摘要:

AbstractAvena seedlings were imbibed and germinated in the presence of inhibitors of carotenoid biosynthesis. After excision and defoliation, the coleoptiles were cultured in the presence of these basally supplied inhibitors and their growth, phototropic behavior and pigment content were subsequently measured. Total carotenoids could be reduced to ca. 20 percent of the control value without marked influence on the dose‐response curve for the first positive curvature. Chromatographic analysis of extracted carotenoids on alumina columns revealed that the inhibitors produced both qualitative and quantitative changes, reducing one fraction and virtually eliminating two others. The total riboflavin content of the coleoptiles was almost completely unaffected by these treatments. The data are applied to an analysis of the nature of the photoreceptor in phototropism of the Avena coleoptil

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1968.tb07235.x

出版商:Blackwell Publishing Ltd    

年代:1968

数据来源: WILEY

摘要:

AbstractBarley roots contain a CO2sensitive respiratory fraction which is inhibited in 50 per cent CO2and is partially restored upon subsequent exposure to air. The residual O2consumption occurring at CO2concentrations between 50 per cent and 95 per cent amounts to about 40 per cent of the O2uptake in air and can support K+uptake for a limited time at a rate equal to or higher than occurs in air. Above 95 per cent CO2both O2and K+uptakes decrease rapidly. 2,4‐dinitrophenol (DNP), in the range of 10−6to 10−5M, stimulates O2uptake by the roots in air. The stimulation is absent when roots are treated with DNP in 80 per cent CO2, presumably because of the reduced demand for inorganic phosphate and phosphate acceptor at the lower respiratory level in high CO2. In either air or CO2, K+uptake is strongly inhibited by DNP. A comparison of the respiratory and K+uptake data indicates that O2consumption is a necessary requirement for the uptake process in high CO2.Protoplasmic streaming in the root cells is rapidly stopped by high CO2although K+uptake and O2consumption continue. The cation uptake mechanism in high CO2appears to be limited to the stationary cytoplasm. It is also possible that a similar mechanism may be involved in cation uptake i

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1968.tb07236.x

出版商:Blackwell Publishing Ltd    

年代:1968

数据来源: WILEY

摘要:

AbstractBiochemical genetic studies on the production of gibberellins by the fungusGibberella fujikuroihave identified two genes which control different steps in the biosynthetic pathway. One gene (g1) controls the production of all of the gibberellins: the second gene (g2) controls the production of GA1and GA3only.Ascospores are not ordered in the ascus of this fungus. This apparent spore slippage precludes mapping of these genes to their respective centromeres.

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1968.tb07237.x

出版商:Blackwell Publishing Ltd    

年代:1968

数据来源: WILEY

摘要:

AbstractThe culture filtrate of the crayfish plague fungus,Aphanomyces astaci(Saprolegniaceae), incubated in a peptone glucose medium was tested for chitinase activity under different conditions. The activities were assayed turbidimetrically using low‐polymerized chitin as a substrate.Adsorption of chitinase was found to occur on chitin and probably on cellulose and sulphomethyl cellulose but not at all or only a little on some other cellulose derivatives.The pH optimum of the enzyme activity was found to lie at about pll 5.0–5.5. The stability was greatest near pH 6.5 and the highest degree of adsorption occurred at still higher pH values. Enzyme adsorption on the substrate seemed to protect the enzyme against inactivation by heating, shaking, and extreme pH‐conditions.The chitinase activity was positively affected by the rest of the culture filtrate.Mercury, cobalt, and copper chlorides, and to a lesser degree some other metal salts, lowered the enzyme activity when present in the test medium. Cellobiose, but neither glucose nor N‐acetyl glucosamine had a pronounced inhibiting effect on the activity. Neither cellobiose nor N‐acetyl glucosamine seemed to affect chitinase adsorption on chitin. Some chelating and reducing compounds inactivated the culture filtrate. This activity‐reducing effect of chelators was strongly prevented by EDTA in

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1968.tb07238.x

出版商:Blackwell Publishing Ltd    

年代:1968

数据来源: WILEY

摘要:

Abstract1Two separate light reactions may be distinguished: (I) the reduction of ferredoxin and NADP probably by oxidation of carotene to xanthophyll; (II) the oxida tion of cytochromefby chlorophyll (probablya). Reaction II implies a return of electrons to the pigments, system III, thus maintaining its normal steady state of oxidation‐reduction. The xanthophyll is hereby again reduced to carotene.2System I is sensitive to violet‐blue‐green and probably also infrared light. Carotene absorbs in these regions, ferredoxin in blue‐violet. System II is primarily sensitive to red light but also to blue‐violet. Both chlorophyll and cytochromes absorb in the latter region, the cytochromes also in green.3The response of systems I and II to different spectral regions was studied by means of a special spectrophotometric flash technique, enabling precise measure ments of the band‐height of the enzymes involved. The initial photic reactions of systems I and II,viz., the reduction of ferredoxin‐NADP and the oxidation of cyto chromefshow a full turnover in less than 0.1 ms but the transfer between systems I and II by means of which the cytochromes are reduced is slowed down to about 10−1‐10−2s. The initial effect may thus be observed during ca. 0.1 s. At continuous illumination the displacement of the steady states of the enzymes may last up to several seconds and then return to a state of only partial reduction. Erroneous inter pretations of these phenomena are corrected.4In the blue‐sensitive system I ferredoxin alone mediates the reduction of NADP but the possibility of the presence of other factors capable of dark chemical elec tron transfer is discussed. In the red‐sensitive system II three cytochromes operate,viz., f, b3andb6. Spectrophotometric evidence for the existence of two cytochromesbis presented. Cytochromesb6andfare approximately synchronously oxidized and reduced, whereasb3reacts somewhat independently. Cytochromeb3probably acts as a decharger of OH−and compensates for the capture of H++ e−at the reduction of triphosphopyridine nucleotide (NAD) or of electrons by other oxidants.5The transfer of electrons between systems I and II maintains a reversible steady state of oxidation‐reduction that may be moved to one side or the other not only by monochromatic light but also in the dark under influence of N2, O2, the ratios NADP/NADPH and ADP/ATP, and various added substances. Spectrophotometric measurements in UV show that a flavoprotein participates in the multiple steady state.6The investigations illustrate many intricate technical problems that are too frequently overlooked. Photostructural reactions must be eliminated by referring band‐heights to an isosbestic level. The photosynthetic activity is strongly dependent on light‐scattering. Reliable measurements of cytochromes must be made in the α‐region owing to a strong interference of rapid changes of the ratio carotene/xant

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1968.tb07239.x

出版商:Blackwell Publishing Ltd    

年代:1968

数据来源: WILEY

摘要:

AbstractThe carbohydrate content (starch, glucose and sucrose) in tomato plants grown in air Containing 0.04, 0.10, 0.15, 0.22, 0.32, or 0.50 vol. per cent CO2was studied at 2 hours’ intervals over a period of 24 hours. The highest starch content was found at 0.22 vol. per cent CO2, while the highest content of soluble sugars were reached at a concentration of 0.10 vol. per cent CO2. A few observations of the morphogenic effects of carbon dioxide were also mad

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1968.tb07240.x

出版商:Blackwell Publishing Ltd    

年代:1968

数据来源: WILEY

摘要:

AbstractThree isozymes specifically concerned with the “branching” of linear polyglucosides have been delected in algae. These enzymes were detected using two‐dimensional polyacrylamide gel electrophoresis, and were found to be present in blue‐green, red and in green algae. Two isozynies were found inOscillatoria princeps;three enzymes were present inSpirogyra setiformis, and two and three such enzymes were detected in red algae of theRhodymeniatype. The significance of the multiple forms of this branching enzyme was assessed in light of the type of storage poly‐glucosides formed by these plants. The “degree of branching” of the storage sugar appeared to be related to the evolutionary status o

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1968.tb07241.x

出版商:Blackwell Publishing Ltd    

年代:1968

数据来源: WILEY

摘要:

AbstractA soluble isocitric lyase is shown to occur in lettuce seeds. Its activity increases during germination till 72 hours and then falls again. No particulate lyase could be detected. In addition both a soluble and a particulate isocitric dehydrogenase is present in the seeds. Both enzymes react with NAD as well as with NADP. The soluble enzyme drops sharply in activity during germination, while the particulate enzyme remains at a more or less constant level of activity. By gel electrophoresis the isocitric lyase and the isocitric dehydrogenase were shown to consist of what appear to be several isozymes. The interrelation between the enzymes and their relation to fat metabolism during germination is discussed. Evidence is brought for an enzymic reaction by which isocitric acid is converted to pyruvic acid. The nature of this reaction is not clear.

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1968.tb07242.x

出版商:Blackwell Publishing Ltd    

年代:1968

数据来源: WILEY

摘要:

AbstractObservations have been made on the effect of synthetic, (±)‐abscisin II (dormin), alone and in combination with gibberellin, kinetin and indoleacetic acid, on seed germination and seedling growth of two strains of lettuce, cv. Attraktion and cv. Hohlblättriger Butter. (±)‐Abscisin II inhibited seed germination and seedling growth in both strains. The inhibitory effect of abscisin II on seed germination as well as seedling growth was completely overcome by kinetin in both dark and light. Gibberellic acid, on the other hand, proved ineffective in exerting its influence on seed germination in presence of abscisin II but affected subsequent seedling growth as usual. Indoleacetic acid was found to be least potent in reversing abscisin II caused inhibition of seed germination and seedling growtb. It is concluded, that like its effect on certain other naturally occurring inhibitors of seed germination, kinetin can effectively undo the inhibitory effects of abscisin II in these growth pro

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1968.tb07243.x

出版商:Blackwell Publishing Ltd    

年代:1968

数据来源: WILEY

摘要:

AbstractThe behaviour of amitrole (3‐amino‐l,2,4‐triazole) in 3‐year old seedlings ofPinus ponderosa(ponderosa pine) andAbies concolor(white fir) is described.Visual symptoms of amitrole action appeared as a chlorosis of young needles, the extent of which varied with time and species. Maximum chlorosis was obtained when the application was made during the stage when no visible growth occurred. The greater susceptibility of ponderosa pine seedlings could be accounted for by the lower resistance to uptake of the herbicide into the needles and not by any difference between the conifer species in the metabolism of amitrole.The translocation and metabolism of amitrole in the two conifer species are discussed. In both of the conifer species amitrole was converted into three metabolic products two of which were found to be identical with the previously described Unknown I and II.Two types of treatment, on exposed phloem and on the needles, provided the possibility for a direct study of the site of amitrole metabolism. This site appeared to be in the stem.Amitrole was the mobile, toxic compound in both species and was translocated in both symplast and apoplast. A circulation of the herbicide in the plant was observed. From the phloem amitrole diffused relatively slowly into the xylem, and during this lateral translocation part of the amitrole was metabolized. The rate of this detoxification process seemed to be dependent upon how fast amitrole moved from phloem to xylem and vice versa. This rate seemed to show a positive correlation with the intensity of the cambial activity. The translocation of amitrole to the roots was greatest when no visible growth could be d

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1968.tb07244.x

出版商:Blackwell Publishing Ltd    

年代:1968

数据来源: WILEY