bluuebunny/crossref_metadata_2025_split huggingface dataset:
COMPARATIVE EFFECTS OF FOLIAR‐OR SOIL‐APPLIED NITRATE ON VESICULAR‐ARBUSCULAR MYCORRHIZAL INFECTION IN MAIZE
Authors: AZCÓN R. , GOMEZ‐ORTEGA M. , BAREA J. M. 
Published: May 2006

SUMMARYVarious concentrations of nitrate were applied either to the rooting medium (soil) or to the foliage of maize (Zea mays L.) plants inoculated or not inoculated with the vesicular‐arbuscular mycorrhizal fungus Glomus mosseae.Certain levels of foliar‐applied nitrate and of soil‐applied nitrate had similar effects on growth of non‐mycorrhizal plants and on concentrations of nitrogen and phosphorus in their shoots. However, when the effects of these concentrations on inoculated plants were compared, plants with soil‐applied nitrate always developed much less infection.These results are further evidence that soil nitrate influences mycorrhizal development by acting on the establishment of infection rather than on spread within the root.
A POLLEN CALENDAR FOR SIENA (CENTRAL ITALY): PRELIMINARY DATA*
Authors: MURGIA M. , DE DOMINICIS V. , CRESTI M. , SILVESTRI S. 
Published: May 2006

SUMMARYA preliminary investigation on airborne pollen in Siena was carried out for 1978 using a Burkard trap. For each day pollen grains were counted according to family and expressed in number of grains trapped per m3 of air. The highest concentrations of airborne pollen grains occur in March with the Cupressaceae, Corylaceae, Butulaceae, Salicaceae and in May‐July with the Poaceae, Pinaceae, Urticaceae, Fagaceae and Oleaceae.
EFFECTS OF BENZO‐18‐CROWN‐6 ON ABAXIAL AND ADAXIAL STOMATAL OPENING AND ITS ANTAGONISM WITH ABSCISIC ACID
Authors: PEMADASA M. A. 
Published: May 2006

SummaryAbaxial and adaxial stomatal responses to benzo‐18‐crown‐6 (a synthetic K+ionophore), alone and in combination with abscisic acid (ABA), were examined on isolated epidermes ofCommelina communis. Increasing ionophore concentration progressively suppressed abaxial opening, while up to an optimum concentration it enhanced adaxial opening although higher concentrations caused closure; stomatal K+changed correspondingly. Increasing KCl progressively alleviated the ionophore‐induced closure. The effects of the ionophore and ABA were strongly antagonistic. Benzo‐18‐crown‐6 is postulated to eliminate an inherent disparity in permeability to K+between the membranes of abaxial and adaxial guard cells by making them more permeable. In normal abaxial functioning a net K+gain promotes wide opening, but the ionophore‐enhanced permeability results in a net K+loss causing closure, because the intensified efflux down a concentration gradient outweighs the influx driven by a proton pump. The normally low adaxial K+accumulation is attributed to an inherently restricted membrane permeability which benzo‐18‐crown‐6 is postulated to alleviate progressively with increasing concentration; an enhanced permeability up to an optimum level allows a net K+gain producing wide apertures, but any further increase in permeability leads to a net K+loss, like that in abaxial guard cells, causing closure. The progressive reduction of the ionophore‐induced closure with increasing external KCl supply and the strong antagonistic interaction between the ionophore and ABA support this postulation. The results suggest that the normal disparity in abaxial and adaxial opening is linked specifically with differential K+accumulation in the guard cells.
RHYTHMS OF ACIDITY AND CO2 PRODUCTION IN ORCHID FLOWERS
Authors: GOH C. J. 
Published: May 2006

SummaryAcidity fluctuations typical of Crassulacean acid metabolism (CAM) were observed in flowers of CAM orchids such as Arachnis, Aranda, Dendrobium and Vanda hybrids, but not in flowers of a C2 orchid, Oncidium Goldiana. The range of fluctuation was however, much smaller in the flowers than in the leaves. Dark 14CO2 fixation yielded labelled malate while day fixation resulted in labelled intermediates of C3 photosynthesis. A diurnal CO2 production rhythm was observed in flowers of both CAM and C3 orchids irrespective of fragrance production.
WATER POTENTIAL MEASUREMENT, WATER COMPARTMENTATION AND WATER FLOW IN DACTYLIS GLOMERATI L. LEAVES
Authors: ROY J. , BERGER A. 
Published: May 2006

SummaryWhen measuring the water potential of leaf samples in a dew‐point hygrometer, it takes several hours to achieve a constant value. It is demonstrated that this is due to water potential gradients within the sample which occur only if the leaf is actively transpiring.Water potentials have been measured on the same leaf or plant using a pressure chamber, a sample dew‐point hygrometer and an in situ hygrometer. Relatively good agreement was found in plants with zero or low transpiration, but results diverged widely when transpiration was high. It is suggested that divergences occur because the methods refer to different compartments of the leaf separated by resistances to water flow. The pressure chamber measures the water potential of the xylem vessels (ψxw), the sample hygrometer gives a value (ψcw) close to the water potential of the vacuoles and the in situ hygrometer yields a value (ψaw) close to the water potential around the evaporation sites. ψawshould logically be the most negative, but this was not always the case. On the other hand, ψxw was always and up to 10 × 105 Pa less negative than ψcw.These findings question the validity of the calibration of the pressure chamber against psychrometers or hygrometers and are relevant to the topic of water pathway in leaves.
SILICON DEPOSITION AND ANATOMICAL STUDIES IN THE INFLORESCENCE BRACTS OF FOUR PHALARIS SPECIES WITH THEIR POSSIBLE RELEVANCE TO CARCINOGENESIS
Authors: SANGSTER A. G. , HODSON M. J. , PARRY D. WYNN 
Published: May 2006

SummaryInflorescence bracts of four grasses, Phalaris canariensis, P. minor, P. paradoxa and P. arundinacea, were investigated using light microscopy, scanning electron microscopy and electron‐probe microanalysis to determine their anatomy and silicon depositional patterns.The heaviest silicon accumulation detected was associated with the outer (abaxial) epidermis of the lemma. Preferential deposition sites were located in the cell walls of the macrohairs, the walls and lumina of the long cells, and external to the epidermis, forming a thin layer of extracellular sheet or cuticular silica. Occasional silicification of internal tissues occurred in two forms, either as elongated, pointed fibres of the dendriform type, resulting from the infilling of lumina and pits of hypoderm fibres, or as rows of spongy mesophyll cells and intercellular spaces.Dimensions and silicon levels, recorded for the various siliceous structures indicated that the macrohairs and the friable sheets formed by silicification of the abaxial epidermal cells were a potential source of sharp, elongated siliceous fibres falling into the critical size range for classification as being carcinogenic. The seeds of all four Phalaris species are known contaminants of the cereal crops of the Middle East, and have been implicated as factors in the high incidence of oesophageal cancer in north‐east Iran.
LIMITED INDEPENDENT GROWTH OF A VESICULAR–ARBUSCULAR MYCORRHIZAL FUNGUS IN VITRO
Authors: HEPPER CHRISTINE M. 
Published: May 2006

SummaryThe hyphae developing from germinating resting spores of the vesicular‐arbuscular mycorrhizal fungus Glomus caledonius remain viable and can continue to grow after they have been detached from their parent spores. This new growth is at least as extensive as that present at the time when the spore was detached and is dependent on nutrients in the medium.
A COMPARISON OF GROWTH EFFICIENCY AND SPECIFIC RATE OF DARK RESPIRATION OF UNINFECTED AND VESICULAR‐ARBUSCULAR MYCORRHIZAL PLANTS OF TRIFOLIUM SUBTERRANEUM L.
Authors: SILSBURY J. H. , SMITH S. E. , OLIVER A. J. 
Published: May 2006

SummarySmall swards of mycorrhizal and non‐mycorrhizal subterranean clover plants were grown in an artificial rooting medium in pots so as to form a closed canopy, by which time plants were about 5 weeks old and had 30 % infection in mycorrhizal roots. Specific rates of dark respiration of mycorrhizal and uninfected populations of plants were compared in an incubation chamber after exposure of the sward to standard light flux density and temperature on a 12 h day/12 h night cycle. Growth efficiencies were measured by exposing a sward to variable light flux density at constant temperature and monitoring the CO2‐exchange rate.The dark respiration rate of whole plants decreased during darkness from an initial value measured immediately after the start of incubation to one about 20% lower after 12 h. Rates for excised roots decreased to about 35% of the initial value. When compared on the same basis the specific rate of dark respiration of mycorrhizal plants did not differ from that of uninfected plants. Likewise, mycorrhizal plants and uninfected plants displayed the same growth efficiency, for both used about 30 % of the net CO2 gain during the light period for purposes of biosynthesis. This parameter was not affected by phosphate nutrition. Mycorrhizal and uninfected plants responded to change in light flux density in a similar manner.It is concluded that when CO2 fluxes are measured on a whole‐plant basis over a 24 h period, mycorrhizal and uninfected plants of subterranean clover grown as swards, have essentially similar carbon economies.
HYPOXANTHINE AND ALLANTOIN AS NITROGEN SOURCES FOR THE GROWTH OF SOME FRESHWATER GREEN ALGAE
Authors: PRASAD P. V. DEVI 
Published: May 2006

SummarySix freshwater green algae, viz. Scenedesmus obliquus, Scenedesmus pannonicus, Chlorella glucotropa, Crucigenia tetrapedia, Tetradesmus cumbricus and Stichococcus mirabilis, were examined for their ability to utilize hypoxanthine and allantoin as sole nitrogen sources for growth in light. All the six algae could utilize both hypoxanthine and allantoin for growth. None of the algae needed any significant period of adaptation and growth was often as rapid on hypoxanthine/allantoin as it was on nitrate. Higher concentrations (3 mat) of the purines inhibited the growth of Stichococcus mirabilis and Crucigenia tetrapedia, possibly because of the formation of intracellular pools of the purines. Activity of the enzyme nitrate reductase was not markedly affected by growth on either hypoxanthine or allantoin. It is concluded that the ready utilization of hypoxanthine and allantoin indicates the operation of the standard pathway of purine catabolism, i.e. hypoxanthine → xanthine → uric acid → allantoin → end products, in these algae.
THE INFLUENCE OF LIGHT ON THE GERMINATION OF SENECIO VULGARIS L.
Authors: HILTON JANET R. 
Published: May 2006

SummaryAchenes of Senecio vulgaris L. show a strong positive requirement for white or red light to attain maximal germination at 20 °C. The response to light is mediated by the photoreversible photoreceptor phytochrome. The light requirement can also be satisfied by short daily irradiations with red light (660 nm) and far‐red light given at the end of daily red light photoperiods depresses germination to Cedeximately 60%. It is suggested that Pfr, the active form of photochrome, once formed, persists for between 8 and 10 h. The interactions between light, KNO3 and constant temperatures between 0 and 30 °C have also been studied.
Ca2+‐ AND MG2+‐STIMULATED ATPases FROM ROOTS OF PLANTAGO SPECIES: RESPONSE TO DIFFERENT LIGHT ENERGY FLUXES
Authors: KUIPER DAAN 
Published: May 2006

SummaryPlants of four Plantago species: P. major L ssp. major L, P. lanceolata L, P. media L and P. coronopus L were grown at two light energy fluxes. In all species, except P. major spp major, the growth of the root was more depressed with low light than that of the shoot, resulting in an increased shoot to root ratio. The shoot to root ratio of P. major ssp major was similar at both light energy fluxes.The Ca2+‐ and Mg2+‐stimulated ATPase activity of microsomal preparations of the roots was also studied. The capacity values (Vmax) of both ATPase activities were usually low in P. major ssp. major and the highest Vmax value for the Ca2+‐stimulated ATPase activity was demonstrated in P. media. Both ATPase activities (Ca2+ and Mg2+) were lower in plants grown with low light except in P. major ssp major, which showed the same Vmax values for enzyme activity in plants grown at both light levels.The lack of response of P. major ssp major to different light energy fluxes is interpreted as a lack of phenotypic plasticity of this species. The data are compared with previous results on plasticity as a response to mineral nutrition. Phenotypic plasticity is discussed as a factor in the plant's strategy for survival.
ACTIVITY OF NITRATE REDUCTASE IN TRIFOLJUMSUBTERRANEUM: EFFECTS OF MYCORRHIZAL INFECTION AND PHOSPHATE NUTRITION
Authors: OLIVEER A. J. , SMITH S. E. , NICHOLAS D. J. D. , WALLACE W. , SMITH F. A. 
Published: May 2006

SummaryActivity of nitrate reductase (NADH‐dependent), measured by in vitro methods, was present in both roots and shoots of non‐mycorrhizal Trifolium subterraneum. As expected, the activity was dependent upon the amount of nitrate supplied and was closely related to the concentration of nitrate in the tissues.Mycorrhizal plants had a greater capacity to synthesize the enzyme in both roots and shoots than non‐mycorrhizal plants when both were grown under phosphate‐limiting conditions. This conclusion was reached from the results of two types of experiment: (1) when constant (relatively low) amounts of nitrate were supplied to the plants each day, the specific activity of the enzyme in the roots declined over the period of the experiment (52 days) as the plants grew larger. There was also a decline in shoots of mycorrhizal plants. However, when the nitrate supply was increased fourfold, the stimulation of activity was considerably greater in the roots of mycorrhizal plants than in non‐mycorrhizal plants; (2) interactions between mycorrhizal infection, phosphate nutrition and nitrate reductase activity were investigated in plants which received different amounts of nitrate according to size. At the two lowest levels of additional soil phosphate (0 and 0.2 mmol phosphate per kg), there was a large mycorrhizal growth response accompanied by reduction in root: shoot ratio, increase in the phosphate concentration in the tissues and considerable stimulation of nitrate reductase activity, both on fresh weight and whole plant bases. This stimulation (together with changes in root: shoot ratio and phosphate concentration) was also apparent at 0.4 mmol phosphate per kg in the absence of any overall mycorrhizal growth response. At 0.67 mmol phosphate per kg, there was neither a growth response nor any stimulation of enzyme activity.NADPH‐dependent nitrate reductase activity, more characteristic of fungi than NADH‐dependent activity, was barely detectable and similar (very low) activity was present in both mycorrhizal and non‐mycorrhizal roots. The conclusions are that mycorrhizal effects on nitrate reductase activity are largely indirect, mediated via improved phosphate nutrition and that direct involvement of the fungi in nitrate assimilation is likely to be very slight.
ULTRASTRUCTURE AND ANALYSIS, BY LASER PROBE MASS SPECTROGRAPHY, OF THE MINERAL COMPOSITION OF THE VESICLES OF TRIFOLIUM PRA TENSE ENDOMYCORRHIZAS
Authors: STRULLU D. G. , CHAMEL A. , ELOY J. F. , GOURRET J. P. 
Published: May 2006

SummaryThe elementary composition of the fungal vesicles of Trifolium pratense L. endomycorrhizas was determined using the laser‐probe mass spectrography. Anatomical and cytological studies were also made so as to locate and describe the Endogonaceae in the infested roots of the host plant. Results obtained with fixed and unfixed samples are compared. The fixatives and embedding procedures are not convenient for elements such as potassium. It appears that the vesicles of the Endogonaceae, in addition to their high lipid contents could act as reservoirs for many elements, the principal elements detected being K, Ca, Mg and Na.
EFFECTS OF TEMPERATURE, LEVELS OF NITRATE SUPPLY AND DURATION OF LIGHT AND GROWTH ON NITRATE REDUCTASE ACTIVITY IN AGEOSTIS TENUIS AND AGROSTIS STOLONIFERA
Authors: HARRIS P. , WHITTINGTON W. J. 
Published: May 2006

SUMMARYNitrate reductase activity (NRA) was assessed at several moments within the day during the early stages of establishment of tiller generated plants and seedling swards of Agrostis tenuis and A. stolonifera grown at different temperatures and levels of nitrate supply. Agrostis tennis consistently exhibited higher NRA values than A. stolonifera at initial developmental stages or low nitrate availability. The reverse situation was found to occur at high nitrate availability or in longer established plants and seedling swards. This emphasizes the difficulties in establishing consistent differences between species in NRA. Both species showed increased NRA with increased nitrate availability, increased night temperature or decreased day temperature. Agrostis stolonifera increased its NRA to a greater extent than A. tenuis as nitrate availability increased. The importance of daily and developmental variation in NRA in establishing differences between these species is discussed.
OSMOREGULATION IN HIGHER PLANTS: EFFECT OF NaCl SALINITY ON NON‐NODULATED PHASEOLUS AUREUS L.
Authors: IMAMUL HUQ S. M. , LARHER F. 
Published: May 2006

SUMMARY Phaseolus aureus L. tolerated up to 150 mM NaClext, but with a diminished growth and an accumulation of various organic solutes characteristic of stress conditions. With increasing external salinity NH4+ accumulated in the tissues, attaining toxic concentrations at the higher levels. In consequence, the production of organic solutes such as asparagine, proline, glycine betaine and free amino acids was different from that in the control plants. Growth reduction corresponding to diminished organic matter production was due to ‘ion excess’ in the plants. NH4+ toxicity resulted in an increased accumulation of ureides and asparagine. K+, NO3−and asparagine played a key role, while sugars only a minor role as osmotica. However, a role for proline and quaternary ammonium compounds as compatible solutes in plants suffering severe salt stress can not be eliminated.
EFFECTS OF VESICULAR–ARBUSCULAR MYCORRHIZAE ON DISTICHLIS SPICATA UNDER THREE SALINITY LEVELS
Authors: BACH ALLEN EDITH , CUNNINGHAM GARY L. 
Published: May 2006

SUMMARYInland and coastal populations of the salt‐tolerant plant Distichlis spicata were grown under three salinity levels (0, 1000 and 2000 mg Na+ added kg−1 soil as NaCl) with and without inoculum of vesicular–arbuscular mycorrhizae. Mycorrhizal infection averaged 28% for the inland plants and 9% for the coastal plants, and was unaffected by soil salinity. Dry mass of non‐mycorrhizal plants was significantly higher at the low salinity for inland plants and at the intermediate salinity for coastal plants. Mycorrhizal roots had higher Na concentrations than did non‐mycorrhizal roots, but also had higher K and P concentrations, and thus maintained a high K/Na ratio. Leaf concentrations of Na were similar in mycorrhizal and non‐mycorrhizal plants. Excretion by salt glands may serve to maintain constant leaf Na concentrations. Stomatal conductances were the same for mycorrhizal and non‐mycorrhizal plants at all salinities. While mycorrhizae had little effect on D. spicata in this short‐term greenhouse experiment, a full evaluation might require long‐term field observations.
NADH CYTOCHROME C REDUCTASE ACTIVITY ASSOCIATED WITH A MEMBRANE FRACTION FROM PROTEIN BODIES OF LUPINUS ANGUSTIFOLIUS COTYLEDONS
Authors: PLANT A. R. , MOORE K. G. 
Published: May 2006

SUMMARYProtein bodies (PBs) were isolated from germinating seeds of Lupinus angustifolius L. (cv. New Zealand Bitter Blue) by centrifugation in an isotonic medium. A membrane vesicle fraction was isolated from the organelle after solubilization of the protein matrix and found to have an associated NADH cytochrome c reductase. The reductase had a broad alkaline pH optimum and NADH was the favoured electron donor (Km=11.0 μM) whilst ferricyanide, dichlorophenol indophenol and cytochrome c were effective as electron acceptors. Cations were found to enhance (NH4+, Li+, Na+, K+, Rb+, Cs+, Mg2+) or decrease (Ca2+, Sr2+) the activity. Inhibitor studies enabled the partial characterization of the PB membrane NADH cytochrome c reductase and suggested that it was of a microsomal rather than mitochondrial type.
SIEVE ELEMENTS IN THE FUCALES
Authors: MOSS BETTY L. 
Published: May 2006

SUMMARYMedullary filaments from the thalli of most of the British species of brown seaweeds belonging to the Fucales have been examined with both scanning and transmission electron microscopy (SEM and TEM). The end walls of each cell in the filament are in the form of a sieve plate. The pores, each 0.1 μm or less in diameter, are irregular in size, shape and distribution across the sieve plate. Through these small pores there is continuity of the cytoplasm. The medullary filaments provide an anatomical system throughout the thallus through which translocation can take place.
COMPARATIVE ULTRASTRUCTURAL STUDY OF THE DEGRADATION IN SOIL OF ISOLATED CUTIN FROM ILEX LEAVES AND MALUS FRUIT
Authors: MACNAMARA O. C. , BEAKES G. W. , DICKINSON C. H. 
Published: May 2006

SUMMARYCutin was dewaxed and removed from leaves of Ilex aquifolium L. (holly) and fruits of Malus pumila Mill, (apple) by a combination of chemical and enzymic techniques. Discs of cutin were then buried in soil under field conditions, retrieved at intervals and examined using electron microscopy. The ultrastructure of cutin before and after burial was compared with that of cuticle of intact holly leaves and apple fruits. Apple cutin was extensively eroded after being buried for 12 months, but neither apple nor holly cutin was completely degraded even after 2 years in soil. The significance of polysaccharide fibrils embedded in the cutin is discussed in relation to the patterns of cutin degradation which were observed and to the distribution of microorganisms in the decaying cutin.
SECRETION AND REDISTRIBUTION OF CHLORIDE IN THE DIGESTIVE GLANDS OF DIONAEAMUSCIPULA ELLIS (VENUS'S FLYTRAP) UPON SECRETION STIMULATION
Authors: REA P. A. , JOEL D. M. , JUNIPER B. E. 
Published: May 2006

SUMMARYThe localization of Cl− in the digestive glands of Dionaea muscipula Ellis (Venus's Flytrap) was studied by the AgCl precipitation technique. From these studies, the digestive cycle of Dionaea is considered to comprise two phases: a preparatory and a secretory phase. During the preparatory phase which ensues within 15 min of the start of stimulation, only the head cells of the gland accumulate Cl−. After about 5 h of stimulation, the vacuoles of the head cells appear to have undergone fragmentation. During the succeeding 2 h the head cells lose most of their Cl− accumulations and, at about the same time, Cl− appears in their outer walls. During the secretory phase, the onset of which can only be demonstrated after about 17 h of stimulation, Cl− can be seen in the endodermoid and basal cells of the digestive glands. At the end of the digestive cycle and during the time between the first and subsequent cycles only the basal cells show large amounts of Cl−.The Cl− that is redistributed is shown to be of endogenous origin and the results are discussed with respect to the functional anatomy of the gland complex.