bluuebunny/crossref_metadata_2025_split huggingface dataset:
Spectral properties of a long‐wavelength absorbing form of protochlorophyll in seeds of Cyclanthera explodens
Authors: SUNDQVIST CHRISTER , RYBERG HANS , BÖDDI BÉLA , LÁNG FERENC 
Published: April 2006

AbstractThe in vivo absorbance spectrum of the inner seed coat of Cyclanthera explodens Naud. showed a main peak in the red region at 671 nm and a weak shoulder at about 640 nm. The pigments were extracted with acetone. separated by paper chromatography and analysed spectrophotometrically. The only detectable pigment was protochlorophyll. The in vivo fluorsecence emission spectra had two main peaks, one at 632 and one at 691 nm. The relation between the two peaks was changed when the exvcitation wavelength was altered from 440 to 460 nm. Excitation at 420 nm gave an additional fluorescence emission peak at 595 nm. These data indicate the presence of at least three forms of protochlorophyll in the Cyclantera seed coat. The spectrum of circular dichroism had a very intence and characteristic signal in the red region with a negative asymmetrical Cotton effect (664 (+), 669 (0) and 687 (−) nm). This indicates that at least one of the protochlorophyll forms is present in a more or less crystalline form.
Effects of cordycepin on IAA‐ and fusicoccin‐stimulated cell enlargement, proton extrusion and potassium uptake in maize coleoptiles
Authors: COCUCCI M.C. , ROSA S. DALLA 
Published: April 2006

AbstractIn maize (Zea mays F, XL 640 A, DEKALB) coleoptiles, cordycepin (3′‐deoxyadenosine) is very active in preventing the cell elongation. H+ extrusion and K+ uptake induced by IAA and, to a much lesser degree, the same phenomena induced by fusicoccin (FC). Cordycepin, while depressing uridine incorporation into RNA, does not decrease the ATP level or significantly influence the pyruvate level and leucine incorporation into proteins in this material. These results support the hypothesis that one or more proteins. whose synthesis is dependent upon short half‐life mRNAs, are essential for a full response to IAA. while this requirement is only partial in FC‐stimulation of growth. They also confirm the view that auxin‐ or FC‐induced activation of H+/K+ exchange plays an important role in mediating the effects of these compounds on cell enlargement.
Fractionation by centrifugation of leaf proteins from varieties and cultivars of Helianthus annuus and Helianthus debilis as a function of pH and temperature
Authors: LUNDBORG TOMAS 
Published: April 2006

AbstractIn order to select plant material for obtaining a high proportion of chlorophyll‐free protein from Helianthus species by heat fractionation, leaf extracts from 11 field grown cultivars of H. annuus and H. debilis were investigated. In addition, press juices from H. annuus cv. Kinesisk were supplied with salts or urea before heat treatment in order to increase the proportion of chlorophyll‐free protein during heat fractionation.The extracts were adjusted to pH 5.0, 6.0 and 8.0; then left for 20 min at 20°C, 50°C or 60°C and centrifuged at 2,500 g. The highest percentage chlorophyll‐free protein of the total protein in the extract, more than 10%, was obtained for H. debilis cv. fl.pl. Sun Gold, H. annuus cv. Giganta, H. annuus cv. uniflorus and H. debilis cv. Stella, at pH 6.0 and 50°C.The low percentage chlorophyll‐free protein obtained could be explained by the fact that a considerable part of the chlorophyll‐free protein sedimented at original pH, low temperature and low centrifugation speed. This sedimentation at low temperature was probably due to interactions of phenolics. Besides, if the chlorophyll‐associated membranes were highly fragmented during the disintegration of the plant material, the high temperature required to precipitate them completely led to further aggregation and thus to loss of chlorophyll‐free proteins.Salts or urea present during heat treatment (pH 6.0/55°C for 20 min) did not considerably increase the proportion of chlorophyll‐free proteins obtained.
Effects of ultraviolet–B irradiances on soybean
Authors: TERAMURA ALAN H. 
Published: April 2006

AbstractSoybean [Glycine max (L.) Merr. cv. Hardee] and wheat (Triticum aestivum L. cv. Jori) were grown from seed under four ultraviolet‐B irradiances and four levels of photosynthetically active radiation in a factorial design. The effects of ultraviolet‐B radiation on leaf number and area, total dry matter production, dry weight of component organs, and plant height were compared between soybean and wheat. Ultraviolet‐B radiation effects were dependent upon the level of photosynthetically active radiation incident during growth. Wheat and soybeans were both affected by low ultraviolet‐B radiation flux densities; however, they differed markedly in their growth responses and biomass allocation patterns. Substantial interactions between ultraviolet‐B and photosynthetically active radiation indicate a need for the measurement of longer wavelength radiation when evaluating the effects of ultraviolet‐B radiation on plant growth in natural conditions.
Effect of photoperiod and temperature on apical growth cessation in two ecotypes of Salix and Betula
Authors: JUNTTILA OLAVI 
Published: April 2006

AbstractApical growth cessation as affected by photoperiod and temperature has been studied in seedlings of two latitudinal ecotypes of Salix 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 of Salix 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 are discussed.
The effect of detergent treatment on methylene blue sensitized cytochrome b photoreduction in fractions from corn coleoptiles
Authors: WIDELL SUSANNE 
Published: April 2006

AbstractIt was previously demonstrated that photoexcited methylene blue can act as electron donor in red light induced reduction of a particulate b‐type cytochrome in fraction from etiolated corn coleoptiles (Zea mays L. 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 particulate b‐type cytochrome is discussed.
Enzymatic, isoelectric, and molecular‐weight characterization of water‐soluble maize‐pollen proteins
Authors: ORTEGA E. I. , BATES L. S. 
Published: April 2006

AbstractMaize (Zea mays L. 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 band
Dichlorophenyl dimethylurea (DCMU) induced increase in chlorophyll a fluorescence intensity – An index of photosynthetic oxygen evolution in leaves, chloroplasts and algae
Authors: KULANDAIVELU G. , DANIELL H. 
Published: April 2006

AbstractDichlorophenyl dimethylurea (DCMU) treatment in photosynthetic samples resulted in an increase in the level of steady state chlorophyll a fluorescence 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.
Varietal variation in uptake and utilization of potassium (rubidium) in high‐salt seedlings of barley
Authors: JENSÉN PAUL , PETTERSSON SUNE 
Published: April 2006

AbstractSeedlings of eleven varieties of barley (Hordeum vulgare L.) showed differences in utilization of K+ from a full nutrient solution containing 3.0 mM K+. The K+ content of both roots and shoots was proportional to the fresh weights and dry weights after a week in the nutrient solution. The K+ use‐efficiency ratio, which indicates the efficiency of nutrient utilization (mg dry weight produced per mg K+ absorbed), differed significantly among the varieties. There was no correlation between influx of Rb+ and the content of K+. It is suggested that there are wide varietal differences in such genetically‐determined properties as ion influx and efflux and net ion transport to the shoot. Further‐more, the influx of Rb+ was closely linked to transpiration, probably due to a variety‐specific non‐metabolic part of Rb+ influx. Varietal differences in influx of Rb+ were more pronounced in high‐K+ roots than in low‐K+ roots with maximum rate of Rb+ uptake, but the rank of varieties was the same in each case. – Criteria for the selection of K+ use‐efficient varieties of barley are discussed.
Diurnal variation of root respiration rates and nitrate uptake as influenced by nitrogen supply
Authors: HANSEN G. K. 
Published: April 2006

AbstractRoot respiration rates of Lolium multiflorum supplied with nitrate or ammonium were measured continuously during several days (Exp. A). Net uptake rate of nitrate was similarly measured by an ion selective nitrate electrode in a system of flowing nutrient solution (Exp. B). Diurnal variation of in vitro nitrate reductase activity and nitrate content of tops and roots were determined (Exp. C). Two levels of irradiance were applied throughout, with day:night of 16:8 h.Root respiration rates showed diurnal patterns, most pronounced in the nitrate treatment, with two peaks appearing about 6 and 16 h after commencement of the photoperiod. Respiration rates were highest in the nitrate treatment and at high irradiance. Respiration rates fell after removal of nitrogen, particularly in the nitrate supplied plant and at high irradiance. Net uptake rate of nitrate exhibited diurnal patterns, often with two peaks occurring at the same times as those of respiration rates. In vitro nitrate reductase activity of tops increased steeply 16 h after commencement of the photoperiod and remained at the high level during the following 8 h of darkness. Nitrate content of tops was highest during the 8 h dark period and fell at the start of the photoperiod. Possible controlling systems of the apparent coincidences of diurnal variation rates, net nitrate uptake and nitrate reduction are discussed.
Ammonium influence on nitrogen assimilating enzymes and protein accumulation in suspension cultures of Paul's Scarlet rose
Authors: MOHANTY BIBEKANANDA , FLETCHER JOHN S. 
Published: April 2006

AbstractThe influence of NH4+ on protein accumulation was examined by growing suspension cultures of Rosa cv. Paul's Scarlet on two defined media. Both contained 1920 μmol of NO3− but only one contained 72.8 μmol of NH4+. At the conclusion of a 14‐day growth period, cultures grown with NH4+ possessed twice as much protein as cultures grown without NH4+. The influence of NH4+ did not appear to be a substrate effect, since the amount of NH4+ provided accounted for only 10% of the nitrogen recovered in protein.The provision of NH4+ in the starting medium increased the activity (μmol substrate. h−1· g−1 fr wt) of glutamate dehydrogenase and glutamate synthase, and reduced the activity of glutamine synthetase. A comparison of the total activity per culture for each of these enzymes with the rate of nitrogen incorporation into protein showed that the enzymatic potential of glutamine synthetase and glutamate dehydrogenase greatly exceeded the actual in vivo rate of nitrogen assimilation through the respective pathways. Thus it was concluded that the availability of either of these enzymes does not limit nitrogen assimilation in rose cells and the fluctuations in their level brought about by NH4+ was of no physiological importance.The activity of glutamate synthase per culture approximated the rate of nitrogen incorporation into protein during early stages of growth, and for that reason may have limited nitrogen assimilation or caused a diversion of nitrogen through the alternative pathway to glutamate catalyzed by glutamate dehydrogenase.
Enzymatic activities of starch synthesis in potato tubers of different sizes
Authors: TSAY J. S. , KUO C. G. 
Published: April 2006

AbstractThe objective of this study was to determine the relationship between tuber weight and enzymatic activities involved in tuber starch synthesis. As tuber weight increased, the activities of sucrose synthetase, UDPG pyrophosphorylase, and granular starch synthetase escalated, whereas the activities of soluble starch synthetase and ADPG pyrophosphorylase stayed constant and that of phosphorylase declined. This suggests that when samples are taken to determine specific enzymatic activities, the sampling procedure should ensure that results do not vary because of differences in the tuber weight or size distribution.
Sucrose metabolism in Sorghum vulgare at ripening
Authors: SHARMA K. P. , BHATIA I. S. 
Published: April 2006

AbstractEnzymes associated with sucrose metabolism in root, stem, leaf and grain of Sorghum vulgare Pers. (cv. JS 263) were studied at the ripening stage. Sucrose phosphate synthetase was dominating in the leaf and sucrose synthetase in the grain. Invertases were more active in leaf, root and stem tissues than in grains. The maximum activities of ADPG pyrophosphorylase and UDPG pyrophosphorylase were found in grains and leaves, respectively. Sucrose synthetase from grains catalyses both synthesis and cleavage of sucrose but the two activities differed in their responses to the effect of temperature, pH and type of buffer. The Km values of the enzyme for UDPG, ADPG, GDPG, TDPG and CDPG were 8.5, 5.3, 16.8 2.2 and 10.7 mM, and for UDP and ADP they were 17.2 and 55.0 mM respectively.
Nitrate assimilation in leaf blades of wheat of different age
Authors: POKHRIYAL T. C. , SACHDEV M. S. , GROVER H. L. , ARORA R. P. , ABROL Y. P. 
Published: April 2006

AbstractA field experiment on wheat (Triticum aestivum L.) ev. Shera grown at 120 kg N ha−1 was conducted. Half of the dose of fertilizer N was applied at the pre‐sowing stage and the other half when the seedlings were one month old. The leaf blades were examined for their NO3− content and NO3− assimilatory activity at various stages of growth and development. Soil nitrate level at 50 cm depth was determined throughout the wheat growing season in terms of cencentration (μg/ml) and total amount (kg ha−1). The upper leaf blades were examined for their capacity to assimilate NO3−. Highly significant correlation between NR (nitrate reductase) activity and NO3− content in the leaf blades. NR activity and soil NO3−, and between soil NO3− and leaf blade NO3− was observed. Findings on low soil NO3− status during the reproductive phase and the capacity of the upper leaf blades to assimilate additional amounts of NO3−, point to the need for developing a programme of soil fertilizer application whereby all the leaf blades can utilize the NO3− optimally and thus result in greater N harvest.
Determination of 4‐chloroindole‐3‐acetic acid methyl ester in Lathyrus, Vicia and Pisum by gas chromatography – mass spectrometry
Authors: ENGVILD KJELD C. , EGSGAARD HELGE , LARSEN ELFINN 
Published: April 2006

Abstract4‐Chloroindole‐3‐acetic acid methyl ester was identified unequivocally in Lathyrus latifolius L., Vicia faba L. and Pisum sativum L. by thin layer chromatography, gas chromatography and mass spectrometry. The gas chromatographic system was able to separate underivatized chloroindole‐3‐acetic acid methyl ester isomers.The quantitative determination of 4‐chloroindole‐3‐acetic acid methyl ester in immature seeds of these three species was performed by gas chromatography – mass spectrometry using deuterium labelled 4‐chloro‐indole‐3‐acetic acid methyl ester as an internal standard. P. sativum contained approximately 25 mg kg‐1, V. faba 1–2 mg kg‐1 and L. latifolius 2 mg kg‐1 dry weight.
Ethylene as an endogenous inhibitor of root regeneration in tomato leaf discs cultured in vitro
Authors: COLEMAN WARREN K. , HUXTER TERRY J. , REID DAVID M. , THORPE TREVOR A. 
Published: April 2006

AbstractWe examined ethylene effects on root regeneration in tomato leaf discs cultured in vitro. Applied ethylene or Ethephon did not stimulate rooting in the leaf discs. In the presence of indoleacetic acid. 5 × 10‐6M, these substances significantly inhibited root formation. Ethylene production (nl C2H4· (24 h)‐1. flask‐1) was positively correlated with increased IAA concentrations at various times during the culture period and, as a consequence, with the rooting response after 168 h. However, separate testing of equimolar concentrations of seven different auxins and auxin‐like compounds showed no positive correlation between the rate of ethylene production and subsequent rooting response. Aeration of gas‐tight flasks containing leaf discs and absorption of ethylene evolved from the discs by mercuric perchlorate in gas‐tight flasks or pre‐treatment of leaf discs with AgNO3 significantly enhanced IAA induced root regeneration. Thus, these studies indicate that ethylene is not a rooting hormone per se. Furthermore, ethylene (whether applied externally or synthesized by the tissue) does not appear to account for the ability of auxin to stimulate rooting.
The utilization of organic nitrogen for growth of algae: physiological aspects
Authors: NEILSON ALASDAIR H. , LARSSON TOMMY 
Published: April 2006

AbstractThe ability of 27 algae belonging to 11 taxonomic divisions to grow at the expense of organic nitrogen was tested in axenic culture. Experiments were carried out in buffered media: morpholine propanesulphonic acid (MOPS) was used successfully for all fresh water strains except diatoms. It was not used as a nitrogen source by any strain examined but served as a good source of sulphur for four strains. The range of substrates used was extensive and included amino acids, urea, acetamide, urate and some nucleosides. Growth rates varied widely but growth yields were generally comparable to those attained with nitrate or ammonia except for substrates containing more than one utilizable nitrogen atom. Limited experiments were carried out in the dark, and it was found that a given substrate was equally suitable for both dark heterotrophic and photolithotrophic growth. Levels of chlorophyll a were measured during growth of two algae with nitrate, glycine and urate. With nitrate, levels of specific chlorophyll a declined some ten‐fold during growth: with poor substrates supporting only slow growth, levels were more uniform but were only 10–15% of those attained during growth with good substrates. One strain grown with MOPS as sole source of sulphur produced cultures with levels of chlorophyll a about half those found in sulphate‐grown cultures. Tolerance of sodium chloride was examined in a few strains and even putatively fresh water strains were found to be appreciably tolerant.
Modification of stress tolerance by dehydration pretreatment in winter rape hypocotyls
Authors: SHCHERBAKOVA ANNA , KACPERSKA‐PALACZ ALINA 
Published: April 2006

AbstractDehydration of isolated rape hypocotyls (Brassica napus L. var. oleifera L. cv. Górczański) to a water saturation deficít of about 60% resulted in increased tolerance to subsequent desiccation and to prolonged immersion in water. Dehydration pretreatment followed by restoration of tissue turgidity, caused a decrease in leakage of electrolytes, ultraviolet‐absorbing materials and ninhydrin‐reactive substances from the desiccated or water immersed hypocotyl tissue. A hardening effect of tissue dehydration is supposed to be related to an improved stability of cell membranes.
Gibberellin‐like substances and indole type auxins in developing grains of normal‐ and high‐lysine genotypes of barley
Authors: MOUNLA M. A. KH. , BANGERTH F. , STORY V. 
Published: April 2006

AbstractChanges in gibberellin‐like activity and content of indole type auxins were investigated during grain development of the two high‐lysine barley (Hordeum vulgare L.) genotypes Sv 73608 and Risø 1508, and their corresponding normal cultivars Mona and Bomi.A peak in gibberellin‐like activity was found in developing grains of the normal cultivars about 18 days after anthesis, whereas the grains of the high‐lysine genotypes showed a two to five times higher maximum about 3–4 days later.The auxin content of the cultivar Bomi showed a maximum between the 22nd and the 29th day after anthesis, whereas, throughout their development the grains of the mutant Risø 1508 exhibited only about 1/10 of the maximum level of auxin found in the grains of Bomi. The normal cultivar Mona also displayed higher contents of auxin than the high‐lysine genotypes Sv 73608, particularly at the later stages of grain growth, but the differences in concentration were considerable smaller than for the pair ‘Bomi’—‘Risø 1508’.It is suggested that auxins play an important role in the development of barley grains.
Changes in diffusion resistance of apple leaves undergoing rapid fluctuations in leaf temperature
Authors: WEST D. W. , GAFF D. F. 
Published: April 2006

AbstractTranspiration was measured in apple leaves (Malus sylvestris Mill.) which were enclosed in a leaf chamber and subjected to rapid changes in leaf temperature. Fluctuations in leaf temperature produced parallel fluctuations in transpiration. The change in transpiration rate with change in temperature was found to be less than the theoretical value calculated from the change in water vapour density gradient from leaf to air. The results suggest the presence of a small and rapidly varying resistance to water vapour loss from the leaf. The magnitude of this additional resistance increased to a maximum value of approximately 1.5 s cm‐1 as the magnitude of the temperature change increased to a maximum of approximately 12°C.