bluuebunny/crossref_metadata_2025_split huggingface dataset:
THE EFFECTS OF NITRATE, AMMONIUM AND TEMPERATURE ON NITRATE REDUCTASE ACTIVITY IN SPHAGNUM SPECIES
Authors: WOODIN S. J. , LEE J. A. 
Published: April 2006

SummaryThe effects of the availability of inorganic nitrogen on in vivo activity of nitrate reductase in Sphagnum capillifolium (Ehrh.) Hedw. and Sphagnum fuscum (Schimp.) Klinggr. were investigated in both field and laboratory experiments. Nitrate reductase activity per unit mass was highest in the capitulum and declined down the stem. Nitrate reductase activity was substrate‐inducible, maximum and total activities induced being correlated with the natural logarithm of nitrate concentration in the range 0 to 10 mM. Repeated treatment with 05 mM nitrate did not give rise to repeated similar patterns of nitrate reductase activity, induction decreasing with later successive applications. An initial ammonium treatment in a field experiment did not affect nitrate‐induced enzyme activity. However, repeated applications of ammonium caused marked changes in the patterns of induction and a general repression of total nitrate reduction. This repression may result from both an effect of ammonium on nitrate uptake and a direct effect of the accumulation of ammonium or ammonium assimilation products on the enzyme itself. Repression by repeated nitrate supply may also operate in a similar way. The effects of ammonium and nitrate supply on the induction of nitrate reductase were shown to interact.The initial rate of induction of nitrate reductase activity increased with temperature, but prolonged nitrate supply resulted in highest enzyme levels at lowest temperatures. This effect may be due to greater rates of activity giving rise to greater repression by the products of nitrate assimilation at the higher temperatures. The results are discussed in relation to the use of nitrate reductase activity as a monitor of atmospheric nitrate deposition in ombrotrophic bryophyte species.
GERMINATION OF BASIDIOSPORES OF MYCORRHIZAL FUNGI IN THE RHIZOSPHERE OF PINUS RADIAT A D. DON
Authors: THEODOROU C. , BOWEN G. D. 
Published: April 2006

SUMMARYA method was developed to inoculate the surfaces of young roots of Pinus radiata D. Don uniformly with basidiospores of mycorrhizal fungi. Germination of basidiospores in the rhizosphere was 46 to 69 % in different experiments with Rhizopogon luteolus Fr. and Nord and 34 and 31 % with Suillus luteus (L. ex Fr.) S. F. Gray and 5. granulatus (L. ex Fr.) O. Kuntze, respectively. This compared with 01 % germination usually obtained for all fungi on synthetic media. Using the method, single spore cultures of R. luteolus were obtained which formed mycorrhizas on P. radiata seedlings. Germination did not respond to roots of Eucalyptus globulus Labill, Medicago truncatula Gaertn., Trifolium subterraneum L. or Lolium perenne L., showing the germination response was specific to P. radiata, although other host tree species may produce a similar response. Specificity in such mycorrhizal associations may operate both at the germination and the infection stages. It is suggested that in vivo the necessity for a host plant to stimulate spore germination is a highly effective method of inoculum conservation in the absence of host plants. The viability of inoculum remained high during storage at freezing temperatures. High spore germination rates were also obtained when the method was used in unsterilized soil.
LEAF MICROMORPHOLOGY OF SEA CLIFF AND INLAND PLANTS OF AGROSTIS STOLONIFERA L. DACTYLIS GLOMERATA L. AND HOLCUS LANATUS L.
Authors: MCNEILLY T. , ASHRAF M. , VELTKAMP C. 
Published: April 2006

SUMMARYScanning electron microscope examination of the morphology of adaxial and abaxial leaf surfaces of salt spray‐tolerant and normal plants of Agrostis stolonifera L., Dactylis glomerata L. and Holcus lanatus L. was carried out. Differences were found in degree and types of waxiness of epidermal cells, number and size of macro‐hairs and prickles, epidermal cell lengths and extent to which stomata were sunken. These differences were consistent with a reduction of the wettability, and hence salt spray damage, to adaxial leaf surfaces. Abaxial leaf surface differences were much less pronounced.
ENVIRONMENTAL CONTROL OF THE SEASONAL GROWTH OF THE SUBMERSED AQUATIC MACROPHYTE LOBELIA DORTMANNA L.
Authors: FARMER ANDREW M. , SPENCE DAVID H. N. 
Published: April 2006

SUMMARYLeaf growth, photosynthesis and soluble carbohydrate content were measured for Lobelia dortmanna L. across one year in a small oligotrophic lochan in the northwest of Scotland at a number of sites, varying in degree of exposure, sediment type, nutrient concentrations and plant form. Leaf production and loss occurred during the entire year, although production and photosynthesis were maximal in the early summer. Soluble carbohydrate was highest in the early spring, and was lowest when leaf production was greatest. Environmental changes (solar irradiance, lochan temperature and water levels) were also related to growth rates, showing a particularly strong correlation between irradiance and the relative leaf growth rate. Little influence of epiphytes or limitation of growth by nutrient or the contribution of inorganic carbon was found.
SPORNE'S ADVANCEMENT INDEX REVISITED
Authors: CHAMPMAN J. L. 
Published: April 2006

SUMMARYA new method of measuring differences between dicotyledonous families – the ‘evolutionary distance’ (ED) – is proposed. This aims to complement Sporne's ‘advancement index’ of correlated characters. The EDs of families from the Chloranthaceae and Magnoliaceae are used to predict which families may have been in existence the longest. As the Hamamelidaceae and Saxifragaceae appear to be most ancient by this method, the EDs from the Hamamelidaceae have been calculated to test this. From these EDs, other ancient or core families can be proposed. Most notable are the Sphaerosepalaceae, Buxaceae, Canellaceae, Cunoniaceae, Euphorbiaceae, Rosaceae and Tetracentraceae. By considering the ED and advancement index together, the Quiinaceae, Dipentodontaceae and Trochodendraceae can be added to this list.
COMPARATIVE ABILITIES OF LEAF SURFACES TO NEUTRALIZE ACIDIC RAINDROPS
Authors: ADAMS C. M. , HUTCHINSON T. C. 
Published: April 2006

SUMMARYA study was made of the ability of leaf surfaces of sunflower, radish, cabbage and sugar beet to neutralize acid rains (pH 30) of varying duration. Sprayings with simulated rain of 5, 15, 45 and 90 min duration were made weekly. The species were selected for their contrasting leaf surfaces (e.g. wettability, droplet retention, hairiness and thickness of epicuticular waxes). Following acidic sprays, the pH of raindrops on leaves was measured at intervals until drops dried. Leaves of cabbage and sugar beet, which had smaller areas of contact with raindrops than those of radish and sunflower, were markedly less able to neutralize acidic droplets. Droplets on the cotyledons of all species had higher pHs than droplets on the true leaves. Differences in age of true leaves, however, did not significantly affect droplet pH. The duration of rain spraying had a significant effect on leaf surface neutralization. In 2‐ and 3‐week‐old plants, long exposures to rain (i.e. 45 and 90 min) markedly increased neutralization in comparison with short exposures. In 6‐week‐old plants, the effect was the reverse; sprays of 45 and 90 min significantly decreased foliar neutralization compared with sprays of 5 and 15 min. Significant decreases in both leaf and root dry weights were found for cabbage and sugar beet treated with rain of pH 30 for 45 and 90 min, compared with both unsprayed plants and those treated with the same pH for shorter periods. Radish showed a similar but non‐significant trend.Chemical analysis of raindrops (initially pH 3–0) left on foliage for 75 min showed an increase in the concentrations of Ca2+, Mg2+ and K+, sometimes up to 50‐fold. The elemental composition of drying droplets collected on 4‐week‐old plants was not affected by the duration of previous rain exposures. In contrast, the Ca2+ and Mg2+ concentrations of drying droplets on 7‐week‐old plants exposed to 45 and 90 min rains were significantly lower than on those exposed to 5 and 15 min rains. Drying droplets differed sharply in their cation concentrations in different species. There was, however, a poor correlation between the degree of droplet neutralization and its acquired cation status. Results from a subsequent experiment using cabbage, radish, broccoli, brussel sprout and tomato, in which droplet pHs were measured over acid rain‐induced lesions and over uninjured leaf tissue, showed significantly higher pHs in the droplets over the foliar lesions.
DEPRESSED METABOLIC ACTIVITY OF VESICULAR‐ARBUSCULAR MYCORRHIZAL FUNGI AFTER FUNGICIDE APPLICATIONS
Authors: KOUGH J. L. , GIANINAZZI‐PEARSON V. , GIANINAZZI S. 
Published: April 2006

SummaryApplication to soil of either benomyl or captan significantly decreased the growth of vesicular‐arbuscular mycorrhizal (VAM) onion (Allium cepa L. cv. Hyper) plants 4 weeks after treatment but non‐VAM plants were not affected. Fungal colonization of the onion roots, as indicated by non‐vital staining with chlorozole black E, was depressed 2 weeks after fungicide application. However, decreases in metabolically active VAM fungal tissue, revealed by a succinate dehydrogenase assay, could be detected as soon as 3 d after fungicide treatment. There was little difference between the fungicides in their effect on the VAM fungi used. The usefulness of the succinate dehydrogenase assay in predicting effects of fungicide is discussed.
COLONIZATION OF WESTERN WHEATGRASS (AGROPYRON SMITHII RYDB.) BY VESICULAR‐ARBUSCULAR MYCORRHIZAL FUNGI DURING THE REVEGETATION OF A SURFACE MINE
Authors: LOREE M. A. J. , WILLIAMS S. E. 
Published: April 2006

SummaryDevelopment of vesicular‐arbuscular mycorrhizas and proliferation of roots of western wheat‐grass (Agropyron smithii Rydb.) were investigated in a revegetated mine soil in southeastern Wyoming, USA. Total rooting density (root length per volume of soil) and spore frequency increased as a function of age of the reclamation (time elapsed since reseeding). Topsoil replaced during reclamation was apparently the primary source of mycorrhizal inoculum in the most recently reclaimed site. Seedlings growing on spoil material without topsoil were generally non‐mycorrhizal, but mycorrhizal rooting density was not significantly correlated with the residual content of soil organic matter (an indicator of the proportion of topsoil in the growth media). Mycorrhizal colonization in sites up to three years old was minimal in spite of rapid increases in overall rooting density. Mean rooting density, mean degree of infection, and mean spore frequencies in older sites (five to seven years) were comparable to those of an adjacent undisturbed rangeland, but were highly variable. Mature, non‐mycorrhizal specimens were observed, suggesting that A. smithii is not highly dependent on mycorrhizal infection for survival on this disturbed site.
THE DISTRIBUTION OF MYCORRHIZAS AMONG FAMILIES OF VASCULAR PLANTS
Authors: NEWMAN E. I. , REDDELL P. 
Published: April 2006

SummaryFrom a literature search, information has been compiled on the mycorrhizal status under field conditions of 20 or more species in each of 25 families. The percentage of species which are mycorrhizal ranged from 100% in seven families to 8% in Cruciferae, many families having additional species that are sometimes mycorrhizal. No family in the list was consistently non‐mycorrhizal. Apart from the Ericaceae, the families were either predominantly ectomycorrhizal or predominantly VA mycorrhizal. However, almost all families had at least one example of each of these mycorrhizal types.
EFFECTS OF PRUNING ON THE BRANCHING HABIT OF MORUS ALBA L. AND THE ABSCISSION OF THE APICES OF THE SHORT SHOOTS
Authors: SUZUKI TAKEO , KOHNO KIYOSHI 
Published: April 2006

SummaryThe formation of long shoots and short shoots, growing out from erect one‐year‐old stems sprouted from six‐year‐old pruned stumps of mulberry (Morus alba L. cv. Shin‐ichinose), has been studied. In contrast to the branches of the unpruned trees showing an acrotonic growth habit, where only several terminal buds elongate, the buds of these stems, including the basal buds, burst simultaneously in the spring. A few upper shoots continued to elongate until autumn, forming long shoots, whilst the other shoots (lateral shoots) formed short shoots, the apices of which abscinded until early June. Excision of the long shoots before abscission of the apices of the short shoots took place resulted in continued growth of the short shoots and formation of long shoots in the upper portion of the pruned stem. The results suggest that the dominance of the upper shoots (long shoots) is maintained by a correlative control system acting between the apices of long shoots and short shoots.
THE PROBLEM OF VARIABILITY IN STOMATAL RESPONSES, PARTICULARLY APERTURE VARIANCE, TO ENVIRONMENTAL AND EXPERIMENTAL CONDITIONS
Authors: SPENCE RICHARD D. 
Published: April 2006

SummaryThe extreme variability observed in stomatal responses to identical treatments has hindered the drawing of specific conclusions about how stomata respond to environmental factors and the mechanisms that drive these responses. This review considers stomatal aperture as a characteristic response and the ramifications of the observed within‐sample variance in aperture. In the wake of past research efforts, the efficacy of experimental techniques developed to observe stomatal aperture is reviewed, environmental, morphological and physiological factors that are thought to contribute to aperture variance are discussed, and the desirability of implementing procedures to reduce aperture variance is assessed. By taking into account these considerations, researchers may be better able to plan their future efforts.
EFFECTS OF SALINITY AND NITROGEN ON GROWTH AND WATER RELATIONS IN THE MANGROVE, AVICENNIA MARINA (FORSK.) VIERH.
Authors: NAIDOO G. 
Published: April 2006

SummaryYoung plants of Avicennia marina (Forsk.) Vierh, were subjected to a factorial experiment with three concentrations of NaCl (0.1, 0.3, 0.5 M) and three of NH4C1 (0.14, 1.4, 14 mg N I−1) in solution culture for three months.Nitrogen and salinity had significant effects on dry matter accumulation in shoots and roots. In general, growth of shoots and roots was significantly greater at 0.1 M NaCl than at 0.3 and 0.5 M NaCl. Added nitrogen at 14 mg N I−1significantly increased shoot growth at 0.1 and 0.3 M NaCl. In roots, differences were significant at 0.3 M NaCl and 14 mg N I−1. Nitrogen had no significant effect on shoot or root growth at 0.5 M NaCl. At lower salinities there was greater allocation of resources to shoots at 14 mg NI−1.Increasing salinity decreased stomatal conductance, tissue water potentials and the concentrations of nitrogen and potassium in tissues. Nitrogen levels had no effect on tissue water potentials. These results are discussed in relation to the effects of salinity and nitrogen on productivity, nutrient uptake and on plant water relations.
EVIDENCE FOR INTERGENERIC TRANSFORMATION IN FILAMENTOUS, DIAZOTROPHIC CYANOBACTERIA
Authors: SINGH D. T. , BAGCHI S. N. , MODI D. R. , SINGH H. N. 
Published: April 2006

SummaryA clonal population of a mutant Nostoc muscorum, with the ability to assimilate azide as a fixed nitrogen source, was used as a source of donor DNA for transforming Anabaena doliolum from an azide‐sensitive to an azide‐assimilating phenotype. The donor DNA. transformed A. doliolum efficiently and the transformation process was sensitive to DNAase, resistant to RNAase A, dependent on photosynthetic light and required a specific contact period between donor DNA and recipient cells. The gene(s) responsible for azide assimilation appear to be located on chromosomal DNA and not on plasmid DNA. The transformants of A. doliolum resemble the azide assimilating mutant strain of N. muscorum in respect of (1) azide repression of heterocyst and nitrogenase formation, (2) azide‐dependent increase in phycocyanin to chlorophyll ratio. These results suggest that the chromosomal DNA of mutant N. muscorum, and not its plasmid DNA, is the carrier of genetic information for its azide assimilatory phenotype and that this can be transferred efficiently to A. doliolum.
BIOMETRIC ANALYSIS OF MODERN AND LATE PLEISTOCENE CONES OF PICEA FROM WESTERN CANADA
Authors: WARNER BARRY G. , CHMIELEWSKI JERRY G. 
Published: April 2006

SummaryLate Pleistocene and early Holocene fossil Picea cones and modern cones of Picea sitchensis (Bong.) Carr. from Cape Ball, Queen Charlotte Islands, British Columbia were compared for morphological variability. Modern cones of P. sitchensis from Cape Ball are most similar to populations in the area of Prince Rupert, British Columbia. The fossil cones resemble most closely modern P. glauca (Moench) Voss. and allopatric P. sitchensis × P. glauca in cone size, scale size and phyllotaxy, which suggests introgression between P. sitchensis and P. glauca in late Pleistocene time on the north coast of British Columbia. These results suggest that P. glauca and P. sitchensis migrated northward shortly after deglaciation along the coast and that P. sitchensis maintained P. glauca cone characteristics before assuming more or less independent distributional ranges along the coast of British Columbia.
WATER RELATIONS OF COCONUT PALMS AFFECTED WITH ROOT (WILT) DISEASE
Authors: RAJAGOPAL V. , SUMATHYKUTTYAMMA B. , PATIL K. D. 
Published: April 2006

SummaryThe water relations of apparently healthy and root (wilt)‐diseased coconut palms (Cocos nucifera L.) were investigated. Leaves of diseased palms had lower stomatal resistances (with relatively high transpiration rates) and leaf water potentials than apparently healthy palms. Although there was a small reduction of osmotic potential in leaves of diseased palms, there was almost complete loss of turgor potential, and flaccidity resulted.
THE HELICOIDAL CELL WALL AS A TIME REGISTER*
Authors: VIAN BRIGITTE , ROLAND JEAN‐CLAUDE 
Published: April 2006

SummaryHelicoidal cell walls are characterized by an oscillatory shift in the arrangement of cellulose microfibrils somewhat reminiscent of the rotating movement of the hands of a clock. The periodic movement can be sustained or perturbed. Thus, the helicoidal cell wall presents a temporal reading.Sensitive to temporal signals, the cell wall keeps a record of cellular events and registers very small variations, storing data at a subcellular level. The present paper emphasizes some aspects of the helicoidal cell wall relevant to timekeeping, revealing its dynamics and flexibility and leading to the question of the mechanisms of its construction.

Contents

I.
Summary
345

II.
Introduction
345

III.
Levels of timekeeping structures
346

IV.
From watch to wall
347

V.
Internal and external alterations
351

VI.
Conclusions
353

References
354
SALT TOLERANCE IN THE HALOPHYTE SUAEDA MARITIMA (L.) DUM.
Authors: CLIPSON N. J. W. , FLOWERS T. J. 
Published: April 2006

SummaryRates of ion transport and transpiration were measured during the day and night in whole seedlings of Suaeda maritima growing over a range of salinities, in order to calculate concentrations of sodium and potassium in the xylem during these periods. Mean sodium concentration in the xylem was maximal at 56 mol m−3 Na with an external salinity of 200 mol m−3 NaCl. The sodium concentration in the xylem was greater in the dark than in the light at all external salinities investigated. Comparison of the external sodium with that in the xylem indicated that sodium was more strongly excluded from the transpiration stream as salinity increased. The mean concentration of potassium in the xylem declined as external NaCl concentration increased, although selectivity for potassium increased at higher salinities. Results are discussed in relation to osmotic adjustment in S. maritima.
QUNTITATIVE ION DISTRIBUTION WITHIN ROOT CELLS OF SALT‐SENSITIVE AND SALT‐TOLERANT MAIZE VARIETIES
Authors: HAJIBAGHERI M. A. , HARVEY D. M. R. , FLOWERS T. J. 
Published: April 2006

SummarySignificant varietal differences were apparent in the survival of seedlings of maize in saline conditions but only at relatively high external concentrations (200 mol m−3 NaCl), where there was a range from 0 to 66% survival, 25 d after salinization. For the varieties examined there was a strong negative correlation between Na concentrations in the third leaf and survival. Two resistant varieties (Across 8024 and Protador) and one salt‐sensitive variety (LG11) were identified. The characteristics of ion accumulation were clearly different in salt‐tolerant and salt‐sensitive types, the difference becoming more pronounced with plant age.The distribution of ions, particular those of Na, K and Cl, was determined within subcellular compartments of roots cells using X‐ray microanalysis of freeze‐substituted tissue. Salinity induced a greater increase (about 1.7 times) in cytoplasmic Na concentration in the salt‐sensitive variety (LG11) than in resistant varieties (Across 8024 or Protador). The mean K:Na ratio in the cytoplasm of the root cortical cells in the salt‐resistant varieties grown for 15 d in saline conditions (100 mol m−3 NaCl) was twice that found for LG11.Sodium and Cl concentrations in the vacuoles decreased radially inwards from the epidermal cells in salt‐treated roots of LG11.
THE PHYSIOLOGY OF BASIDIOMYCETE LINEAR ORGANS
Authors: CLIPSON N. J. W. , CAIRNEY J. W. G. , JENNINGS D. H. 
Published: April 2006

SummaryPhosphate uptake as a function of external medium concentration has been determined for mycelium grown in the laboratory, segments of cords collected from the field and cords in the field for a range of wood‐decay basidiomycetes. Hofstee plots in all cases can be interpreted as indicating the presence of two uptake systems. Uptake of phosphate by mycelium is reduced by increasing the concentration of phosphate in the growth medium from 10 μM to 10 mM. The major portion absorbed by cords in the field remains within the segment exposed to radioactive solution, suggesting conversion of the phosphate to an immobile form unavailable for translocation.
ABSCISIC ACID AND DORMANCY IN ROOT‐NODULATED ALNUS GLUTINOSA (L.) GAERTN.
Authors: WATTS S. H. , WHEELER C. T. , HILLMAN J. R. 
Published: April 2006

SummaryTreatment of three‐month or six‐month‐old water culture plants of Alnus glutinosa with 0.1 mol m−3 (±) abscisic acid (ABA) induced formation of resting buds after 30 to 60 d. Leaf dry weight per plant decreased by 40 to 45 % during this period but root and nodule dry weights were unchanged relative to control plants. [2‐14C] ABA was taken up by the root system within 5 d and after 30 or 60 d the ABA content of plants fed 01 mol m−3 ABA was 60 and 119 times that of control plants. In control plants, the levels of ‘free’cis(Z) ABA were similar to or exceeded ‘free’trans(E) ABA in all plant parts while, in general, the converse was true for these isomers in ‘bound’ form. In ABA‐treated plants, all isomeric forms of ABA were present at much higher amounts than in the controls but, whereas in leaves and shoot apices the amount of cis ABA in both ‘free’ and ‘bound’ forms was much greater than the trans isomer, in roots and nodules trans ABA was the dominant isomer in both ‘bound’ and ‘free’ forms. Most biologically active ‘free’cis ABA thus accumulated in the leaves and shoot apex, where effects of ABA treatment on growth were most evident, whereas in roots and nodules where biologically inactive ‘free’ and ‘bound’trans ABA were dominant, growth was relatively unaffected. Amounts of ‘free’ ABA in nodules were several times those recorded previously in nodules of dormant plants, in keeping with earlier suggestions that ABA is unlikely to have a precise regulatory role in growth and dormancy of nodules.