bluuebunny/crossref_metadata_2025 huggingface dataset:
The surface charge density of wheat root membranes
Authors: Bérczi Alajos , Møller Ian M. , Lundborg Tomas , Kylin Anders
Published: April 2006

Seedlings of winter wheat (Triticum aestivum L. cv. Hildur) were grown at 18°C for 7 days in darkness in a complete growth medium in the presence or absence of 1 mM KCl to produce roots with different ion contents (high and low K+ respectively). The roots were homogenized, the 3 000 g, 10 000 g, 30 000 g (further fractionated by two phase partitioning) and 100 000 g pellets isolated, and their surface charge densities (σ) determined by the use of 9‐aminoacridine fluorescence. The average σ for all membrane fractions weighted for protein content was the same (−18 mC m−2) for low and high K+ roots. The K+, Na+, Mg2+ and Ca2+ content of roots was determined and used to calculate an average σ following the procedure of Bérczi et al. [Physiol. Plant. 61: 529–534 (1984)]. The predicted value (−11 mC m−2) does not deviate much from the experimentally determined value. It is concluded as a useful working hypothesis that the average surface charge density is constant and that the ionic content of plant cells is regulated such that the average surface potential is constant.
Oscillations in stomatal conductance of hybrid poplar leaves in the light and dark
Authors: Reich Peter B.
Published: April 2006

Cycling of stomatal conductance in three hybrid poplar (Populus sp.) cultivars was observed under a variety of conditions. Illumination of plants kept previously in the dark induced very large oscillations with a period of about 40 min and large oscillations with a shorter period (< 10 min) were superimposed on the longer cycles. During these oscillations, large changes in conductance could occur very rapidly (1.0 cm s−1 in 3 min). Plants in constant light also displayed both long and short term cycles in conductance, but these were smaller in amplitude than those induced by sudden illumination. Stomatal oscillations were also observed in darkness and after darkening of previously illuminated plants. These oscillations had shorter (< 30 min) and less regular periods than those observed in the light. Such cycling in the dark is rare. Cycling of the two leaf surfaces was sometimes in synchrony in the light, and more so after a perturbation. Little synchrony between the two surfaces was observed in the dark. Stomatal movements of different leaves on a plant were usually relatively independent. Transient stomatal opening occurred following leaf excision in the light or dark, and often after sudden darkening of intact leaves. Also, stomata of intact leaves sometimes transiently closed following illumination.
Photosynthate partitioning and nodule formation in soybean plants that received red or far‐red light at the end of the photosynthetic period
Authors: Kasperbauer M. J. , Hunt P. G. , Sojka R. E.
Published: April 2006

The influence of row orientation on spectral distribution of light received by growing soybean [Glycine max (L.) Merr. (cv. Coker 338)] plants was measured under field conditions, and light spectrum effects on photosynthate partitioning were studied under controlled environments. Light received by leaves under field conditions differed among those grown in north‐south vs east‐west oriented rows. In morning and late afternoon, the far‐red/ red ratio received by leaves at the surface of the canopy differed about 3‐fold from the east to west sides of north‐south rows, but only 1.3‐fold from the south to north sides of east‐west rows.

In controlled environments, brief exposures to red or far‐red light at the end of the photosynthetic period influenced partitioning of photosynthate among leaves, stems and roots. The top/root ratios differed significantly between the red and far‐red treated plants. Red treated plants partitioned less photosynthate to stems and more to roots than did those treated with far‐red. Also, plants with larger root systems developed more nodules. Phytochrome effects on photosynthate partitioning between tops and roots may influence yield of soybean plants grown in soils with low water‐holding capacity.
Turgor‐sensitive sucrose and amino acid transport into developing seeds of Pisum sativum. Effect of a high sucrose or mannitol concentration in experiments with empty ovules
Authors: Wolswinkel Pieter , Ammerlaan Ankie
Published: April 2006

Sugar and amino acid transport into empty ovules of Pisum sativum L. cv. Marzia was examined. In fruits containing 4–6 developing seeds, the embryo was removed from four ovules. After this surgical treatment, each empty seed coat was filled with a solution (pH 5.5) containing a low (0, 50 or 200 mM), medium (350, 400 or 500 mM) or high (0.7 or 1 M) concentration of sucrose and/or mannitol. In pulse‐labelling experiments with sucrose and α‐aminoisobutyric acid (AIB), transport of sucrose and AIB into an empty ovule filled with a solution containing a high sucrose concentration was the same as transport into an ovule filled with a mannitol solution of similar osmolarity, demonstrating that a high sucrose concentration in the seed coat apoplast affects phloem transport of sucrose and AIB into the seed coat only by the osmotic effect. The osmolarity of a given solution filling the seed coat cavity appeared to be important for phloem transport of sucrose and AIB into empty ovules.

In our experiments, 350 mM appeared to be the optimal concentration for sucrose and AIB transport into the cavity within an empty ovule, giving results comparable with transport into intact ovules. A lower osmolarity of the solution induced less transport. Very high sucrose or mannitol concentrations caused a strong inhibition of sucrose and AIB unloading from the seed coat, so that transport into the empty ovules was inhibited. A low (strongly negative) but not too low osmotic potential of the solution in the seed coat apoplast seems necessary to maintain a normal rate of phloem transport into developing seeds. Apparently, the “sink strength” of developing seeds is turgor‐sensitive.
Effects of 2‐iodobenzanilide on potassium uptake, H+ extrusion and K+‐stimulated ATPase of corn roots
Authors: Maggioni A. , Varanini Z. , Macrì F. , Vianello A.
Published: April 2006

The carboxanilide systemic fungicide 2‐iodobenzanilide (2‐IB) after 2 h pretreatment at 0.25 mM inhibited K+ and SO42‐ uptake by excised corn roots (Zea mays L., cv. Dekalb 342) up to ca 70 and 40%, respectively. Proton extrusion from corn roots was also reduced by ca 50% after 1 h contact, and the microsomal K+‐stimulated ATPase activity from corn roots and pea stems (Pisum sativum L., cv. Alaska) inhibited by 50 and 72%, respectively. In contrast, the Mg2+‐ATPase activities of microsomes and mitochondria at pH 6.0 and 8.7, respectively, were unaffected. After 2 h of preincubation with 0.25 mM 2‐IB, O2 consumption by corn roots and pea stems was inhibited by 12 and 18%, respectively. ATP content of corn roots was not altered by 2‐IB treatment. Therefore, energy availability “in vivo” was unaffected and the primary effect on corn roots is suggested to be at the plasmalemma ATPase which forms the proton gradient.

With isolated pea stem mitochondria, 0.25 mM 2‐IB inhibited O2 consumption by ca 60% when NADH or malate plus pyruvate were added as substrates; when succinate was used O2 consumption was unaffected. The mode of action on isolated mitochondria was different from that shown for carboxin and also formerly attributed to the whole class of carboxanilide fungicides.
Glycinebetaine content of halophytes: Improved analysis by liquid chromatography and interpretations of results
Authors: Guy Robert D. , Warne Patricia G. , Reid David M.
Published: April 2006

The glycinebetaine content of plants can be determined by simple isocratic high performance liquid chromatography. The method is applicable to extracts from a wide range of species and, in most cases, is suitably rapid and specific to be preferable to other methods of analysis. The chromatographic system employed permits accurate and sensitive ultraviolet detection, free of most interferences. Because the principle plant carbohydrates elute well before glycine betaine, preparative ion exchange procedures can be simplified. Twenty‐seven species, mostly inland halophytes, were screened by these methods and 13 were found to be glycinebetaine accumulators. On a dry weight basis, the glycinebetaine content of Salicornia europaea L. actually declined with exposure to progressively higher levels of NaCl. When expressed as a proportion of plant organic matter, however, patterns were more typical (up to 7.7% at higher salt concentrations).
Is indolyl‐3‐acetic acid involved in the wave‐like pattern of auxin efflux from Pinus sylvestris stem segments?
Authors: Wodzicki Tomasz J. , Knegt Erik , Wodzicki Alina B. , Bruinsma Johan
Published: April 2006

The coleoptile curvature bioassay of agar diffusates from successive cambial‐region sections of Pinus silvestris L. stem tissue reveals the existence of a wave‐like pattern, possibly of auxin translocation. Spectrofluorometric determinations of indolyl‐3‐acetic acid (IAA) in these diffusates gave only a poor correlation. Probably another phytohormone, also an auxin, plays a more important role in the pattern.

The amplification in the amplitude of the pattern, brought about by apically applied IAA, cannot be induced by the synthetic auxin, 2,4‐dichlorophenoxyacetic acid.
Diurnal variations of nitrite reductase, glutamine synthetase, glutamate synthase, alanine aminotransferase and aspartate aminotransferase in barley leaves
Authors: Lillo Cathrine
Published: April 2006

Diurnal variations of in vitro activity of 5 enzymes of nitrogen metabolism were studied. Barley (Hordeum vulgare L. cv. Herta) seedlings were grown in 8 h short days, in daylight or under fluorescent lamps. During, the photoperiod nitrite reductase (EC 1.7.7.1) increased by an average of 18% in daylight and 10% under fluorescent lamps. Glutamine synthetase (EC 6.3.1.2) activity increased by 14 and 10%, respectively. The increase in enzyme activity reflected the overall increase in soluble proteins which was 8% in daylight and 3% under fluorescent lamps. Alanine aminotransferase (EC 2.6.1.2) increased by 82% in daylight and 37% under fluorescent lamps. Desalting of the extracts did not alter the enzyme activity and thus supported the assumption that changes in extractable enzyme activity are due to changes in the amount of (active) enzyme protein. Glutamate synthase (EC 1.4.7.1) activity did not show regular diurnal variations, and aspartate aminotransferase (EC 2.6.1.1) activity was almost constant.
Kinetic parameters in the compartmental analysis of lithium transport in Lemna gibba using the stable isotopes, 6Li and 7Li, as tracers
Authors: Bielenski U. , Garrec J. P. , Demarty M. , Ripoll C. , Thellier M.
Published: April 2006

Due to the lack of a convenient radiotracer of Li, we have used the stable isotopes, 6Li and 7Li, for unidirectional flux measurements in Lemna gibba L. (GI). Detection was performed using an ionic microanalyser. The conventional method of compartmental analysis has been improved in several ways. Growth of the plant samples has been taken into consideration. The possible non‐uniqueness of the kinetic solution fitting the experimental points has been considered by numerical calculation. The derivatives and not only the direct functions have been used in order to detect whether a constant term had to be added to the first‐order terms. The validity of the estimates of the characteristic parameters of transport has been checked by using efflux and influx data simultaneously. The “manipulation‐shock” effects have been shown not to be negligible. The kinetic data have no simple biological significance per se, but they can serve to calculate cellular parameters of transport when combined with appropriate stereometric data. These considerations are relevant not only to our present problem, but to any type of compartmental analysis, whatever the plant sample and the absorbed substrate.
Changes in the activities of enzymes involved in amino acid metabolism during the senescence of detached wheat leaves
Authors: Kar Manoranjan , Feierabend Jürgen
Published: April 2006

The activities of several enzymes related to amino acid metabolism were investigated in senescing detached wheat leaves (Triticum aestivum L. cv. Diplomat) in light and darkness and after kinetin treatment. Glutamine synthetase and glutamate synthase activities rapidly declined in darkness. In light, the decline of glutamate synthase activity was retarded, while the activity of glutamine synthetase remained high and even increased transitorily. Kinetin treatment counteracted the decline of the activities of both enzymes. The activity of glutamate dehydrogenase markedly increased during senescence, particularly in light, and kinetin treatment lowered its activity. The activities of glutamate‐oxaloacetate and glutamate‐pyruvate amino‐transferases and of NADP‐dependent isocitrate dehydrogenase also increased in detached wheat leaves in light. Kinetin treatment prevented the rise of these enzyme activities. In darkness, the activities of glutamate‐oxaloacetate aminotransferase and NADP‐dependent isocitrate dehydrogenase decreased slowly while the decline of glutamate‐pyruvate aminotransferase activity was more rapid. The activity of NAD‐dependent malate dehydrogenase decreased both in light and, more rapidly, in darkness. The pattern of changes of the enzyme activities provides an explanation for the amino acid transformations and the flow of amino nitrogen into transport metabolites in senescing leaves.
Cytofluorometric measurements of nuclear DNA in adventitious buds and shoots of Picea abies regenerated in vitro
Authors: Hakman I. , von Arnold S. , Bengtsson A.
Published: April 2006

Nuclear DNA content of adventitious buds and shoots of Picea abies (L.) Karst. developed in vitro was compared to that of buds collected from field‐grown trees. Protoplasts were isolated from the different tissues and after fixation and staining with ethidium bromide the DNA content of their interphase nuclei was determined cytofluorometrically. The DNA pattern of the different tissues was within the same range and had the same distribution with one main peak.
Role of phytochrome in photoperiodic regulation of bulbing and growth in the long day plant Allium cepa
Authors: Lercari Bartolomeo
Published: April 2006

Plant elongation in Allium cepa L. cv. Dorata di Parma was stimulated by end‐of‐day far‐red radiation, while the same treatment was ineffective with respect to bulbing response. It was concluded that the Pfr‐dependent reactions which control bulbing are completed during the long daily light period (18 h). Day breaks of 3 h fluorescent white light, in the middle of the inductive photoperiod were inhibitory to bulbing. Repeated brief far‐red irradiations could substitute for continuous far‐red irradiations lasting 3 h in the middle of the photoperiod. Red light alone or applied immediately after each far‐red irradiation inhibits bulb formation.
Binding of phytochrome to plasma membranes in vivo
Authors: Widell Susanne , Sundqvist Christer
Published: April 2006

A microsomal fraction was prepared by differential centrifugation from the homogenate of dark grown shoots of oats (Avena sativa L. cv. Sol II). Plasma membranes were prepared from the microsomal fraction by means of an aqueous polymer two phase partition method. The content of phytochrome in the microsomal fraction and the plasma membrane fraction, respectively, were studied after different irradiation treatments of the intact shoots. Red irradiation increased the content of phytochrome in both the microsomal and plasma membrane fraction, especially in the presence of Mg2+. The increase induced by red light was fully reversible by far‐red light for the plasma membrane fraction both in the presence and absence of Mg2+, in contrast to the microsomal fraction where Mg2+ had to be omitted. KI treatment of the membranes destroyed the binding of phytochrome whereas agents such as KCI, EDTA, CaCl2 and Triton X‐100, did not have this effect, indicating that the phytochrome attachment to the membrane is hydrophobic. This in vivo binding resembles to a large extent the one obtained in vitro by Sundqvist and Widell (Physiol. Plant. 59: 35–41, 1983) even though some differences between the phytochrome species and the membrane side exposed probably occur; so that the present interaction between phytochrome and the plasma membrane does not necessarily reflect the interaction that leads to physiological responses, and there could be more than one type of interaction.
Comparative electrophoretic studies of polypeptides in leaf, petiole and root mitochondria from spinach
Authors: Sahlström Stefan , Ericson Ingemar
Published: April 2006

Essentially chlorophyll‐free preparations of mitochondria from different tissues of the same plant can be obtained by a combined three step preparation procedure involving differential centrifugation, partition in aqueous polymeric two‐phase system and centrifugation in a Percoll gradient. The polypeptide patterns of mitochondria from photosynthetic (leaves) and non‐photosynthetic (petioles and roots) tissue from spinach were compared by use of SDS‐electrophoresis.

About 35 polypeptides were found in leaf mitochondria with molecular weights from 14 to 103 kdalton. The polypeptide patterns of the membrane fractions and matrix fractions showed great differences. The membrane fractions contained significantly more polypeptide bands than the matrix fractions. The polypeptide patterns of mitochondria from photosynthetic and non‐photosynthetic tissues showed some striking differences. The 15.9, 41.7, 50.7 and 101 kdalton polypeptides were clearly detected in leaf mitochondria but these polypeptides were not found or found in only small amounts in petiole and root mitochondria. The differences were mainly associated with the matrix fractions. Staining with 3,3′,5,5′‐tetramethylbenzidine and hydrogen peroxide for heme containing polypeptides showed that the polypeptides which differ do not contain heme.
Transport and accumulation of indole‐3‐acetic acid in pea cuttings under two levels of irradiance
Authors: Baadsmand Søren , Andersen Arne Skytt
Published: April 2006

The transport and accumulation of 2‐[14C]‐IAA applied to the apex of cuttings of Pisum sativum L. cv. Alaska was greater in cuttings from stock plants grown under 38 W m−2 than 16 W m−2. Accumulation of 14C in the base of the cuttings from the highest level of irradiance was correspondingly more significant. The level of irradiance to the stock plants greatly affected the rate of accumulation, while the light conditions during IAA transport had a minor effect. The amount of IAA reaching the base of the cuttings increased with increasing concentration of IAA in the treatment solution, but the percentage of applied IAA reaching the base decreased.

The relative chromatographic partition of ethanol‐extractable 14C showed that, after 12 h of IAA‐transport, the amount of 2‐[14C]‐IAA was higher in the base of cuttings from 38 W m−2 than in those from 16 W m−2. After a further 12 h of transport the relative amounts of 2‐[14C]‐IAA in the two types of cuttings were reduced to the same lower level.

A possible role of an irradiance‐mediated difference in the topographic distribution of IAA in the base of pea cuttings on the subsequent adventitious root formation is discussed.
Dual effect of light on flowering and sprouting of rose shoots
Authors: Mor Yoram , Halevy Abraham H.
Published: April 2006

Shade, caused by a dense leaf canopy in the light conditions of a normal greenhouse, reduced sprouting of the third axillary bud (from the top) on decapitated rose branches (Rosa hybrida cv. Marimba) in comparison to less shaded buds on branches protruding above the canopy and sparsely spaced. Flowering of the third young shoot on shaded branches bearing 3 lateral shoots was totally inhibited. Mixed fluorescent and incandescent light in a growth chamber reduced sprouting of the third bud on decapitated rose branches in comparison to decapitated branches on rose plants held in fluorescent light of similar photon flux density. This was attributed to the higher R:FR ratio in fluorescent vs mixed light that reached the third bud, and in exposed vs shaded branches. Flowering of the third shoot was promoted by several factors: high photon flux density, 0.5 mM gibberellic acid (GA) or 0.2 mM benzyladenine (BA). BA was the most effective treatment. Treatments promoting flowering of the third shoot did not reduce growth or flowering of the upper shoots. However, spraying the uppermost shoot with BA suppressed the growth of the shoots below. It is concluded that light affects flowering in two ways. The effect on bud sprouting is related mainly to R:FR ratios, while the effect on flower development is related mainly to photon flux density. Cytokinins may substitute for the light effect on flower development.
Changes in the composition of in vitro translated leaf m‐RNA caused by photoperiodic flower induction ofHyoscyamus niger
Authors: Warm E.
Published: April 2006

Flowering of the long day plantHyoscyamus nigerL., which is strictly photoperiodically controlled, was induced by 58 h continuous white light. The RNA from the leaves was isolated from photoperiodically induced and non‐induced plants and the poly(A)‐rich RNA separated by affinity chromatography on oligo‐dT‐cellulose. The poly(A)‐rich RNA was translated in vitro in the presence of35S‐methionine using a rabbit reticulocyte lysate. Subsequent separation of the translation products by two‐dimensional polyacrylamide gel electrophoresis and fluorography allowed a comparison of the polypeptide pattern from induced and non‐induced leaf m‐RNA. The results indicate that induction of flowering is reflected by changes in the translation of several leaf polypeptides. These polypeptides were characterized by their isoelectric points and molecular masses.
Inhibition of gravitropism in oat coleoptiles by the calcium chelator, ethyleneglycol‐bis‐(β‐aminoethyl ether)‐N′‐tetraacetic acid
Authors: Daye Sun , Biro Ronald L. , Roux Stanley J.
Published: April 2006

A treatment period as brief as 8 h in 10−3M EGTA completely blocks gravitropism in 70–80% of the treated coleoptiles of oats (Avena sativa, L. cv. Garry) without inhibiting growth. Only about 10% of the plants perfused in water failed to exhibit gravitropism. Subsequent perfusion of EGTA‐treated plants with calcium completely restores gravitropism; post‐perfusion with water does not. After perfusion in water for 10 h, gravistimulated oat coleoptile segments show the same asmmetry of 45Ca distribution as reported earlier for non‐perfused coleoptiles and sunflower hypocotyls. The degree of this asymmetry is reduced in those coleoptiles partially completely inhibited by perfusion in EGTA and is essentially absent in those coleoptiles completely inhibited by EGTA. The fact that calcium reverses the inhibitory effects of EGTA on gravitropism indicates that the inhibition was probably due to a reduction in the availability of free calcium required for one or more of the transduction steps of gravitropism.
Transmission of a traumatic signal via a wave of electric depolarization, and induction of correlations between the cotyledonary buds in Bidens pilosus
Authors: Frachisse Jean‐Marie , Desbiez Marie‐Odile , Champagnat Paul , Thellier Michel
Published: April 2006

Pricking one cotyledon of decapitated plantlets of Bidens pilosus L. induces, i) the induction of a wave of electric depolarization progressing towards the bud at the axil of this cotyledon, and ii) the inhibition of the growth of this bud. The electrophysiologic and morphogenetic responses are dependent on the number of pricks and on the location of these pricks on the cotyledon midribs. When a prick is delivered on the hypocotyl prior to those on the cotyledons, then it prevents the effect of the latter pricks. When it is delivered after those on the cotyledons, it does not change the effects of cotyledon pricking. Our experiments suggest that there is a causal relationship between the electrophysiological and morphogenetic responses.
Resumption of cellular activity induced by cytokinin and gibberellin treatments in tomato flowers targeted for abortion in unfavorable light conditions
Authors: Kinet Jean‐Marie , Zune Véronique , Linotte Colette , Jacqmard Annie , Bernier Georges
Published: April 2006

Mitotic activity and nuclear DNA synthesis in tomato (Lycopersicon esculentum Mill., cv. King plus) flowers targeted for abortion under unfavorable light conditions are completely stopped 6 days after macroscopic appearance of the inflorescence. Ovular cells are arrested at the G1 (80%) and G2 (20%) stages of the cell cycle. Exogenous applications of a mixture of N6‐benzyladenine (BA) and gibberellins A4+7 (GA) directly on the inflorescence may prevent its failure. Nuclear DNA synthesis and mitoses resume in ovules of the flower 16 to 20 h after the BA+GA treatment. When applied alone, BA and GA are able to mimic the effect of the mixture upon the progression of ovular cells through their cycle. Sporogenesis processes are also set in motion by the exogenous plant growth regulators. The mechanism of action of cytokinins and gibberellins in the control of floral development is discussed.
Anatomical observations on somatic embryogenesis from scutellar tissues of immature zygotic embryos of Triticum aestivum
Authors: Magnusson Ingrid , Bornman Chris H.
Published: April 2006

Somatic embryos were observed as early as six days after subculturing immature embryos of Triticum aestivum L. (cvs Froid‐Centurk and Helge) in vitro on 2,4‐dichloro‐phenoxyacetate‐containing nutrient media. Embryo formation followed three pathways, each involving one of the scutellum's three basic tissue systems: dermal, ground and vascular.

(1) Single epithelial layer cells divided tangentially to give pseudothallus‐like structures which, through radial and oblique divisions, assumed polar, proembryoid symmetry.

(2) In actively dividing ground tissues, localized asymmetrical division in some cells resulted in proembryoids. When contiguous with each other, the proembryoids could be identified as a proembryonic mass.

(3) Oblique divisions in some cells of the scutellum's procambium resulted in daughter cells of unequal size, from the smaller of which the embryoid's root would eventually form.
Controlling plant growth via the gibberellin biosynthesis system – I. Growth parameter alterations in apple seedlings
Authors: Steffens G. L. , Byun J. K. , Wang S. Y.
Published: April 2006

‘York Imperial’ apple seedlings (Malus domestica Borkh.) were continuously supplied via the roots with paclobutrazol [(2RS, 3RS)‐1‐(4‐chlorophenyl)‐4,4‐dimethyl‐2‐(1,2,4‐triazol‐1‐yl)pentan‐3‐ol)], a triazole GA biosynthesis inhibitor, at 0.68 μM in a nutrient solution. In comparison to controls, seedlings treated with paclobutrazol for 66 days showed a 91% reduction in shoot length, a 66% reduction in leaf area but only a 17% reduction in leaf number. This effect could be reversed by GA3 applied to the foliage at 71.4 μM 0, 19 or 35 days after paclobutrazol was initially supplied and leaf area values for paclobutrazol‐treated seedlings given both treatments did not differ significantly from controls. Plots of growth data indicate linearity of shoot longitudinal growth of GA3‐treated seedlings. Leaf area increase was non‐linear after GA3 treatment up to approximately 30 days, when the rate dropped. On a per shoot basis, leaf weight closely followed leaf area but on a per unit area basis, paclobutrazol‐treated leaves were heavier than controls; GA3 applications temporarily reversed this trend.
La glutamate déshydrogénase au cours de la gamétogénèse mâle chez Medicago sativa
Authors: de Vienne Dominique , Savina François , Daussant Jean
Published: April 2006

Glutamate dehydrogenase during male gametogenesis in Medicago sativa.

The multiple forms of the alfalfa (Medicago sativa L.) glutamate dehydrogenase (GDH; EC 1.4.1.2–4) are much more numerous in the pollen than in other organs, and in particular in the floral parts. The appearance of the pollen‐specific GDH pattern during male gametogenesis has been followed using electrophoretic, cytological and immunochemical techniques. After the tetrad stage the uninucleate microspore has no glutamate dehydrogenase activity. This activity appears only in the mitochondria of the binucleate young pollen. At this stage the electrophoretic pattern displays a faint intensity, but is already identical to that of mature pollen. On the other hand, the use of monospecific antibodies has revealed the presence of antigen in the microspore, and in the young pollen there is as much antigen as in the mature pollen. Therefore the synthesis of GDH precedes its activation, which follows the first pollen mitosis.
Interdependence of growth, water relations and abscisic acid level in Phaseolus vulgaris during waterlogging
Authors: Schravendijk H. Wadman‐van , van Andel O. M.
Published: April 2006

The interdependence between changes in growth and water relations after waterlogging was investigated by recording simultaneously growth, transpiration, water potential, turgor, leaf diffusion resistance and abscisic acid content in Phaseolus vulgaris L. cv. bruine Noord‐Hollandse. Growth was inhibited immediately after flooding, whereas transpiration decreased gradually to a low level in about three days. The first two days after flooding a small increase in abscisic acid content in the leaves was observed which was accompanied by an increase in diffusion resistance. The increase in abscisic acid content could result from an inhibited export from the leaves. After the first two days a decrease in water potential and turgor was accompanied by a drastic increase in both abscisic acid content and diffusion resistance. This large increase in abscisic acid content occurred before the turgor had reached its minimum value. The change in diffusion resistance kept showing a lag of about one day with the change in abscisic acid content. The possibility is discussed that besides abscisic acid also its metabolite phaseic acid is involved in stomatal closure. After the formation of adventitious roots on the hypocotyl, abscisic acid level, diffusion resistance, water potential and turgor returned to the control values. Transpiration showed a slow recovery from the sixth day after flooding, whereas growth was inhibited for at least nine days. A remarkable similarity exists between our observations on the responses of bean plants to flooding and the well known responses to drought.
Acetone production during the germination of fatty seeds
Authors: Murphy J. Brad
Published: April 2006

Acetone production at various stages of seed germination of a number of different species was analyzed by gas chromatography. In four agronomic species, the level of acetone production by the embryo axes had a strong positive correlation with the lipid content of the seeds, while in the embryos of three pine species the acetone level was much higher and did not show such a close correlation with lipid content. Acetone was produced only during germination and did not occur simply in response to imbibition of the seeds. Acetone production occurred predominantly in the embryos/embryo axes for the pines/angiosperms, respectively, and appeared at an early period during germination in which weight loss of the nutritive tissue was occurring at a rate greater than the growth of the embryos.
A comparison of the effects of Ca2+ and gibberellic acid on enzyme synthesis and secretion in barley aleurone
Authors: Carbonell Juan , Jones Russell L.
Published: April 2006

The effects of the addition and withdrawal of gibberellic acid (GA3) and Ca2+ on enzyme synthesis and secretion by barley (Hordeum vulgare L. cv. Himalaya) aleurone layers were studied. Incubation of layers in GA3 plus Ca2+ affects the total amount of secreted α‐amylase (EC 3.2.1.1) and acid phosphatase (EC 3.1.3.2) by promoting the appearance of different isoenzymic forms of these enzymes. The release of α‐amylase isoenzymes 1–4 in response to GA3 plus Ca2+ has a lag of 6 h. When layers are incubated in GA3 alone for 6 h prior to the addition of Ca2+, isoenzymes 1–4 appear in the medium after only 30 min. When the addition of Ca2+ to layers pretreated in GA3 is delayed beyond 12 h, its effectiveness in stimulating the synthesis and release of isoenzymes 3 and 4 is diminished. After 35 h of preincubation in GA3, addition of Ca2+ will not stimulate synthesis of α‐amylase isoenzymes 3 and 4. Aleurone layers preincubated for 6 h in GA3 will respond to Ca2+ when the GA3 is withdrawn from the incubation medium by producing α‐amylase isoenzymes 1–4. The converse is not the case, however, since layers preincubated in Ca2+ for 6 h will not produce all isoenzymes of α‐amylase when subsequently incubated in GA3. The Ca2+‐stimulated release of α‐amylase from GA3 pre‐treated layers is dependent on the time of incubation in Ca2+ and the concentration of the ion. The response to Ca2+ is temperature‐dependent, and other divalent cations such as Mg2+ cannot substitute for Ca2+. We conclude that Ca2+ influences α‐amylase release by influencing events at the biochemical level.
Internode length in Pisum. Gibberellins and the slender phenotype
Authors: Potts Wendy C. , Reid James B. , Murfet Ian C.
Published: April 2006

Pea plants (Pisum sativum L.) possessing the slender phenotype (conferred by the gene combination la crys) have extremely long, thin internodes and are phenotypically similar to dwarf plants (possessing genes La and/or Cry) that have been treated with a non‐limiting dose of gibberellin (GA3). In contrast to tall and dwarf plants, slender plants are virtually insensitive to treatment with AMO 1618, PP333 or GA3 and addition of the “gibberellin‐less” mutant gene na does not alter the phenotype of slender plants. Na slender segregates possessed lower levels of gibberellin‐like substances than comparable dwarf segregates when extracts from shoots were assayed using the lettuce hypocotyl or rice seedling bioassays. In addition, na slenders possessed little or no gibberellin‐like activity even though they possessed a slender phenotype. Thus the gene combination la crys causes slender plants to respond as if they are saturated with gibberellins for growth. In addition, the gene combinations la crys and le la cryc (allele cryc is less extreme in effect than crys) are shown to be almost completely epistatic to the alleles at the na locus. All these results suggest that gibberellin levels are not important in determining the internode length of slender peas (genotype la crys). The possible mechanisms by which this could occur are discussed.
Ethylene formation in plant mitochondria. Dependence on the transport of 1‐aminocyclopropane‐1‐carboxylic acid across the membrane
Authors: Vinkler Chana , Apelbaum Akiva
Published: April 2006

The mitochondrial fraction isolated from plumular hooks of etiolated pea seedlings (Pisum sativum L. cv. Kelvedon Wonder) displayed a ten‐fold higher rate of ethylene formation from 1‐aminocyclopropane‐1‐carboxylic acid [ACC; 3.2 nmol C2H4 (mg protein −1)h−1], than the tissue from which it was isolated. When the ionophores valinomycin or nigericin were added, a 60‐ to 70‐fold increase in activity in intact mitochondria over the activity in plumular hooks was obtained for ethylene formation under the same conditions, and a 20‐fold increase was obtained upon addition of gramicidin. The addition of ionophores did not affect the rate of ethylene formation in submitochondrial particles (55% inside‐out as determined by cytochrome oxidase latency) which already exhibited a 2–3‐fold higher specific activity than intact mitochondria. Low concentrations of the detergents cholate and deoxycholate increased mitochondrial ethylene formation activity and had no effect on the rate of the reaction in submitochondrial particles. These results support the suggestion that ACC conversion to ethylene is associated with the inner side of the inner mitochondrial membrane and that transport across the intact mitochondrial membrane is rate‐limiting in the reaction.
Effects of ultraviolet‐B irradiance on soybean. VI. Influence of phosphorus nutrition on growth and flavonoid content
Authors: Murali N. S. , Teramura Alan H.
Published: April 2006

Soybeans Glycine max (L.) cv. Essex were hydroponically grown in a greenhouse at 2 levels of ultraviolet‐B (UV‐B) radiation (0 and 2 500 J m−1 day−1 biologically effective UV‐B radiation) and 4 levels of P (6.5, 13, 26 and 52 μM). Plants were grown in each treatment combination to the complete expansion of the 4th trifoliolate leaf. UV‐B radiation and reduced P supply generally decreased plant height, leaf area and total biomass, but increased specific leaf weight and flavonoid content (measured as absorbance of methanolic extracts). Although both UV‐B radiation and low P supply produced deleterious effects on plant biomass, the effects were non‐additive. The combination of UV‐B and the lowest P level (6.5 μM) had no effect on total biomass or leaf area. This was at least partially due to the accumulation of flavonoids and leaf thickening. The results show that the sensitivity of soybean to UV‐B radiation is dependent upon plant P supply. Plants experiencing P deficiency are less sensitive to UV‐B than plants at optimum P levels.
Translocation of photoassimilate from leaves of two popyploid genotypes of tall fescue differing in photosynthetic rates
Authors: Wong Joshua H. H. , Randall Douglas D.
Published: April 2006

The photosynthetic rate of a decaploid genotype (1‐16‐2) of tall fescue (Festuca arundinacea Schreb.) is about twice that of a common hexaploid genotype (V6‐802) (Plant Physiol. 72: 16–21, 1983). Translocation of photosynthate out of the leaves is a possible means of regulating carbon assimilation. To evaluate this possibility, we have examined a) translocation velocity, b) time course of translocation from leaves, c) photoassimilate partitioning pattern into whole plants in pulse and chase experiments, and d) interveinal distances between two ploidy genotypes. Most of the 14C accumulated in sucrose, and the labelled carbon moved down the leaf blades at similar velocities (6 to 10 cm h−1) in both genotypes. Recent 14C assimilate was rapidly translocated from the fed area of the leaf blade. For example, the decaploid and the common hexaploid had translocated 40 and 26% of the 14C, respectively, at 6 h, and 79 and 49% of the 14C, respectively, at 24 h. Partitioning of 14C among plant organs was considerably different between the genotypes after a 24 h chase. For example, out of the total 14C recovered from the whole plant, the decaploid had retained 40% in the labelled leaf with 10, 33 and 29% in other leaves, stem bases and roots, respectively; whereas the hexaploid had retained 91% in the labelled leaf with 4, 3 and 2% in other leaves, stem bases and roots, respectively. However, the higher rate of translocation was correlated with greater interveinal distances in the decaploid genotype. These results suggested that the higher translocation percentage in the decaploid than the hexaploid genotype was due to greater sink activity.
A relationship between plant responses to cytokinins and cyanide‐resistant respiration
Authors: Musgrave Mary E. , Siedow James N.
Published: April 2006

Cytokinin bioassay material from six sources (Amaranthus caudatus L.; Avena sativa L.; Cucumis sativus L.; Funaria hygrometrica Hedw.; Pisum sativum L., cv. Alaska and cv. Progress No. 9; Xanthium pensylvanicum Wallr.) was analyzed for cyanide‐resistant oxygen consumption (alternative respiration) during the course of a response to benzyladenine (40 μM). In five of the six bioassay systems, the alternative pathway was found to be present but disengaged (ϱ=0) in the cytokinin‐treated material while untreated controls continued to fully utilize the pathway (ϱ=1). The moss, Funaria hygrometrica, was the exception to this pattern, with the alternative pathway fully engaged in both treated and untreated protonemata throughout the period of cytokinin‐induced bud formation. Respiration via the alternative pathway was not inhibited by benzyladenine in this latter tissue, although titrations with benzyladenine in carrot (Daucus carota L.) cell suspensions mimicked those obtained using salicylhydroxamic acid, an inhibitor of the alternative pathway. The dwarf pea, Progress No. 9, showed no response to cytokinin application in terms of increased ethylene production, and was also found to lack any capacity for the alternative pathway. Taken together, these results point to a role for the alternative pathway in responses of at least some plant tissues to cytokinins.
Tunicamycin‐induced growth and inhibition of glucosamine incorporation into cell walls of rice coleoptiles
Authors: Hoson Takayuki , Wada Shunji
Published: April 2006

Tunicamycin, 0.25 to 2.5 μM, promotes elongation of rice coleoptile sections after a 2 h lag. Tunicamycin decreased the minimum stress‐relaxation time of the cell wall, T0; and the wall loosening is recognized as the cause of this growth promotion. Bacitracin did not have significant effects on growth or T0 except for inhibition of elongation at high concentration. Coleoptile sections were incubated with [14C]‐glucosamine, and the synthetic pathway of the hexosamine‐containing cell wall component was examined by a pulse‐chase experiment. This component seems to be synthesized in the particulate fraction and secreted mainly into the hemicellulose I fraction. Tunicamycin strongly inhibited glucosamine incorporation into the particulate fraction and stopped the labeling of the cell wall. At 2.5 μM, tunicamycin had no effect on incorporation of mannose, leucine or proline. These results suggest that the hexosamine‐containing wall component is a kind of asparagine‐linked glycoprotein, and that this component plays a principal role in formation of the cell wall network and in growth regulation.
Regulation of resynthesis of the CO2‐acceptor in photosynthesis. Feedback inhibition of transketolase
Authors: Knowles Francis C.
Published: April 2006

The presence of ribulose‐5‐phosphate epimerase (EC 5.1.3.1, epimerase) in samples of ribose‐5‐phosphate isomerase (EC 5.3.1.6, isomerase) obtained from spinach (Spinacea aleracea L. cv. Bloomsdale Long Standing) was determined using (i) a sampling procedure which measured the quantity of xylulose‐5‐phosphate formed in the reaction mixture and (ii) a coupled enzyme assay in which the rate of oxidation of NADH was measured after establishing steady‐state concentrations of xylulose‐5‐phosphate, dihydroxacetonephosphate and glyceraldehyde‐3‐phosphate by the action of epimerase, transketolase (EC 2.2.1.1), triosephosphate isomerase (EC 5.3.1.1) and glycerol‐3‐phosphate dehydrogenase (EC 1.1.1.8). In preparations where the ratio of isomerase to epimerase activities was less than 100, both assay procedures yielded valid indications of epimerase activity. The steady‐state assay system was found, however, to seriously underestimate epimerase activity in enzyme preparations which were enriched in isomerase. Cross plots of epimerase activity determined by the sampling and steady‐state procedures demonstrated that an inhibitor of the coupling enzyme mixture was formed in the presence of high relative concentrations of the isomerase. The inhibited coupling enzyme mixture was fully active with glycer‐aldehyde‐3‐phosphate. Inhibition of the coupling enzyme mixture was attributed to transketolase. Feedback inhibition of transketolase is proposed to be of physiological significance in the photosynthesis cycle, operating to restrict resynthesis of CO2‐acceptor under conditions where high steady‐state concentrations of the intermediates of the photosynthesis cycle are maintained.
Measurement of enzymes related to sucrose metabolism in permeabilized Chlorella vulgaris cells
Authors: Salerno Graciela L.
Published: April 2006

Sucrose phosphate synthase (UDP‐glucose: D‐fructose‐6‐phosphate‐2‐glucosyl transferase, EC 2.4.1.14), sucrose synthase (UDP‐glucose: D‐fructose‐2‐glucosyl transferase, EC 2.4.1.13) and invertase (β‐D‐fructofuranoside fructohydrolase, EC 3.2.1.26) were measured in toluene permeabilized cells of Chlorella vulgaris Beijerinck. All three activities were detected at all stages of the growth curve; sucrose synthase and sucrose phosphate synthase showed a zone of maximum activity, while invertase increased with time of growth. Sucrose phosphate synthase and sucrose synthase (sucrose synthesis direction) were stimulated by divalent cations and inhibited by UDP. This inhibition could be reversed by Mg2+ or Mn2+. Sucrose phosphate synthase activity was inhibited by inorganic phosphate and was enhanced by glucose‐6‐phosphate, but was insensitive to sucrose. Arbutine decreased sucrose synthase activity in both directions. Sucrose cleavage was inhibited by divalent cations and by pyrophosphate. The effects on the enzyme activities of the presence of 2,4‐dichlorophenoxyacetic acid (2,4‐D), gibberellic acid, abscisic acid and kinetin in the growth medium were investigated. Sucrose synthase activity was practically unaffected by all plant hormones tested, except for the presence of kinetin which stimulated the activity. Sucrose phosphate synthase activity was increased by both kinetin and abscisic acid. The effect of the latter was partially reversed by the presence of gibberellic acid. 2,4‐D and kinetin were potent stimulators of invertase activity.
Stimulation of some litter‐decomposing basidiomycetes by shikimic acid
Authors: Lindeberg Gösta
Published: April 2006

Shikimic acid, which constitutes 1.5‐2.5% of the dry matter in needles of Scots pine, was found to stimulate the growth of various litter‐decomposing basidiomycetes of the genera Marasmius, Mycena and Xeromphalina in a synthetic nutrient medium. Out of eighteen litter‐decomposing species, ten were stimulated by shikimic acid, wheras the eight mycorrhizal and four wood‐rotting species tested were not affected. Maximal effect was obtained at a concentration of ca 2 mM. Growth experiments at varying pH‐values indicated active uptake of shikimic acid. Even in the presence of aromatic amino acids, shikimic acid stimulated the growth of the fungi. In certain species the strong inhibiting effect of phenylalanine, tyrosine and tryptophan, when added simultaneously, was reversed in the presence of shikimic acid. Fungi which were stimulated by shikimic acid were also able to use this compound as their sole carbon source. Maximal stimulating effect of shikimic acid occurred when glucose had been added at optimal concentration.
Glycolipids of turions and leaves of Utricularia vulgaris at different stages of development
Authors: Simola Liisa Kaarina , Koskimies‐Soininen Kristiina , Tomell Marja
Published: April 2006

Turions of Utricularia vulgaris L. were germinated in long‐day conditions at 15°C for 1,3 and 6 days and their glycolipid composition was compared with that of resting but vernalized turions. Digalactosyldiacylglycerides (DGDG), monogalactosyldiacylglycerides (MGDG) and cerebrosides were present at all stages of development. No great changes were found in the glycolipid classes during sprouting but some differences were noted in the proportions of fatty acids. The most common fatty acids in all three glycolipid classes studied were 16:0, 18:0 and 18:2. MGDG and DGDG also contained relatively much 18:3 and its proportion increased during germination. Young turions and full‐grown leaves collected from nature contained the same glycolipid classes as the sprouting turions. The developmental stage of the organs studied is reflected in the fatty acid composition of DGDG and MGDG but is not so evident in the cerebrosides. The 18:2 fatty acid is rather typical of the resting turions, especially in DGDG.