bluuebunny/crossref_metadata_2025_split huggingface dataset:
Early quantitative method for measuring germination in non‐green spores of Dryopteris paleacea using an epifluorescence‐microscope technique
Authors: Scheuerlein Robert , Wayne Randy , Roux Stanley J. 
Published: May 2006

A method is described to determine germination by blue‐light excited red fluorescence in the positively photoblastic spores of Dryopteris paleacea Sw. This fluorescence is due to chlorophyll as evidenced from 1) a fluorescence‐emission spectrum in vivo, where a bright fluorescence around 675 nm is obtained only in red light (R)‐irradiated spores and 2) in vitro measurements with acetone extracts prepared from homogenized spores. Significant amounts of chlorophyll can be found only in R‐treated spores; this chlorophyll exhibits an emission band around 668 nm, when irradiated with 430 nm light at 21°C.Compared to other criteria for germination, such as swelling of the cell, coat splitting, greening, and rhizoid formation, which require longer periods after induction for their expression, chlorophyll fluorescence can be used to quantify germination after two days. This result is confirmed by fluence‐response curves for R‐induced spore germination; the same relationship between applied R and germination is obtained by the evaluation with the epifluorescence method 2 days after the light treatment as compared with the evaluation with bright‐field microscopy 5 days after the inducing R.Using this technique we show for the first time that Ca2+ contributes to the signaltransduction chain in phytochrome‐mediated chlorophyll synthesis in spores of Dryopteris paleacea.
Oxygen‐dependent stomatal opening in Zea mays leaves. Effect of Light and carbon dioxide
Authors: Vavasseur Alain , Lascève Gérard , Couchat Philippe 
Published: May 2006

The oxygen requirement for stomatal opening in maize plants (Zea mays L. hybrid INRA 508) was studied at different CO2 concentrations and light intensities. In the absence of CO2, stomatal opening always required O2, but this requirement decreased with increasing light intensity. In darkness, the lowest O2 partial pressure needed to obtain a weak stomatal movement was about 50 Pa. This value was lowered to ca 10 Pa in light (320 μmol m−2 s−1).On the other hand. in the absence of O2, CO2enabled stomatal opening to occur in the light, presumably due to the evolved photosynthetic O2. Thus, CO2, which generally reduced stomatal aperture, could induce stomatal movement in anoxia and light. The effect of CO2 on stomatal opening was closely dependent on O2 concentration and light intensity. Stomatal aperture appeared CO2‐independent at an O2 partial pressure which was dependent on light intensity and was about 25 Pa at 320 umol m−2 s−1.The presence of a plasmalemma oxidase, in addition to mitochondrial oxidase, might explain the differences in the O2 requirement at various light intensities. The possible involvement of such a system in relation to the effect of CO2 is discussed.
NADH‐dependent nitrate reductase from two‐row barley roots: Purification, characteristics and comparison with leaf enzyme
Authors: Oji Yoshikiyo , Takahashi Masakazu , Nagai Yasuo , Wakiuchi Nariaki 
Published: May 2006

NADH‐nitrate reductase (EC 1.6.6.1) was purified 800‐fold from roots of two‐row barley (Hordeum vulgare L. cv. Daisen‐gold) by a combination of Blue Sepharose and zinc‐chelate affinity chromatographies followed by gel filtration on TSK‐gel (G3000SW). The specific activity of the purified enzyme was 6.2 μmol nitrite produced (mg protein)−1 min−1 at 30°C.Besides the reduction of nitrate by NADH, the root enzyme, like leaf nitrate reductase, also catalyzed the partial activities NADH‐cytochrome c reductase, NADH‐ferricyanide reductase, reduced methyl viologen nitrate reductase and FMNH2‐nitrate reductase. Its molecular weight was estimated to be about 200 kDa, which is somewhat smaller than that for the leaf enzyme. A comparison of root and leaf nitrate reductases shows physiologically similar or identical properties with respect to pH optimum, requirements of electron donor, acceptor, and FAD, apparent Km for nitrate, NADH and FAD, pH tolerance, thermal stability and response to inorganic orthophosphate. Phosphate activated root nitrate reductase at high concentration of nitrate, but was inhibitory at low concentrations, resulting in increases in apparent Km for nitrate as well as Vmax whereas it did not alter the Km for NADH.
Role of carboxylate in the nitrogen metabolism of plants from different natural habitats
Authors: Wollenweber B. , Kinzel H. 
Published: May 2006

The carboxylate and organic nitrogen content was studied in plants from 5 different habitats in Austria in order to determine both the form of nitrogen utilized by the plants and the preferential site of nitrate reduction within the plant, if nitrate is the predominant nitrogen form and is reduced mainly in the shoots, the ratio between carboxylate and organic nitrogen should be about 1. Ratios less then 1 would indicate either participation of root reduction, transport of carboxylate from shoots to roots or ammonium/ammonia nutrition.In the plants investigated, the lowest ratios were found in a bog, where ammonium is usually the predominant nitrogen form. Species from a xerophytic and a nutrient‐rich habitat, as well as from a carr, showed higher organic nitrogen values. Highest contents of carboxylate and organic nitrogen were found in halophytes from the area around the take Neusiedlersee. As additional bicarbonate uptake is known to occur at these sites, accumulation of carboxylate here may not he related to nitrate reduction alone.The relationship between the carboxylate/organic nitrogen ratio and N indicator values revealed the same pattern of differences in the plant species, indicating that the determination of these values could give information of ecophysiological characteristics of, and differences between, plant species from various habitats.
High yield isolation of mesophyll protoplasts from wheat, barley and rye
Authors: Sarhan Fathey , Cesar Dismie 
Published: May 2006

Efficient procedures are described for high‐yield isolation of mesophyll protoplasts from spring wheat (Triticum aestivum L. cv. Glenlea), winter wheat (Triticum aestivum L. cv. Frederick), barley (Hordeum vulgare L. cv. Bruce) and rye (Secale cereale L. cv. Puma). Factors such as plant age, composition of the incubation medium during isolation, purification procedures and culture medium affect protoplast yield, viability and metabolic competence, as measured by light‐dependent CO2 fixation. Optimal osmolarity of the isolation medium was equivalent to 1.8 times that measured in the leaves of all plant material used. The presence of 2 mM ascorbic acid in the preincubation and isolation medium increased the yield by 50% and conserved viability and metabolic competence. The protoplasts were stable for up to 48 h without loss of either viability or of original activity of CO2 fixation, which was in the order of 100 μmol CO2 (mg chl)−1h−1.In our MC‐56 liquid medium these protoplasts regenerated cell walls within 72 h and a few divided.
Metabolic and structural responses of pine buds under climate chamber conditions
Authors: Lindfors Aija , Kupila‐Ahvenniemi Sirkka 
Published: May 2006

Scots pine (Pinus sylvetris L.) plants, about 2 m high, were placed in controlled conditions for 2 weeks in January, April and November. During the experiments made in January, the conditions in the climate chambers simulated either a gradual or abrupt advancement of spring. In April they simulated either the advancement of the season or its reversal back to January. In November the plants were transferred to conditions that resembled spring. In January, pieces of buds collected at the end of the experiment were also fixed for electron microscope studies.Isolation of the ribosomes and the determination of their in vitro translation capacity revealed that in January the response to environmental changes was evident. An increase in synthesized proteins was caused by a rise in the translation capacity of ribosome assemblies rather than by an increase in their quantity. The cellular ultras‐structure changed in conformity with the changes characteristic of the spring. In April, the plants transferred to the climate chambers maintained their ability to synthesize proteins, but the buds were judged to be under stress. In November die ability of the buds to respond to environmental changes was retarded or inhibited.
Early changes in morphology and polypeptide pattern of plastids from watermelon cotyledons induced by benzyladenine or light are very similar
Authors: Bracale Marcella , Longo Giovanna P. , Rossi Gianfranca , Longo Claudio P. 
Published: May 2006

Watermelon (Citrullus vulgarisSchrad. cv. Fairfax) cotyledons were excised from the embryo and grown in the dark for 4 days. They were then transferred to 10 μm benzyladenine (BA) solution or illuminated with white light. We have compared changes in ultrastructure of the plastids and of their polypeptide pattern induced by the two treatments.At the end of the 4‐day‐period in the dark the plastids differentiated to amyloplasts and had few polypeptides: only the two subunits of ribulose bisphosphate carboxylase (RuBP) were clearly observed. Both light and BA induced starch depletion and gratia formation after 12–24 h. BA was less efficient than light in inducing thylakoid formation and more efficient in inducing starch depletion. After 6 h both factors induced the appearance of the same new polypeptides in the 28–53 kDa range. Most prominent among them is a 32 kDa band. Light is much more effective in inducing the formation of a 29 kDa band than is BA. In mature chloroplasts this band stains very strongly, while the 32 kDa band disappears. We suggest that the 29 kDa polypeptide is the light harvesting complex (LHC), since a purified LHC preparation from cotyledons grown either on water in light or on BA in the dark migrates on the polyacrylamide gel as a single 29 kDa band.
Effects of lithium ions on the circumnutations of Helianthus hypocotyls
Authors: Zachariassen Eli , Johnsson Anders 
Published: May 2006

The influence of Li+ on the circumnutations of hypocotyls of Helianthus annuus L. cv. Californicus was investigated. LiCl at concentration levels from 0 to 40 mM (lethal) was added to intact hypocotyls grown in liquid nutrient medium. The Li+ concentration in the hypocotyls was measured by flame photometry. The growth of the hypocotyls was not affected by the LiCl.Amplitude and frequency of the circumnutations were determined by correlation analysis. The oscillatory pattern of the movements became less regular at concentrations above 10 mM LiCl. The amplitude of the movements was reduced for concentrations above 7 mM LiCl. The frequency of the movements was reduced when LiCl was increased from 0 to 10 mM. Above 10 mM LiCl the frequency of the circumnutations was higher than for control plants. The results showed that circumnutations of sunflower hypocotyls can be added to the group of oscillators in biological organisms that are affected by Li+.
The roles of carbon dioxide and abscisic acid in the production of ethylene
Authors: Tan  , Zhi‐Yi  , Thimann Kenneth V. 
Published: May 2006

Since CO2 is liberated in the conversion of ACC to ethylene, the evidence that ethylene production by plant tissues is actually promoted by CO2 calls for an explanation. Accordingly, the formation of ethylene by oat (Avena sativa L. cv. Victory) leaves and by apple (Golden Delicious) and pear (Pyrus communis L. cv. Anjou) tissue in very low levels of CO2 has been studied. The gas chromatograph was modified to measure CO2 and ethylene at the same time, by reducing both to methane. (Response of the gas chromatograph to CO2 concentrations is linear.) The work establishes a clear difference between the endogenous production of ethylene and its production from applied ACC, a difference which holds about equally for leaves and for fruit tissue. The difference is in the CO2 requirement, namely, lowering the CO2 level by 99% or more decreases the production of ethylene from applied ACC by 50–60%, but it does not decrease, or even slightly increases, its production from endogenous precursors. Thus, while the need for CO2 has not been explained, it has at least been delimited.The responses to abscisic acid (ABA) also differ, but in the reverse direction, the endogenous production of ethylene being decreased up to 70% by ABA. while the liberation from ACC is promoted about 20%. ABA also promoted the respiratory CO2 production by 30% or, in presence of 1‐aminocyclopropane‐1‐carboxylic acid (ACC), by over 50%. Inhibition of ethylene production by cobalt or EDTA shows no such differentiation, while inhibition by Na catechol‐4,6‐disulfonate (Tiron) shows a small difference. It is concluded either that endogenous ethylene is formed by an enzyme system different from that reacting with ACC, or (more likely) that when ethylene arises from endogenous precursors the reaction does not proceed by way of free ACC, but by some activated form of it.
The role of light and CO2 in optimising the conditions for shoot proliferation of Actinidia deliciosa in vitro
Authors: Infante R. , Magnanini E. , Righetti B. 
Published: May 2006

Proliferating cultures of Actinidia deliciosa A. Chev., C. F. Liang and A. R. Ferguson cv. Tomuri (♂) were grown under photosynthetic photon flux density (PPFD) rates ranging from 30 to 250 μmol m−2 s−1 in order to determine certain physiological parameters in vitro: CO2 evolution, photosynthesis at three CO2 atmospheric concentrations (330, 1450 and 4500 μl l−1), fresh and dry matter accumulation and proliferation rate.A proportional response in dry weight, dry/fresh weight ratios and PPFD was found. The proliferation rate increased up to 120 μmol m−2 s−1 but decreased at higher rates. At the highest PPFD, the CO2 released from cultures and accumulated in the vessels reached 200 μl l−1 of; at the lowest rate the CO2 concentration reached 10500 μl l−1 after 28 days of culture. The photosynthetic rate at 1450 and 4500 μl l−1 of CO2 was nearly 4 times higher than at the lowest concentration tested.
Effects of exogenously applied growth regulators on shoot growth of inbred lines of Plantago major differing in relative growth rate: differential response to gibberellic acid and (2‐chloroethyl)‐trimethyl‐ammonium chloride
Authors: Dijkstra Paul , Kuiper Pieter J. C. 
Published: May 2006

The possibility of modulating shoot growth charaeteristics of seedlings of two inbred lines of Plantago major L., differing in relative growth rate (RGR), by exogenously applied 6‐benzylaminopurine (BA), α‐naphthalene acetic acid (NAA), (gibberellic acid (GA3) and (2‐chloroethyl)‐trimethyl‐ammonium chloride (CCC) was investigated. BA completely inhibited growth of the shoot at a concentration of 1 mM, while lower concentrations had no effect. NAA reduced growth of the shoot at 10 üM, while 1 mM completely inhibited growth. Addition of 10 μM GA3 or higher stimulated shoot fresh weight up to 20% and leaf area up to 30% for the slow growing inbred line (W9), but less for the fast growing line (A4). Application of 1 mM CCC, an inhibitor of gibberellin metabolism, reduced growth of both inbred lines, but to a larger extent in the fast growing seedlings.The lower shoot growth of W9 was associated with a lower specific leaf area (SLA) and a higher dry matter percentage of the shoot, as compared with A4. NAA reduced growth by reducing SLA and increasing leaf thickness, but the percentage dry matter of the leaves was unaffected. Stimulation of the shoot growth by GA3 application was associated with higher SLA and lower dry matter percentage. Application of CCC had opposite effects on SLA and dry matter percentage as compared with GA3. GA seems to be involved in the regulation of at least part of the genetic difference in RGR in Plantago major.
Mechanisms of chloride partitioning in the leaves of salt‐stressed Sorghum bicolor L.
Authors: Boursier P. , Läuchli A. 
Published: May 2006

Chloride transport in sheath and blade tissue and the cellular distribution of Cl‐ were investigated in an attempt to determine the physiological basis of the preferential accumulation of Cl‐ in sheaths of salt‐stressed sorghum (Sorghum bicolor L.). Import and export of 36Cl‐ in leaf sheaths and blades of intact sorghum were followed over a 2 week period. X‐ray microanalysis of frozen‐hydrated bulk tissue samples was used to determine the accumulation of Cl‐ and other elements in the vacuoles of sheath and blade cells.Sheath tissue accumulated Cl‐ despite a relatively high Cl‐ turnover rate. Chloride was shown to accumulate in most cell types of the sheath, particularly in adaxial epidermal cells. After an initial increase in the concentration of Cl‐, blade tissue regulated Cl‐ levels within certain limits. Chloride levels in blades were greater in the abaxial and adaxial epidermal cells than in other cell types. The epidermal cells of blades accumulated Cl‐ to approximately the same concentration as sheath epidermal cells. The Cl‐ concentration in the photosynthetically active mesophyll and bundle sheath cells, however, remained low.Thus, the partitioning of Cl‐ previously observed in the leaves of salinized sorghum apparently results from the ability of bundle sheath and mesophyll cells to maintain concentrations of Cl‐ at lower levels than do epidermal cells. In addition, the relatively large sheath parenchyma cells tend to serve as reservoirs for the storage of Cl‐.
Responses to internal potassium ion concentrations of two Taraxacum microspecies of contrasting mineral ecology: The role of inorganic ions in growth
Authors: Hommels C. H. , Kuiper P. J. C. , Haan A. de 
Published: May 2006

The two microspecies were Taraxacum sellandii Dahlst., which usually occurs in heavily fertilized grasslands, and Taraxacum nordstedtii Dahlst., which on the whole is restricted to undisturbed and mineral‐poor habitats. Growth response curves were established, depicting the relative yield of (whole) plant tissue water and the internal K+ concentration (on a whole plant basis). The critical K+ concentration, i.e. the lowest [K+]i associated with maximal growth, was derived from the response curve. T. nordstedtii, the microspecies with the low maximal growth, showed a distinctly lower critical K+ concentration than T. sellandii. A relationship between growth potential and critical K+ concentration is proposed. Responses to a declining [K+]i differed between the two microspecies. The roots of T. nordstedtii stopped functioning as a sink for inulin, and mobilized additional carbohydrates for maintaining osmotic potential and growth. The productive strategy of the fast‐growing T. sellantlii is lacking such a mechanism to buffer effects of a declining [K+]i.Various changes were noted as regards the internal concentrations of other inorganic ions, measured as a function of [K+]i, With declining [K+]i, internal NO‐3 decreased considerably in shoot and roots, especially in T. nordstedtii, while Mg2+ accumulated, especially in the roots of T. sellandii. The interactions between growth potential and the accumulation of inorganic ions are discussed.
Luxury consumption and specific utilization rates of three macroelements in two Taraxacum microspecies of contrasting mineral ecology
Authors: Hommels C. H. , Kuiper P. J. C. , Tanczos O. G. 
Published: May 2006

Plants of Taraxacum sellandii Dahlst., a microspecies adapted to fertile, and Taraxacum nordstedtii Dahlst., adapted to infertile soils, were cultured hydroponically, either on a complete nutrient solution or on one deprived of nitrogen, phosphorus, or potassium ions. For all four treatments, the growth and internal mineral concentration of the plants was monitored. For plants cultured on a complete nutrient solution, the uptake rates of nitrate, phosphate, and potassium ions were determined. Luxury consumption of the three macronutrients was computed as the excess of ion absorption over the ion uptake rates minimally required to sustain maximum growth. In these calculations the critical N, P, or K+ concentrations, earlier derived, were used as parameters describing the mineral status minimally required to allow maximum growth. Efficiency in use of the three macroelements at various levels of mineral accumulation was also computed. Finally, the response to phosphate starvation as related to phosphate uptake capacity and the accumulation of P was investigated.The physiological properies investigated provide a causal background for the superior adaptation of T. nordstedtii as compared to T. sellandii to infertile sites. Taraxacum nordstedtii had a higher relative luxury consumption of NO3–, H2PO‐4, and K+, a higher efficiency in N and P use at N– and (severe) P‐deficiency, respectively; and, after phosphate starvation, a relatively high preservation of phosphate uptake capacity and an enlargement of P storage. In combination with the low potential growth, luxury consumption will be particularly effective in T. nordstedtii in preventing or minimizing mineral deficiency. The distribution of minerals between cytoplasm and vacuoles as a factor in mineral use efficiency is discussed.
Lateral bud development and shoot growth in low‐pruned Morus alba as affected by stem orientation
Authors: Suzuki Takeo , Kitano Minoru 
Published: May 2006

Two phases of bud activity were identified in the new growth of one‐year‐old erect coppice shoots on 11‐year‐old low‐pruned stumps of mulberry (Morus alba L. cv. Shin‐ichinose) in spring, the sprouting phase in which the majority of the buds, including the basal ones, sprout and elongate, and the dominance phase (starting 4–5 weeks after sprouting) during which the upper laterals begin to assert dominance and suppress the growth of lower laterals, becoming new leading shoots. In contrast, arching before sprouting markedly inhibited buds on the under side, leading to poor shoots. By late April, the sprouts on the upper side grew readily into new erect shoots, resulting in considerable dominance over those from the lateral sides. Of these erect shoots, those located closer to the stem base grew more in May and June. The effects of arching made during the sprouting phase (late April) on bud activity and shoot lengths were generally similar to those of earlier archings before spring bud bursting. Separation of the shoots from the upper and under sides by longitudinal, horizontal splitting of the arched stems in late April did not affect the inhibited elongation of the shoots from the under side. These results suggest that in the response to arching before and in late April, the effects are related to spring bud bursting and gravimorphism. In contrast, arching during and after the dominance phase (May) had no gravimorphic effects on growth of the shoots on the upper side, although there was a stimulation of outbreak of the buds on the upper side, which remained dormant during spring bud bursting.Continuous basal applications of abscisic acid in aqueous solution inhibited bud break and shoot growth of the postdormant erect stem segments, and defoliation of the new shoots markedly. In contrast, similar applications of an ethylene‐releasing compound, Ethephon, depressed shoot elongation slightly, but enhanced defoliation greatly. Gibberellic acid (GA3) stimulated shoot elongation, but depressed leaf enlargement.