bluuebunny/crossref_metadata_2025_split huggingface dataset:
Foliar metabolic heat rate of seedlings and mature trees ofPinus ponderosaexposed to acid rain and ozone
Authors: MOMEN B. , HELMS J. A. , CRIDDLE R. S. 
Published: April 2006

ABSTRACTWe investigated the effects of acid rain and ozone on respiration rates of 1‐year‐old and current‐year foliage of half‐sib seedlings and mature clones of a ponderosa pine genotype by measurement of foliar metabolic heat rates. Two rain regimes (pH 5‐1 and 3‐0) were applied weekly to foliage only, from January to April 1992. Two ozone regimes (ambient and twice‐ambient) were applied from September 1991 to November 1992. Metabolic heat rate was measured in April on 1‐year‐old foliage, in June on both 1‐year‐old and current‐year foliage, and in November on current‐year foliage in 1992. Except for current‐year foliage in June, the metabolic heat rate was calculated per unit of both foliar dry mass and N mass. In seedlings, both measures of metabolic heat rate increased in late June for 1‐year‐old foliage exposed to twice‐ambient ozone, and in November for current‐year foliage exposed to the combination of twice‐ambient ozone and pH 3‐0 rain. In mature trees, metabolic heat rate was not affected significantly by ozone, rain acidity, or their interaction. In June, when both 1‐year‐old and current‐year tissues were examined, the metabolic heat rate of expanding, current‐year foliage was higher than that of fully expanded, 1‐year‐old foliage regardless of plant age or treatment combination.
The vacuolar localization of a basic peroxidase isoenzyme responsible for the synthesis of α‐31,41‐anhydrovinblastine in Catharanthus roseus (L.) G. Don Leaves
Authors: SOTTOMAYOR M. , de PINTO M. C. , SALEMA R. , DiCOSMO F. , PEDREÕO M. A. , ROS BARCELO A. 
Published: April 2006

ABSTRACTPartially purified protein extracts of Catharanthus roseus leaves were able to couple catharanthine and vindoline to produce α‐3′,4′‐anhydrovinblastine (AVLB) in a reaction strictly dependent on H2O2. This result, and the co‐purification of peroxidase with AVLB synthetase activity, strongly suggest a peroxidase‐like nature for the coupling enzyme. Only one peroxidase isoenzyme was detected in C. roseus leaves, and it was shown that this isoenzyme consists of a molecularly‐heterogeneous basic peroxidase (EC 1‐11‐1‐7) mainly located in the vacuole. These results suggest that a basic peroxidase located in the vacuole may be the main enzyme responsible for AVLB synthesis in C. roseus leaves. This isoenzyme was also found in cell walls where a peroxidase inhibitor was detected.
Comparison of plant and fungal gravitropic responses using imitational modelling
Authors: STOČKUS A. , MOORE D. 
Published: April 2006

ABSTRACTThe mechanisms of gravity perception are still hypothetical, but there are sufficient data from experiments with plants to enable mathematical modelling to imitate the behaviour of gravitropic response systems. We have a much less complete picture of gravitropic kinetics in agaric mushrooms. However, some existing mathematical models which imitate plant responses are in principle universal because their conceptual components are not limited to any specific cellular entities. In this work we have used such models to compare plant and fungal gravitropism, using recently acquired kinetic data from the agarics Coprinus cinereius and Flammulina velutipes. The results show striking similarities between plants and fungi. First, it is evident that the basic assumptions of the plant models are logically applicable to fungi. Secondly, the mechanism of bending is the same (differential growth of opposite flanks of the growing organ). Thirdly, the distribution of growth seems very similar: in both plants and fungi growth of the organ is most intensive just behind the apex and is almost absent at the apex and at the base. Fourthly, in both fungi and plants the gravitropic response exhibits a substantial time delay suggesting that many time‐consuming processes are involved in reception, transduction and realization of gravitropic stimuli. Important differences in plant and fungal gravitropism kinetics were: (i) the agaric stem apex always returned to the vertical, whereas some plant organs show stable plagiogravitropic growth; (ii) inflections were usually seen in C. cinereus stem gravitropism time courses suggesting that a curvature compensation process delayed bending for a time; (iii) C. cinercus stems very rarely overshot or oscillated around the vertical although many plant subjects oscillate and the (limited) data for F. velutipes showed a single, exaggerated overshoot and oscillation. In this latter case, experimental modelling with parameters characteristic of a low level of perception improved the fit to the F. velutipes data, indicating that the two fungi may differ in this factor. Application of the plant models focused future research attention on the urgent need for data bearing on angle‐response and acceleration–response relationships in fungi, and their detection–level thresholds for gravitational acceleration. Since the modelling also highlighted some fundamental kinetic differences between the only two fungi for which sufficient data are available at the moment, it is also clear that detailed observations need to be made of gravitropism kinetics in a larger number and wider range of fungi.
Distribution and activity of microsomal NADPH‐dependent monooxygenases and amino acid decarboxylases in cruciferous and non‐cruciferous plants, and their relationship to foliar glucosinolate content
Authors: BENNETT R. N. , KIDDLE G. , HICK A. J. , DAWSON G. W. , WALLSGROVE R. M. 
Published: April 2006

ABSTRACTThe NADPH‐dependent conversion of amino acids to their aldoximes is an initial step in glucosinolate biosynthesis. A number of microsomal aldoxime‐forming monooxygenase activities were detected in leaves from a variety of glucosi‐nolate‐containing species, whereas barley, bean and tobacco leaves did not contain any such activities. The substrates for these monooxygenases in each species largely correlated with the spectrum of glucosinolates found in that species. No activity was detected that metabolized homomethionine (supposed precursor of 2‐propenylglucosinolate [sinigrin]), even in species where sinigrin was the major glucosinolate. In Sinapis species containing hydroxybenzylglucosinolate (sinalbin), activity with L‐Tyr was detected, whereas Brassica species containing sinalbin had no such activity. However, these Brassicas did contain an L‐Phe monooxygenase activity. Partial characterization of the monooxygenases indicated that in Brassica species, Nasturtium officinalis and Raphanus sativus these resembled the flavin‐linked monooxygenases previously found in oilseed rape (Brassica napus) and Chinese cabbage (Brassica campestris). The L‐Tyr‐dependent activity in Sinapis species, and the L‐Phe‐dependent activity in Tropacolum majus, had characteristics of cytochrome P450‐type enzymes. No similarity was found with any other known amino acid metabolizing enzymes (including decarboxylases, amino acid oxidases and diamine/polyamine oxidases).
Turgor regulation in Lamprothamnium papulosum. I. I/V analysis and pharmacological dissection of the hypotonic effect
Authors: BEILBY M. J. , SHEPHERD V. A. 
Published: April 2006

ABSTRACTCurrent‐voltage (I/V) analysis and pharmacological dissection were applied to membranes of Lamprothamnium at the time of hypotonic stress. At least three types of process were found to be involved in the response to this stress.

The first 10min of exposure to hypotonic medium resulted in a depolarization of about 50mV accompanied by a decrease or no change in conductance. This depolarization occurred with either K+ or Ca2+ (and consequently C− channels inactivated.
The CI− channels opened mainly in the first 15min of the hypotonic stress, increasing the membrane conductance by about an order of magnitude.
The K+ conductance rose as the Cl− conductance started to diminish and reached a maximum after about 40 min.

Both types of channel were strongly potential‐dependent with a conductance peak between ‐150 and 0mV. An inactivation of K+or CI− channels resulted in moving the membrane potential away from the conductance maximum toward either EK or ECI, diminishing the ion efflux (and turgor regulation). The time courses of the conductance increases remained the same, suggesting that the conductance changes are not driven by feedback to some preset turgor level. The electrophysiology of the Lamprothamnium transporters is compared to that of salt‐sensitive charophytes.
Effects of salinity on turgor pressure and fertility in Tolypella (Characeae)
Authors: WINTER U. , SOULIÉ‐MÄRSCHE I. , KIRST G. O. 
Published: April 2006

AbstractWe present the first experimental results on salinity tolerance and regulation mechanisms in the genus Tolypella. The two species investigated, T. nidifica and T. glomerata, regulate turgor pressure with almost complete effectiveness by adjustment of K+ and CT concentrations. Sucrose is also involved. The mechanism is basically identical to the mechanism of turgor pressure regulation previously identified in representatives of the genera Chara and Lamprothamnium. Since Chara and Lamprothamnium on the one hand and Tolypella on the other belong to different phylogenetic branches that separated early in the geological history of the Characeae, the K+ regulation mechanism can be assumed to represent an ancient pattern derived from a salt‐tolerant common ancestor. Furthermore, our experiments provide evidence that salinity is a limiting factor for fertility in both T. nidifica and T. glomerata. Although the onset of gametangia covers the whole range of salinities tested here (0–29 psu), 12psu was the inhibitory level for the formation of mature oospores. Fertilization is probably disturbed by an increase in salinity. An inability to reproduce sexually under euryhaline conditions could explain why the distribution of the two species is restricted to oligo‐ and mesohaline environments, despite the wide range of salinity tolerance of their vegetative apparatus.
Prevention of aluminium toxicity with supplemental boron. I. Maintenance of root elongation and cellular structure
Authors: LENOBLE M. E. , BLEVINS D. G. , SHARP R. E. , CUMBIE B. G. 
Published: April 2006

ABSTRACTAluminium toxicity is an important factor limiting plant growth mi acid soils. Symptoms of B deficiency and Al toxicity are very similar and generally associated with impaired membrane Function and root growth. Thus the objective of this study was to determine whether supplemental B prevents Al inhibition of root growth and development. Squash (Cucurbita pepo L. cv. Sunbar) was grown in hydroponic nutrient media with 44 mmol m−3 free Al and B concentrations extending from 5 to 100 mmol m−3. Our results establish that B protects against Al inhibition of root growth. Protection was apparent at all levels of organization examined: primary root and lateral root lengths; primary root cell elongation, cell production rate, tissue organization and cell structure; primary root morphology and maturation. Protection against Al inhibition was also apparent for shoot growth. These studies were undertaken in solution culture to limit the variables examined; however, the underlying motivation for this study is the problem of worldwide Al toxicity in soils. Therefore, the effect of adding additional B to a high‐Al soil was also investigated and is the subject of the companion paper (Le Noble. Blevins & Miles 1996, Plant, Cell and Environment 19, 1143–1148).
Prevention of aluminium toxicity with supplemental boron. II. Stimulation of root growth in an acidic, high‐aluminium subsoil
Authors: LENOBLE M. E. , BLEVINS D. G. , MILES R. J. 
Published: April 2006

ABSTRACTRoot growth inhibition is an early symptom of Al toxicity and B deficiency. Our hypothesis is that Al toxicity may induce B deficiency, and it was our objective to determine if incorporation of supplemental B would promote root penetration into an acidic, high‐Al subsoil. Alfalfa (Medicago sativa L. cv. Hy‐Phy) was grown in slanted tubes with a Plexiglas window along their length. The top half of the tub contained silt loam soil and the bottom half contained subsoil from the Bt1 horizon (26% Al saturation) of a Creldon silty clay loam. Both soils originally contained 0–9 kg B ha−1. When root growth was measured in the bottom half of the high‐A1 subsoil, all measurements—depth of rooting, total root growth, final root lengths and root dry weight—demonstrated greater root growth in treatments where additional B was incorporated into the high‐Al subsoil. Results from this soil study extend those obtained in our hydroponic study in which supplemental B presented Al inhibition of root growth. Boron concentrations may need to he increased under acidic ‘high‐Al’ soil conditions to promote root penetration into these soil zones, and this could be especially important during periods of drought stress.
Gravitropism of maize and rice coleoptiles: dependence on the stimulation angle
Authors: IINO M. , TARUI Y. , UEMATSU C. 
Published: April 2006

ABSTRACTGravitropism of maize and rice coleoptiles was investigated with respect to its dependence on the angle of displacement or the initial stimulation angle (ISA). Close examination of curvature kinetics and the response to a drop in stimulation angle (SA) indicated that the gravitropic response during an early but substantial part of curvature development is directly related to the ISA, there being no effect of the reduction of SA resulting from the curvature response itself. On the basis of this finding, the relationship between the steady SA and the curvature rate was determined. In maize, the curvature rate increased linearly with the sines of SAs up to an SA of 90°. Rice coleoptiles. however, showed a saturation curve in the same range of SAs. The saturation profile was nearly identical between coleoptiles grown in air and those submerged in water, although the latter elongated much faster. Rice coleoptiles appeared to be far more sensitive to gravity than maize coleoptiles. It is concluded that the sensitivity to gravity, assessed through dependence on ISA, is a property inherent to a given gravitropic organ. Long‐term measurements of curvature indicated that the coleoptiles bend back past the vertical. This overshooting was marked in submerged rice coleoptiles.
Shoot and root physiological responses to localized zones of soil moisture in cultivated and wild lettuce (Lactuca spp.)
Authors: GALLARDO M. , JACKSON L.E. , THOMPSON R.B. 
Published: April 2006

ABSTRACTCultivated crisphead lettuce (Lactuca sativa L.) has a shallower root system than its wild relative, Lactuca serriola L. The effects of localized soil water, at depth, on plant water relations, gas exchange and root distribution were examined in the two species using soil columns with the soil hydraulic‐ally separated into two layers, at (0–20 cm and 20–81) cm, but permitting root growth between the layers. Three treatments were imposed on 7‐week‐old plants, and maintained for 4 weeks: (i) watering, both layers to field capacity; (ii) drying the upper layer while watering the lower layer to field capacity, and (iii) drying both layers.Drying only 0–20 cm of soil had no effect on leaf water status, net photosynthesis, stomatal conductance or biomass production in L. serriola compared to a well‐watered control, but caused a short‐term reduction (10 d) in leaf water status and photosynthesis in L. sativa that reduced final shoot production. The different responses may be explained by differences in root distribution. Just before the treatments commenced, L. serriola had 50% of total root length at 20–80 cm compared to 35% in L. sativa. Allocation of total biomass to roots in L. serriola was approximately double that in L. sativa. The wild species could provide germplasm for cultivated lettuces to extract more soil water from depth, which may improve irrigation efficiency.
Stomata from growth‐chamber‐grown Vicia faba have an enhanced sensitivity to CO2*
Authors: TALBOTT L. D. , SRIVASTAVA A. , ZEIGER E. 
Published: April 2006

ABSTRACTAbaxial stomata from Vicia faba leaves grown in a growth chamber under constant light, temperature and humidity showed an elaborate pattern of aperture changes over the course of a light cycle. These aperture changes were tightly correlated with changes in chamber CO2 concentration (r2=0.83). Changes in chamber [CO2] resulted, in turn, from substantial daily fluctuations in ambient [CO2], typical of the Los Angeles environment with a constant offset caused by photosynthesis and respiration of the plants within the chamber. The dominant role of the stomatal response to CO2 in the control of aperture was confirmed by manipulation of chamber [CO2]. Fast (15 min) increases and decreases in [CO2] caused rapid decreases and increases in aperture, while constant |CO2] resulted in constant aperture. In contrast, aperture changes in comparable plants grown under greenhouse conditions were tightly correlated with changes in incident solar radiation (r2=0.80), and poorly correlated with changes in [CO2] (r2=0.09). Greenhouse‐grown plants transferred to growth chamber conditions showed no apparent response to CO2. These data indicate that growth‐chamber‐grown V, faba leaves provide an experimental system optimally suited for the study of the stomatal response to CO2, and suggest that acclimation to environmental conditions alters the sensitivity of stomata to CO2.
Gravisensitivity of cress roots: investigations of threshold values under specific conditions of sensor physiology in microgravity*
Authors: VOLKMANN D. , TEWINKEL M. 
Published: April 2006

ABSTRACTThe minimum dose (dose = stimulus × time), one of three threshold values related to gravity, was determined under microgravity conditions for cress roots. Seedlings were cultivated on a 1g centrifuge in orbit and under microgravity, respectively. After continous stimulation on a threshold centrifuge, minimum doses of 20–30 gs for microgravity roots and 50–60 gs for roots grown on a 1g centrifuge were estimated, which indicated that micro‐gravity roots have a higher sensitivity than 1g roots. These results do not confirm the threshold value of 12gs which was determined for cress roots using the slow rotating clinostat. Following application of intermittent stimuli to microgravity‐grown roots, gravitropic responses were observed after two stimuli of 13‐5 gs separated by a stimulus‐free interval of 118 s. Generally, this demonstrates that higher plants are able to ‘sum up’ stimuli which are below the threshold value. Microscopic investigations of the cellular structure corresponding to stimulations in the range of the threshold value demonstrated a small displacement of statoliths in root statocytes. No significant correlation was observed between gravitropic curvature and statolith displacement. If the statolith theory is accepted, it can be concluded that stimulus transformation must occur in the cytoplasm in the near vicinity of the statoliths and that this transformation system – probably involving cytoskeletal elements – must have been affected during microgravity seedling cultivation.
Photosystem II and oxygen regulation in Sesbania rostrata stem nodules
Authors: JAMES E.K. , IANNETTA P.P.M , NIXON P.J. , WHISTON A.J. , PEAT L. , CRAWFORD R.M.M , SPRENT J.I. , BREWIN N.J. 
Published: April 2006

ABSTRACTThe tropical wetland legume Sesbania rostrata Brem. produces nitrogen‐fixing stem nodules which are green and contain chlorophyll, the chloroplasts being concentrated in a hand in the inner and mid‐cortex close to the nitrogen‐fixing cells. The photosystem II thylakoid membrane proteins D1, D2 and PsbO, which are essential for photo‐synthetic O2 evolution, were shown by immunoblotting to be present in extracts of leaves and stem nodules. Immunogold labelling confirmed their presence on stem nodule thylakoids and showed that labelling was most intense in well‐developed chloroplasts in the mid‐cortex and least intense in the smaller, less‐abundant chloroplasts adjacent to the nitrogen‐fixing cells. Concentrations of the oxygen‐carrying protein leghaemoglobin (Lb) did not differ between stem and S. rostrata root nodules, and Lb was localized in bacteroid‐containing cells, including those immediately adjacent to the cortex, in both nodule types. Moreover, nitrogenase component 2 was localized in bacteroids within the outermost layers of infected cells, suggesting that a low pO2 was maintained, despite the nearby chloroplasts. Nodule extracts examined by ELISA and immunoblots, using the monoclonal antibody MAC265, showed greatly enhanced expression of a 139 kDa glycoprotein in stem compared to root nodules. Immunogold labelling showed that material containing the MAC265 antigen occluded intercellular spaces, and was present in cell walls, throughout the cortex of stem nodules (particularly in the chloroplasl‐rich inner and mid‐cortex), but was considerably less evident in root nodules.
Response of transpiration and photosynthesis to a transient change in illuminated foliage area for a Pinus radiata D. Don tree
Authors: WHITEHEAD D. , LIVINGSTON N. J. , KELLIHER P.M. , HOGAN K. P. , PEPIN S. , MCSEVENY T.M. , BYERS J.N. 
Published: April 2006

ABSTRACTSudden but transient changes in the fraction or illuminated foliage area in a well‐watered 7‐year‐old Pinus radiata D. Don tree were imposed by completely covering either the upper 22% or the lower 78% of the foliage for periods of up to 36 h. Measurements of transpiration flux density (E), tree conductance (gt), stomatal conductance (gs) and net photosynthesis (A) were made to test the hypothesis that compensatory responses would occur in the remaining illuminated foliage when the cover was installed. When the lower foliage was covered there was an immediate decrease in gt. However, when tree conductance was normalized with respect to the illuminated leaf area (gt'), it increased between 50 and 75%, depending on the value of air saturation deficit (D). The effect was also apparent from concurrent measurements of increases in gs and A up to 59 and 24%, respectively, for needles in the top third of (he crown. When the cover was removed these effects were reversed. The changes in the lower foliage when the upper foliage was covered were much smaller. Changes in bulk needle water potential were small. It is suggested that the observed responses occurred because of a perturbation to the hydraulic pathway in the xylem that could have triggered the action of a chemical signal to regulate stomatal conductance and photosynthesis.
Differential expression during drought conditioning of a root‐specific S‐adenosylmethionine synthetase from jack pine (Pinus banksiana Lamb.) seedlings
Authors: MAYNE M. B. , COLEMAN J. R. , BLUMWALD E. 
Published: April 2006

ABSTRACTDifferential screening of a cDNA library constructed from root mRNA from jack pine (Pinus banksiana Lamb.) seedlings exposed to two cycles of drought conditioning identified a S‐adenosylmethionine synthetase (sam‐s) cDNA. A cDNA encoding the entire open reading frame of SAM‐S was identified and characterized. Analysis of the full‐length sam‐s cDNA revealed that it was 1675 bp, encoded an open reading frame of 393 amino acids and had a predicted protein mass of 43 kDa. Jack pine sam‐s was found to be highly similar to several other plant sam‐s genes. RNA gel blot analysis showed that sam‐s mRNA abundance increased following two cycles of drought conditioning and remained abundant after 3 d of rewatering. Expression of this gene appears to be root‐specific. Quantitative slot blot analysis showed that two cycles of drought conditioning caused a 6‐fold increase in sam‐s mRNA abundance whereas heat shock, cold stress and anoxia did not result in the accumulation of sam‐s mRNA. SAM‐S enzyme activity increased 2‐fold following two cycles of drought conditioning. The increase in the rate of SAM‐s enzyme activity was also correlated with changes in rates of ethylene and betaine synthesis, biosynthetic pathways that utilize SAM as a substrate. Ethylene evolution and betaine abundance increased following two cycles of drought conditioning.