bluuebunny/crossref_metadata_2025_split huggingface dataset:
Growth, sucrose synthase, and invertase activities of developing Phaseolus vulgaris L. fruits
Authors: SUNG S. S. , SHEIH W. J. , GEIGER D. R. , BLACK C. C. 
Published: April 2006

ABSTRACTActivities of the sucrose‐cleaving enzymes, acid and neutral invertase and sucrose synthase, were measured in pods and seeds of developing snap bean (Phaseolus vulgaris L.) fruits, and compared with 14C‐import, elongation and dry weight accumulation. During the first 10 d post‐anthesis, pods elongated rapidly with pod dry weight increase lagging behind by several days. The temporal patterns of acid invertase activity and import coincided closely during the first part of pod development, consonant with a central role for this enzyme in converting imported sucrose during pod elongation and early dry weight accumulation. Later, sucrose synthase became the predominant enzyme of dry weight accumulation and was possibly associated with the development of phloem in pod walls. Sucrose synthase activity in seeds showed two peaks, corresponding to two phases of rapid import and dry weight accumulation; hence, sucrose synthase was associated with seed sink growth. Acid invertase activities in seeds were low and did not show a noticeable relationship with import or growth. All neutral invertase activities, during pod and seed development, were too low for it to have a dominant role in sucrose cleavage. Changes in activities of certain sucrose‐cleaving enzymes appear to be correlated with certain sink functions, including import, storage of reserves, and biosynthetic activities. The data supports the association of specific sucrose‐cleaving enzymes with the specific processes that occur in the developing pods and seeds of snap bean fruits; for example, acid invertase with pod elongation and sucrose synthase with fruit dry matter accumulation.
A new equation for calculating osmotic potential
Authors: COCHRANE T. T. 
Published: April 2006

ABSTRACTA new equation for calculating osmotic potential was developed that is based on a molecular model of the structure of water. Its formulation involves no sub‐equations that cannot be fully derived from established physical principles. The equation was first tested by calculating the osmotic potentials of a series of aqueous NaCl solutions with concentrations ranging from 0.103 to 4.382 kmol m−3, and comparing those calculations with calculations made using equations recorded in the literature. Virtually the same results were obtained. Subsequently, it was tested successfully by comparative calculations on a selection of inorganic and organic aqueous solutions. The principles it embodies provide for the visualization of the molecular role of water in plants as a unifying mechanism. Factors that affect the size of the structure of water, and the consequent distance an individual molecule must travel to and fro across its cage, determine direction and rate of flow. It is considered that the equation will provide a new research tool for many osmotic‐potential‐related questions.
Temperature dependence of trans plasma membrane electron transport in Zea mays L. roots
Authors: DÖRING O. , BÖTTGER M. 
Published: April 2006

ABSTRACTIntact Zea mays L. cv. Golden Bantam seedlings which were not cold adapted were exposed to various temperatures. Trans plasma membrane potential difference was measured in a temperature range from 0 to 40 °C using intracellular microelectrodes. The depolarization caused by electron transfer across the PM to artificial external electron acceptors was investigated. Active membrane potential increased with temperature in the range from 0 to 15 °C but was independent of temperature above 20 °C. Depolarization caused by the non‐membrane‐permeating electron acceptors hexacyanoferrate III (HCF III) and hexabromoiridate IV (HBIIV) took place over the whole temperature range investigated. The effect of HBI IV increased up to 10 °C whereas the HCF III effects increased up to 25 °C.
Scaling sun and shade photosynthetic acclimation ofAlocasia macrorrhizato whole‐plant performance – I. Carbon balance and allocation at different daily photon flux densities
Authors: SIMS D. A. , PEARCY R. W. 
Published: April 2006

ABSTRACTWe determined the carbon allocation patterns and construction costs ofAlocasia macrorrhizaplants grown at different photon flux densities (PFD) as well as the whole‐plant carbon gain of these plants at different daily PFDs. Growth at high PFD resulted in thicker leaves with a higher leaf mass per unit area, and increased biomass allocation to petioles and roots, as compared to growth at low PFD. Increased allocation to petioles may have been necessary to support the heavier leaves, whereas increased allocation to roots may have been necessary to supply sufficient water for the higher transpiration rates in high PFD. Root biomass was highly correlated with the daily, whole‐plant transpiration rate. Tissue construction costs per unit dry mass were unchanged by acclimation, but, since the mass per unit areas of leaves, roots and petioles all increased, construction costs per unit leaf area were much higher for plants grown at high PFD. On a per unit leaf area basis, daily whole‐plant carbon gain measured at high daily PFD was higher in high‐ than in low‐PFD‐grown plants. However, on a per unit leaf mass basis, low‐PFD‐grown plants had a daily carbon gain at least as high as that of high‐PFD‐grown plants at high daily PFD. At low daily PFD, low‐PFD‐grown plants maintained an advantage over high‐PFD‐grown plants in terms of carbon gain because of their larger leaf area ratios. Thus, in terms of carbon gain, low‐PFD‐grown plants performed better than sun plants at low PFD and as well as high‐PFD‐grown plants at high PFD, despite their lower photosynthetic capacities per unit area. For high‐PFD‐grown plants, the higher construction costs per unit leaf area resulted in lower leaf area ratios, which counteracted the advantage of higher photosynthetic rates per unit leaf area.
The interactive effects of light and inorganic carbon on aquatic plant growth
Authors: MADSEN T. V. , SAND‐JENSEN K. 
Published: April 2006

ABSTRACTSubmerged aquatic macrophytes grow across a wide, often coupled, range of light and inorganic carbon availabilities, and each single factor influences photosynthesis and acclimation. Here we examine the interactive effects of light and inorganic carbon on the growth of Elodea canadensis and Callitriche cophocarpa. The plants were grown in the laboratory at a range of light intensities (0–108 μmol m−2s−1) and four inorganic carbon regimes in a crossed factorial design. Plant growth rates, measured over 3–4 weeks of incubation, increased in response to increasing light intensity and inorganic carbon availability, and significant interactive effects were observed. The light‐use efficiency for growth at low light increased 2‐fold for Callitriche and 6‐fold for Elodea between the lowest and highest inorganic carbon concentrations applied. Also, the growth rate at the highest light intensity increased with inorganic carbon availability, but the relative increase was smaller than at low light. Both species acclimated to the light and carbon regime such that the chlorophyll content declined at low and high light intensities and the initial slopes of the photosynthetic CO2 and HCO3− response curves declined at high levels of CO2. Callitriche responded less markedly than Elodea to changing inorganic carbon availability during growth, and the initial slope of the photosynthetic HCO3− response curve, in particular, was greatly reduced (>90%) in Elodea by high CO2. It is suggested that the coupled responses of aquatic macrophytes to light and inorganic carbon influence their ability to develop dense stands at high light in shallow water and to extend to greater depths in waters rich in inorganic carbon.
The chemical composition and anatomical structure of leaves of grass species differing in relative growth rate
Authors: VAN ARENDONK J. J. C. M. , POORTER H. 
Published: April 2006

ABSTRACTTo arrive at a better understanding of variation in specific leaf mass (SLM, leaf weight per unit leaf area), we investigated the chemical composition and anatomical structure of the leaves of 14 grass species varying in potential relative growth rate. Expressed on a dry weight basis, the fast‐growing grass species with low SLM contained relatively more minerals and organic N‐compounds, whereas slow‐growing species with high SLM contained more (hemi)cellulose and lignin. However, when expressed per unit leaf area, organic N‐compounds, (hemi)cellulose, total structural carbohydrates and organic acids increased with increasing SLM.For the 14 grasses, no trend with SLM was found for the leaf volume per unit leaf area. Leaf density was positively correlated with SLM. Variation in density was not caused by variation in the proportion of intercellular spaces. The proportion of the total volume occupied by mesophyll and veins did not differ either. A high SLM was caused, at least partly, by a high proportion of non‐veinal sclerenchymatic cells per cross‐section. The epidermal cell area was negatively correlated with SLM.We conclude that the differences in SLM and in the relative growth rate (RGR) between fast‐ and slow‐growing grass species are based partly on variation in anatomical differentiation and partly on chemical differences within cell types.
Changes in net photosynthesis and growth of Pinus eldarica seedlings in response to atmospheric CO2 enrichment
Authors: GARCIA R. L. , IDSO S. B. , WALL G. W. , KIMBALL B. A. 
Published: April 2006

ABSTRACT Pinus eldarica L. trees, rooted in the natural soil of an agricultural field at Phoenix, Arizona, were grown from the seedling stage in clear‐plastic‐wall open‐top enclosures maintained at four different atmospheric CO2 concentrations for 15 months. Light response functions were determined for one tree from each treatment by means of whole‐tree net CO2 exchange measurements at the end of this period, after which rates of carbon assimilation of an ambient‐treatment tree were measured across a range of atmospheric CO2 concentrations. The first of these data sets incorporates the consequences of both the CO2‐induced enhancement of net photosynthesis per unit needle area and the CO2‐induced enhancement of needle area itself (due primarily to the production of more needles), whereas the second data set reflects only the first of these effects. Hence the division of the normalized results of the first data set by the normalized results of the second set yields a representation of the increase in whole‐tree net photosynthesis due to enhanced needle production caused by atmospheric CO2 enrichment. In the solitary trees we studied, the relative contribution of this effect increased rapidly with the CO2 concentration of the air to increase whole‐tree net photosynthesis by nearly 50% at a CO2 concentration approximately 300 μmol mol−1 above ambient.
Does proline play a special role in bacteroid metabolism?
Authors: KOHL D. H. , STRAUB P. F. , SHEARER G. 
Published: April 2006

ABSTRACTDicarboxylates are generally considered the main energy‐bearing compounds imported from plant cells into bacteroids in root nodules. Evidence reviewed herein supports the hypothesis that other compounds contribute and that proline catabolism may have particular importance in bacteroid metabolism during environmental stress.
Leaf extension in the slender barley mutant: delineation of the zone of cell expansion and changes in translatable mRNA during leaf development
Authors: SCHÜNMANN P. H. D. , OUGHAM H. J. , TURK K. S. 
Published: April 2006

ABSTRACTThe slender mutant of barley (Hordeum vulgare L.) results from an alteration to a single nuclear gene. Plants homozygous for the mutant allele have long, attenuated leaves as a result of a greatly increased extension rate. Although the growth rate at any one position in the extension zone appears not to differ between slender and normal (wild‐type) barley, in slender the length of the zone over which cells extend is approximately 50% greater than that in normal barley. Epidermal cells are both longer and narrower in slender, so the whole‐plant phenotype is mirrored at the cell level. Translation in vitro of RNA extracted from successive sections of the young primary leaf, followed by one‐dimensional SDS‐PAGE separation, facilitated the alignment of equivalent developmental stages in the two genotypes, but failed to demonstrate major differences between the two genotypes. Two‐dimensional separation of translation products from total leaf tissue revealed a few small differences between normal and slender. Growth of plants at 8°C compared with 20°C caused changes in some translation products, with one (unknown) product decreasing in abundance in cold‐treated normal tissue but not in slender tissue.
Blue‐light‐induced pH changes associated with NO3−, NO2− and Cl− uptake by the green alga Monoraphidium braunii
Authors: APARICIO P. J. , WITT F. G. , RAMÍREZ J. M. , QUIÑONES M. A. , BALANDÍN T. 
Published: April 2006

ABSTRACTIn M. braunii, the uptake of NO3− and NO2− is blue‐light‐dependent and is associated with alkalinization of the medium. In unbuffered cell suspensions irradiated with red light under a CO2‐free atmosphere, the pH started to rise 10s after the exposure to blue light. When the cellular NO3− and NO2− reductases were active, the pH increased to values of around 10, since the NH4+ generated was released to the medium. When the blue light was switched off, the pH stopped increasing within 60 to 90s and remained unchanged under background red illumination. Titration with H2SO4 of NO3− or NO2− uptake and reduction showed that two protons were consumed for every one NH4+ released. The uptake of Cl− was also triggered by blue light with a similar 10 s time response. However, the Cl− ‐dependent alkalinization ceased after about 3 min of blue light irradiation. When the blue light was turned off, the pH immediately (15 to 30 s) started to decline to the pre‐adjusted value, indicating that the protons (and presumably the Cl−) taken up by the cells were released to the medium. When the cells lacked NO3− and NO2− reductases, the shape of the alkalinization traces in the presence of NO3− and NO2− was similar to that in the presence of Cl−, suggesting that NO3− or NO2− was also released to the medium. Both the NO3− and Cl−‐dependent rates of alkalinization were independent of mono‐ and divalent cations.
Seasonal variation of leaf glutamine synthetase isoforms in temperate deciduous trees strongly suggests different functions for the enzymes
Authors: PEARSON J. , JI Y.‐M. 
Published: April 2006

ABSTRACTChanges in the activities of leaf glutamine synthetase (GS) isoforms were followed in four temperate deciduous trees from full leaf expansion to senescence (May to November). In the early part of the season, total GS activity was high in all species, with values ranging from 90 to 200 μmol h−1 g−1 fw. During this early period this activity comprised only the activity of the chloroplastic (GS2) isoform in all species. These high GS2 activities are consistent with the role of GS2 in the re‐assimilation of photorespired ammonia. The early high values also coincided with high nitrate reductase activity in one of the species, the highly nitrophilous species Sambucus nigra, with values of up to 16μmol h−1 g−1 fw. This indicates that GS2 is also important in the assimilation of ammonia produced from nitrate reduction. From mid‐ to late‐season, the cytosolic isoform (GS1) was detected in all four species and became increasingly more active in comparison to GS2. By the time of senescence it was the dominant enzyme of the two forms in both S. nigra and Carpinus betulus. The results provide strong support for recent findings that GS1 is an important enzyme for the mobilization of nitrogen for translocation or storage.
Negative phototropism in young gametophytes of the fern Schizaea pusilla
Authors: KISS J. Z. 
Published: April 2006

ABSTRACT Schizaea pusilla is a rare fern that occurs in acidic bogs and is one of the few fern species that maintains a filamentous gametophyte throughout its development. To expand our knowledge of the physiology of this fern, phototropic responses were examined in young gametophytes. In contrast to germ filaments of other fern species, apical protonemata of young gametophytes are negatively phototropic in continuous white, red and blue light at all fluence rates tested. The expression of phototropic curvature is not limited by time since apical protonemata are also negatively phototropic when they are given brief exposures of light and then placed in the dark. In other lower plant groups such as mosses and some algae, the direction of phototropic curvature can change depending on light quality and intensity, but in young gametophytes of Schizaea, negative phototropic curvature was observed in all conditions studied. Blue light is the most effective in promoting the negative phototropic response in Schizaea.
The influence of nitrogen availability on carbon and nitrogen storage in the biennial Cirsium vulgare (Savi) Ten. I. Storage capacity in relation to resource acquisition, allocation and recycling
Authors: HEILMEIER H. , FREUND M. , STEINLEIN T. , SCHULZE E.‐D. , MONSON R.K. 
Published: April 2006

ABSTRACTPlants of Cirsium vulgare (Savi) Ten. were cultivated under five different nitrogen regimes in order to investigate the effects of nitrogen supply on the storage processes in a biennial species during its first year of growth.External N supply increased total biomass production without changing the relationship between ‘productive plant compartments’ (i.e. shoot plus fine roots) and ‘storage plant compartments’ (i.e. structural root dry weight, which is defined as the difference between tap root biomass and the amount of stored carbohydrates and N compounds). The amount of carbohydrates and N compounds stored per unit of structural tap root dry weight was not affected by external N availability during the season, because high rates of N supply increased the concentration of N compounds whilst decreasing the carbohydrate concentration, and low rates of N supply had the opposite effect. Mobilization of N from senescing leaves was not related to the N status of the plants. The relationship between nitrogen compounds stored in the tap root and the maximum amount of nitrogen in leaves was an increasing function with increasing nitrogen supply. We conclude that the allocation between vegetative plant growth and the growth of storage structures over a wide range of N availability seems to follow predictions from optimum allocation theory, whereas N storage responds in a rather plastic way to N availability.
Replacement of nitrate by ammonium as the nitrogen source increases the salt sensitivity of pea plants. I. Ion concentrations in roots and leaves
Authors: SPEER M. , BRUNE A. , KAISER W. M. 
Published: April 2006

ABSTRACTPea seedlings (Pisum sativum L. cv ‘Kleine Rheinlän‐derin’) were grown hydroponically in solutions containing either nitrate (3 or 14 mol m−3) or ammonium (3 mol m−3) as the nitrogen source. Ammonium nutrition as such had no negative effect on plant biomass production, but drastically increased the sensitivity to moderate salinity (50 mol m−3 NaCl). The reasons for this effect are investigated here and in a subsequent paper. The appearance of visible symptoms of salt damage (wilting of marginal leaf areas followed by progressive necrosis) was paralleled by the development of several characteristic modifications in the solute and metabolite contents. Major changes were: (i) high salt (NaCl) accumulation in leaves; (ii) accumulation of ammonium (up to 20 mol m−3) and amino acids (up to 110 mol m−3) in leaves, but at decreased ammonium uptake rates; and (iii) decreased protein content. In a comparison paper we report on the subcellular distribution of salts, ammonium and metabolites under the above conditions.
Intra‐ and inter‐plant variation in xylem cavitation in Betula occidentalis
Authors: SPERRY J. S. , SALIENDRA N. Z. 
Published: April 2006

ABSTRACTA modified version of a method that uses positive air pressures to determine the complete cavitation response of a single axis is presented. Application of the method to Betula occidentalis Hook, gave a cavitation response indistinguishable from that obtained by dehydration, thus verifying the technique and providing additional evidence that cavitation under tension occurs by air entry through interconduit pits. Incidentally, this also verified pressure‐bomb estimates of xylem tension and confirmed the existence of large (i.e. >0·4 MPa) tensions in xylem, which have been questioned in recent pressure‐probe studies. The air injection method was used to investigate variation within and amongst individuals of B. occidentalis. Within an individual, the average cavitation tension increased from 0·66±0·27 MPa in roots (3·9 to 10·7 mm diameter), to 1·17±0·10 MPa in trunks (12 to 16 mm diameter), to 1·36±0·04 MPa in twigs (3·9 to 5 mm diameter). Cavitation tension was negatively correlated with the hydraulically weighted mean of the vessel diameter, and was negatively correlated with the conductance of the xylem per xylem area. Native cavitation was within the range predicted from the measured cavitation response and in situ maximum xylem tensions: roots were significantly cavitated compared with minimal cavitation in trunks and twigs. Leaf turgor pressure declined to zero at the xylem tensions predicted to initiate cavitation in petiole xylem (1·5 MPa). Amongst individuals within B. occidentalis, average cavitation tension in the main axis varied from 0·90 to 1·90 MPa and showed no correlation with vessel diameter. The main axes of juveniles (2–3 years old) had significantly narrower vessel diameters than those of adults, but there was no difference in the average cavitation tension. However, juvenile xylem retained hydraulic conductance to a much higher xylem tension (3·25 MPa) than did adult xylem (2·25 MPa), which could facilitate drought survival during establishment.
Long‐term responses of Melilotus segetalis to salinity. I. Growth and partitioning
Authors: ROMERO J. M. , MARAÑÓN T. 
Published: April 2006

ABSTRACTAnnual sweetclover plants [Melilotus segetalis (Brot) Ser.] were grown for a complete life cycle with and without saline (NaCl treatment of CE=15 dS m−1). Growth and partitioning analyses were performed. Sequential harvests (every 15 d) during the life cycle, and separation of plant material into roots, stems, petioles, leaves and reproductive structures were carried out Salt treatment reduced growth during the early and middle stages of the life of the plant, but did not significantly affect RGR in the reproductive phase. The root–shoot allometric coefficient of salinized plants in the generative phase decreased more than in control plants. We suggest that salinity‐induced growth reduction in M. segetalis was primarily a result of a lower unit leaf rate (ULR) despite an increased leaf area ratio (LAR). Earlier flowering, higher biomass allocation to shoot and greater reproductive investment, but similar relative growth rate (RGR), were some of the main characteristics of salt‐stressed plants compared to controls during the reproductive phase, these apparently being associated with increased sink strength caused by developing flowers and fruits.