‐6‐P, F‐6‐P and ATP concentrations are lower if fructose is the substrate fermented.The results are indicative for different control characteristics of the phosphofructokinase step, but on their basis it cannot be distinguished between a direct interaction of fructose (or one of its derivatives) on the phosphofructokinase kinetics or the existence of a bypass for fructose which might be able to withdraw a part of the substrate from the control point

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1975.tb03170.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY