bluuebunny/crossref_metadata_2025 huggingface dataset:
Biochemical changes induced by accelerated aging in sunflower seeds. I. Lipid peroxidation and membrane damage
Authors: Gidrol X. , Serghini H. , Noubhani A. , Mocouot B. , Mazliak P.
Published: May 2006

When stored at 42°C and 100% relative humidity for 1 to 8 days, sunflower seeds (Helianthus annuus L. cv. Rodeo) aged prematurely and lost 25% of their initial viability. A ten‐fold increase in conjugated dienes as well as a decrease of unsaturated fatty acids in diacylglycerol and polar lipids fractions were observed after 8 days of accelerated aging, demonstrating the occurrence of lipid peroxidation in prematurely aged sunflower seeds. However, the viability remained relatively high. The absence of membrane damage in seeds and of lipid peroxidation in isolated microsqmes suggested that lipid peroxidation concerned mainly lipid reserves. These results suggest that, at least within the first 8 days of treatment, the lipid reserve in sunflower seeds might act as a detoxifying trap, protecting membranes from excessive damage.
Clacium ion involvement in growth inhibition of mechanically stressed soybean (Glycine max) seedlings
Authors: Jones Russell S. , Mitchell Cary A.
Published: May 2006

A 40–50% reduction in soybean [Glycine max (L.) Merr. cv. Century 84] hypocotyl elongation occurred 24 h after application of mechanical stress. Exogenous at 10 mM inhibited growth by 28% if applied with the Ca2+ ionophore A23187 to the zone of maximum hypocotyl elongation. La3+ was even more inhibitory than Ca2+, especially above 5 mM. Treatment with ethyleneglycol‐bis‐(β3‐aminoethylether)‐N, N, N′, N′‐tetraacetic acid (EGTA) alone had no effect on growth of non‐stressed seedlings at the concentrations used but negated stress‐induced growth reduction by 36% at 4 mM when compared to non‐treated, stressed controls. Treatment with EDTA was ineffective in negating stress‐induced growth inhibition. Calmodulin antagonists calmidazolium, chlorpromazine, and 48/80 also negated stress‐induced growth reduction by 23, 50, and 35%, respectively.
Dominance among fruits/sinks and the search for a correlative signal
Authors: Bangerth Fritz
Published: May 2006

The present problems with hormonal signals transferring dominance effects are reviewed and, as a new hypothesis, it is stated that the sequence of sink development may establish the dominance effect. ‘Primigenic dominance’ (PD) is suggested to describe this kind of correlative inhibition, in which the earlier developed sink inhibits later developed organs.

New results show that the polar IAA export of the earlier developed sink inhibits the IAA export of later developed sinks. This ‘autoinhibition’ occurs at ‘junctions’, where auxin streams from various sinks meet. It is suggested that this depressed IAA‐export of the subordinated fruit/sink acts as the signal that leads to inhibited development.

This hypothesis avoids some of the problems related with other hypotheses, such as the requirement of a multidirectional signal. Primigenic dominance is a unifying hypothesis, which can be applied to most correlative dominance phenomena in the plant. Primigenic dominance is less complicated than the traditional ‘apical dominance’ (AD) hypothesis, because it does not require secondary messengers.
Sequence information and preparation of resolved by; two‐dimensional gel electrophoresis: no longer just spots on gels
Authors: Guy Charles L.
Published: May 2006

In 1975 O'Farrell described, in detail, a procedure to separate proteins by polyacrylamide gel electrophoresis in two dimensions. This powerful new technique relied on two characteristics of proteins: charge and molecular mass. In the first dimension, proteins were separated on the basis of net charge in a pH gradient by isoelectric focusing, and in the second dimension the proteins were further fractionated exclusively on the basis of their molecular mass by SDS gel electrophoresis. Since two‐dimensional gel electrophoresis (2DGE) has a resolving power of at least 20 fold greater than one‐dimensional electrophoresis, it has found wide spread application in modern biological research. However, beyond the detection of a given protein, 2DGE provides little additional information about a specific protein other than molecular mass, isoelectric point, and approximate relative abundance. In recent years, the development of new technologies have made it possible to directly obtain sequence information, and produce specific antisera for proteins resolved by 2DGE. These new technological developments serve to further increase the power and utility of 2DGE in the analysis of proteins of importance to plant physiology.
Partial purification of cell wall β‐galactosidases from Cicer arietinum epicotyls. Relationship with cell wall autolytic processes
Authors: Dopico Berta , Nicolás Gregorio , Labrador Emilia
Published: May 2006

The protein extracted from the cell wall of the epicotyls of Cicer arietinum L. cv. Castellana was separated by ion exchange chromatography in four different fractions with β‐D‐galactosidase (EC 3.2.1.23) activity. These were called βI, βII, βIII and βIV, according to their order of elution. βII was associated with a particularly high β‐D‐glucosidase (EC 3.2.1.21) activity. Gel filtration chromatography of each of the fractions gave further subdivision of fractions βI and βIII. Subfractions 1 βI, 1 βII and 1 βIV have glucosidase activity and subfractions 2 βI and 2 βIII have galactosidase activity.

The studies on the hydrolytic capacity of these fractions and its relationship with the autolytic process seem to show that subfraction 2 βIII is responsible for autolysis. The release of total and reducing sugars is very similar for autolysis and hydrolysis by 2 βIII. The sugars released are mainly galactose and, to a lesser extent arabinose and glucose. Galactose is released as a monosaccharide, while arabinose remains associated to a polysaccharide component together with glucose and small amounts of galactose.
Partial purification of cell wall α‐galactosidases and α‐arabinosidases from Cicer arietinum epicotyls. Relationship with cell wall autolytic processes
Authors: Dopico Berta , Nicolás Gregorio , Labrador Emilia
Published: May 2006

Two protein fractions with activity as α‐galactosidase (EC 3.2.1.22) and α‐arabinosidase (EC 3.2.1.55), respectively, were identified in the proteins of cell wall of Cicer arietinum L. cv. Castellana extracted with 3 M LiCl. These fractions were partially purified by gel filtration chromatography (Bio Gel P‐150), increasing the specific arabinosidase activity 57‐fold and the α‐galactosidase activity 6‐fold. Other protein fractions with glucosidase (EC 3.2.1.21) and glucanase (EC 3.2.1.6) activity also appeared. According to earlier authors, α‐arabinosidases and α‐galactosidases are related to alterations in linkages occurring in cell walls, since the enzymes are able to hydrolyze isolated wall polymers. However, our preparations hydrolyze intact cell walls only to a very limited extent, such that their participation in the autolytic processes of cell walls can be ruled out.
Bivariate cytofluorimetric analysis of nuclear protein and DNA relative to cell kinetics during germination of Pisum sativum seed
Authors: Sgorbati Sergio , Sparvoli Elio , Levi Marisa , Chiatante Donato
Published: May 2006

By means of a biparametric cytofluorimetric analysis it is possible to distribute meristematic plant cells in a variety of cell cycle sub‐compartments, unidentifiable by DNA measurements alone. In this work, an asynchronous proliferating cell population of pea root meristems was divided into different sub‐compartments of the cell cycle phases, i.e. G1A, G1B, S. G2A and G2B on the basis of their DNA‐nuclear protein content. By means of the same biparametric analysis, differentiated mesophyll cells and quiescent cells of embryo roots, indicated as G0 and G2Q, were distinguished from cycling cells by their low nuclear protein content. These results conform to those of some analyses performed on animal cells in culture and show that it is possible to get a major insight into cell cycle kinetics and its control in a natural system such as root meristem.
Effects of organic amines on α‐aminoisobutyric acid uptake into the vacuole and on ethylene production by tomato pericarp slices
Authors: Saftner Robert
Published: May 2006

Experiments were conducted to test the possibility that organic amines inhibit ethylene production by inhibiting transport of the ethylene precursor, 1‐aminocyclopro‐pane‐1‐carboxylic acid (ACC), into the vacuole. α‐Aminoisobutyric acid (αAIB) was used as a model substrate to study ACC uptake into the vacuole in relationship to ethylene production in pericarp slices of Lycopersicon esculentum Mill. cv. Liberty treated with and without organic amines and related substances. Organic amines (polyamines and other basic amines) inhibited αAIB uptake into the vacuole. These amines also enhanced ACC accumulation in the tissue and reduced the passive efflux of αAIB from the vacuole. Overall, ethylene production was inhibited. The inhibition of αAIB transport and of ethylene production followed a polyvalent cationic progression in the order polyamines > diamines> basic 1‐amino acids. Ca2+, but not Mg2+, strongly stimulated αAIB uptake into the vacuole and ethylene production. At equal concentrations, Ca2+ counteracted the inhibitory effects of polyamines on both αAIB uptake and ethylene production. Competitive and irreversible inhibitors of polyamine biosynthesis stimulated αAIB uptake into the vacuole and ethylene production. The results indicate an apparent relationship between polyamines, ACC uptake into the vacuole and ethylene production.
Utilization of nitrogen from storage and current‐year uptake in walnut spurs during the spring flush of growth
Authors: Deng X. , Weinbaum S. A. , DeJong T. M. , Muraoka T. T.
Published: May 2006

[15N]‐depleted (NH4)2SO4 applied to the soil in 1985 resulted in residual labeling of about 16% of the storage nitrogen (N) pool of mature walnut (Juglans regia L. cv. Serr) trees in 1987. Application of [15N]‐depleted (NH4)2SO4 fertilizer to a different set of mature walnut trees in 1987 allowed monitoring of the kinetics and utilization of N from current year uptake in 1987 and resulted in >20% labeling of fruit N following completion of leaf expansion. Redistribution of storage N to the new growth predominated during the spring flush of growth although N derived from the soil during current‐year uptake contributed increasingly during leaf expansion. Labeled N from current year uptake accumulated preferentially in the leaves as compared with reproductive organs during leaf expansion but subsequent to leaf expansion, fruit were more highly labeled with N derived from current‐year uptake than leaves. Pistillate flower abortion was coincident with an apparent competition for N among developing vegetative and reproductive organs and preceded the period of significant N contribution from current‐year uptake.
Mediation of sterol‐induced calmodulin synthesis in Phaseolus vulgaris roots by Ca2+ and its possible relationship to plant growth regulators
Authors: Vega Manuel A. , Fernández Luis M. , Boland Ricardo
Published: May 2006

Vitamin D3 and stigmasterol have been previously shown to stimulate growth, Ca2+ fluxes and calmodulin synthesis in Phaseolus vulgaris roots. In this study, these sterols (10−9M) were shown to accelerate the incorporation of [3H]‐thymidine into DNA in Phaseolus vulgaris (L. cv. Contraancha) root apices, similarly to a mixture of the mitogenic plant growth factors 2,4‐dichlorophenoxyacetic acid and kinetin (4.6 μM each). The effects of stigmasterol were blocked by flufenazine, a calmodulin antagonist. Analogously to stigmasterol, the plant hormones stimulated calmodulin synthesis as shown by double labeling of root proteins with [14C]‐leucine and [3H]‐leucine, respectively, followed by their separation on sodium dodecyl sulfate‐po‐lyacrylamide gels and a calmodulin affinity column, immunoblot analysis and cyclic AMP phosphodiesterase activation assays. The stimulation of root calmodulin formation by stigmasterol was abolished in the absence of Ca2+ in the incubation medium and was mimicked by the Ca2+ ionophore A–23187. The results suggest that the sterols, like plant mitogenic hormones, promote DNA synthesis, and that these compounds stimulate calmodulin synthesis as a consequence of their mitogenic activity. Ca2+ appears to mediate the action of the sterols.
Lack of influence of photoperiod on the metabolism of gibberellin A20 in Salix pentandra
Authors: Rood Stewart B. , Junttila Olavi
Published: May 2006

The influence of photoperiod on the metabolism of GA20 in Salix pentandra was studied by feeding [3H]‐GA20 to seedlings which had been grown previously under long day (LD) or short day (SD) conditions. After 48 h in LD or SD, metabolites were separated on sequential, silica gel partition columns and reversed‐phase C18 HPLC. The principal metabolite co‐chromatographed with [3H]‐GA1 and this conversion was confirmed by feeding [2H]‐GA20, which was converted to [2H]‐GA1 as identified by gas chromatography‐selected ion monitoring. Chromatographic evidence also indicated the minor conversion of [3H]‐GA20 to [3H]‐GA8 (via [3H]‐GA1) and trace conversion to [3H]‐GA29 (GAs A1.8,20.29 are native in Salix). Ethyl acetate‐insoluble [3H] metabolites were formed and could be cleaved by cellulase to release putative [3H]‐GA20 and [3H]‐GA1 suggesting the conversion to glucosyl conjugates of these GAs. Metabolism of [3H]‐GA20 was slightly more rapid in plants previously grown under LD than SD, an effect which reflected the generally increased shoot growth under LD. However, altering the photoperiod after [3H]‐GA20 addition had only a slight effect on the metabolism of [3H]‐GA20 in Salix seedlings. This indicates that the conversion of GA20 to GA1 is not a controlling step in the photoperiodic regulation of growth cessation in Salix.
Cytokinin concentration in relation to mineral nutrition and benzyladenine treatment in Plantago major ssp. pleiosperma
Authors: Kuiper Daan , Kuiper Pieter J. C. , Lambers Hans , Schuit Jacqueline , Staal Marten
Published: May 2006

Cytokinins in shoot and root tissue were studied in plants of Plantago major L. ssp. pleiosperma (Pilger) grown on a concentrated and on a dilute nutrient solution. Cytokinins of plants transferred from the concentrated to the dilute solution were compared with plants treated similarly but with 10−8M benzyladenine (BA) added to the dilute solution. Cytokinin concentrations were also measured in plants that had been grown throughout on one of the two nutrient solutions. A restricted supply of minerals was correlated with low cytokinin concentrations. Transfer from a concentrated nutrient solution to a dilute solution depressed the cytokinin concentration by 50% within two days of transfer. This decline did not appear if similar plants were supplied with 10−8M BA in the dilute solution. The glucosides were the only major cytokinins enhanced by mineral shortage. This effect of low mineral supply was retarded but not entirely prevented by exogenous BA. The increased synthesis of glucosides in the BA‐treated plants was accompanied by lowered concentrations of free bases and their ribosides and of nucleotides. The sum of cytokinins in BA‐treated plants was thus similar to that in plants grown at the high mineral level. The results are discussed in relation to a possible role of cytokinins in regulating growth responses to changes in mineral nutrition.
Polarity of statocytes in lentil seedling roots grown in space (Spacelab D1 Mission)
Authors: Perbal Gérald , Driss‐Ecole Dominique
Published: May 2006

A morphometric analysis of root statocytes was performed on seedlings of lentil (Lens culinaris L., cv. Verte du Puy) in order to determine the effects of microgravity on the polarity of these cells. Seedlings were grown: (1) on the ground, (2) in microgravity, (3) on a 1 g centrifuge in space, (4) first in microgravity and then placed on a 1 g centrifuge for 3 h. Dry seeds were hydrated in space (except for the ground control) for 25 h in darkness at 22°C in the Biorack facility developed by the European Space Agency. At the end of the experiment, the seedlings were photographed and fixed in glutaraldehyde in the Biorack glove box. The average shape of the statocytes and the location of endoplasmic reticulum, amyloplasts and nucleus in the cells were analysed in the four samples. By considering the cell shape, it appears that the morphology of the statocytes on the ground was different from that observed in the space samples. Cell polarity was similar in microgravity and in the centrifuged samples except for the distribution of the amyloplasts. These organelles were not distributed at random in near zero gravity, and they were more numerous in the proximal than in the distal half. Moreover, the statoliths were more voluminous in microgravity than in the centrifuged samples. The nucleus was closer to the cell center in the statocytes of roots grown in microgravity than in statocytes of roots grown in microgravity and then placed on the 1 g centrifuge for 3 h. It is hypothesized that the nucleus is attached to the cell periphery and that its location is dependent upon gravity.
An integrated view of the hormonal regulation of tuber formation in potato (Solanum tuberosum)
Authors: Vreugdenhil Dick , Struik Paul C.
Published: May 2006

The hormonal regulation of the consecutive steps in the formation of tubers on the potato plant (Solanum tuberosum L.) is described and discussed. An integrated view of the complex regulation of the initiation and growth of stolons and tubers is presented, with special emphasis on the commonly observed lack of synchronization of the various steps in tuber formation within a plant.
On the aggregational states of protochlorophyllide and its protein complexes in wheat etioplasts
Authors: Böddi Béla , Lindsten Agneta , Ryberg Margareta , Sundqvist Christer
Published: May 2006

The inner membranes from wheat (Triticum aestivumL. cv. Walde) etioplasts were separated into membrane fractions representative of prolamellar bodies and prothylakoids by differential and gradient centrifugations. The isolated fractions were characterized by absorption‐, low‐temperature fluorescence‐, and circular dichroism (CD) spectroscopy, by high performancy liquid chromatography and by sodium dodecyl sulphate polyacrylamide gel electrophoresis.

The prolamellar body fraction was enriched in NADPH‐protochlorophyllide oxidoreductase (E.C. 1.6.99.1), and in protochlorophyllide showing an absorption maximum at 650 nm and a fluorescence emission maximum at 657 nm. Esterified protochlorophyllide was mainly found in the prothylakoid fraction. The carotenoid content was qualitatively the same in the two fractions. On a protein basis the carotenoid content was about three times higher in the prolamellar body fraction than in the prothylakoid fraction. The CD spectra of the membrane fractions showed a CD couplet with a positive band at 655 nm, a zero crossing at 643–644 nm and a negative band at 623–636 nm. These results differ from earlier CD measurements on protochlorophyllide holochrome preparations. The results support the interpretation that protochlorophyllide is present as large aggregates in combination with NADPH and NADPH‐protochlorophyllide oxidoreductase in the prolamellar bodies.
Elicitation of the hypersensitive response by Pseudomonas syringae
Authors: Hutcheson Steven W. , Collmer Alan , Baker C. Jacyn
Published: May 2006

The hypersensitive response (HR), a rapid local necrosis accompanied by the production of antimicrobial compounds, is a manifestation of the primary defense mechanisms through which plants prevent colonization by potentially pathogenic microorganisms. The pathogen factors that trigger HR‐associated defense mechanisms have yet to be established. Application of transposon mutagenesis and molecular cloning techniques have provided new insights into the bacterial elicitation of the HR. This review focuses on the interaction of Pseudomonas syringae with non‐host plants as a model system for the bacterial induction of the HR and discusses (a) the genetics of Pseudomonas syringae pathogenicity and HR elicitation, (b) the environmental conditions controlling expression of Pseudomonas syringae pathogenicity/HR determinants, (c) the nature of the HR elicitor and (d) early plant responses to the pathogen.
Internode length in Pisum. Estimation of GA1 levels in genotypes Le, le and led
Authors: Ross John J. , Reid James B. , Gaskin Paul , MacMillan Jake
Published: May 2006

The levels of GA1, 3‐epiGA1 and GA8 in genotypes Le, le and led of Pisum sativum L. were determined by gas chromatography‐selected ion monitoring (GC‐SIM) after feeds of [3H, 13C]‐GA20 to each genotype. The levels of endogenous and [13C]‐labelled metabolites were determined by reverse isotope dilution with unlabelled GA1, 3‐epiGA1 and GA8. The results demonstrate a quantitative relationship between the level of GA1 and the extent of elongation both on a per plant and a per g fresh weight basis. These results are consistent with previous findings in peas and other species possessing a predominant early 13‐hydroxylation pathway for GA biosynthesis.

The levels of 3‐epiGA1 also decreased in the genotypic sequence Le, le, led although not as rapidly as for the level of GA1. This may suggest that the alleles at the le locus also influence the formation of 3‐epiGA1.
The distribution of the receptor for 1‐N‐naphthylphthalamic acid in different tissues of maize
Authors: Katekar Gerard F. , Geissler Art E.
Published: May 2006

Phytotropins with a range of activity, chemistry and stereochemistry were used to detect the presence of the receptor for 1‐N‐naphthylphthalamic acid (NPA) in leaves, stems, roots and coleoptiles in Zea mays L. cv PX‐80 through their ability to bind to the recognition site(s) on the receptor. Their ability to bind to membrane preparations from each of the tissues was found to be very similar. It is concluded that NPA receptors with similar recognition characteristics exist throughout the plant. It is suggested that the data are further evidence in favour of the proposition that NPA receptors are physiologically significant.
Plasmolytic behavior of the donor cell may affect protoplast response
Authors: Smith M. A. L. , Palta J. P. , McCown B. H. , Steffen K. L.
Published: May 2006

Protoplast donor tissues (leaves of shoots in culture) from a herbaceous plant (Solanum etuberosum) and two woody species (Populus alba × P. grandidentata cv. Crandon and Betula platyphylla szechuanica) were compared during plasmolysis in a range of osmotic agents and potentials. Cells from both Solanum and Populus, species proven to be amenable to protoplast division and regeneration, plasmolyzed readily at higher osmotic potentials than cells from Betula, a species recalcitrant to prolonged culture after protoplast isolation. Betula leaf mesophyll cells exhibited persistent membrane‐to‐wall attachments and many failed to plasmolyze even under extreme osmolarity. Although their leaves exhibited similar photosynthetic rates, photosynthetic capacity was lost from Betula protoplasts upon isolation, and retained by Solanum protoplasts. Differential stress after isolation was not detectable through vital staining, but only Solanum and Populus gave both high protoplast yields and high plating efficiencies in continued culture.
Effects of vesicular‐arbuscular mycorrhizal infection and phosphate on Plantago major ssp. pleiosperma in relation to internal cytokinin concentrations
Authors: Baas Rob , Kuiper Daan
Published: May 2006

Relations between cytokinin concentrations and effects of P and vesicular‐arbuscular mycorrhizal (VAM) infection were investigated in Plantago major L. ssp. pleiosperma Pilger. Both mycorrhizal infection by Glomus fasciculatum (Thaxt. sensu Gerdemann) Gerdemann and Trappe and P addition increased the shoot to root ratio, specific leaf area (SLA), and P concentrations of shoot and roots, and decreased the percentage of dry matter in the shoot during the experiment. In general, P concentration in the shoot and roots of each treatment correlated positively with the shoot to root ratio and specific leaf area, and negatively with the percentage of dry matter in the shoot. Cytokinin concentrations in the tissue of shoots and roots were determined using an enzyme‐linked immunosorbent assay. Concentrations of zeatin and zeatin‐ribosides in the free base and nucleotide fractions had increased more after P addition than in the case of mycorrhizal infection in both shoot and roots, whereas the P concentrations had increased less. It is suggested that zeatin and zeatin‐ribosides are not the primary growth‐substances involved in mediating VAM effects.
Change in phosphorylase isoenzymes during dedifferentiation of potato tuber cells
Authors: Catz Diana S. , Moreno Silvia , Tandecarz Juana S.
Published: May 2006

The phosphorylase isoenzyme composition of soluble preparations isolated from potato (Solanum tuberosum L. cv. Spunta) tuber‐derived callus has been studied by polyacrylamide gel electrophoresis and affinity electrophoresis. Native electrophoretic profiles indicate that dedifferentiated callus tissue contains a single form of phosphorylase that differs in primer requirement, charge and affinity towards branched α‐1,4/1,6‐glucans from the major phosphorylase form (phosphorylase II) in potato tuber. This latter molecular form is missing in dedifferentiated callus. However, callus phosphorylase appears to be closely related to tuber phosphorylase I, a minor form found in the original explant tissue.
The Glycine‐Glomus‐Bradyrhizobium symbiosis. IX. Nutritional, morphological and physiological responses of nodulated soybean to geographic isolates of the mycorrhizal fungus Glomus mosseae.
Authors: Bethlenfalvay Gabor J. , Franson Raymond L. , Brown Milford S. , Mihara Keiko L.
Published: May 2006

The objective of the work was to determine differences in plant response to geographic isolates of a vesicular‐arbuscular mycorrhizal (VAM) fungus, and to demonstrate the need for such determinations in the selection of desirable host‐endophyte combinations for practical applications. Soybean (Glycine max (L.) Merr.) plants were inoculated with Bradyrhizobium japonicum and isolates of the VAM‐fungal morphospecies Glomus mosseae (Nicol. & Gerd.) Gerd. and Trappe, collected from an arid (AR), semiarid (SA) or mesic (ME) area. Inoculum potentials of the VAM‐fungal isolates were determined and the inocula equalized, achieving the same level of root colonization (41%, P>0.05) at harvest (50 days). Plants of the three VAM treatments (AR, SA and ME) were evaluated against von VAM controls. Significant differences in plant response to colonization were found in dry mass, leaf K, N and P concentrations, and in root/shoot, nodule/root, root length/leaf area and root length/root mass ratios. The differences were most pronounced and consistent between the AR and all other treatments. Photosynthesis and nodule activity were higher (P<0.05) in all VAM treatments, but only the AR plants had higher (P<0.05) photosynthetic water‐use efficiency than the controls. Nodule activity, evaluated by H2 evolution and C2H2 reduction, differed significantly between treatments. The results are discussed in terms of nutritional and non‐nutritional effects of VAM colonization on the development and physiology of the tripartite soybean association in the light of intraspecific variability within the fungal endophyte.
The effect of photoperiod on flower formation in vitro in a quantitative short‐day cultivar of Nicotiana tabacum
Authors: Altamura Maria Maddalena , Monacelli Barbara , Pasqua Gabriella
Published: May 2006

Superficial cell layers of a quantitative short‐day tobacco plant (Nicotiana tabacum L. cv. White Burley) were excised from different parts of the inflorescence (i.e. pedicels, branch internodes, rachises), and cultured in continuous darkness, continuous light or 8 h light/16 h dark daily. The flowering response in vitro of the different types of explants was investigated with respect to the effect of light on the post‐evocation phases of the flowering process and explant commitment. Treatment effect was qualitatively and quantitatively influenced by explant origin. Three morphogenic features were observed: flower neoformation, caulogenesis and rhizogenesis (the latter on rachis explants only). Under all treatments, the highest flowering potential was shown by pedicels, while the highest vegetative potential was shown by rachises. Branch internodes showed an intermediate response, but with a tendency towards caulogenesis, which probably reflects their phylogenetic origin. Thus, opposite gradients of the neoformation of flowering and vegetative buds on explants were observed under all treatments. Pedicels formed new single flowers rather than inflorescences, while rachises regenerated mainly inflorescences. In darkness, flowering was limited mostly to pedicels. Vegetative bud formation was higher than floral bud regeneration in all types of explant. Continuous light enhanced the flowering response mostly in pedicel and branch internode explants. Short days enhanced flower bud formation in vitro on all types of explant. Results with respect to microsporogenesis, flower and inflorescence anomalies observed under darkness also seem to support the existence of a quantitative photoperiodic control on floral neoformation in vitro in this plant. These results suggest that in Nicotiana tabacum cv. White Burley in vivo floral induction, initiation and development are governed by the same photoperiodic requirements.
Phototropism in hypocotyls of radish. VI. No exchange of endogenous indole‐3‐acetic acid between peripheral and central cell layers during first and second positive phototropic curvatures
Authors: Sakoda Masako , Hasegawa Koji
Published: May 2006

Using a physicochemical method, the distribution of endogenous indole‐3‐acetic acid (IAA) was measured in the peripheral and central cell layers, as well as in the illuminated and shaded sides of phototropically stimulated radish hypocotyls (Raphanus sativus var. hortensis f. gigantissimus Makino). The IAA was evenly distributed over the illuminated and shaded sides in the first and second positive phototropic curvatures induced by a pulse or a continuous unilateral illumination with blue light. Also, no net exchange of the IAA between the peripheral and central cell layers was observed during these curvatures. These results suggest that phototropism of radish hypocotyls cannot be described by the Cholodny‐Went theory.
The grana margins of plant thylakoid membranes
Authors: Anderson Jan M.
Published: May 2006

Plant thylakoid membranes contain three structurally distinct domains: the planar appressed membranes of the grana; the planar non‐appressed stroma thylakoids; and the highly curved, non‐appressed margins of the grana. Evidence is presented to suggest that the grana margins form a significant structural domain, which has hitherto been neglected. If indeed the grana margins contain some of the cytochrome b/f complex, photosystem (PS) I complex and ATP synthase, they form a third functional domain of the laterally heterogeneous continuous thylakoid membrane network. The consequences of grana margins containing complexes are explored with respect to linear electron transport under light‐saturating and light‐limiting conditions, non‐cyclic vs cyclic photophorylation, and the regulation of light energy distribution to both PS I and PS II.
Regulation of lateral root formation in lettuce (Lactuca sativa) seedling roots: Interacting effects of α‐naphthaleneacetic acid and kinetin
Authors: MacIsaac S. A. , Sawhney V. K. , Pohorecky Y.
Published: May 2006

Growth substances, α‐naphthaleneacetic (NAA) and kinetin, had an important role in the regulation of lateral root (LR) formation in lettuce (Lactuca sativa L. cv. Grand Rapids) seedling roots. NAA (10‐5M) was a potent stimulator of LR initiation and caused a 600% increase in the number of lateral root primordia (LRP) compared to untreated roots. NAA was required for only the first 20 h of the 72 h treatment period for maximum stimulation of LRP initiation. Kinetin (2 × 10‐5M) effectively prevented the spontaneous formation of LRP and inhibited the NAA‐stimulated production of LRP. Kinetin inhibition was maximal during the first 20 h of NAA treatment and this effect was not overcome by subsequent supply of NAA. Also, lettuce roots were most sensitive to kinetin at 20 h of NAA treatment, when the first signs of cell division were observed in the pericycle.
De novo root formation in thin cell layers of tobacco: changes in free and bound polyamines
Authors: Torrigiani Patrizia , Altamura Maria Maddalena , Capitani Francesca , Serafini‐Fracassini Donatella , Bagni Nello
Published: May 2006

Thin cell layers excised from tobacco (Nicotiana tabacum L. cv. Samsun) stem internodes, with an appropriate exogenous hormonal balance, were able to form a greater number of roots, and in a larger percentage of the explants (93%) than when they were excised from pedicels (40%). The developmental sequence of root formation and explant growth were followed by histological analysis. Free and bound [trichloroacetic acid (TCA)‐soluble and ‐insoluble] putrescine and spermidine increased in the explants, particularly when root meristemoids appeared. These meristemoids originated in the superficial (day 6 in culture) or deep (days 10–11) layers and inside the newly formed callus (day 25). At those times, TCA‐soluble and, to a lesser extent, TCA‐insoluble bound putrescine predominated over the other polyamines. Spermine was always present in trace amounts. Polyamines decreased again when root and callus formation was completed (day 30). The involvement of these three classes of polyamines (free, TCA‐soluble and ‐insoluble) in morphogenic processes is discussed.
Superoxide dismutase and catalase activities in purified Frankia vesicles
Authors: Puppo Alain , Dimitrijevic Lilliana , Rigaud Jean
Published: May 2006

Superoxide dismutase (EC 1.15.1.1.) and catalase (EC 1.11.1.6.) activities of Frankia cells grown in the presence of ammonium were very high in comparison with those of other prokaryaotes and particularly Rhizobium. Furthermore, these activities were significantly enhanced under nitrogen‐fixing conditions where vesicles were produced. By using a single‐step sucrose gradient, Frankia vesicles were isolated and appeared intact and free of hyphal contamination. The contents of superoxide dismutase and catalase in the purified vesicles were similar to those in preparations containing both vesicles and hyphae. These results suggest an important role of superoxide dismutase and catalase in the protection of the overall nitrogen‐fixation process against O2 in Frankia vesicles. Beside the protective role played by the thick walls of the vesicles, the presence of specialized enzymes is emphasized.
Chlorophyll accumulation and breakdown in light‐grown barley transferred to darkness: effect of seedling age
Authors: Walmsley Jane , Adamson Heather
Published: May 2006

Diurnally grown barley (Hordeum vulgare L. cv. Clipper) seedlings of various ages (3–4, 5–6 and 10–11‐days‐old) were transferred to darkness for 17 h and changes in leaf fresh weight, chlorophyll a, chlorophyll b and protochlorophyllide measured. The results were consistent with previous evidence of a light‐independent chlorophyll biosynthetic pathway in light‐grown barley. There was a net gain in chlorophyll (μg leaf‐1) in 5–6‐ and 10–11‐day‐old plants after 17 h dark treatment. The amounts of chlorophyll that accumulated were similar (5.9 and 4.3 μg Chl leaf‐1), despite a twofold difference in leaf size at T0. The rate of leaf expansion in 5–6‐day‐old plants greatly exceeded the rate of chlorophyll accumulation and leaves were noticeably paler after dark treatment i.e. there was a reduction in chlorophyll concentration (μg g fresh weight‐1) in spite of an increase in chlorophyll content (μg leaf‐1). The ability of light‐grown barley to accumulate chlorophyll in darkness was a function of seedling age. Very young seedlings (3–4‐day‐old) generally lost chlorophyll in darkness. The decrease in chlorophyll per leaf resulted mainly from loss of chlorophyll b. Preferential loss of chlorophyll b resulted in dramatic increases in the chlorophyll a:b ratio. Since 3–4‐day‐old seedlings (1) accumulated 5‐aminolevulinic acid in the presence of levulinic acid at a rate comparable to older seedlings, and (2) converted exogenous 5‐aminolevulinic acid to chlorophyll in the absence of light, it is unlikely that failure of the youngest plants to accumulate chlorophyll in darkness was due to blocks at these steps in the pathway. Net loss of chlorophyll (μg leaf‐1) in 3–4‐day‐old seedlings in darkness was eliminated by the addition of chloramphenicol, which occasionally produced a small, but significant, gain in total chlorophyll. These results imply that chlorophyll degradation in young barley leaves is strongly influenced by the chloroplast genome, and is a major factor influencing changes in chlorophyll levels in darkness. The present findings are consistent with the suggestion that the failure of 3–4‐day‐old barley seedlings to accumulate chlorophyll in darkness may be due to chlorophyll turnover in which the rate of degradation exceeds the rate of synthesis.
Enhanced potassium uptake and phosphatidylinositol ‐phosphate turnover by hypertonic mannitol shock
Authors: Srivastava Alaka , Pines Mark , Jacoby Benjamin
Published: May 2006

A hypertonic mannitol shock enhanced K+ uptake by Beta vulgaris L. (cv. early flat Egyptian) storage tissue slices and also increased the inositol 1,4,5‐trisphosphate [Ins(1,4,5)P3) content of the slices as well as of Sorghum bicolor L. (cv. Hazera) and Vigna radiata L. (cv. unknown) roots. K+ uptake by B. vulgaris slices could be enhanced, in the absence of mannitol, by application of effectors that mimic products of the phosphatidylinositol 4,5‐bisphosphate (PIP2) turnover cycle. Maximal Ins (1,4,5)P3 content was found 10 min after hypertonic induction and maximal K+ uptake was obtained 10 min later. The hypertonic mannitol shock, administered to intact B. vulgaris slices, also enhanced the phosphorylation of a 39 kDa protein in the plasmalemma.
The role of Mg2+ in proton transport by the tonoplast pyrophosphatase in Riccia fluitans vacuoles
Authors: Johannes Eva , Felle Hubert H.
Published: May 2006

The Mg2+‐dependent activity of the tonoplast pyrophosphatase (PPase) was investigated by measuring proton transport and by using the acridine orange technique on intact vacuoles of the aquatic liverwort Riccia fluitans L. In solutions with both Mg2+ and pyrophosphate present, a number of complexes are formed, which could all influence the enzymatic and hence the transport activity of the PPase. Therefore, the individual concentrations of these complexes were calculated and their contributions to proton transport across the tonoplast were tested. From these experiments we conclude that Mg2+ has three different roles: (i) Mg2+ stimulates transport activity of the PPase. (ii) Mg2PPi inhibits PPase‐mediated H+ transport, (iii) MgPPi* (= MgPPi2‐+ MgHPPi‐) is the substrate with an apparent K1/2= 5–10 μM, with no discrimination between MgPPi2‐ and MgHPPi‐.
The nectar of the Strelitzia reginae flower
Authors: Kronestedt‐Robards Eva C. , Greger Maria , Robards Anthony W.
Published: May 2006

The nectar of Strelitzia reginae Ait. was analysed using enzymatic methods and found to contain glucose, fructose and sucrose. Sugar composition changed considerably over the nectar producing period: there was an increase in the amount of glucose (41%) and fructose (32%) between the early and middle stage of secretion and thereafter a decrease of 13 and 24%, respectively, towards the end of secretion. Although the amount of sucrose secreted was initially as much as the glucose and fructose combined, it subsequently decreased, first by 14% and then by 70% at the end of the secretory period so that, whereas in the initial stages of secretion sucrose was quantitatively the dominant sugar, glucose and fructose made up the major part of the nectar as secretion reached its conclusion.

The amounts of potassium and sodium remained at the same low level (around 150 and 30 μg g‐1 [w/v) respectively) throughout secretion, while calcium (initially 18 μg g‐1) and magnesium (initially 8.0 μg g‐1) increased by 47 and 56% respectively, between the early and late stages of secretion. No free amino acids, inorganic phosphate or iron could be detected. Enzymatic analysis revealed only a trace amount of starch. Transmission electron micrographs from both immature and mature plants, however, showed starch grains among other cytoplasmic remnants in the nectary lumen. Mitochondria, vesicles, lipid droplets and ribosomes could also be identified among the luminal cytoplasmic remnants.
Contamination of oat mesophyll protoplasts by apoplastic polyamine oxidase
Authors: Li Zhen‐Chang , McClure Jerry W.
Published: May 2006

Mesophyll protoplasts isolated from peeled oat (Avena sativa L. cv Victory) leaves with 1% (w/v) Cellulysin in 20 mM KPO4, pH 5.5 and 0.6 M sorbitol retain about 6% of the polyamine oxidase (PAO, EC 1.4.3.4) activity of the whole peeled leaf. However, more than 99% of the oat leaf PAO activity is apoplastic and can be extracted by vacuum infiltration with 200 mM NaCl and this procedure extracts no activity for the cytoplasmic marker enzyme glucose‐6‐phosphate dehydrogenase (G6PD, EC 1.1.1.49). By these criteria we consider PAO in oat leaves to be totally apoplastic and PAO found in the isolated protoplast to be contamination. The degree of protoplast contamination by PAO depends on the pH and ionic strength of the isolating and washing medium. It can be eliminated by washing protoplasts in 0.6 M sorbitol with 100 mM KPO4, pH 6.5. Pellets of lysed protoplasts incubated with dialyzed apoplastic enzymes in 5 mM KPO4, pH 5.5 adsorb about 87% of the added PAO activity but only about 25% of the added peroxidase (EC 1.11.1.7) activity. The adsorbed activity can be solubilized from the pellet by extraction with 1 M NaCl. The results demonstrate that weakly ionically bound cell wall enzymes may contaminate protoplasts isolated and purified by conventional techniques.
Photoperiod and gibberellic acid – control of the cell cycle in the meristem of Silene armeria and its effects on flowering
Authors: Besnard‐Wibaut Christiane , Cochet Thierry , Noin Michèle
Published: May 2006

Plants of Silene armeria L., strain S2.1, a quantitative long‐day (LD) species which is known to react to GA3 by flowering after attaining, the‘intermediate stage’, were induced by two LD or by two GA3 applications. Changes in the mitotic index and DNA content (microdensitometric estimation) of cells in the axial zone, lateral zone and rib meristem of the shoot apex were observed during the first 48 h of each treatment. Similar mitotic activation occurred in response to LD or GA3 after a 6‐8 h lag period. This was preceded by a decrease in the proportion of nuclei with a 2C DNA content, indicating that in this species the control point for the shortening of the cell cycle was essentially in G1. A second mitotic peak was observed 16 h later in photoinduced meristems, resulting in more pronounced cellular synchronization. These further events were not seen in GA3‐treated plants where only the meristematic activity was slightly, but reproducibly higher than in the control. Thus, two successive synchronizations of cell division are a typical feature of LD induction. The data are discussed with regard to the competence of shoot apical cells to be reactivated. The essential changes for the transition to flowering depend on these differential patterns of cell reactivation.
Effects of applied nitrogen upon aspects of nitrogen metabolism and transport in developing nodulated winged bean plants
Authors: Chapleo S. , Hall J. L.
Published: May 2006

Nodulated winged bean [Psophocarpus tetragonolobus (L.) DC., cv. UPS 122] were grown under constant environmental conditions and supplied with mineral nutrient solution in which nitrogen was absent or was present as nitrate (12 mg N week‐1 plant‐1).

Nitrate treatment dramatically promoted plant growth, increased fruit weight 1.6 fold, was necessary for tuberisation and enhanced nodulation. The in vitro accumulation of 14C into asparagine and aspartate components of excised nodules supplied with exogenous 14CO2 and [14C]‐D‐glucose was greater for nitrate‐treated plants, whilst accumulation into ureides was reduced by nitrate treatment. Levels of amino acids in xylem sap were greater for plants supplied with a complete nutrient solution, than those grown without applied nitrate, particularly for asparagine, glutamine and proline. Xylem ureide levels were greater for plants grown in the absence of supplementary nitrate.

Nitrogen accumulated in leaf, stem and petiole, and root nodule tissues for utilisation during fruit development; peak nitrogen levels and time of anthesis were retarded for plants grown without applied nitrate. The shoot ureide content increased during fruiting, coincident with decreases in the total nitrogen content, indicating that ureide pools are not utilised during the early reproductive phase. However ureide reserves, particularly allantoin, were utilised during the later stages of pod fill.

Enzyme activity which metabolised asparagine was found throughout the plant and was identified as K+‐dependent asparaginase (EC 3.5.1.1) and an aminotransferase. Apart from temporal differences in developmental profiles of enzyme activity, the activity of these enzymes and of allantoinase (EC 3.5.2.5) in developing tissues were similar for both treatments. The main differences were greater asparaginase and asparagine:pyruvate aminotransferase activities in root tissues and fruit of nitrate‐supplied plants; allantoinase activity in the primary roots of plants grown without nitrate decreased during development, whilst activity in developing tubers (nitrate‐supplied plants) increased.
Ethylene requirement during germination of Botrytis cinerea spores
Authors: KępczyńAska Ewa
Published: May 2006

Application of 2,5‐norbornadiene, a competitive inhibitor of ethylene, effectively inhibited the germination of Botrytis cinerea Pers. ex Fr. spores. The transfer of spores from 2,5‐norbornadiene to air relieved inhibition by norbornadiene, indicating that its effects are non‐toxic and reversible. Ethephon (2‐chloroethylophosphonic acid), which stimulates spore germination of B. cinerea, does not affect germination in the presence of norbornadiene. However, ethephon appeared to be effective in relieving inhibition, when norbornadiene was removed from the atmosphere surrounding spores. The addition of ethylene to an atmosphere enriched with norbornadiene, counteracted the inhibition of spore germination. The inhibition of spore germination by 2,5‐norbornadiene and the reversal of this effect by ethephon or ethylene, indicate that the action of ethylene is indispensable for germination of B. cinerea spores.
Measurements of pH, sucrose and potassium ions in the phloem sap of castor bean (Ricinus communis) plants
Authors: Vreugdenhil Dick , Koot‐Gronsveld Elly A. M.
Published: May 2006

The composition of phloem sap, sampled at different heights along, the stem of castor bean (Ricinus communis L. cv. Gibsonii) plants, was determined. A gradient in pH was observed; the highest pH values occurred near the shoot apex, decreasing towards the base of the stem. The sucrose content of the exudate exhibited a similar gradient. The concentration of potassium ions was highest near the uppermost, full‐grown leaves, decreasing towards the apex and the base of the stem. The importance of these findings for the understanding of phloem translocation and unloading is discussed.