bluuebunny/crossref_metadata_2025 huggingface dataset:
Ascorbic acid as negative effector of the peroxidase‐catalyzed degradation of indole‐3‐acetic acid
Authors: Palmieri S. , Giovinazzi F.
Published: April 2006

Ascorbic acid is a strong inhibitor of indole‐3‐acetic oxidation catalyzed by commercial horse‐radish peroxidase. In the presence of excess ascorbic acid, the indole‐acetic acid oxidation catalysis is apparently blocked. The activity of peroxidase for indoleacetic acid at pH 3.7 and 33°C, in the presence of 2,4‐dichlorophenol and MnCl2 as promotors was measured by polarographic technique. The Km was 0.27 mM and the maximum velocity was 1.02 mmol O2 (mg protein)−1 min−1. Dixon plots lead to an apparent Ki of 1.25 (μM for ascorbic acid and the inhibition was apparently competitive. Ascorbic acid, besides appearing to be a strong inhibitor of the IAA oxidase activity of peroxidase, seemed to protect IAA from total degradation. Addition of more than 5 μM ascorbic acid produced both an exponential increase in the lag time before the onset of reaction and, at the end, an oxidation protection of 26 μM IAA when 111 μM IAA was present at the stawrt. The possibility of ascorbic acid‐IAA auxin from endogenous oxidation in plants, is proposed.
Effects of desiccation on the excitation energy distribution from phycoerythrin to the two photosystems in the red alga Porphyra perforata
Authors: Öquist Gunnar , Fork David C.
Published: April 2006

Low temperature (77°K) fluorescence emission and excitation spectra were recorded for wet and desiccated thalli of Porphyra perforata. The photosystem I (F730) and photosystem II (F695) fluorescence emission kinetics during photosystem II trap closure were also recorded at 77°K. Desiccation induced a lowering of the fluorescence yield over the whole emission spectrum but the decrease was most pronounced for the photosystem II fluorescence bands, F688 and F695. It was shown that the desiccation‐induced changes of the phycoerythrin sensitized emission spectrum were due to 1) a decrease in the fluorescence yield of the photosystem I antenna, 2) an even stronger decrease in the fluorescence of photosystem II, which was mediated by an increased spillover (kT(II→I)) of excitation to photosystem I and an increase in the absorption cross section, α, for photosystem I. We hypothesize that the increase of both kT(II→I) and α are part of a mechanism by which the desiccation‐tolerant, high light exposed, Porphyra can avoid photodynamic damage to photosystem II, when photosynthesis becomes inhibited as a result of desiccation during periods of low tide.
In vitro adventitious budding on Pinus pinaster cotyledons and needles
Authors: David A. , David H. , Mateille T.
Published: April 2006

Adventitious budding can be induced on two types of Pinus pinaster Ait. organs. Cotyledons (10‐mm‐long), derived from 8 to 10‐day‐old seedlings, show morpho‐genetic response when an appropriate mineral solution is used (NH4+/K+= 1). Of the various cytokinin concentrations added to this optimal mineral medium, 0.8 μM BAP (6‐benzylaminopurine), with 5 nM NAA (1‐naphtaleneacetic acid), promoted organogenesis best. Buds were induced from outer mesophyll layers.

Short shoots and the elongating needles (70‐mm‐long) were collected from cuttings of a mature tree (10‐years‐old). These cuttings benefited from physiological advantages of a well‐developed root system (by heating the substrate). In order to stimulate in vitro organogenesis, they had been sprayed every week from March to May with 10 μM BAP.

When cultivated in the presence of 10 μM BAP and 25 nM NAA, 79% of the explants produced buds from dome‐shaped meristematic cell clusters that pre‐existed at the top of the short shoots. Moreover, among these, 42% gave rise to adventitious buds induced from proliferating mesophyll cells at the needle base. The morphologies of the two kinds of shoots were similar. Adventitious budding on these two different explants should allow vegetative multiplication of selected seedlings and elite trees.
The effects of organic nitrogen sources on growth of cell cultures of Douglas‐fir
Authors: Kirby Edward G.
Published: April 2006

In order to establish rapidly growing, friable cell cultures of Douglas‐fir (Pseudotsuga menziesii [Mirb. (Franco)], the effects of organic sources of nitrogen on growth were investigated. Of the nitrogen sources studied, including allantoin, allantoic acid, glutamine and glutamic acid, all were capable of increasing growth. Glutamine (50 mM) produced the most marked increase in growth boosting dry weight production to a level of four times that of controls. Glutamine additions also eliminated the lag phase of growth and caused cells to become densely cytoplasmic. Results are discussed in relation to the pathway for assimilation of nitrogen.
Influence relative de la BAP et de l'IBA sur la néoformation de bourgeons et de racines sur les plantules du Biota orientalis (Cupressacées)
Authors: Thomas M. J. , Tranvan H.
Published: April 2006

Relative influence of BAP and IBA on the induction of adventitious buds and roots on plantelts of Biota orientalis (Cupressaceae)

Both cytokinin (BAP) and auxin (IBA) have an influence upon the intensity of adventitious bud induction in vitro on hypocotyls of Biota orientalis.

Increase in either the concentration or the length of contact with cytokinin enhances the mean number of neoformed buds per explant, while that of auxin results in an increase of the mean number of reactive explants as well as in the nature of neoformations. Auxin contributes to a restoration of the induction when the length of contact with cytokinin is too short. However, this synergism is only observed when the contract with IBA is simultaneous or follows that with contract with BAP.

Rhizogenesis is also influenced by the auxin‐cytokinin balance. An increase in the duration of contact with IBA is always followed by an increased in the mean number of explants forming roots. This organogenesis may be partially or completely inhibited if the duration of contact with cytokinin – before, simultaneously or after that with auxin‐ exceeds two weeks.
Seasonal changes in adventitious root formation in hypocotyl cuttings of Pinus sylvestris: Influence of Photoperiod during stock plant growth and of indolebutyric acid treatment of cuttings
Authors: Hansen Jürgen , Ernstsen Arild
Published: April 2006

Seedlings of Pinus sylvestris were grown for 6 weeks under natural light conditions in a temperature controlled environment room. Cuttings from these plants were rooted in tap water or in indolebutyric acid (IBA) solutions for 60 days at an irradiance of 16 W m‐2. Experiments were performed at 3‐week intervals during two growth seasons. — Seasonal changes in root formation were found in control cuttings as well as in IBA treated cuttings. The number of roots and the percentage of cuttings that rooted were high during early spring and autumn. During the summer period hardly any roots were formed. Stimulation of root formation by IBA occurred manily during spring and autumn when cuttings already possessed the ability to form roots. — The influence of photoperiod during stock plant growth was also investigated. Shorter photoperiod resulted in an increase in the number of roots and rooting percentage. The period during summer where rooting was inhibited under natural light conditions was considerably shortened when stock plants were grown at a photoperiod of only 4 h. The results demonstrate the importance of the growing conditions for stock plants for subsequent root formation. The results are discussed with special reference to the role of irradiance.
Uptake and translocation of calcium in cucumber
Authors: Bengtsson Bengt
Published: April 2006

Uptake and translocation of Ca2+(45Ca) were compared with water translocation in 12‐day old intact plants and excised roots of cucumber (Cucumis sativus L. var. Cilla), which had been cultivated in nutrient solution. No immediate reduction of Ca2+ uptake was found when water translocation was reduced by excision of the shoot. In the presence of 2,4‐dinitrophenol Ca2+ translocation was reduced in the intact plants while water translocation was unchanged. It is suggested that regulation of Ca2+ uptake is primarily achieved in the root. The DNP‐sensitive mechanism of Ca2+ uptake was associated with the root and probably represented transport through the endodermis into the stele.
Age‐dependent content of polymerized lipids in Sphagnum fuscum
Authors: Karunen Pirjo , Ekman Rainer
Published: April 2006

The polymerized lipids of Sphagnum fuscum cell wall fragments were found to be composed of long chain hydroxy acids, long chain dicarboxylic acids, fatty alcohols and fatty acids. Their content, on a dry weight basis, was low in the topmost 3 cm of the shoot and increased with shoot age (and depth). A pronounced increase (16‐fold) occurred in the contents of hydroxy acids which comprised 76% of the totals at the depth of 40–43 cm. The increase at the depth of 40‐43 cm is considered to be at least partly associated with the frequently found destruction of the most suscptible part, the thin‐walled stem center. The results suggest that aliphatic lipid polymers are present and acumulated in cell walls resistant to breakdown.
Mise en évidence de I'AIA‐5‐3H par autoradiographie dans le coléoptile de Blé
Authors: Perbal Gérald , Leroux Yves , Driss‐Ecole Dominique
Published: April 2006

Two methods of fixation of 3H‐IAA on macromolecules were studied in order to obtain autoradiographs of semi‐thin sections after a routine treatment for electron microscopy. Glutaraldehyde and DCC [1‐(3‐dimethylaminopropyl)‐3‐ethylcarbodiimide hydrochloride] could be used to obtain in vitro fixation of auxin on proteins. However, the rate of reaction with DCC was greater, so that the method using this compound is preferable. A cytological study was performed on wheat coleoptiles (Triticum sativum L., var. Capitole) after application of 3H‐IAA to their tips. Almost no radioactivity was found in the phloem elements while the procambium and the vessels were intensively labelled. In parenchyma cells, cell walls, nuclei and intercellular spaces contained a large amount of 3H‐IAA. These results are consistent with the hypothesis that auxin is transported, from cell to cell, via the apoplast. The extraction of auxin by methanol before cytological fixation indicates that this hormone is not bound (by a covalent binding) to cellular structures, except perhaps in the secondary wall of vessels.
Purification and properties of protein Z – a major albumin of barley endosperm
Authors: Hejgaard J.
Published: April 2006

A major albumin of barley grain, called protein Z, has been purified from endosperm flour. Extraction with 0.05 Mβ‐mercaptoethanol and successive use of (NH 4)2SO4‐precipitation, anion exchange at pH 7.5, cation exchange at pH 4.5, and anion exchange at pH 8.0 resulted in a highly pure protein as judged from various electrophoretic and immunoelectrophoretic tests. As protein Z is a major protein component of beer, antibodies towards a protein‐rich beer fraction could be used to detect the protein during purification. Protein Z consists of at least four antigenically identical molecular forms with isoelectric points in the range 5.55–5.8, but same molecular mass near 40000. Dimer and, probably, tetramer forms were detected by gel filtration in the absence of reducing agents. Monospecific antibodies towards protein Z were prepared. Immunoelectrophoretic properties of the protein were not affected by treatment at pH 1–13 (30 min at 30°C) or up to 100°C (30 min at pH 7). Commonly grown barley varieties contained about 1.5–2.5 mg protein Z/g grain, but a much lower content (∼ 0.2 mg/g grain) was found in a few varieties. Like barley β‐amylase, protein Z was present in both salt‐extractable “free” (20–30%) and thiol‐extractable “latent” (70–80%) forms in the grain. Protein Z contains 2 cysteine and 20 lysine residues per monomer molecule and is relatively rich in leucine and other hydrophobic residues. Protein Z may contribute up to 5% of the total grain lysine in normal varieties and more than 7% in some high‐lysine barleys.
Polyamines and wounded storage tissues – Inhibition of RNase activity and solute leakage
Authors: Altman Arie
Published: April 2006

The “protective” effect of polyamines and related metabolites on wounded storage tissues was investigated in two experimental systems: RNase activity of potato (Solanum tuberosum L.) tuber discs, and betacyanin leakage from beet root (Beta vulgaris L.) discs. Potato tuber discs evince a dramatic rise in RNase activity 24 h after excision, and this rise is completely blocked by the polyamines, spermidine and spermine. The effect is concentration‐dependent, and several precursors of polyamines are also effective to various degrees in inhibiting the rise in RNase activity. Polyamines inhibit both the wound‐induced RNase and the rise in RNase activity which may result from other senescence‐linked events. Betacyanin leakage from beet root discs is enhanced upon aging of discs and in response to various treatments which may cause membrane damage. Spermidine and spermine effectively inhibit betacyanin leakage which results from aging at 25°C, from incubation at higher temperatures (35–40°C), from freezing of discs, or from treatment of discs with RNase or protease. It is suggested that polyamines decrease RNase activity and solute leakage in sliced storage tissues by affecting primary wound‐induced destabilization of cell membranes.
Lipid biosynthesis by chloroplasts from olive tree leaves
Authors: Daza Luis M. , Donaire Juan P.
Published: April 2006

In vitro incubation of isolated chloroplasts from young olive tree leaves (Olea europaea L. cv. Marteño) in acetate‐1‐14C showed a high labelling of saturated fatty acids (palmitic + stearic) and, above all, of the monounsatured ones (oleic); the low biosynthetic rate of α‐linolenic acid being noteworthy. These fatty acids are mainly found as free ones, or incorporated in mono‐and diglyceride molecules. Phosphoand galactolipids, the most abundant acyl‐lipid components of chloroplast lamellae, showed low incorporation rates. The fatty acid synthesis by isolated chloroplasts depends on exogenous CoA, ATP, NADPH and, especially, on added ACP (acyl carrier protein) preparation from Escherichia coli, whereas it was strongly inhibited by Triton X‐100.

In vivo experiments with acetate‐1‐14C infiltration into young excised leaves showed a high labelling of chloroplast phospholipids, but a low 14C incorporation into galactolipids, a remarkable feature because these latter are main components of chloroplast lamellae. The high biosynthetic rate of α‐linolenic acid is noteworthy and appears mainly linked to monogalactosyldiglycerides. Also the low incorporation of saturated fatty acids to neutral lipids is remarkable. The low in vitro synthesis of α‐linolenic acid in comparison with that of the in vivo conditions, suggests the existence of a cooperation between chloroplasts and other parts of the cell to carry out the synthesis of this compound.
Physiological and biochemical changes associated with cotton fibre development
Authors: Naithani S. C. , Rao N. Rama , Singh Y. D.
Published: April 2006

Growth kinetics and levels of auxin substances were studied in three cotton cultivars, designated as long, medium and short staple cultivars. Fibre length and dry weight plotted against boll age showed sigmoidal patterns and were fitted to a logistic curve by computer curvilinear regression analysis. The final length of the fibre in different cultivars was the product of the rate of elongation per day and the total period of elongation. Further, considerable overlap between the elongation and the secondary thickening phases was recorded.

No relationship between auxin substances and rate of fibre elongation was discernible. The peak levels of auxin substances in all the cultivars were recorded before or about the time when elongation had just started, and it is concluded that the auxin synthesized during the elongation phase is consumed in elongation growth. Thus there is necessarily no relationship between remaining auxin and growth.
The inhibition of photosynthesis and photorespiration in isolated mesophyll cells of Phaseolus and Lycopersicon by reduced osmotic potentials
Authors: Mawson Bruce T. , Colman Brian
Published: April 2006

Mesophyll cells isolated from Phaseolus vulgaris and Lycopersicon esculentum show decreasing photosynthetic rates when suspended in media containing increasing concentrations of osmoticum. The photosynthetic activity was sensitive to small changes in osmotic potential over a range of sorbitol concentrations from 0.44 M (−1.08 MPa) to 0.77 M (−1.88 MPa). Photorespiration assayed by 14CO2 release in CO2‐free air and by 14CO2 release from the oxidation of [1–14C] glycolate also decreased as the osmotic potential of the incubation medium was reduced. The CO2 compensation points of the cells increased with increasing concentration of osmoticum from approximately 60 μ I−11 at −1.08 MPa to 130 μl 1−1 for cells stressed at −1.88 MPa. Changes in photosynthetic and photorespiratory activities occurred at moderate osmotic potentials in these cells suggesting that in whole leaves during a reduction in water potential, non‐ stomatal inhibition of CO2 assimilation and glycolate pathway metabolism occurs simultaneously with stomatal closure.
Interaction of phytohormones and far‐red irradiation on the nyctinastic closing of Albizzia julibrissin pinnules
Authors: Tanada Takuma
Published: April 2006

In order for far‐red radiation at 760 nm to delay dark closing of Albizzia julibrissin pinnules, red light must be given simultaneously with or just prior to it. Studies have been made to determine whether a phytohormone can replace this red light requirement. Abscisic acid, gibberellin, kinetin, and indole‐3‐acetic acid have been found to replace the red light. Indole‐3‐carboxylic acid and a cytokinin antagonist are ineffective. In this hormone and far‐red interaction, all hormones are effective at μM or lower concentrations. The hormones show no interaction with red light at 660 nm. Simultaneous irradiation at 550 nm negates the effect of hormone and far‐red interaction in delaying leaflet closing. These results are additional evidence that an unidentified far‐red absorbing pigment could be involved with phytochrome in some far‐red‐mediated processes.
Inhibition of the glucose and amino‐acid carriers of Lemna gibba by pretreatment with HgCl2
Authors: Golle Bernd , Lüttge Ulrich
Published: April 2006

The electrical resting potential across the plasmalemma of Lemna gibba L. (G 1) cells is −230 to −250 mV and the diffusion potential in the presence of 1 mol m−3 KCN + 1 mol m−3 salicylhydroxamic acid is about −100 mV. A concentration of 0.01 mol m−3 HgCl2 depolarises the transmembrane electrical potential in a largely reversible way. When the cells after 16 min of HgCl2‐application are returned to Hg‐free solution, the transmembrane electrical potential is only depolarised by 24 × 13 mV (SD, n = 13) compared with the potential prior to HgCl2 treatment. In contrast, a 16 min pretreatment with HgCl2 followed by a wash with mercury‐free solution reduces the transient depolarisations of transmembrane potential observed after addition of 5 mol m−3 D‐glncose or 1 mol m−3 L‐alaoine to about 60% of controls. These transient depolarisations are due to the onset of solute uptake. Accordingly, HgCl2‐pretreatment inhibits uptake of 14C‐3‐O‐methyl‐d‐glucose by more than 50% and uptake of 14C‐l‐alanine by more than 70%. Washing with 1 mol m−3 1,4‐dithiothreitol does not reverse this inhibition. It is, therefore, concluded that Hg2+ irreversibly binds to essential SH‐groups of the H+‐hexose and the H+‐amino‐acid cotransport carriers of Lemna gibba and inhibits these carriers without appreciably affecting the electrogenic proton‐extrusion pump.
Photosynthesis and photoassimilation of glucose during photomixotrophic growth of Marchantia polymorpha cells in suspension culture
Authors: Katoh Kenji
Published: April 2006

Even in the presence of glucose the growth of Marchantia polymorpha L. (cell line HYH‐2F) requires light, and growth is more sensitive to 10−6M 3‐(3, 4‐dichlorophenyl)‐1, 1‐dimethylurea than to 10−4 Antimycin A. The inability of the cells to grow in the dark is due to the low level of respiration. The respiration rate under light increased to four times the dark value. The values of the compensation ratio (the photosyntehtic rate/the respiration rate) for the oxygen exchange were below 1.0 daring the growth period, although oxygen evolution was found. At the early exponential phase, oxygen evolution was 0.373 μmol (mg cell dry weight)−1 h−1 [61.7 μmol (mg chlorophyll)−1 h−1]. M. polymorpha cells are unable to grow anaerobically in the light without a supply of carbon dioxide. When 1% carbon dioxide in nitrogen is supplied, photochemically produced oxygen and energy are sufficient for sustained growth although at significantly reduced yields in both cell dry weight and chlorophyll. Photosyntehtic CO2 assimilation rate was 0.13 μmol (mg cell dry weight)−1 h−1[11.3 μmol (mg chlorophyll)−1 h−1]. At least one‐third of the carbon atoms in cellular constituents seem to be derived from atmospheric carbon dioxide, which indicates that M. polymorpha cells grow photomixotrophicaily.
Long‐term effects of low levels of SO2 on bean plants (Phaseolus vulgaris). II. Immission‐response effects on biomass production: quantity and quality
Authors: Saxe Henrik
Published: April 2006

Bean plants (Phaseolus vulgaris L. cv. Processer) were grown in water culture with separate air supply to roots for four to five weeks at five levels of SO2 ranging from 10 μg m−3 to 950 μg m−3. At harvest the plant material was divided into six fractions: root, stem, fruit and leaves of three age groups.

Plants were mainly affected at and above approx. 250 μg m−3 SO2. Fresh weight was reduced in mature and old leaves, and roots and fruit. Dry weight was also reduced in mature and old leaves, and roots and stem. A reduction was found in chlorophyll a and chlorophyll b in mature and old leaves, and also starch was reduced in the leaves. Sulfur content of leaves and fruit increased with exposure time and concentration, while Br, Ca, Cl, K, Mn, P and Zn increased at the highest SO2 level only. Total (but not specific) peroxidase activity increased in all aerial fractions, i.e. soluble protein increased just like peroxidase activity. Seventeen studied amino acids all increased on the average by 38% in mature bean pods.

The observed effects may be parts of a reaction for survival and propagation of the plant, as fruit quality was not affected, indeed, it sometimes improved slightly. The latter observation is of commercial interest.
The effect of light on cotyledon and primary leaf growth in white light grown Sinapis alba
Authors: Beggs Christopher J. , Barth Joachim , Schäfer Eberhard
Published: April 2006

The growth of cotyledons and primary leaves of I‐day‐old Sinapis alba L. plants were studied under various light conditions and action spectra produced. For both responses blue and red light are most effective and a strong fluence rate dependency can be observed. The red light effect appears to be mediated through phytochrome, that of blue light being due to a separate blue light receptor, although this receptor requires the presence of far‐red absorbing phytochrome (Pfr) in order to be effective.
Influence of light on phosphoenol pyruvate carb xoylase in sorghum leaves
Authors: Vidal Jean , Gadal Pierre
Published: April 2006

Chromatography on DEAE‐cellulose of an extract from etiolated leaves of sorghum (Sorghum vulgare Pers. cv. INRA 450), a C4 plant, gave only one form of phosphoenol pyruvate carboxylase with functional and regulatory properties of a C3 type plant enzyme. Greening of the leaves resulted in a significant increase in activity. This increase was due to the appearance of a new form of the enzyme, which eluted at lower ionic strength and exhibited new properties. This form was glucose‐6‐P activated and showed a sigmoidal curve response to the concentration of the substrate phosphoerralpyruvate. These kinetic properties are typical of a C4 plant enzyme.
Analysis of [14C] indole‐3‐acetic acid metabolites from the primary roots of Zea mays seedlings using reverse‐phase high‐performance liquid chromatography
Authors: Nonhebel Heather M. , Crozier Alan , Hillman John R.
Published: April 2006

Methanolic extracts of Zea mays L. cv. Fronica root segments which had been incubated in [14C] indole‐3‐acetie acid were analysed by reverse‐phase high‐performance liquid chromatography. Metabolism of indole‐3‐acetic acid was found to be rapid and extensive with at least 11 products apparent after a 2 h incubation. A comparison of metabolites of [1‐14C]– and [2‐14C] IAA, calculations of 14CO2 evolution, and data on the polarity of products indicated that decarboxylation had not occurred. An average of 34% of the radioactivity remained associated with the indole‐3‐acetic acid peak.
Mise en évidence ?amines liées à des structures cellulaires chez Nicotiana tabacum et Lycopersicum esculentum
Authors: Vallée J. C. , Vansuyt G. , Négrel J. , Perdrizet E. , Prévost J.
Published: April 2006

Demonstration of amines connected with cellular structures in Nicotiana tabacum and Lycopersicum esculentum.

The level of free and bound amines in various tissues of Nicotiana tabacum cv. Xanthi was investigated. After acid hydrolysis of different pellets from ethanol or buffer extractions, three aliphatic polyamines (putrescine, spermidine, spermine) and one aromatic monoamine (tyramine) were found in different proportions according to the nature of the tissue. Roots contain high quantities of insoluble tyramine bound very strongly to cellular structures. On the contrary, there were only traces of bound tyramine in leaves and stem. After extraction and purification of cell structures, tyramine was shown to be bound to one component of the cell wall. Addition of pronase or cellulase to the extract did not break the tyramine complex. In tobacco roots, insoluble tyramine concentration increased with plant development. High content of bound tyramine was also found in Lycopersicum esculentum roots. The possibility that tyramine binds with lignin is discussed.
Time‐dependent changes in the in vitro effects of sodium chloride on photosynthetic electron transport of isolated chloroplasts
Authors: Dominy Peter J. , Baker Neil R. , Meek Ian T.
Published: April 2006

The effects of a wide concentration range of NaCl and sorbitol on three photosynthetic electron transport reactions of Pisum sativum L. cv. Feltham First chloroplasts were examined as a function of time from thylakoid membrane isolation. Rates of electron flow from water to diaminodurene (DAD) and ferricyanide were determined polarographically, whilst photoreduction of 2,6‐dichlorophenolindophenol (DCPIP) was monitored spectrophotometrically. Assay of thylakoids immediately after isolation showed that the rate of photoreduction of all three electron acceptors decreased with increasing salt concentration. However, 100 min after leaf homogenisation the response pattern of ferricyanide and DCPIP photoreduction to increasing NaCl, but not increasing sorbitol concentration, became significantly modified. This was not the case for DAD photoreduction. The results are discussed in relation to the assessment of the possible effect of salinity on photosynthetic electron transport in vivo.
Water deficit enhancement of proline and α‐amino nitrogen accumulation in potato plants and its association with susceptibility to drought
Authors: Levy David
Published: April 2006

Potato plants (Solanum tuberosum L. cvs ‘Up‐to‐Date’, ‘Desiree’, ‘Alpha’, ‘Spunta’, ‘Elvira’ and ‘Troubadour’) were exposed to cycles of water stress and relief during growth. Severe water deficit induced increased proline content 6‐ to 7‐fold in nonturgid leaves which just started to wilt, and 8‐ to 27‐fold in fully wilted leaves of potatoes. However, proline content was not affected during the early stages of stress development over a range of osmotic potentials in the leaves. The rising proline content was related to turgor loss of leaves independent of changes in the osmotic potentials, which indicates that proline involvement in osmoregulation of potato leaves is unlikely.

Repeated cycles of water stress and relief resulted in increased proline and α‐amino nitrogen content in the tuber tissue of some of the cultivars. The smallest increase in proline content was obtained in ‘Alpha’ tubers and the content of α‐amino nitrogen remained unaffected by the water stress. Concomitantly, ‘Alpha’ was the most drought‐tolerant cultivar, as determined by its capacity to accumulate dry matter in tubers under stress conditions. On the other hand, in tubers of cultivars which were more susceptible to drought, a marked increase in proline and α‐amino nitrogen was observed in response to water stress. The possible association of these findings with tolerance of potatoes to repeated short periods of drought is discussed.
Increase of cotton cotyledon resistance to the herbicide endothall by abscisic acid
Authors: Rikin Arnon , Rubin Baruch
Published: April 2006

The herbicide endothall (7‐oxabicyclo 2.2.1 heptane‐2, 3‐dicarboxylic acid) was applied to cotton (Gossypium hirsutum L. cv. Acala SJ‐1) cotyledon discs. Treatment with 10−4M endothall for 24 h resulted in injury which was expressed by increased leakage of electrolytes, development of necrotic areas, increased level of polyphenols and tissue browning. We examined whether treatments which decrease chilling injury would also decrease injury caused by the herbicide. Tissue from seedlings grown at 28°C was more sensitive to endothall than that from seedlings grown at 15°C. Pretreatment with 10−5M abscisic acid greatly decreased the leakage of electrolytes, necrotic areas, and tissue browning caused by endothall. Similar pretreatment did not prevent the increase of polyphenols caused by the herbicide. The treatment with abscisic acid was more effective in protection against the herbicide injury when applied several hours prior to the herbicidal treatment. This time requirement indicates that the mechanism by which abscisic acid induces resistance to the herbicide depends, at least partially, on active metabolism. We suggest that the increased resistance to herbicide stress by abscisic acid is another example of a common resistance mechanism to various stresses in which abscisic acid is involved.
Varietal differences in the toxicity of sodium ions in rice leaves
Authors: Yeo A. R. , Flowers T. J.
Published: April 2006

Visual damage is commonly used as the criterion for assessment of salinity resistance in rice breeding programmes. The use of other indicators, such as sodium uptake, is being evaluated: a correlation between initial sodium uptake to the third leaf and varietal survival was established and the physiological basis of this examined.

Chlorophyll was used as an indicator of metabolic status and the relationship between leaf sodium and chlorophyll concentrations investigated for nine varieties differing in their resistance to salinity. By sampling a population of leaves having a wide range of salt concentrations, inverse relationships between chlorophyll and sodium concentrations were established. The salt concentration in the leaf tissue which causes equivalent toxicity (50% loss of chlorophyll) differed 3‐fold amongst these varieties. Varieties showing the greatest tolerance to salt within the leaves were not necessarily those showing the greatest overall phenotypic resistance to salinity.

The enzymes malate dehydrogenase and nitrate reductase were activated equally by sodium and potassium ions at 60–80 mol m−3 in both control and saline grown plants and severely inhibited at higher concentrations. If all the salt in the tissue of leaves with 50% chlorophyll remaining was in solution and uniformly distributed the concentration would be 135–500 mol m−3. This is improbable and some level of compartmentation is likely.

It is concluded that while initial sodium uptake has predictive value for salinity resistance of varieties, there are other characteristics which are masked by excess salt entry and require independent assessment; no single factor confers resistance.
Effect of abscisic acid on exudation from deficient and aged sunflower roots
Authors: Glinka Zvi , Abir Noemi
Published: April 2006

The effect of abscisic acid (ABA) was observed on exudation from roots of sunflower (Helianthus annuus L. cv. Habad) plants whose mineral nutrition was cut off or which were deprived of K+ or NO−3 for 90 h prior to excision. In spite of a marked decrease in exudation rate, the magnitude of the promotive effect of ABA on both volume flow and release of ions to the xylem was similar to that obtained in roots of plants grown in full nutrient solution. Application of ABA to the medium at different times after excision increased the promotive effect of ABA as the time from excision increased. The magnitude of the ratio ABA‐treated/control in roots which were treated 74 h after excision was twice that in freshly‐excised roots. The effect of ABA lasted up to 50 h and during that period it followed the endogenous rhythm in exudation from the control roots. It is concluded that since a steady promotive effect of ABA persists under a variety of experimental conditions, this may be considered a genera! phenomenon in sunflower roots.
Stress‐induced ripening of the non‐ripening tomato mutant nor
Authors: Arad Shoshana (Malis) , Mizrahi Yosef
Published: April 2006

Tomato (Lycopersicon esculentum Mill.) plants of the non‐ripening mutant nor (3rd backcross to the normal cultivar Rutgers) were grown under water stress induced in two different ways: a) reduction of water supply and b) increase in transpiration rate by adding kinetin to the nutrient solution. Both drought treatments induced fruits of the non‐ripening mutant nor to ripen, that is, the parameters characteristic of ripening – red pigment, taste, pectolytic activity, softening, and the evolution rates of CO2 and ethylene – all increased, although not to the normal level. Such an increase does not normally take place in the nor mutant under control conditions. It is suggested that fruits of the nor mutant can be induced to ripen by any kind of water stress. The induction mechanism is still to be explored.
The fate of carbon during the assimilation of carbamoyl phosphate in white spruce seedlings as revealed by [14C]‐carbamoyl phosphate, [14C]‐cyanate, and [14C] ‐bicarbonate labeling patterns
Authors: Durzan D. J.
Published: April 2006

The fate of carbamoyl phosphate in white spruce seedlings revolves around the production of spontaneous degradation products, cyanate, bicarbonate, and carba‐mate. When [14C]‐carbamoyl phosphate and [14C]‐cyanate are assimilated, urea is a common early metabolic intermediate that appears in the alcohol soluble N. By contrast, urea is not detected among the products of [14C]‐bicarbonate. Carbamoyl phosphate and glutamic acid are implicated as having pivotal roles in the production of amides, arginine, and biotin. Within 2‐h exposures to radioactive substrates considerably more carbon from bicarbonate was diverted into amino acids Incorporated into proteins than with carbon‐nitrogen substrates. Specific activities of bound amino acid residues support the view that proteins formed from these [14C]‐substrates have different rates of metabolic turnover.
Effect of light and phosphate on conidiation in the fungus Verticillium agaricinum
Authors: Kumagai Tadashi , Hsiao Ke‐Cheng
Published: April 2006

Verticillium agaricinum (Link) Corda, grown in a yeast extract‐sucrose medium, conidiated abundantly in darkness after irradiation with near ultraviolet (290–400 nm) for 15 min or blue light (400–550 nm) for 60 min. Few conidia were formed in total darkness. Exposure to 30 min of near ultraviolet light suppressed conidiation. Conidiation was also suppressed by phosphate in excess of 10−4M irrespective of light condition. After irradiation with near ultraviolet light for more than 30 min, there was a cessation of growth and a change in colony color from yellow to reddish. The color does not appear to be due to a carotenoid because the colonies turned from red to yellow when covered with acid. At pH lower than 6.0 the pigment has an absorption maximum around 390 nm, whereas at higher pH it is around 540 nm. Thus, it appears that irradiation of V. agaricinum with near ultraviolet may cause an increase in pH, which in turn produces the change of colony color from yellow to reddish.
Species of RNA synthesized during early germination in the radicle of the lentil embryo
Authors: Van de Walle Claude , Deltour Roger , Forgeur Ginette
Published: April 2006

RNA synthesis is activated in cells of the plant embryo very soon after the start of imbibition by the seed. This study was undertaken to determine whether synthesis of one particular RNA or all the major RNA species was initially activated in the radicle of lentil embryos (Vicia lens). Two different methods were used after incorporation of radioactive precursor to identify the newly synthesized RNA species. First, RNA was extracted and analyzed using gel electrophoresis, gel filtration, affinity chromatography and base composition analysis. The second method was to localize the labelled RNA molecules within cells using autoradiography of sections of embryonic radicles. The data indicate that newly synthesized heterogeneous nuclear RNA and possibly messenger RNA, transfer RNA, 5S ribosomal RNA and precursor of ribosomal RNA are detectable 3 h after the start of imbibition of the decoated embryo and before completion of initial water uptake. It is concluded that synthesis of all major species of RNA is simultaneously initiated in the radicle of the germinating embryo.
Salinity and root conductivity: differential responses of a coastal succulent halophyte, Salicornia virginica, and a weedy glycophyte, Raphanus sativus
Authors: Ownbey R. S. , Mahall B. E.
Published: April 2006

The water relations and growth responses of an extreme halophyte, Salicornia virginica, and a common glycophyte, Raphanus sativus, were comparatively examined in a hydroponic growth experiment employing a broad range of salinities. Root conductivity (in growth solutions and distilled water), expressed sap osmolality, water use efficiency, relative growth rate, and salt uptake were the primary responses monitored. Salicornia responded to increasing salinity by decreasing root conductivity (in the growth solutions) and increasing salt uptake, while water use efficiency and growth rates were minimally affected. The inhibitory effects of salinity upon root conductivity were reversible in distilled water, and, importantly, the highest recovery rates were from plants grown in the moderate and high salinities. Salicornia displayed an enhanced ability to absorb water in distilled water following growth in solutions with elevated salinities. In contrast, Raphanus responded to comparatively small increases in growth solution salinity by drastically decreasing growth rates as well as root conductivity (in the growth solutions), while salt uptake and water use efficiency increased under the moderate salinity level. In Raphanus the inhibitory effects of increased salinity upon root conductivity were only partially reversible in distilled water, and the highest recovery rates were from plants grown in the low salinity Thus, once salinity stress was withdrawn, Raphanus exhibited a suppressed ability to move water through the roots. The results are discussed in the light of selected, commonly proposed mechanisms of salinity‐induced growth inhibition.
Measurement of intracellular potassium activity in protoplasts of Acer pseudoplatanus: origin of their electropositivity
Authors: Cornel D. , Grignon C. , Rona J. P. , Heller R.
Published: April 2006

Membrane resistances, electrical potentials and intracellular K+ activity have been studied in protoplasts of Acer pseudoplatanus L. using microelectrodes. The plasmalemma appears to be damaged during protoplast processing, so that it is almost completely depolarized. The positive polarization of the protoplasts is a property of their tonoplast. The osmotic shock of general dilution of the medium brings about a slight positive polarization of the protoplasts, which probably is the consequence of a dilution of the ionic contents of the cell. A rapid dilution of extracellular potassium produces the same effect by a considerable efflux of K+, which changes the concentration gradient so that electropositivity is accentuated. In general, certain states of shock can cause such polarization. These results, particularly the development of internal potassium activity, help in understanding the initial cause of the positive polarization that is sometimes observed in protoplasts.
Genetic differentiation in Plantago major: Growth and root respiration and their role in phenotypic adaptation
Authors: Kuiper Daan
Published: April 2006

The root respiration and the growth of plants of four inbred lines of Plantago major L. were followed at two levels, of mineral nutrition. In addition the response to a transfer of plants from one condition to the other was studied. The activities of the cytochrome and of the alternative pathway wee determined and used to distinguish between genetic differences among the inbred lines and the plasticity within each inbred line. Root respiration and growth parameters differed significantly between the lines and were directly related to seed number per capsule (low respiratory activity and slow growth – 11 seeds per capsule; high respiratory activity and fast growth – 33 seeds per capsule).

Plasticity of respiration and growth parameters is expressed as differences in the total respiration, the activities of the cytochrome and of the alternative pathway, and in the shoot to root ratio, as a response to nutritional level or to changes of the strength of the nutrient solution. Differences in this plasticity in the four selected lines and in quickness of response to a change in mineral nutrition were directly related to the ecological strategy. These results are discussed in relation to the strategy of the genotypes for survival in the field. The high growth rate and the presence of plasticity in line 4 (ssp. Pleiosperma) make this genotype act like an annual, following a ruderal strategy. The lower growth rate and the absence of plasticity in line 1 (ssp. major) fit a more competitive strategy.
In vitro and in vivo regulation of chloroplast glyceraldehydes‐3‐phosphate dehydrogenase isozymes from Chenopodium rubrum. I. Purification and properties of isozymes
Authors: de Looze Stephen , Wagner Edgar
Published: April 2006

Chloroplast glyceraldehyde‐3‐phosphate dehydrogenase (GPD, EC 1.2.1.13) was purified from leaves of Chenopodium rubrum L. Aggregated (≥ 106) and disaggregated (165 × 103) molecular weight forms were obtained by gel filtration in the presence of NAD+ and NADP+, respectively. The disaggregated enzyme was separated into two isozymes by inverse ammonium sulphate gradient solubilization: “NADP‐GPD I” was homotetrameric (subunit molecular weight 39 × 103); “NADP‐GPD II” was heterotetrameric (subunit molecular weights 39 × 103 and 43 × 103). Isoelectric focusing of the isozymes, both aggregated and disaggregated, revealed two isoelectric forms in each case, at 4.3 and 7.7. Chloroplast GPD was “NADP‐suppressed” in crude extracts due to partial oxidation, incubation with dithioerythritol restored full activity.
In vitro and in vivo regulation of chJoroplast glyceraldehyde‐3‐phosphate dehydrogenase isozymes from Chenopodium rubrum. III. The molecular basis of the aggregation phenomenon: chloroplast glyceraldehyde‐3‐phosphate dehydrogenase as an ambiquitous enzyme
Authors: de Looze Stephen , Wagner Edgar
Published: April 2006

The nature of the aggregated form of chloroplast glyceraldehyde‐3‐phosphate dehydrogenase isozymes (GPD, EC 1.2.1.13) from Chenopodium rubrum leaves was investigated. After disaggregation of the isozymes in NADP + buffer, and resuspension of the disaggregated isozymes in NAD+ buffer, complete reaggregation could only be achieved by remixing the enzyme with a high molecular weight fraction, from which the isozymes had dissociated during the NADP+ filtration. After separation of the isozymes by inverse ammonium sulphate gradient solubilization, spontaneous extensive reaggregation of each isozyme was observed in NAD+ buffer. The high molecular weight material consisted of ribonucleoprotein, and RNase treatment impaired its ability to promote reaggregation of chloroplast GPD. It is proposed that pyridine nucleotide‐controlled aggregation and binding to ribonucleoprotein in vitro are artifacts which reflect an in situ binding to cellular components. Since uncontrolled NAD+‐linked activities of the bifunctional isozymes in the chloroplast would lead to an equalization of the NAD + and NADP + redox couples, it is suggested that the reversible binding of the isozymes forms the basis of a regulatory system in vivo.
Relationships among nitrogen accumulation, nitrogen assimilation and plant growth in chrysanthemums
Authors: Elliott George C. , Nelson Paul V.
Published: April 2006

Relationships among growth, N accumulation and assimilation were investigated in Chrysanthemum morifolium Ramat cv. Fiesta in experiments testing the effects of varying levels of NO–33supply and of increasing NH+4 added to a constant level of NO–33 Flowing solution culture systems were used to provide NO−3at concentrations of 0.03 to 5.0 mol m–3 and NH+4 levels from 0.05 to 0.3 mmol m–3 added to 0.1 mol m–3NO−3. Rates of growth, N absorption, accumulation, distribution and utilization were estimated by regression analysis of data obtained from sequential plant harvests, and rates of NO−3 and NH−4 net uptake were estimated from solution depletion.

A sustained ambient NO−3 concentration of 0.03 mol m–3 was evidently adequate to support growth, since relative growth rates were not affected by increasing NO−3 supply from 0.03 to 1.0 mol m–3, nor from 0.25 to 5.0 mol m–3, in separate experiments. Shoot growth rates were stimulated by NH4 added to NO−3 one experiment, but not when the experiment was repeated under ambient conditions less favorable to growth.

Relative accumulation rates for total N increased with increasing NO−3 and with NH+4added to NO−3 A constant proportion of NO−3 taken up was reduced when NO−3 alone was supplied. Both the proportion of total N taken up as NO−3 and the proportion of NO−3 reduced decreased with increasing NH+3 added to NO−3 NH+4 uptake apparently must exceed a threshold of about 30% of the total uptake to inhibit NO−3 uptake.

Utilization of N in chrysanthemum was apparently limited by redistribution since relative accumulation rates for total N were equal to or greater than relative growth rates, in contrast to results reported for several other species. Results of this study and other information support the postulate that NH+4 added to NO−3might stimulate growth by increasing transport of reduced N from roots to shoots, thus increasing the supply of reduced N available to support growth of shoot meristems.
Protein synthesis by chloroplasts during the senescence of barley leaves
Authors: García Sebastián , Martín Mercedes , Sabater Bartolomé
Published: April 2006

Chloroplasts were isolated from senescent leaf segments of barley (Hordeum vulgare L. var. Mozoncillo) and assayed for protein synthesis. Protein synthesis activity of the chloroplasts greatly increased after 10–20 h of incubation of leaf segments in the dark in spite of an intense degradation of chloroplast rRNA. The rise in the activity of protein synthesis was more pronounced when kinetin was present in the incubation medium. However, as deduced from SDS‐polyacrylamide gel electrophoresis of the products, different proteins were synthesized under the two conditions of incubation of the leaf segments. The activity of protein synthesis of the chloroplasts decreased during the first hours of incubation of the leaf segments in the light.

Cutting and incubation in the dark of the leaf segments enhanced the synthesis of a few proteins also formed by chloroplasts in attached senescing leaves. Hormone and senescence treatments changed the type and the rate of the protein synthesized by chloroplasts, which suggests that hormones may control senescence through a modulation of the protein synthesized by the chloroplasts.