bluuebunny/crossref_metadata_2025 huggingface dataset:
A comparison of the influence of iron on the growth and nitrate metabolism of Anabaena and Scenedesmus
Authors: VERSTREATE DAVID R. , STORCH THOMAS A. , DUNHAM VALGENE L.
Published: April 2006

A comparative study of growth and nitrate metabolism of Anabaena flos‐aquae (Lyng.) Bréb. and Scenedesmus bijugatus var. seriatus Chodat investigated possible mechanisms for the iron‐stimulated increases in growth specific for blue‐green algae in mixed algal communities. Algae were separately grown in an morganic medium with varying concentrations of iron and nitrate to determine the effects on each organism.

Iron was found to be a limiting nutrient for cultures of both Anabaena and Scenedesmus as determined by chlorophyll a concentrations and cell enumeration. Both iron and nitrate stimulated the specific activity of nitrate reductase, nitrite reductase, and glutamine synthetase in Anabaena. Iron enrichment did not increase the activity of the enzymes in Scenedesmus, but inhibited the activity of nitrate reductase and glutamine synthetase. The stimulation of growth by iron in cells grown under iron limiting conditions was associated with increased nitrate metabolism in Anabaena but not in Scenedesmus.
Photooxidative damage to the photosynthetic apparatus during chilling
Authors: VAN HASSELT PHILIP R. , VAN BERLO HAN A. C.
Published: April 2006

Short periods of chilling in the presence of light (up to 6 h: 1°C; 270 W/m2) decreased the subsequent apparent photosynthesis and chlorophyll fluorescence of leaf discs of Cucumis sativus L. cv. Kleine Groene Scherpe. The extent of the injury depended on the duration of the chilling pretreatment. After 6 h the subsequent apparent photosynthesis even reached a negative value, and it increased only slightly during the next 2 1/2 h. The decrease of apparent photosynthesis was not a consequence of increased dark respiration but was of photooxidative origin since the presence of both light and oxygen was required. Preincubation in the light for 2 h at 20°C sensitized leaf discs to subsequent photooxidation during chilling. Prompt and delayed chlorophyll fluorescence decreased simultaneously after chilling and light treatment. The corresponding decrease of photosynthesis and chlorophyll fluorescence is discussed in relation to primary photooxidative damage to the photosystems in the chloroplast membrane.
Nitrogen fixation, stomatal response and transpiration in Medicago sativa, Trifolium repens and T. subterraneum under water stress and recovery
Authors: APARICIO‐TEJO PEDRO M. , SÁNCHEZ‐DÍAZ MANUEL F. , PEÑA JOSÉ I.
Published: April 2006

Stomatal behaviour, transpiration and nitrogen fixation were investigated in Medicago sativa L. (cvs. Tierra de Campos and Aragon, Hidalgo‐Maynar 1966), Trifolium repens L. (cv. Aberystwyth S‐184) and Trifolium subterraneum L. (cv. Clare) subjected to drought by withholding water and then to three days’ recovery after rewatering. Dawn leaf water potential was measured with pressure chamber, stomatal response with a diffusion porometer and nitrogen fixation by using acetylene reduction technique.

At low water potentials, the leaf resistance was higher in Medicago than in Trifolium. As water stress developed all species decreased their transpiration, T. subterraneum being the one most affected by moderate deficits. During water stress ‘Tierra de Campos’ always maintained higher acetylene reduction levels than ‘Aragon’ and the Trifolium species, except for the lowest water potentials.

During recovery from water stress only ‘Tierra de Campos’ reached predeficit transpiration rates. In ‘Tierra de Campos’ acetylene reduction recovery after rewatering was more rapid and intense than in ‘Aragon’. It is concluded that, of the plants investigated, ‘Tierra de Campos’ was best adapted to water deficits.
Callus formation from protoplasts of cell suspension cultures of Rosa ‘Paul's Scarlet’
Authors: STRAUSS ANDRÉ , POTRYKUS INGO
Published: April 2006

Sustained divisions of protoplast‐derived cells obtained from cell suspension cultures of Rosa‘Paul's Scarlet’ leading to colony and callus formation was achieved. The rather low plating efficiencies observed for agar‐plated protoplasts were partly due to early arrests in further development of dividing protoplast‐derived cells and cell clusters. Successful cultivation of dividing protoplast‐derived cells was particularly dependent upon frequent subculturing of the precultures and on an efficient procedure for viable protoplast isolation. Colony formation was largely independent of medium composition.
Cytokinin activity in oak (Quercus robur) with particular reference to transplanting
Authors: SMITH DAVID J. , SCHWABE W. W.
Published: April 2006

Cytokinin activity in sap collected under vacuum from field grown oaks (Quercus robur L.) was determined at monthly intervals throughout the year. A very low level in January was followed by an increase in February and March which reached its maximum 20–25 days before bud‐break. Levels decreased through April and May during leaf expansion, rising once more in June, 10–15 days before a second shoot growth flush. The levels then progressively decreased to reach a minimum in November and December.

Cytokinin activity in roots, 24 h and one week after root‐tip removal did not differ significantly from that in intact control plants. Cytokinin activity in roots and shoots determined in relation to shoot growth flushes revealed no differences in the shoot while the activity in root extracts was lowered after a single flush of shoot growth.

The effects of applying growth regulators at the time of transplanting were investigated by soaking entire transplants in hormone solution. Gibberellin promoted shoot growth at the expense of root growth, but root growth could be restored to normal levels by a simultaneous application of auxin. Cytokinin treatment increased leaf number, but resulted in small bushy plants.

The seasonal changes in cytokinin activity are discussed with regard to successful transplanting.
Localization of divalent cations in phosphate‐rich cytoplasmic granules in yeast
Authors: ROOMANS GODFRIED M.
Published: April 2006

Phosphate‐rich yeast cells (Saccharomyces cerevisiae) take up more calcium and strontium than phosphate‐deficient cells. The divalent cations appear to be tightly bound in phosphate‐rich cells. Electron microscopical investigations, combined with energy‐dispersive X‐ray microanalysis, showed that divalent cations were sequestered in cytoplasmic granules, together with a large amount of phosphorus. The major part of the divalent cations is retrieved in the polyphosphate fraction, a minor part is bound to lipids. The results suggest that polyphosphate granules may serve as an important store for divalent cations.
Variation in cell composition and utilization of N and P for growth of Selenastrum capricornutum
Authors: CLAESSON ANDERS
Published: April 2006

Cell material from different phases of growth for the green alga Selenastrum capricornutum Printz was analysed for major elements and chlorophyll a content. The ranges in percentage of the dry weight were 50–80%, 4.4–8.8%, 0.24–3.0%, and 0.20–3.23% for C, N, P and chlorophyll a, respectively. The dry weight per cell varied 2.3 times between different growth phases. A N/P‐quotient of about 10 (by weight) was found to be a critical level for Selenastrum when these elements were the most limiting nutrients for growth. 31 different organic N‐compounds were tested as single N sources in growth experiments with Selenastrum. At least 19 of them could be utilized to varying extent for algal growth. Three organic P‐compounds of six tested, were utilized for algal growth.

Yield coefficients (mm3 cell volume/mg limiting nutrient element) for Selenastrum were determined with NO3, ‐N (yN= 134). NH4‐N (YN= 111) and PO4‐P (YP= 2580).
Control of respiration of binucleate and trinucleate pollen under humid conditions
Authors: HOEKSTRA FOLKERT A. , BRUINSMA JOHAN
Published: April 2006

The equal rates of water vapour absorption by both bi‐ and trinucleate pollen indicate that their widely‐differing rates of respiration have an intrinsic, biochemical basis. This was investigated with various metabolic inhibitors that were previously introduced into dry pollen via anhydrous acetone.

The uncoupler, carbonyl cyanide m‐chlorophenyl hydrazone, inhibited the O2 uptake of rapidly respiring pollen and stimulated that of slowly respiring types to similar absolute values, that probably reflect the rates of substrate transport across the mitochondrial membranes.

The extent of inhibition of the O2 uptake by oligomycin, dicyclohexyl carbodiimide, antimycin A, and salicyl hydroxamic acid, alone and in combinations, indicates that hardly any oxidative phosphorylation and anabolic activities occur in slowly respiring, binucleate pollen species, having low‐developed mitochondria and high energy charge values. The presence of the alternative pathway was insignificant.

In other binucleate pollen species, characterized by recognizable mitochondria and low energy charge values, a limited ATP synthesis was established. The low energy charge values point to imbalance between phosphorylative and anabolic activities.

In rapidly respiring, trinucleate pollen, containing well‐developed mitochondria, a significant activity of the alternative oxidase was found. The energy charge values were high notwithstanding the large demand for ATP, mounting to 1.7 μmol h−1 (mg pollen)−1.

In some pollen species, oligomycin highly stimulated the flow of electrons through the cytochrome pathway, which made an estimation of the ATP synthesis impossible.
Analysis of newly synthesized proteins during differentiation of cultured Douglas fir cotyledons
Authors: YASUDA TAKESHI , HASEGAWA PAUL M. , CHENG TSAI‐YING
Published: April 2006

Addition of plant growth regulators (5 nM NAA and 5μM BAP) to a defined basal medium stimulated adventitious bud formation of Douglas fir (Pseudotsuga menziesii [Mirb.] Franco) cotyledon explants in culture. Cytoplasmic soluble proteins synthesized during early stages of adventitious bud formation were analyzed by electrophoresis of 3H‐ and 14C‐leucine labeled proteins on SDS polyacrylamide gels. Increased synthesis of low molecular weight proteins (16,000 to 20,000 daltons) was detected after 2 days in culture and reached a maximal level at day 4. When cotyledon explants cultured on bud medium for 2 days were transferred to callus medium (which suppressed adventitious bud formation), suppression of the synthesis of low molecular weight proteins was also observed, suggesting that these proteins may be associated with early stages of adventitious bud formation.
Seasonal variation in ribulose bisphosphate carboxylase activity in Pinus silvestris
Authors: GEZELIUS KERSTIN , HALLÉN MONICA
Published: April 2006

Ribulose bisphosphate carboxylase activity was examined in Pinus silvestris L. during successive seasons. The enzyme activities were studied both in seedlings, kept under controlled conditions in a climate chamber, and in needles from a 15‐year‐old tree in a natural stand. The enzyme activities were analysed in cell‐free extracts prepared with Tween 80 as protective agent.

The carboxylase activity fluctuated periodically both in the seedlings and in the natural stand. In the seedlings, the weight‐related activity in the older needles increased 50–100% (in the cotyledons c. 200%) in the beginning of the “summer”. It decreased as the new shoot developed. The specific activity increased c. 100%. With chlorophyll as base, the activity usually decreased during “summer”. In the developing current needles the carboxylase activity increased when expressed on a weight or on a protein basis. The decrease in weight‐related carboxylase activity in the older needles was preceded by, or simultaneous with, loss of total protein. It is suggested that protein, including the carboxylase, is utilized as nitrogen reserve for the new shoot. During hardening by combined photoperiod and thermoperiod, the carboxylase activity decreased when expressed relative to dry weight and protein. Calculated on a chlorophyll basis, the activity was rather constant.

In the natural stand the activity in the one‐ and two‐year‐old needles increased during spring and summer and decreased during autumn and winter. Even at severe winter stress substantial carboxylase activity remained in the needles. The activity of the enzyme in vivo is discussed with respect to electron transport and net photosynthesis.
Differentiation in Lilium bulbscales grown in vitro. Effects of activated charcoal, physiological age of bulbs and sucrose concentration on differentiation and scale leaf formation in vitro
Authors: TAKAYAMA SHINSAKU , MISAWA MASANARU
Published: April 2006

Organ differentiation and growth of tissue cultured bulbscales of Lilium auratum Lindl. was investigated. Benzyladenine stimulated bulb and bulbscale differentiation but inhibited root formation. Addition of activated charcoal to the medium negated the effect of BA on differentiation, while the growth of bulbs was markedly stimulated. Organ formation was also influenced by the physiological age of bulbs. From bulbscales of a 3‐week‐old bulb, a large number of bulbs and roots was formed but callus was not produced.

A high sucrose concentration (90 g/1) reduced the subsequent sprouting after planting in soil. Scale leaf formation was also regulated. Sucrose (30 g/1) stimulated scale leaf formation but 90 g/1 were inhibitory.
Inhibitors of endogenous proteinases in the seeds of Scots pine, Pinus sylvestris
Authors: SALMIA M. AULIKKI , MIKOLA JUHANI J.
Published: April 2006

Extracts of resting pine seeds inhibited the proteinase activities present in extracts of endosperms of germinating seeds (hydrolysis of haemoglobin at pH 3.7 and hydrolysis of casein at pH 5.4 and 7.0). Heating the extracts of resting seeds at 60°C destroyed their own proteinase activity but their proteinase inhibitor activity decreased by only 25 to 30%. Some properties of the inhibitor(s) were studied using extracts treated at 60°C. The inhibitor activities were non‐dialysable. the inhibition increased linearly with increasing inhibitor concentration up to 80% of total proteinase activity, and the maximal inhibition was 80% at pH 3.7. 90% at pH 5.4. and 97% at pH 7.0.

The extracts of resting seeds did not inhibit the pepsin‐like acid pine proteinase that accounts for a minor part of the proteolytic activity of endosperm extracts at pH 3.7. Neither did they have any effect on the acid pine carboxypeptidase or trypsin and chymotrypsin.

Fresh extracts of endosperms of germinating seeds contained relatively high proteinase activity (assayed directly) and moderate inhibitor activity (assayed after treatment at 60°C). When fresh extracts were dialysed at 50°C for 48 h their proteinase activities increased considerably while the corresponding inhibitor activities disappeared. It is concluded that the decrease of inhibitors during dialysis is due to enzymatic inactivation and that the corresponding increase of proteinase activities is at least partly due to the destruction of the inhibitors.
Water stress and root formation in pea cuttings
Authors: RAJAGOPAL VELAMOOR , ANDERSEN A. SKYTT
Published: April 2006

Eleven day old pea plants (Pisum sativum L. cv. Alaska), grown at 16 W m−2 or 38 W m−2 were stressed with different concentrations of polyethyleneglycol (PEG): –3.0 (mild), –6.4 (moderate) or –13.9 bar (severe) for 2, 4 or 6 h. The leaf osmotic potential, ψπ, and the endogenous abscisic acid (ABA) level and ethylene production were determined at the end of the stress treatment.

The ψπ decreased with stress treatments. The reduction was greater at 38 W m−2 than at 16 W m−2; severely‐stressed plants had less ABA content than those under moderate or mild stress. Ethylene production was higher with the 2 h stress treatment than the non‐stressed only at 38 W m−2. Prolongation of stress to 6 h decreased the ABA level and also ethylene production under both levels of irradiance.

The relationship between the changes in ABA and ethylene and the adventitious root formation in pea cuttings is discussed.
The effects of temperature and inhibitors of protein biosynthesis on the recovery from gas‐shock of Acer pseudoplatanus cell cultures
Authors: THOIRON BERNARD , THOIRON ARLETTE , ESPEJO JOSÉ , GUIEL JEANNE LE , LÜTTGE ULRICH , THELLIER MICHEL
Published: April 2006

The resumption of solute uptake capacity lost after gas‐shock of Acer pseudoplatanus L. cell suspension cultures is severely inhibited by low temperatures (1°C) and by inhibitors of transcription and translation of protein synthesis such as 2‐mercapto‐1 (β‐4‐pyridethyl) benzimidazole (MPB, 40 μg ml−1), puromycin (around 100 μg ml−1) and actinomycin (100 μg ml−1). Cells that have already attained maximum uptake capacity loose it again after less than 1 h in 40 μg ml−1 MPB. Gel‐electrophoresis of the external media of the cells shows that the release of proteins into the solution is affected by shock. The results demonstrate that proteins are involved in the mechanism of solute uptake by the cells, so that these proteins are among the factors altered during shock and recovery, and are important for the understanding of the after‐effects of shock.
Fractionation by centrifugation of leaf proteins in press juices from Brassica and other species as a function of pH
Authors: LUNDBORG TOMAS
Published: April 2006

Non‐green leaf protein concentrates can be produced after separation of chlorophyll‐associated proteins from chlorophyll‐free proteins by sedimenting the chlorophyll‐containing membranes suspended in press juice. To make the use of low speed centrifugation possible, the influence of pH on protein sedimentation rate was investigated, especially for Brassica Oleracea (17 cultivars). Press juices produced on a laboratory scale from greenhouse grown plant material were adjusted to the desired pH and centrifuges briefly at 5000 g or 15,000 g. The chlorophyll‐associated protein from B. Oleraces sedimented rapidly at pH values both below and above 6.0(original pH of the press juice). When the pH of the press juice was adjusted to 7.5, all the chlorophyll‐associated protein sedimented at 15,000 g, whereas about 45%of the original protein remained in the supernatant. An increase in sedimented chlorophyll‐associated protein at higher pH was also observed for Brassica napus, Helianthus annuus and Vicia faba, but not for Beta vulgaris and Dactylis glomerata.

Theoretically, the protein sedimentation pattern typical for B. oleracea might depend primarily on protein aggregation, but shrinking of thylakoids at pH values higher than 6 could contribute. The deviation from this pattern observed for B. vulgaris and D. glomerata might be caused by differences in composition of proteins or low molecular species. In practice, a pH above 7.0 seems to be useful for separation of chlorophyll‐associated proteins from chlorophyll‐free proteins by centrifugation of press juice from Brassica species without heat treatment.
Multiphasic uptake of potassium by barley roots of low and high potassium content: Separate sites for uptake and transitions
Authors: NISSEN PER
Published: April 2006

In the range 10−6M ‐ 5 × 10−2M uptake of K+ in excised roots of barley (Hordeum vulgare L. cv. Herta) with low and high K content could in both cases be represented by an isotherm with four phases. Uptake, especially in the range of the lower phases, was reduced in high K roots through decreases in Vmax and increases in Km. Similar data for other plants are also shown to be consistent with multiphasic kinetics. The concentrations at which transitions occurred were not affected by the K status, indicating the existence of separate uptake and transition sites. Uptake was markedly reduced in the presence of 10−5M 2,4‐dinitrophenol, especially at low K+ concentrations, but the isotherms remained multiphasic. This contraindicates major contributions from a non‐carrier‐mediated, passive flux. A tentative hypothesis for multiphasic ion uptake envisions a structure which changes conformation as a result of all‐or‐none changes in a separate transition site. The structure is “tight” at low external ion concentrations (low Vmax. low Km. active uptake, allosteric regulation) and “loose” at high concentrations (high Vmax‐ high Km‐ facilitated diffusion, no regulation).
Photosynthetic CO2 fixation in spinach chloroplasts inhibited by pine chloroplasts or extracts of pine chloroplasts
Authors: MARTIN BJÖRN , BASSHAM JAMES A.
Published: April 2006

Chloroplasts isolated from pine needles were found to be inactive with respect to CO2 fixation. Since it was suspected that pine needles may contain substances inhibitory to photosynthesis, studies were carried out using photosynthetically active isolated spinach chloroplasts and chloroplasts isolated from pine needles. When isolated pine chloroplasts were suspended in buffer and were added to isolated spinach chloroplasts they inhibited photosynthetic CO2 fixation. When the pine chloroplasts were separated from the medium by centrifugation, the separated pine chloroplasts severely inhibited CO2 fixation by isolated spinach chloroplasts, but the supernatant solution from the pine chloroplasts was not inhibitory. As little as 5% pine chloroplasts (based on chlorophyll content) produced 50% inhibition of CO2 fixation by the spinach chloroplasts. Studies of fixation of 14C‐labelled CO2 by spinach chloroplasts were carried out in which after 5 min photosynthesis the pine chloroplasts were added. It was found that the subsequent inhibition of spinach CO2 fixation was neither due to any effect on the rate of export of photosynthetic metabolites from the chloroplasts to the medium, nor to a direct effect on the RUBP carboxylase reaction. The principal effect was found to be an inhibition of the conversion of fructose‐1,6‐bisphosphate and sedoheptulose‐1,7‐bisphosphate to the respective monophosphates and inorganic phosphate. From this finding it was concluded that a principal effect of the inhibition by pine chloroplasts is probably an inhibition either directly or indirectly of the bisphosphatase enzymes in the spinach chloroplasts. Based on its distribution between organic and aqueous acidic or neutral solutions, the inhibitory factor of the pine chloroplasts must be lipophilic. Most of the factor could be transferred to an aqueous phase in a strongly alkaline solution. Following subsequent acidification of the aqueous phase the activity could be completely transferred back into the organic phase. This procedure allowed for separation of the inhibitory factor from most of the pigments and other lipophilic substances present in the pine chloroplasts and yielded a preparation which could be subsequently fractionated by thin layer chromatography. UV absorption was found in two fast moving spots and at the origin. The fastest running spot from the thin layer chromatography plate was found to be the one containing most of the inhibitory activity.
Inhibitors of endogenous proteinases in Scots pine seeds: Fractionation and activity changes during germination
Authors: SALMIA M. AULIKKI
Published: April 2006

Resting seeds of Scots pine (Pinus sylvestris L.) contain inhibitors which inhibit the proteinase activity present in germinating seeds but have no effect on trypsin or chymotrypsin. When a crude inhibitor preparation was chromatographed on Sephadex G‐75, the inhibitor activity separated into four peaks with elution volumes corresponding to the molecular weights 24,000, 14,600, 14,000, and 9000. Each of the inhibitors affected both the hydrolysis of haemoglobin at pH 3.7 and the hydrolysis of casein at pH 5.4 and 7.0 by proteinase extracts prepared from “germinating” endosperms. These results suggest that one major proteinase was possibly acting in all the assays.

In resting seeds inhibitor activity was present in both the embryo and the endosperm, the activity (per mg dry weight) in the embryo being about 2‐fold that in the endosperm. In the endosperms of germinating seeds the inhibitor activity per seed decreased at about the same rate as total N and dry weight. In the seedlings the activity per seedling remained approximately constant. The patterns of the activity changes suggest that the inhibitors do not control the breakdown of storage proteins; a more probable function is the protection of other cellular components from the high proteinase activities required for the rapid proteolysis during germination.
Turnover of cell wall polysaccharides of a Vinca rosea suspension culture
Authors: TAKEUCHI YUICHI , KOMAMINE ATSUSHI
Published: April 2006

Turnover of cell wall components was examined in two growth phases of a batch suspension culture of Vinca rosea L. Three‐day‐cultured cells (cell division phase) and 5‐day‐cultured cells (cell expansion phase) were incubated with d‐[U‐14C]glucose. After various periods of incubation, extra‐cellular polysaccharides (ECP) and cell walls were isolated, and then the cell walls were fractionated to pectic substance, hemicellulose, and cellulose fractions. The results of the measurement of radioactivities and amounts of total carbohydrate in the ECP and cell wall fractions indicated that synthesis of pectic substance was more active in the cell division phase than in the cell expansion phase. From the results of the pulse‐chase experiments, in which cells prelabelled by incubation with d‐[U‐14C]glucose for 3 h were incubated in a medium containing unlabelled glucose for various periods, the gross degradation, net synthesis, and gross synthesis of cell wall components were estimated. Active degradation and synthesis were observed in the hemicellulose fraction, indicating that active turnover occurred in the hemicellulose fraction, while little degradation was found in the pectic substance and cellulose fractions.
Polyribosomes and protein synthesis in after‐ripening pear seeds
Authors: ALSCHER‐HERMAN RUTH , KHAN A. A.
Published: April 2006

Polyribosomes have been isolated from pear seeds which show a capacity for in vitro protein synthesis. Translational capacity increased during stratification with a peak after 13 days of stratification. This increase was greatly diminished in seeds which were incubated at 25°C (“warm stratification”). The peak in protein synthetic activity coincides with the period of stratification required for normal development of excised embryos.
Fate of nitrate during initial nitrate utilization by nitrogen‐depleted dwarf bean
Authors: BRETELER HANS , CATE CHARLOTTE H. HÄNISCH TEN
Published: April 2006

The fate of nitrate and nitrogen‐15 was followed during the apparent induction phase (6h) for nitrate uptake by N‐depleted dwarf bean (Phaseolus vulgaris L. ev. Witte Krombek). Experiments were done with intact plants and with detached root systems. Qualitatively and quantitatively, xylem exudation from detached roots was a bad estimate of the export of NO−3 or NO−3‐15N from roots of intact plants.

In vivo nitrate reductase activity (NRA) agreed well with in situ reduction, calculated as the difference between uptake and accumulation in whole plants, provided NRA was assayed with merely endogenous nitrate as substrate (‘actual’ NRA). The majority (75%) of the entering nitrate remained unmetabolized. Both nitrate reduction and nitrate accumulation occurred predominantly in the root system. Some (< 25%) of the root‐reduced nitrate‐N was translocated to the shoot. Nitrate uptake occurred against the concentration gradient between medium and root cells, and probably against the gradient of the electro‐chemical potential of nitrate. Part of the energy expended for NO−3 absorption came from the tops, since decapitation and ringing at the stem base restricted nitrate uptake.
Physiology of the tomato mutant alcobaca
Authors: KOPELIOVITCH E. , MIZRAHI Y. , RABINOWITCH H. D. , KEDAR N.
Published: April 2006

Alcobaca is commonly regarded as an abnormally ripening mutant of the tomato (Lycopersicon esculentum Mill.). Alcobaca fruits were found to be similar to cv. Rutgers fruits in the following characteristics: time between full anthesis and the onset of ripening, response to ethephon, flavor, pH and concentrations of titratable acids, total soluble solids and reducing sugars. The pattern of CO2 and ethylene climacteric are similar in the two plant types, but the peak levels were lower and occurred later in alcobaca than in ‘Rutgers’. The mutant fruits differed from fruits of normal varieties in their greatly prolonged shelf life, their relatively low activity of polygalacturonase (PG) and polymethylgalacturonase (PMG), and their low level of endogenous ethylene. Fruits of the mutant harvested before the onset of ripening failed to reach normal pigmentation and remained yellow. Fruits harvested at the onset of ripening reached an orange color, while fruits ripened while attached to the plant reached almost normal pigmentation. These results suggest that alcobaca is a slow ripening mutant and does not belong to the category of non‐ripening mutants.
Biochemical studies on blossom end rot of tomatoes
Authors: DEKOCK P. C. , VAUGHAN D. , HALL A. , ORD B. G.
Published: April 2006

The causes of cell wall necrosis in Blossom End Rot (BER) of tomatoes have been investigated by comparing enzyme activities in healthy and affected tissues in the cultivars Grenadier and Moneymaker. Changes in the mineral contents of the tomatoes were in accordance with those of calcium deficient tissues. The phenolic contents of the affected tissues were increased as also were caffeic and chlorogenic acids. Phenolase and peroxidase activities were higher in affected fruits white catalase activities were higher in healthy fruits. 14C‐labelled leucine was incorporated into the proteins of the healthy fruits to the greatest extent but cell wall proteinbound hydroxyproline was greatest in affected fruits.
Radiation‐induced improvement of the freeze‐resistance of a cold‐sensitive wheat variety: Freeze‐tolerance and fatty acid patterns
Authors: TÓTH ECATERINA T. , VIGH LÁSZLÓ , KARVALY BÉLA , FARKAS TIBOR
Published: April 2006

Effects of 3–15 krad 60Co gamma radiation on cereal seeds were investigated with regard to the frost hardiness of leaves of 5–7‐day‐old seedlings. Comparative studies were carried out on the gas‐chromatographically determined distribution patterns of fatty acids in different pools (total fatty acid, total lipid, polar lipids) of a cold‐resistant (cv. Mironowskaya 808) and a cold‐sensitive (cv. Penjamo 62) cultivar of wheat (Triticum aestivum L.). Parallelism between fatty acid distribution pattern, empirical parameters suggested for quantitative measures of cold tolerance (the ratio unsat/sat and double‐bond index), and the low‐temperature behaviour of shoots grown from radiation treated seeds of ‘Penjamo 62’, was also examined. To monitor differences in the fatty acid syntheses of ‘Mironowskaya 808’and ‘Penjamo 62’, and to demonstrate radiation‐induced changes in fatty acid turnover a [1–14C]‐acetate incorporation technique was employed.

The results of practical importance are:

1. A significant improvement in the frost‐resistance of the cold‐sensitive ‘Penjamo 62’variety could be achieved with 6–9 krad irradiation, the half‐freeze‐killing temperature dropping from −6 to about −18°C.

2. Freeze‐hardiness, no matter whether inherited or gained, could be abolished by gamma irradiation with higher dose.

The following conclusions of theoretical interest can be drawn:

1. Low‐temperature behaviour of plant tissues is a dynamic property rather than a static one, not only the formation but also the breakdown of certain hydrocarbon chains may be of paramount relevance in cold‐tolerance.

2. Not the linolenic (18:3) component, but rather the overall distribution pattern of the C18 family seems to correlate with low‐temperature‐responses of shoots.

3. Empirical parameters investigated do not provide reliable quantitative measures of the susceptibility to freeze (and cold‐) injuries.

4. Changes in the syntheses of some key proteins (e.g. peroxidase, water‐soluble proteins, etc.) may also be important in adaptation to low‐temperature conditions.
Photosynthetic activities of cadmium‐treated tomato plants
Authors: BASZYŃKI TADEUSZ , WAJDA LUCYNA , KRÓL MARIA , WOLIŃSKA DANUTA , KRUPA ZBIGNIEW , TUKENDORF ANNA
Published: April 2006

Tomato plants (Lycopersicum esculentum Mill. 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 activity.
Pattern of sulfate uptake during root elongation in maize: its correlation with productivity
Authors: CACCO G. , FERRARI G. , SACCOMANI M.
Published: April 2006

The 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.
K+ uptake in the early phases of germination of the photoblastic and thermosensitive seed of Phacelia tanacetifolia
Authors: PARDI D. , MORGUTTI S. , COCUCCI S.
Published: April 2006

Germination of Phacelia tanacetifolia Benth. (cv. Bleu Clair) seeds is accompanied in its early phases by the development of the K+ 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 the K+ uptake capacity. The relationship between the development of K+ uptake and seed germination in Phacelia tanacetifolia is discussed.
The nitrate reductase stabilizing factor in cotton seeds
Authors: PURVIS ALBERT C. , TISCHLER CHARLES R. , FUNKHOUSER EDWARD A.
Published: April 2006

A heat‐stable factor present in dry cotton (Gossypium hirsutum L.) 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) 2 SO4 saturation, 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 proteinaceous.
Electrical resistance and ion movement through excised discs of sugar beet root tissue
Authors: AIKMAN D. P. , HARMER R. , RUST T. S. O.
Published: April 2006

Electrical 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 vulgaris L. 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 of 86Rb through the disc are consistent with those of diffusion, with a coefficient of diffusion, D, of 0.19 × 10−9 m2 s−1 and 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 for D, but has a k reduced 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 capacity.
Interactions of chlorophyll a and terpenoid alcohols with chloroplast acyl lipids in monomolecular films
Authors: LILJENBERG CONNY , SELSTAM EVA
Published: April 2006

Surface pressure‐area measurements of purified chlorophyll a and monogalactosyl diacylglycerol in mixed monolayers were performed at 20°C with an automatic recording surface film balance at a constant compression rate. In addition structural parts of the chlorophyll and the monogalactosyl diacylglycerol as phytol and geranylgeraniol on one hand and different fatty acids on the other were studied pure and in mixed films. All components studied formed stable monomolecular films. Chlorophyll a and monogalactosyl diacylglycerol showed miscibility. Phytol was immiscible with synthetized monogalactosyl diacylglycerol containing only stearic acid. Mixed monolayers of phytol and monogalactosyl diacylglycerol isolated from barley containing 83 mol % a‐linolenic acid showed a strong interaction. An increased miscibility and association were found between phytol and fatty acids with increasing unsaturation. The results are discussed as a model for the localization of part of chlorophyll a in the thylakoid membrane.
Simple identification of the neutral chlorinated auxin in pea by thin layer chromatography
Authors: ENGVILD KJELD C.
Published: April 2006

One of the neutral chlorinated auxins of immature pea seeds was readily identified by thin layer procedures simple enough to serve in student's laboratory courses.

4‐Chloroindole‐3‐acetic acid methyl ester was extracted from 50 g of commercial, frozen peas by either water or acetone, concentrated to small volumes and chromatographed in CHCl3 or CCl4 solvent systems separating the chlorinated auxin from indoleacetonitrile and the methyl or ethyl esters of indoleacetic acid.

Colour reaction was carried out with some of the Salkowski FeCl3 sprays of which Ehmann's FeCl3/dimethylaminobenzaldehyde modification gave the most stable blue colour.
Changes in cold hardiness of introduced and native interior Alaskan evergreens in relation to water and lipid content during spring dehardening
Authors: KEDROWSKI RICHARD A.
Published: April 2006

Needle hardiness of introduced yellow pine, Pinus banksiana Lamb., lodgepole pine, P. contorta Dougl, and native white spruce, Picea glauca (Moench) Voss, were assessed by the effective prefreezing temperature method. Yellow pine needles were less hardy than lodgepole pine or white spruce needles in Alaska on each date measured. Although hardiness decreased in springtime in all species, decreases in hardiness in yellow pine began before temperatures were above −20°C, apparently in response to day length, while decreases in hardiness in lodgepole pine and white spruce began only when mean temperatures were above 0°C. Hardiness was increased by decreasing the water content of yellow pine and spruce needles. However, only the latter increased its field hardiness by decreased water contents, and only to a small degree. Large decreases in phospholipid occurred during the dehardening period, indicating the presence of major membrane‐associated changes. However, changes in hardiness did not closely parallel those in phospholipid; hardiness decreased before phospholipid did in spruce and after phospholipid did in lodgepole pine. In yellow pine, changes in hardiness were more closely related to changes in phospholipid content. Decreases in phospholipid appeared to be correlated with the day length in all species.
Seasonal abscisic acid accumulation in stem cambial region of Pinus silvestris, and its contribution to the hypothesis of a late‐wood control system in conifers
Authors: WODZICKI TOMASZ J. , WODZICKI ALINA B.
Published: April 2006

Gradual accumulation of natural inhibitor in tissues comprising the cambial zone and about 1 mm of the youngest phloem of the basal region of the Pinus silvestris stem during the season was detected by both extraction and diffusion methods followed by bioassays. The purified inhibitor was chromatographically identified as similar to abscisic acid. Taking into account earlier numerous results, the hypothesis is formulated that the seasonal accumulation of abscisic acid affects phenomena associated with auxin polar transport, so that autolytic breakdown of protoplasts, which terminates differentiation of tracheids in stem secondary xylem is delayed. This effect extends the maturation phase and results in formation of thick‐walled tracheids, characteristic for the late‐wood in conifers.
Leaf age and salinity influence water relations of pepper leaves
Authors: HOFFMAN G. J. , SHALHEVET J. , MEIRI A.
Published: April 2006

Plant growth is reduced under saline conditions even when turgor in mature leaves is maintained by osmotic adjustment. The objective of this study was to determine if young leaves from salt‐affected plants were also osmotically adjusted. Pepper plants (Capsicum annuum L. cv. California Wonder) were grown in several levels of solution osmotic potential and various components of the plants' water relations were measured to determine if young, rapidly growing leaves could accumulate solutes rapidly enough to maintain turgor for normal cell enlargement.

Psychrometric measurements indicated that osmotic adjustment is similar for both young and mature leaves although osmotic potential is slightly lower for young leaves. Total water potential is also lower for young leaves, particularly at dawn for the saline treatments. The result is reduced turgor under saline conditions at dawn for young but not mature leaves. This reduced turgor at dawn, and presumably low night value, is possibly a cause of reduced growth under saline conditions. No differences in leaf turgor occur at midday.

Porometer measurements indicated that young leaves at a given salinity level have a higher stomatal conductance than mature leaves, regardless of the time of day. The result of stomatal closure is a linear reduction of transpiration.
Phycochromes b and d: their occurrence in some phycoerythrocyanin‐containing blue‐green algae (cyanobacteria)
Authors: BJÖRN G. S.
Published: April 2006

Abstract

Phycochromes b and d, two types of photoreversibly photochromic pigments previously extracted from the blue‐green alga Tolypothrix distorta, which contains phycoerythrocyanin, have now been found in three Anabaena strains also containing phycoerythrocyanin. Tests for the presence of phycochromes b and d in a number of blue‐green algae lacking phycoerythrocyanin have been negative. The possibility that phycochrome b‐type absorbance changes are due to changes in the α‐subunit of phycoerythrocyanin is discussed.
Nicotiana tabacum callus studies. X. ABA increases resistance to cold damage
Authors: BORNMAN CHRIS H. , JANSSON EVA
Published: April 2006

The effects of cis. trans abscisic acid on response to chilling was investigated in callused Nicotiana tabacum L. pith explants. Explants pretreated with 10‐4M ABA underwent approximately 50% less cellular leakage when chilled at 2°C under short‐day conditions for 10 d than the comparable non‐treated tissue. Growth in terms of fresh and dry weights, although poor in comparison to non‐chilled (20°C, long days) treatments, was more than twice that of the non‐ABA‐treated material. On an absolute dry weight basis proline content increased on chilling from 0.7 to 3.4 mg g‐1 in non‐ABA‐treated explants, but rose to nearly 17 mg g‐1 in the tissue treated with ABA. Only in the case of cold‐hardened. ABA‐treated tissue could some cells survive subzero temperatures and regenerate callus again. It is suggested that at least part of the ameliorating effects of ABA result from an increase in the level of proline.
Mesophyll cell properties for some C3 and C4 species with high photosynthetic rates
Authors: LONGSTRETH DAVID J. , HARTSOCK TERRY L. , NOBEL PARK S.
Published: April 2006

Leaves of twelve C3 species and six C4 species were examined to understand better the relationship between mesophyll cell properties and the generally high photosynthetic rates of these plants. The CO2 diffusion conductance expressed per unit mesophyll cell surface area (gCO2cell) cell was determined using measurements of the net rate of CO2 uptake, water vapor conductance, and the ratio of mesophyll cell surface area to leaf surface area (Ames/A). Ames/A averaged 31 for the C3 species and 16 for the C4 species. For the C3 species gCO2cell ranged from 0.12 to 0.32 mm s‐1, and for the C4 species it ranged from 0.55 to 1.5 mm s‐1, exceeding a previously predicted maximum of 0.5 mm s‐1. Although the C3 species Cammissonia claviformis did not have the highest gCO2cell, the combination of the highest Ames and highest stomatal conductance resulted in this species having the greatest maximum rate of CO2 uptake in low oxygen, 93 μmol m‐2 s‐1 (147 mg dm‐2 h‐1). The high gCO2cell of the C4 species Amaranthus retroflexus (1.5 mm s‐1) was in part attributable to its thin cell wall (72 nm thick).
Extracellular invertase of Rhizobium japonicum and its role in free sugar metabolism in the developing root nodules of Sesbania grandiflora
Authors: SINGH RANGIL , SIDHU P. S. , VADHERA SHYAMA , SITAL J. S. , BHATIA I. S.
Published: April 2006

Extracellular invertase of Rhizobium japonicum and its role in free sugar metabolism in the developing root nodules of Sesbania grandiflora L. was studied. The enzyme hydrolysed sucrose extracellularly, and its release was substrate inducible. 0.1 Mβ‐mercaptoethanol released the cell‐bound form of this enzyme. The production of invertase was low when glucose, galactose, mannose, fructose and raffinose were used as carbon sources in the growth medium. In the developing nodules sucrose was the major sugar. The content of fructose was low in comparison with that of glucose – suggesting that in the nodules, fructose is converted to glucose prior to its entry into the bacterial cell. The content of glucose synchronised with the pattern of change in the activity of invertase in the nodules.