摘要:

AbstractApical growth cessation as affected by photoperiod and temperature has been studied in seedlings of two latitudinal ecotypes ofSalix and Betula. The critical photoperiod for apical growth cessation at constant temperatures of 15 and 21°C was about 22 h for a northern (69°C39′N) and about 15–16 h for a southern (59°C40′N) ecotype ofSalix pentandra.Fluctuating day/night temperatures (21°C/9°C, 15°C/6°C) induced apical growth cessation in northern ecotypes even at 24–h photoperiod. Disagreements in critical photoperiods found in various studies

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1980.tb03266.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY

摘要:

AbstractIt was previously demonstrated that photoexcited methylene blue can act as electron donor in red light induced reduction of a particulateb‐type cytochrome in fraction from etiolated corn coleoptiles (Zea maysL. WF 9 × Bear 38). It was postulated that the same cytochrome as the one active in blue light photoprocesses was involved. This study describes the effect of detergents upon such red light induced reductions in corn coleoptile preparations fractionated after differential centrifugation into 9 KP, 21 KP and 50 KP (500–9000 g pellet, 9000–21,000 g pellet and 21,000–50,000 g pellet, spun for 20, 20, and 45 min, respectively). Both Triton X‐100 (more effective) and deoxycholate (less effective and somewhat destructive) could be used as solubilizers if concentrations above the critical micellar concentration were chosen. Tween 40 was ineffective and dodecyl sulphate affected the cytochrome so that it lost its accessibility to electrons from photoexcited methylene blue. The recovery, measured as the ratio between light induced absorbance change (LIAC) in the Soret region after and before solubilization, was highest in 9 KP (70%) and lower in 21 and 50 KP fractions (50% and 43% respectively). The band in the Soret region in light minus dark spectra had its peak at longer wavelengths compared to the dithionite reduced minus no addition absorption difference band, whether the sample was solubilized or not. Similar results were obtained when the material was separated on a discontinuous sucrose gradient (15/28/33/45% w/w sucrose). In such a separation, the distribution of LIAC between fractions (collected at the interfaces) was about the same after solubilization as before (solubilization brought about a slight shift towards heavier fractions). The ratios of LIAC to the dithionite reduced minus no addition absorbance difference decreased upon detergent treatment. The LIAC still had its peak at longer wavelengths compared to the peak obtained upon dithionite reduction.The usefulness of detergents in the purification of the particulateb‐type cytochrome

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1980.tb03267.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY

摘要:

AbstractFactors influencingin vivonitrate reductase activity in triticale (×TriticosecaleWittmack) primary leaves were investigated. Nitrate reductase activity was found to be a function of reaction time or tissue weight. In the range of 1–10 mm, the optimum slice width for nitrate reductase activity in triticale was found to be 1–2 mm. The optimum exogenous nitrate concentration is 300 mM. Substantial nitrite production was obtained even when exogenous nitrate was omitted from the assay. Of the five low molecular weight organic solvents tested,n‐propanol is the most effective in enhancing enzyme activity. The optimumn‐propanol concentration is 1% (v/v). The concentration of phosphate buffer (pH 6) does not affect nitrate reductase activity. Enzyme activity drops significantly below or above pH 6. In our system, nitrite production is enhanced by incubating under nitrogen, instead of air. The highest level ofin vivoactivity of nitrate reductase was found to be 10–15 cm from tip, which is close to the basal meristem of triticale primary leaves. Younger but physiologically mature leaves have higher nitrate reductase activity than

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1980.tb03268.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY

摘要:

AbstractTomato plants (Lycopersicum esculentumMill. cv. Moneymaker) grown on nutrient medium containing cadmium exhibit reduced net photosynthesis and reduced contents of chlorophyll and accessory pigments. In chloroplasts isolated from cadmiumtreated plants photosystem II activity, as measured by 2,6‐dichlorophenolindophenol photoreduction, and photosystem II + I activity (H2O → methyl viologen) were both inhibited to about 60%. When 1,5‐diphenylcarbazide was used as artificial electron donor, no significant cadmium effect was observed. Photosystem I activity was not affected by cadmium. The fine structure of chloroplasts in cadmium‐treated plants was degenerated, similarly to senescence response. The principal symptom of cadmium action was the occurrence of large plastoglobules and a disorganization of the lamellar structure, mainly grana stacks. Transfer of cadmium‐treated plants into a medium with increased manganese level caused grana stacking and restoration of photosystem II

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1980.tb03269.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY

摘要:

AbstractMaize (Zea maysL. cv. Kansas Drought Synthetic) pollen proteins were fractionated via a continuous tandem cascade ultrafiltration system into three molecular‐weight classes. Proteins from the whole extract and each fraction were further separated by polyacrylamide gel electrofocusing in the pH 5 to 9 range and characterized by their enzymatic activity and isoelectric point.Twenty‐one protein bands were detected with Fast Green FCF staining. Esterase, peroxidase, leucine aminopeptidase, catalase, and amylase activities were located in 16 bands. Five bands remained unclassified. All the enzymes assayed, except amylase, were polymorphic. The extractions, fractionations and zymograms were reproducible and indicated that several protein bands contained at least two different enzymes with very similar molecular weight class and isoelectric point for each enzyme and protein

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1980.tb03270.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY

摘要:

AbstractThe efficiency of sulfate uptake was evaluated in excised roots of 22 maize genotypes, 12 inbreds and 10 hybrids, in order to study the relationship between the kinetic characteristics of the uptake and the grain productivity. During root elongation, the uptake capacity showed a pulse which appeared when the root reached 1/3 to 1/2 of its final length. The size of the accumulated pool of sulfate was significantly correlated with the productivity. The kinetic parameters of the uptake, Vmax and Km, followed the same trend, showing pulses, whoxe maximum had the same position for Vmax and Km in each genotype. The variability with the genotype of the size and duration of the Vmax pulse was not strictly connected with that of Km. The main correlation between Vmax and Km patterns was the following; inbreds were generally characterized by low Vmax and low Km; hybrids by high Vmax and high Km. As a consequence, in most cases, the benefit of the heterotic stimulation of Vmax was contrasted by the loss of affinity of the transport system or the nutrients.

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1980.tb03271.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY

摘要:

AbstractGermination ofPhacelia tanacetifoliaBenth. (cv. Bleu Clair) seeds is accompanied in its early phases by the development of theK+uptake capacity. Dormancy due to light and high temperatures and the negative effect on seed germination of a medium with low water potential inhibit the development of potassium uptake. Fusicoccin, which promotes seed germination under all examined conditions, accelerates also the appearance of theK+uptake capacity. The relationship between the development ofK+uptake and seed germination inPhacelia tanacetifoliais discussed.

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1980.tb03272.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY

摘要:

AbstractDichlorophenyl dimethylurea (DCMU) treatment in photosynthetic samples resulted in an increase in the level of steady state chlorophyllafluorescence at room temperature which was directly proportional to the photosynthetic efficiency. The applicability of this method for the rapid determination of the efficiency of oxygen evolution in leaves, algae, mesophyll cells and chloroplasts has been investigated. Especially reliable values with less than 5% error were obtained if the fluorescence measurements were made under low excitation intensities with a sample chlorophyll concentration below 1.0 μg/ml

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1980.tb03273.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY

摘要:

AbstractA heat‐stable factor present in dry cotton (Gossypium hirsutumL.) seed, or in cotyledons until day 4 of germination, is capable of stabilizing labile nitrate reductase from other species. The stabilizing factor has no effect on stability of glyceralde‐hyde‐3‐phosphate dehydrogenase, but slightly improves the stability of glucose‐6‐phosphate dehydrogenase. Treatment with protease III, and to a lesser extent, trypsin, reduces the effectiveness of the stabilizer. The stabilizer is not a trypsin inhibitor. Dialysis demonstrates that the stabilizing factor has a molecular weight greater than 12,000 daltons. The factor precipitates between 25 and 75% (NH4)2SO4saturation, and is effective at protein concentrations much lower than those required when casein is employed. – From the results of this study, we conclude that the factor which stabilizes labile nitrate reductase from cotton seed is

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1980.tb03274.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY

摘要:

AbstractElectrical and tracer techniques were used to investigate the movement of Na+, K+and Cl−through discs of a range of thicknesses cut from the root tissue of sugar beet,Beta vulgarisL. cv. Amono. At low external concentration the electrical resistance across a discs is less than that of an equivalent volume of solution. This does not appear to be due to a low resistance symplastic pathway but rather, to an enhanced concentration of cation in the apoplast. The resistance is proportional to the thickness of tissue. Although measurement of diffusion potential gives about 25 mV difference across the disc for a ten‐fold change in cation concentration, there is little discrimination between K+and Na+.The observed tracer kinetics of86Rb through the disc are consistent with those of diffusion, with a coefficient of diffusion,D, of 0.19 × 10−9m2s−1and a tissue partition coefficient,k, of 0.27 (or of 2.7 if referred to the cell wall phase only).36Cl gives a similar value forD, but has akreduced by a factor of 3.3, a result that is consistent with the diffusion potential observation. However, a much larger discrimination would have been expected from the chemically measured cation exchange

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1980.tb03275.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY