bluuebunny/crossref_metadata_2025_split huggingface dataset:
CHLOROPLAST AUTONOMY FOR THE BIOSYNTHESIS OF ISOPENTENYL DIPHOSPHATE IN GUAYULE (PARTHENIUM ARGENTATUM GRAY)
Authors: REDDY A. RAMACHANDRA , DAS V. S. RAMA 
Published: April 2006

SUMMARYPurified chloroplasts (80% intact) with a photosynthetic activity of 195 μmol O2 mg chlorophyll−1 h−1 were prepared from the leaves of guayule. The activities of phosphoglyceromutase, enolase and pyruvate kinase were estimated in the purified chloroplasts and compared with those of Phaseolus radiatus Roxb. Activity of the pyruvate dehydrogenase complex (PDC) in the chloroplasts of guayule (448 nkat mg protein−1) was substantially higher than the PDC activity of Phaseolus (282 nkat mg protein−1). Incorporation of carbon from the added labelled carbon compounds, [14C]bicarbonate, [2‐14C]pyruvate and [U‐14C]‐3‐phosphoglycerate into isopentenyl diphosphate (IDP) was significant, indicating the ability of the chloroplasts to utilize Calvin cycle intermediates for IDP biosynthesis via acetyl CoA and mevalonate. DCMU inhibited the incorporation of 14CO2 and [14C]pyruvate into IDP. Acetoacetyl CoA thiolase, HMG‐CoA reductase, mevalonate kinase, phosphomevalonate kinase and pyrophosphomevalonate decarboxylase activity were localized in the isolated chloroplasts. It is believed that the chloroplasts in the leaf of guayule are autonomous for the biosynthesis of IDP and this is presumed to be dependent on photosynthetic energy and carbon flow.
DEVELOPMENT OF ‘EPIDERMAL’ GRAFTS ON CULTURED INTERNODES OF DATURA STRAMONIUM
Authors: HOLDEN M. A. , JEFFREE C. E. , YEOMAN M. M. 
Published: April 2006

SUMMARYThis paper describes a novel system of graft assembly in vitro performed on excised Datura stramonium internodes. The grafted material is a 2 × 10 mm strip of superficial tissue consisting of the epidermis plus three to seven layers of underlying tissue and the technique is therefore called ‘epidermal’ grafting. The excision of the strip of superficial tissue initiates cell division in the wounded tissue. At 10 d, control internodes, where tissue was excised but not replaced, had significantly higher cell numbers than the corresponding homografts. The assembly of the graft therefore appears to limit the cell division caused by tissue injury. Only two cell types are brought into contact during ‘epidermal’ graft assembly, thereby circumventing the problems associated with the study of the union of multiple cell types. This technique, therefore, represents a simplified system in which the cellular interactions during graft formation can be studied.
ZINC TOLERANCE IN BETULA SPP.
Authors: DENNY HILARY J. , WILKINS D. A. 
Published: April 2006

SUMMARYClones of zinc‐tolerant and non‐tolerant genotypes of Betula pendula Roth, and B. pubescens Ehrh. were cultured aseptically on media containing different concentrations of zinc. The location, concentration and form of zinc in root tissues of both groups of genotype were compared using various microanalytical techniques. At concentrations of zinc at which all genotypes were viable, there were no obvious differences between the tolerant and non‐tolerant genotypes. When the roots were subjected to concentrations above the lethal threshold, zinc accumulated intracellularly, at the endodermis, in the form of electron‐dense granules. This form of accumulation was symptomatic of tissue inundation with zinc. The results do not support the presence of cell wall binding or intracellular detoxification mechanisms of tolerance. The possibility that zinc tolerance, control of zinc uptake and zinc‐induced inhibition of cell extension are all linked by common events centred on the plasma membrane are discussed.
LITTLE ICE AGE DECLINE OF A COLD MARGINAL PINUS SYLVESTRIS FOREST IN THE SWEDISH SCANDES
Authors: KULLMAN LEIF 
Published: April 2006

SUMMARYThe natural decline of a virgin high‐altitude Pinus sylvestris forest during the Little Ice Age (approximately AD 1300–1850) was studied in the Swedish Scandes. Methods included 14C and cross‐dating of wood remnants, soil analyses, year‐ring chronologies and age structures. A closed pine forest started a gradual decline in the 11th century or somewhat later, which proceeded until the mid‐19th century. Long‐term failure of regeneration and premature death of trees are postulated to have caused the forest dieback, mainly owing to a negative shift of the carbon budget, including weather‐induced loss of photosynthetic tissue and root disfunction. Temperature measurements on the study site stressed its current marginality. Especially thermal conditions in and close to the ground were deduced to be decisive. The decline of the forest is considered to indicate a long‐term lowering during the Little Ice Age of the summer (June‐September) mean temperature by 1°C or more, compared with the 1931–1960 mean.
CARBON DIOXIDE AND WATER DEMAND: CRASSULACEAN ACID METABOLISM (CAM), A VERSATILE ECOLOGICAL ADAPTATION EXEMPLIFYING THE NEED FOR INTEGRATION IN ECOPHYSIOLOGICAL WORK
Authors: LÜTTGE U. 
Published: April 2006

SummaryPlants having crassulacean acid metabolism (CAM) tend to occupy habitats where the prevailing environmental stress is scarcity of water. These are semi‐arid or arid regions, salinas or epiphytic sites. CAM plants manage the dilemma of desiccation or starvation by nocturnal malic acid accumulation in the vacuoles. Malic acid serves as a form of CO2 storage and as an osmoticum. In this way malic acid accumulation allows, firstly, separation of uptake and assimilation of atmospheric CO2 with water‐saving daytime stomatal closure and, secondly, osmotic acquisition of water. There is no very special trait which is specific for CAM. An array of biophysical and biochemical functional elements, which are also found in other plants, is integrated in CAM performance. This leads to a large diversity of behaviour which makes CAM plants highly versatile in their response to environmental variables. Besides CO2 dark fixation, transport of malic acid across the tonoplast is one of the key elements in CAM function. This is examined in detail at the level of membrane biophysics and biochemistry. The versatility of CAM is illustrated by examples from field work, with comparisons involving different species, seasons, modes of photosynthesis (CAM vs C3), kinds of stress and ways of stress imposition.

Contents

Summary
593

I.
Studies of CAM: an example for the ecophysiological approach
594

II.
Malic acid transport at the tonoplast
602

III.
Regulation
605

IV.
Desiccation or starvation
610

V.
Comparative autecology
614

VI.
Ecology: promise of integration
621

Acknowledgements
622

References
622
THE MINIMUM PHOTON REQUIREMENT FOR PHOTOSYNTHESIS
Authors: OSBORNE BRUCE A. , GEIDER RICHARD J. 
Published: April 2006

SummaryVariations in the apparent photon requirement for photosynthesis (Φ−1co2) or (Φ−1co2) in the data of Warburg & Burk (1950) and Yuan, Evans & Daniels (1955) can be ascribed to changes in O2uptake and energy‐dependent processes which result in aberrant photon requirements in organisms subjected to non‐optimal conditions. The increase in Φ−1co2with increases in the gas exchange quotient (γ) in the observations of Yuan et al. (1955) is consistent with increases in photorespiratory production of glycollate, whilst changes in Φ−1co2and Φ−1co2in the results of Warburg & Burk (1950) can be explained by a variable Kok effect associated with nitrate assimilation at low light levels. When these O2and energy‐dependent processes are minimal, the lowest values should be observed. The minimum value obtained whenChlorellais photosynthesizing under optimal conditions is 6 mol photons mol−1O2. These results provide direct independent evidence for a photon requirement for photosynthesis of less than 8 mol photons mol−1O2. Such a value is not consistent with the Z scheme of photosynthesis.
OSMOTIC ADJUSTMENT IN MARINE EUKARYOTIC ALGAE: THE ROLE OF INORGANIC IONS, QUATERNARY AMMONIUM, TERTIARY SULPHONIUM AND CARBOHYDRATE SOLUTES
Authors: DICKSON D. M. J. , KIRST G. O. 
Published: April 2006

SummaryThe unicellular marine algae, Phaeodactylum tricornutum Bohlin, Cyclotella cryptica Reimann and Cyclotella meneghiniana Kützing (Bacillariophyceae) and Porphyridium aerugineum Geitler (Rhodophyceae) synthesized and accumulated glycine betaine and proline in response to increases of the NaCl concentration (150 to 1000 mol m−3NaCl) of the growth medium. C. cryptica and C. meneghiniana also synthesized and accumulated homarine (N‐methyl picolinic acid betaine). Both P. tricornutum and P. aerugineum synthesized increasing amounts of intracellular glycerol and P. aerugineum also formed the heteroside, floridoside [O‐α‐D‐galactopyranosyl (1 → 2)‐glycerol], in response to the elevated salinities. No major low molecular weight carbohydrates were found in Cyclotella. Sucrose was not detected in the algal extracts. Only P. tricornutum synthesized the tertiary sulphonium compound, β‐dimethylsulphoniopropionate (DMSP), and the quantity of this solute in the alga was dependent on the amount of NaCl in the medium. Intracellular K+concentrations in the algae were three to six times greater than those of Na+. Increases of the salinity of the media led to the uptake and accumulation of K+by the cells, and smaller increases of Na+and Cl−1and loss of intracellular NO3−. The inorganic cations Na+and K+, with their accompanying anions, and the estimated organic solutes could largely account for the osmotic balance of P. tricornutum and P. aerugineum.
OSMOTIC ADJUSTMENT IN MARINE EUKARYOTIC ALGAE: THE ROLE OF INORGANIC IONS, QUATERNARY AMMONIUM, TERTIARY SULPHONIUM AND CARBOHYDRATE SOLUTES
Authors: DICKSON D. M. J. , KIRST G. O. 
Published: April 2006

SummaryThe effects of steady state salinities (150 to 700 mol m−3NaCl) on the growth rates and intracellular solutes of the prasinophyte algae Tetraselmis chui Butcher and Prasinocladus Kuckuck and the prymnesiophyte algae, Prymnesium parvum Carter and Ruttnera spectabilis Geitler, are described. Maximum growth rates were reached in media approximating to the NaCl concentration of oceanic waters (about 500 mol m−3). The following intracellular organic solutes paralleled the increases of external salinity: the tertiary sulphonium compound β‐dimethylsulphoniopropionate (DMSP) in T. chui, Prasinocladus, P. parvum and R. spectabilis; the polyhydric alcohol, mannitol, in T. chui, Prasinocladus and R. spectabilis; the quaternary ammonium compounds (QACs), glycine betaine and homarine, in T. chui and Prasinocladus. QACs were not detected in P. parvum and R. spectabilis. An unknown polyol, which may be the cyclitol, 1,4/2,5 cyclohexanetetrol, was synthesized by P. parvum and R. spectabilis and in addition P. parvum contained significant concentrations of glucose. Sucrose was not detected in the algal extracts. Proline was an insignificant osmoticum in all the algae.Increases of the media NaCl concentration led to the uptake and accumulation of K+in T. chui and Prasinocladus, with smaller increases of Na+and Cl−. The intracellular K+concentrations in the prasinophyte algae were about five times greater than those of Na+. The inorganic cations Na+and K+, and their accompanying anions, and the organic solutes found could largely account for the osmotic balance of T. chui and Prasinocladus. The inorganic ions in P. parvum and R. spectabilis were not determined.
THE INFLUENCE OF AIR POLLUTION ON THE CONCENTRATION OF ATP AND ON CHLOROPHYLL DEGRADATION IN THE LICHEN, RAMALINA DURIAEI (DE NOT.) BAGL.
Authors: KARDISH NITZA , RONEN R. , BUBRICK P. , GARTY J. 
Published: April 2006

SummaryThe most efficient of five methods used for the extraction of ATP from lichens was found to be the use of Tris + EDTA after acetone treatment. Changes in the concentration of ATP in transplanted Ramalina duriaei (De Not.) Bagl. reflected the influence of air pollution on this lichen. The ATP concentration remained constant at a control station in a rural site, whilst at urban stations it decreased to 10% of the control value. Changes in the concentration of ATP were compared with chlorophyll degradation, as expressed by the ratio OD 435 nm/OD 415 nm. The values of this ratio also decreased in the urban sites, but less so than the ATP.
VESICULAR‐ARBUSCULAR MYCORRHIZA IMPROVE BOTH SYMBIOTIC N2 FIXATION AND N UPTAKE FROM SOIL AS ASSESSED WITH A 15N TECHNIQUE UNDER FIELD CONDITIONS
Authors: BAREA J. M. , AZCÓN‐AGUILAR C. , AZCÓN R. 
Published: April 2006

SummaryA technique using 15N‐labelled inorganic fertilizer was applied to estimate N2 fixation by the forage legume Hedysarum coronarium L. and to ascertain the role of vesicular‐arbuscular (VA) mycorrhizas in plant N nutrition throughout a growing season under field conditions. The absence of the specific Rhizobium for the forage legume in the test soil allowed us the use of 15N methodology with the same legume as reference ‘non‐fixing’ crop.At the first harvest, mycorrhizal inoculation behaved similarly to the phosphate addition in improving the percentage (70 %) and the total amount of N derived from fixation. But thereafter, mycorrhizal inoculation not only enhanced dry matter yield, N concentration and total N yield but also the amount of N derived from soil and from fixation, as compared with either phosphate‐added or control plants. This indicated that mycorrhizas acted both by a P‐mediated mechanism to improve N2 fixation and by enhancing N uptake from soil. The latter agrees with recent findings by others that VA mycorrhizal hyphae can translocate and assimilate ammonium, a fact of physiological and ecological interest.
THE SPREAD OF MYCORRHIZAL INFECTION BY GIGASPORA CALOSPORA FROM A LOCALIZED INOCULUM
Authors: SCHELTEMA M. A. , ABBOTT L. K. , ROBSON A. D. , DE'ATH G. 
Published: April 2006

SummaryThe lateral spread of Gigaspora calospora (Nicol. and Gerd.) Gerdemann & Trappe was examined in Trifolium subterraneum L. (subterranean clover) grown on a steamed lateritic podsol. Plants were sown in a sward in pots 29 cm long × 12 cm wide and inoculum of G. calospora was placed at one end. Mycorrhizal infection was estimated 21, 35, 63, 91 and 119 d after sowing at points 2, 4, 6, 8, 10, 12, 14, 16, 18, 20, 22, 24 and 26 cm from the inoculum. The lateral spread of Glotnusfasciculatum (Thaxter sensu Gerd.) through roots of T. subterraneum was measured 35 d after sowing.The percentage root length infected by G. calospora declined exponentially with distance from the inoculum. In contrast, infection by G. fasciculatum spread with a distinct front and hence was best described by a Gompertz curve.The number of spores of G. calospora recovered at increasing distances from the point of inoculation at the final harvest was correlated with the proportion of roots infected at an earlier harvest, and therefore provided a useful measure of the pattern of spread of G. calospora within roots.
PLANT SIZE AND SEED PRODUCTION IN THE MONOCARPIC PERENNIAL CYNOGLOSSUM OFFICINALE L.
Authors: KLINKHAMER PETER G. L. , DE JONG TOM J. 
Published: April 2006

SummaryIn a study of Cynoglossum officinale L. it was found that the number of seeds per flower increased with plant weight, and that flower production was inversely related to the number of seeds per flower. As a result, the number of seeds and total seed weight increased proportionally with plant weight. Seed size was not related to plant weight. Differences in seed size within the individual were, in part, related to the position of the seed on the cyme and not related to the number of seeds within a flower. The relationship, between plant size and female fitness found in this study is discussed in relation to life‐history theory.
THE DEGRADATION OF CHLOROPHYLL — A BIOLOGICAL ENIGMA
Authors: Hendry GEORGE A. F. , HOUGHTON JENNIFER D. , BROWN STANLEY B. 
Published: April 2006

SummarySome 109tonnes of chlorophyll are destroyed each year on land and in the oceans. The fate of these chlorophylls is, however, largely unknown. This review describes the developmental stages at which chlorophyll breakdown occurs in aquatic and terrestrial biological systems, and the destruction arising from herbivory, disease, pollution and other physical hazards. At the cellular level, an attempt is made to separate the breakdown of chlorophyll during senescence from the many other events associated with cell destruction and death.A consideration of the more important chemical and biophysical properties of chlorophylls and their derivatives is provided, together with data on their spectral properties. The biosynthetic and biodegradative pathways of chlorophyll metabolism are, so far as is possible, described with some predictions as to the likely fate of the missing tonnes. Two types of degradation are recognized; the first involves up to five defined enzymes concerned with the early stages, the second covers the less well defined enzymic and non‐enzymic destruction of the macrocyclic structure. These degradative reactions are compared with the reactions implicated in the breakdown of other porphyrins including haems in plants and animals.A brief description is given of the occurrence of breakdown products of chlorophyll in past biomass, including those of geological significance and those in a more recent archaeological context.Finally, the economic significance of chlorophyll breakdown is considered in the context of agriculture and horticulture, veterinary and medical sciences, food colouring and cosmetic industries, and the multi‐million‐dollar attraction of autumn leaf fall to tourism.ContentsSummary256I.Introduction256II.Chlorophylls: global production and destruction259III.Chlorophylls: nomenclature and chemical characteristics260IV.Chlorophyll metabolism268V.Chlorophyll degradation during senescence274VI.Other degradative conditions278VII.Breakdown products in past biomass287VIII.Pathways of degradation289IX.Economic importance291Acknowledgements294References294
EFFECT OF NITROGEN FEEDING SOURCE ON THE SUPPLY OF NITROGEN FROM ROOT TO SHOOT AND THE SITE OF NITROGEN ASSIMILATION IN MAIZE (ZEA MAYS L. CV. R201)
Authors: MURPHY A. T. , LEWISF O. A. M. 
Published: April 2006

SummaryMaize plants (Zea mays L. cv. R201) were grown to 21 d in pH‐controlled gravel culture with 2 mM inorganic N supplied as nitrate alone, ammonium alone or 1:1 nitrate + ammonium. At 21 d, the 14N feeding solutions were replaced with 15N solutions, and xylem sap collections were made 4 and 8 h after the commencement of feeding. Leaf and root material was harvested also for in vitro nitrate reductase and glutamine synthetase activity assays.Xylem sap analyses showed that in nitrate‐only fed plants the major supply of nitrogen from root to shoot was in the nitrate form (60%) with 35 % carried as amino compounds. However, 93% of 15N was transported to the shoot as nitrate and only 6% in amino compounds, indicating the more direct routing of newly absorbed nitrogen to the shoot via the former. Leaf NRA was seven‐fold greater than that of the root, confirming the shoot as the major site of nitrogen assimilation in plants fed only nitrate. In ammonium‐only fed plants, 84% of xylem N was found in organic form (66%16N), the remainder translocating as ammonium, identifying the root as the major site of ammonium N assimilation. In ammonium + nitrate fed plants, 64% of xylem N was present as organic N (55%16N), 34% as nitrate (43 %16N), indicating shared N assimilation between shoot and root, with root assimilation predominating. In plants receiving nitrate, glutamine was the major N compound translocated, in plants receiving only ammonium, asparagine predominated. GS activity was approximately the same in root and shoot and showed no response to N source.The significance of these results is discussed with respect to the reported increased productivity of maize fed a mixed nitrate‐ammonium N source.
MEMBRANE THERMOSTABILITY AND NITRATE REDUCTASE ACTIVITY IN RELATION TO WATER STRESS TOLERANCE OF YOUNG SUGAR‐CANE PLANTS
Authors: VENKATARAMANA S. , NAIDU K. MOHAN , SINGH SUDAMA 
Published: April 2006

SummaryAn assessment of tolerance to water stress based upon measurements of cellular membrane thermostability and in vivo nitrate reductase activity (NRA) was made using young leaves of sugar‐cane (Saccharum officinarum L. commercial hybrids, Co 419, Co 740 and Co 1148) subjected to stress (51 to 61 d old) and subsequent hydration.An average reduction in leaf water potential (ΨL) from −0.97 to −1.91 MPa was associated with a decrease in NRA from 2.68 to 1.13 Ψmol g f. wt−1h−1, and an increase of the membrane injury from 30.8 to 70.9%. A highly significant positive correlation between ΨL and NRA and a negative correlation between ΨL and membrane injury were demonstrated. As ΨL declined, the concentration of malondialdehyde, a lipid peroxidation product, doubled. Following rehydration, at 63 d, increases in ΨL and NRA were higher than those of membrane thermostability and malondialdehyde concentration.
15N NUCLEAR MAGNETIC RESONANCE STUDY OF AMMONIUM ION ASSIMILATION BY LEMNA GIBBA L.
Authors: MONSELISE EDNA BEN‐IZHAK , KOST DANIEL , PORATH DAN , TAL MOSHE 
Published: April 2006

Summary 15N Nuclear magnetic resonance (NMR) spectroscopy was used to follow nitrogen assimilation and amino acid production in Lemna gibba L. exposed to 0.4 mM 15NH4Cl solution for 24 h. NMR analysis of the 16N content of the treated plant tissues (aqueous extract) revealed 15N incorporation into glutamine (N‐amide plus amino‐N or amide‐N only) and glutamic acid and no detectable free ammonium ion.Methionine sulphoximine (MSO), an inhibitor of glutamine synthetase, at 1.0 mM inhibited completely the incorporation of 15N. In the presence of 0.5 mM azaserine (AZA), a glutamate synthase inhibitor, the incorporation of 15N was detected only in the amide group of glutamine. The results confirm the involvement of the glutamine synthetase/glutamate synthase (GS/ GOG AT) pathway in the assimilation of ammonium ions.
FOLIAR ENTRY AND INCORPORATION OF ATMOSPHERIC NITROGEN DIOXIDE INTO BARLEY PLANTS OF DIFFERENT NITROGEN STATUS
Authors: ROWLAND A. J. , DREW M. C. , WELLBURN A. R. 
Published: April 2006

SummaryThe uptake of atmospheric NO2 through leaf surfaces and the influence on uptake of combined nitrogen by the roots were investigated in hydroponically grown barley plants exposed to 0.3 μI 1−1nitrogen dioxide (NO2). The response to NO2 was dependent on the nitrogen status of the plant at the time of exposure. Only with low nitrate supplies to the roots did exposure of leaves to atmospheric NO2 cause significant increases in the nitrogen (N) content of barley. Levels of both nitrate and reduced forms of N increased in plants in response to the pollutant and were directly due to uptake of NO2 by leaves, since the root environment was completely sealed from atmospheric sources of NO2. Moreover, these increases were not due to the stimulation of nitrate uptake by the roots from the nutrient solution, although levels of activity of both nitrate and nitrite reductases were affected by exposure to NO2. Atmosphere NO2 did, however, affect the ability of a plant to respond to a change in the amount of nitrate supplied to the roots, and the use of both 18N‐labelled NO2 and nitrate indicated that the cycling of nitrogen within the plant was also influenced by exposure to atmospheric NO2.