bluuebunny/crossref_metadata_2025_split huggingface dataset:
Biolistic plant transformation
Authors: Sanford John C. 
Published: May 2006

The biolistic process represents a completely new approach to the problem of how to deliver DNA into intact cells and tissues. High velocity microprojectiles are used to carry DNA or other substances past cell walls and membranes. Because DNA is being ‘shot’ into cells, it represents a type of biological ballistics, hence the term “biolistics”.There are several fundamental advantages to the biolistic process over other plant transformation techniques. The biolistic process appears to be effective regardless of species or tissue type, it is a rapid and very simple procedure, and it should facilitate the direct transformation of totipotent tissues such as pollen, embryos, meristems and morphogenic cell cultures. In addition, the biolistic process appears to be uniquely suitable for organelle transformation.The disadvantages of the biolistic process are that it requires special instrumentation, and is still in the early stages of its development. Consequently, delivery efficiencies are still not as high as can be achieved in highly optimized transformation systems such as electroporation or agrobacterial‐infection of tobacco. Furthermore, potential users should be prepared to spend some time adapting existing protocols to their specific species or tissue of interest.
Plant transformation by microinjection techniques
Authors: Neuhaus Gunther , Spangenberg German 
Published: May 2006

Several techniques have been developed for introducing cloned genes into plant cells. Vectorless delivery systems such as PEG‐mediated direct DNA uptake (e.g. Pasz‐kowski et al. 1984), electroporation (e.g. Shillito et al. 1985), and fusion of protoplasts with liposomes (Deshayes et al. 1985) are routinely used in many experiments (see several chapters of this issue). A wide range of plant species, dicotyledonous as well as monocotyledonous, has been transformed by these vectorless DNA transfer systems. However, the availability of an efficient protoplast regeneration system is a prerequisite for the application of these techniques.For cells with intact cell walls and tissue explants the biological delivery system of virulent Agrobacterium species has been routinely used (for review see Fraley et al. 1986). However, the host range of Agrobacterium restricts the plant species, which can be transformed using this vector system. In addition, all these methods depend on selection systems for recovery of transformants. Therefore a selection system has to be established first for plant species to be transformed.The microinjection technique is a direct physical approach, and therefore host‐range independent, for introducing substances under microscopical control into defined cells without damaging them. These two facts differentiate this technique from other physical approaches, such as biolistic transformation and macroinjection (see chapters in this issue). In these other techniques, damaging of cells and random manipulation of cells without optical control cannot be avoided so far.In recent years microinjection technology found its application in plant sciences, whereas this technique has earlier been well established for transformation of animal tissue culture cells (Capecchi 1980) and the production of transgenic animals (Brin‐ster et al. 1981, Rusconi and Schaffner 1981). Furthermore, different parameters affecting the DNA transfer via microinjection, such as the nature of microinjected DNA, and cell cycle stage, etc, have been investigated extensively in animal cells (Folger et al. 1982, Wong and Capecchi 1985), while analogous experiments on plant cells are still lacking.
The structure and function of the photosystem I reaction centre
Authors: Evans M. C. W. , Bredenkamp G. 
Published: May 2006

Current models of the photosystem I reaction centre are reviewed. The polypeptide composition of the reaction centre is described and the genetic origin of the peptides is documented. The properties of the redox components bound to the complex are reviewed. The chemical identity of the components, their location in the complex and the kinetics of electron transfer are discussed. It is concluded that a linear electron transport chain remains the best description of the function of the complex, but that the function and identity of the component A1 remains uncertain.
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Factors controlling nitrate and ammonium accumulation in mustard (Sinapis alba) seedlings
Authors: Hecht Ursula , Mohr Hans 
Published: May 2006

Prolonged application of ammonium as a source of nitrogen leads to serious physiological and morphological disorders in many plants, including mustard (Sinapis alba L,) seedlings (ammonium toxicity syndrome). Ammonium tolerance was previously observed in mustard seedlings in the presence of considerable amounts of nitrate in the medium. In the present study, the question was addressed as to what extent accumulation of nitrate and ammonium occurs in the mustard seedling and how this relates to ammonium toxicity and tolerance. Emphasis was on light control of accumulation in the attached cotyledons. Both NQ3 and NH4 became strongly accumulated in the mustard cotyledons once the concentration in the medium exceeded 1 mM, In the cotyledons, we measured concentrations > 30 mM in the case of nitrate and > 50 mM in the case of ammonium 4 days after sowing. Accumulation of inorganic nitrogen in the mustard cotyledons did not depend on photosynthesis nor on intact chloroplasts. However, the rate of nitrate accumulation was strongly stimulated by light, operating through phytochrome, while ammonium accumulation was not affected by light in short‐term experiments, i,e, within 24 h and only weakly (and probably indirectly) in long‐term light.We conclude that strong interaction between NQ3 and NHJ is characteristic for accumulation of inorganic nitrogen. In the presence of NQ3, accumulation of NH3 is diminished and, to a lesser extent, vice versa. Using [15N]‐labelling it was found that incorporation of inorganic nitrogen into organic compounds was stimulated strongly whenever nitrate and ammonium were provided simultaneously. It appears from the data that accumulation of nitrate is strictly controlled by the mustard cotyledons while the accumulation of ammonium is not. The data indicate that the level of ammonium is governed primarily by the rate of ammonium assimilation. Stimulation of ammonium assimilation by simultaneously applied nitrate appears to explain nitrate‐mediated ammonium tolerance in the mustard plant.
Apical dominance in mulberry (Morus alba): Effects of position of lateral and accessory buds and leaves
Authors: Suzuki Takeo 
Published: May 2006

Suzuki, T. 1990. Apical dominance in mulberry (Morus alba): Effects of position of lateral and accessory buds and leaves. – Physiol. Plant. 78: 468‐474.Removing apical portions of current growth coppice shoots from field‐grown, low‐pruned stumps of mulberry (Morus alba L. cv. Shin‐ichinose) caused sprouting of one or more upper main buds, almost concurrently with that of accessory buds. However, removal of the new sprouts, including those from accessory buds, slightly enhanced the sprouting of buds immediately below them, and did not affect buds lower down. In contrast, mature leaves inhibited the buds in their axils. Budless, leafy nodes on the upper part of pruned shoots tended to swell after treatment, perhaps due to the accumulation of substances translocated from the roots and possibly from the remaining leaves. Lateral buds at different positions along the shoot differed in their sprouting ability with buds lower on the shoot being more inhibited. This inhibition gradient dissappeared when all coppice shoots on one stump were pruned to the same bud position, suggesting inhibition from neighboring, actively growing shoots. These results demonstrate that acropetal influences are important in bud dominance relationships.
Calcium‐calmodulin in germination of Phacelia tanacetifolia seeds: effects of light, temperature, fusicoccin and calcium‐calmodulin antagonists
Authors: Cocucci Maurizio , Negrini Noemi 
Published: May 2006

Germination in the dark and at 16°C of photoblastic and thermosensitive seeds of Phacelia tanacetifolia was inhibited when incubated with EGTA and the Ca2+‐ionophore A 23187; A 23187 in the presence of Ca2+ still inhibited germination, but to a lesser extent. Treatments with EGTA or Ca2+ at different concentrations in the presence or in the absence of A 23187 did not remove light inhibition. The calmodulin (CaM) inhibitor, calmidazolium, strongly inhibited germination. The specificity of these inhibitors and their effects on seed germination are discussed.CaM from Phacelia tanacetifolia seeds has been purified and its characteristics (molecular weight, heat and acid stability, kinetics of phosphodiesterase [EC 3.1.4.17] activation) were very similar to those of other plant sources. More than 90% of total CaM was present in the soluble fraction (ca 41 μg g‐1 fresh weight in ungerminated seeds). The CaM level greatly increased in the early phases of seed germination; this increase did not take place when germination was inhibited by light or high temperature. When fusicoccin, a toxin which promotes germination by activating membrane functions, relieved light or high temperature inhibition, CaM increased up to the control value in the dark at 16°C. The parallel increase in CaM and seed germination suggest that CaM plays an important role in the process. Fusicoccin in the dark at 16°C stimulated CaM and fresh weight increase, but not the metabolic reactivation measured as increase in DNA and total RNA levels; at 30°C fusicoccin stimulated the increase in fresh weight and in CaM level, but the increases in DNA and total RNA were very low. These results suggest that the activation of membrane functions with cell enlargement induced by fusicoccin is related to CaM increase.
Polyamine concentrations and arginine decarboxylase activity in wheat exposed to osmotic stress
Authors: Foster Sally A. , Walters Dale R. 
Published: May 2006

The activity of L‐arginine decarboxylase (ADC: EC 4.1.1.19)and polyamine content were examine in intact wheat plants (Triticum aestivum L. cv. Sappo) exposed to osmotic stress (0.4 M mannitol) for 5 days. ADC activity was increased in first and second leaves and in roots of mannitol‐stressed plants. Concentrations of putrescine, cadaverine and spermine were generally increased in leaves and roots of plants exposed to mannitol, whereas spermidine was reduced in first leaves and roots of these plants. In an attempt to determine the localization of mannitol in stressed wheat. 14C‐mannitol was fed to plants grown in liquid culture. Most of the mannitol was detected in roots (84%), while small amounts were found in first (9%) and second (7%) leves.Since it seemed possible that some of the effects on polyamine metabolism caused by exposure to mannitol could have been the result of water stress. polyamine metabolism was also studied in plants water stressed by exposure to 2% polyethylene glycol (PEG) 4000. ADC activity was not altered by exposure to PEG. but concentrations of putrescine, spermidine and spermine were generally reduced in leaves and roots of stressed plants. Cadaverine concentrations were not significantly affected by exposure to PEG. Spermidine and spermine concentrations were reduced in first and second leaves but remained unchanged in roots of plants exposed to PEG.
Aluminium effects on transmembrane potential in cells of fibrous roots of sugar beet
Authors: Lindberg Sylvia , Szynkier Krystyna , Greger Maria 
Published: May 2006

The effect of aluminium (Al) on the electrical transmembrane potential of epidermal and outer cortical root cells of intact seedlings of sugar beet (Beta vulgaris L. cv. Monohill) was studied. The potential difference to the surrounding medium was recorded with microelectrodes inserted into the vacuoles (PDv) and cytoplasm (PDc) of intact roots. Both long‐term effects of AlCl3 (100, μM present during cultivation) and immediate effects of AlCl3 (10, 50, or 100 μM present in the assay medium), were measured. The effect of Al was measured at pH 4.0, 5.0 and 6.5 in order to obtain information on the toxicity of different Al forms existing at different pH values.Low pH and/or the presence of AlCl3 during cultivation caused large depolarizations of the PDv. Since the immediate effect of 2,4‐dinitrophenol (DNP) on the resting potential of cells from Al‐cultivated plants was negligible, it is likely that Al affects the metabolic component of the transmembrane potential.Aluminium also had an immediate effect on the PD in root cells of plants cultivated without Al. Addition of 10 or 50 μM Al to the assay medium caused hyperpolarization of PDv in the presence of 0.5 mM Ca2+ at all pH values studied, depolarization of PDc at pH 6.5, and hyperpolarization of PDc at lower pH. At 1 mM Ca2+, or in the presence of K+ (≥ 2 mM), however, the same Al concentrations had little effect on PDc.The strongest depolarizing effects of 10 or 50 μM Al in short‐term treatments were obtained at pH 6.5, and were probably due to the soluble species Al(OH)3, which is more frequent at pH 6.5 than at a lower pH. Addition of 50 μM Al caused alkalinization of the root medium at pH 6.5, but not at pH 4.0. Therefore, it is possible that Al at pH 6.5 is bound to, or translocated across, the membrane without the accompanying hydroxide ions. It is likely that most of the Al is bound to the root cells, since removal of Al from the buffer surrounding the roots did not cause the changed PD values to return to the original values. Aluminium also interacts with effects of Ca2+ and K+ on the membrane potential, since changes in PD, induced by changes in concentrations of Ca2+ and K+ are different in the absence and presence of Al.
Spectrophotometric characterization of phytochromes in dimorphic cocklebur seeds in relation to capacity for germination
Authors: Manabe Katsushi , Nakazawa Miki , Sato Yuuichi , Esashi Yohji 
Published: May 2006

Phytochrome was measured spectrophotometrically in different tissues of the upper (positively photoblastic) and lower (negatively photoblastic) seeds of the cocklebur (Xanthium pennsylvanicum Wallr.). Axial parts of the seeds, in particular parts of the radicle, contained high levels of phytochrome, while cotyledonary parts contained only low levels. These results were consistent with the distribution of the light‐sensitive areas of the seeds that were associated with germination. Phytochrome levels in both types of dimorphic seeds increased gradually with increasing duration of dark imbibition for 4–8 h, then the rates of increase in levels of phytochrome accelerated. In both types of seed, some phytochrome was measurable even before imbibition. In the lower seeds, up to 20% of the phytochrome was occasionally observed as Pfr in samples imbibed in darkness for a short time (up to 12 h). A slight blue shift of the peak of PT in the difference spectrum of phytochrome was observed in the case of lower seeds imbibed for 0–2 h. These results suggest that, to some extent, the lower axes contain dehydrated Pfr or intermediate(s) in the photoconversion of phytochrome.The dark reactions of Pfr were also examined in excised axes of both types of dimorphic seed after they had been pre‐imbibed for 16 h in darkness. Dark destruction of Pfr was observed in both types of seed. In addition, net increases in levels of Pr were observed in the dark controls and in the samples irradiated with red light after the level of Pfr diminished. No ‘inverse’ dark reversion from Pr to Pfr was detected. Thus, after 16 h of imbibition, there were no differences in terms of properties of phytochrome between the two types of seed, and the different responses to light of upper and lower seeds might depend mainly on a difference in the physiological state of the two types of seed rather than the properties of phytochrome.
Water relations of Picea abies. I. Comparison of water relations parameters of spruce shoots examined at the end of the vegetation period and in winter
Authors: Gross K. , Koch W. 
Published: May 2006

Seasonal changes of some water relations parameters of Norway spruce shoots (Picea abies [L.] Karst.) were studied during two experiments using the pressure‐volume analysis. For each experiment only shoots of a single tree were used.During the first study, the course of the turgor loss point (as bulk osmotic pressure when turgor first reaches zero, πp) of shoots developed in late 1986 vegetation period, were measured in 1987. The turgor loss point decreased temporarily from –2.5 MPa at the beginning of the year to –3.3 MPa at the end of March, but then increased to the original level for the rest of the year.During the second study, water relations parameters were measured in late summer 1987 and in late winter 1988. Winter shoots at full water saturation contained up to 20% less water than in late summer. Accordingly, the bulk osmotic pressure at full water saturation (πp) decreased from –1.7 MPa in late summer to –1.9 MPa in winter, πp decreased also from –2.2 MPa to –2.8 MPa. However, the amount of osmotically active substances (mOsmol, N) remained unchanged. The relative amount of apoplastic water in the total shoot water content appeared to drop insignificantly from 17% to 15%.The results show that the decrease in πo and πp in late winter is not due to an accumulation of osmotically active substances in the vacuoles but is due to a decrease in tissue water content. The temporary reduction of the symplastic volume by deposition of osmotically inert substances seems to be the most probable cause of this phenomenon.
Water relations of Picea abies. II. Determination of the apoplastic water content and other water relations parameters of needles by means of capillary microcryoscopy and the pressure‐volume
Authors: Gross K. , Koch W. 
Published: May 2006

Using the pressure volume analysis (PV analysis) on the shoots of Norway spruce (Picea abies [L.] Karst.) and the here presented capillary microcryoscopy of the needle press sap of the same shoots, it was possible to determine the amount of apoplastic water in the needles (Wan) as well as in the defoliated shoots (Was). Additionally, the bulk osmotic pressure at full water saturation in the symplast of the needles and defoliated shoots (πon and πos) was determined. The dependence of the bulk‐averaged turgor pressure (Pt) on the water content and the relationship between the bulk modulus of elasticity of the needles (ɛn) and the bulk‐averaged needle turgor pressure (Ptn) was shown with help of the PV analysis on the whole shoots and defoliated shoots. The study was conducted at the end of the vegetation period in 1987 and during winter 1988.The proportion of Wan in the total needle water content (Wtn) was 14% in September 1987 and 12.5% in March 1988. The respective percentage of Was in Wts were 27% and 25%. The amount of apoplastic water depended on the ratio of the dry weight of defoliated shoots to the dry weight of the whole shoots. A standard mean value for the amount of Wan in the total water content of the shoots (Wt) was therefore not possible. The bulk osmotic pressure at full water saturation in the needle symplasts was –1.9 MPa in September 1987 and –2.2 MPa in winter 1988. The respective values of the bulk osmotic pressures in the symplast of the defoliated shoots (πos) were –1.5 MPa and –1.7 MPa. Thus πon was 0.1 MPa lower and πos 0.3–0.4 MPa higher than the average osmotic pressure during full water saturation in the symplast of the whole shoots (πo).The relation between bulk‐averaged turgor pressure and water content showed that during water loss Ptn dropped more rapidly than the turgor pressure of defoliated shoots (Pts). Consequently the needles were less elastic than the defoliated shoots. The turgor values of whole shoots followed an intemediate course between Ptn and Pts. The flat course of Pts seems to be the main reason for the often observed “plateau” of ψ‐isotherms of whole shoots near full turgor.
Re‐evaluation of the role of ureides in the xylem transport of nitrogen in Arachis species
Authors: Peoples M.B. , Atkins C.A. , Pate J.S. , Chong K. , Faizah A. W. , Suratmini P. , Nurhayati D.P. , Bagnall D.J. , Bergersen F.J. 
Published: May 2006

There are conflicting reports in the literature of the possible role of the ureides, allantoin and allantoic acid, in the nitrogen economy of Arachis species. Therefore, xylem sap composition in food peanut (Arachis hypogaea L.), and two forage peanuts (A. pintoi L. and A. glabrata Benth.) has been studied in detail. Xylem saps were collected from peanuts grown under different nutritional regimes and environmental conditions in the glasshouse and field in Australia, Malaysia and Indonesia, and the N‐containing solutes analysed. The relative amounts and concentrations of ureides in these peanut exudates were compared with those of soybean (Glycine max [L.] Merr.) – a species known to export ureides in its xylem stream as the major product of N2 fixation.Xylem concentrations of ureides in soybean were high in N2‐fixing plants (2.9 to 3.7 μmol ml−1), representing 60 to 88% of xylem solute nitrogen, but it contributed only 9% (0.7 μmol ml−1) if plants were unnodulated and supplied nitrate. In all species of peanut, concentrations of ureides measured in xylem sap were generally much smaller (0.02 to 0.37 μmol ml−1; 1–7% of xylem nitrogen) and were unaffected by peanut species or cultivar, rhizobial strain, plant size, growth rate, or stage of development, and were not related to N2 fixation (less than 0.1% of currently fixed nitrogen exported as ureides) or the assimilation of nitrate. Apparently high levels of ureides in sap from some field‐grown plants were shown to be due to interference with the ureide colorimetric assay by some contaminating compound rather than represent increased ureides per se.
Changes in endogenous levels of three cytokinins during development of excised watermelon cotyledons
Authors: Rossi Gianfranca , Marziani Giovanna P. , Uneddu Paola , Longo Claudio P. 
Published: May 2006

We have determined by an immunological method the endogenous levels of three cytokinins: dihydrozeatin riboside (DHZR), transzeatin riboside (tZR) and isope‐ntenyladenosine (IPA) in watermelon (Citrullus vulgaris Schrad., cv. Fairfax) cotyledons that were either attached to the seedling or excised from the seed after imbibition and then grown on water. Both seedlings and cotyledons were grown either for 5 days in continuous light or for 3 days in the dark and 2 days in light. Our aim was to verify whether endogenous cytokinin levels are lower in excised than in attached cotyledons as could be expected since excised cotyledons are much more sensitive to exogenous cytokinin application. The levels of the three cytokinins were very low immediately after imbibition, but gradually increased during the following days. They were higher in excised cotyledons after 5 days of culture in the dark than in cotyledons of the same age that had developed on the seedling. Dihydrozeatin riboside was by far the most abundant of the three cytokinins in cotyledons as well as in the hypocotyl and the root.Irradiation reduced the level of DHZR, negating the concept that light promotes cotyledon development by increasing endogenous cytokinins. Transzeatin riboside when supplied exogenously, stimulated cotyledon development at a lower concentration than the other two cytokinins. Exogenous supply of ben‐zyladenine (BA) induced a strong increase in endogenous tZR already after 24 h.