bluuebunny/crossref_metadata_2025_split huggingface dataset:
Nitrogen fixation by Alnus incana and nitrogen transfer from A. incana to Pinus sylvestris influenced by macronutrients and ectomycorrhiza
Authors: EKBLAD ALF , HUSS‐DANELL KERSTIN 
Published: April 2006

summaryThe aims of this study were to evaluate the effect of macronutrients on nitrogen fixation in mycorrhizal and non‐mycorrhizal grey alder (Alnus incana (L.) Moench), and to evaluate the effect of ectomycorrhizal mycelium on the transfer of symbolically fixed nitrogen from grey alder to Scots pine (Pinus sylvestris L). One alder and one pine were grown together in pots with root systems separated by a 20μm mesh nylon filter which allowed hyphae but not roots to penetrate. Half the plants of both species were inoculated with Paxillus involutus (Ft.) Ft. and all alders were inoculated with Frankia. Nutrient solutions were added with macronutrient (N, K, P, Ca, Mg and S) concentrations varied according to a two‐level fractional factorial design. The plants were harvested after two growing periods in a growth chamber. Nitrogen fixation by alder and transfer of symbiotically fixed N from alder to pine was measured by 15N‐dilution. Fixed N (mg) correlated with nodule biomass in both mycorrhizal and non‐mycorrhizal alders. On average, specific nodule activity over the two periods was 510 mg N fixed R' nodule d. wt. This was not affected by mycorrhizal infection or by the different nutrient treatments. By contrast there was a strong nutrient effect on the proportion of N derived from fixation. These results indicate that the regulation of nitrogen fixation was via nodule growth rather than via nodule specific activity. Nitrogen had a strong negative effect and P a positive effect on the percentage of N derived from fixation (%Ndfa). However, the effect of N depended on the level of P. This N × P interaction resulted in a %Ndfa when N was high, of 5‐10%, at low P and 45–48%, at high P. The highest value of 90% Ndfa was found at the combination of low N and high P. Potassium had a small but statistically significant effect on the %Ndfa but Ca, Mg and S had no significant effects. No mycorrhizal effect was found on the %Ndfa in alder. By contrast, the %Ndfa and biomass were lower in mycorrhizal than in non‐mycorrhizal alders. The proportion of fixed N in pine, transferred from alder, was greatest (9%) when the pine was nitrogen starved and mycorrhizal and the alder was fixing maximally (low N and high P). However, the amount of fixed N transferred to pine was not statistically different from zero.
Allocation of carbon in mycorrhizalPinus ponderosaseedlings exposed to ozone
Authors: ANDERSEN CHRISTIAN P. , RYGIEWICZ PAUL T. 
Published: April 2006

summaryThe effect of ozone on tree growth and metabolism has been studied widely. Despite the research emphasis, relatively little is known about how the below‐ground component responds when shoots are exposed to ozone, even though evidence suggests that ozone can affect roots more than shoots. Undemanding how ozone affects carbohydrate allocation throughout the plant is essential to understanding the mechanisms of response to ozone. The purpose of this study was to follow the allocation and metabolism of carbon in aPinus PonderosaLaws.‐Hebeloma crustuliniforme(Bull.: St. Amans) Quel seedling system under ozone stress. The hypothesis that ozone affects carbon transport below ground and overall sink strength of roots. similarly in mycorrhizal and non‐mycorrhizal seedlings was tested. To test the hypothesis, a unique culturing system was used to quantify carbon movement to all components of the symbiosis and to construct an overall budget for carbon for both mycorrhizal and non‐mycorrhizal seedlings. Fluxes of CO2and carbon allocation were followed by measuring instantaneous CO2flux and by14C labelling. Two experiments were conducted that differed in their total ozone exposure (39.3 ppm h in expt 1, and 58.1 ppm h in expt 2). Mycorrhizal inoculation significantly increased CO., assimilation rates(A)and A/R (R = shoot respiration) ratios in both experiments compared with non‐mycorrhizal seedlings. Ozone exposure in expt 2 significantly decreased theA/Rratio (P < 0.003) in both mycorrhizal treatments. Below‐ground respiration was significantly greater in mycorrhizal than in non‐mycorrhizal seedlings in both experiments, and was not affected by ozone exposure, Intact, extramatrical hyphal respiration was lower by 33% in seedlings exposed to ozone, but differences were not statistically significant (P ≤ (0.167). Mycorrhizal seedling roots reached maximum respiratory14CO2release rates c. 5 h and < 20 h earlier than non‐mycorrhizal seedlings in expts 1 and 2, respectively, suggesting accelerated transport of14C below ground in mycorrhizal seedlings. Mycorrhizal seedlings also exhibited greater rates of14C release below ground than non‐mycorrhizal controls. The maximum rate of respiratory release of14CO2below ground was significantly reduced by exposure to ozone in both mycorrhizal and non‐mycorrhizal treatments. Ozone significantly reduced14C activity in the fungus of mycorrhizal plants. This constitutes the first report of an ozone‐induced reduction in carbon allocation to the fungal symbiont in a mycorrhizal association. The results suggest a substantial impact of ozone on the carbon balance of the mycorrhiza: however, there was no evidence to suggest that mycorrhizal and non‐mycorrhizal ponderosa pine seedlings responded differently to ozone stress.
An improved Solardome system for exposing plants to elevated CO2 and temperature
Authors: RAFAREL C. R. , ASHENDEN T. W. , ROBERTS T. M. 
Published: April 2006

summaryVentilated Solardomes (hemispherical glasshouses) have been used for 20 yr for studying the effects of gaseous pollutants on plants. This paper describes a computer‐operated facility for studying the effects of CO2× temperature regimes on plants. The eight chambers were set up for factorial design experiments ‐ with two levels of CO2 (ambient and ambient + 340 ppmv), two levels of temperature (ambient and 3 °C tracked continuously above ambient) and two replicates of each CO2× temperature treatment. Monitoring of environmental conditions within the chambers over a 2 yr period has shown highly effective control of CO2 and temperature regimes. Even with high‐quality and u.v.‐B transmitting glass, the irradiance in the PAR region Was reduced by 18% within the domes. Variation in temperature across the radii of the domes increased with higher photosynthetic photon flux density (PPFD). Vapour pressure deficits CVPDs) in the ambient temperature domes compared well with outside conditions hut were higher in the elevated temperature domes. The watering regime within the domes affected intermittently the relationship between ‘dome’ and ‘outside’ VPDs. The Solardome facility has been used extensively for studies of the impacts of climate change within the UK Programme on Terrestrial Initiative on Global Environmental Research (TIGER).
Growth responses of Polytrichum commune and Hylocomium splendens to simulated environmental change in the sub‐arctic
Authors: POTTER J. A. , PRESS M. C. , CALLAGHAN T. V. , LEE J. A. 
Published: April 2006

summaryTotal moss cover and the growth responses of the two dominant bryophytes within a sub‐arctic heath ecosystem,Polytrichum communeHedw, andHylocomium splendens(Hedw.) Br. Eur., were investigated in response to simulated environmental change. Temperature, water supply and nutrients (NPK fertilizer) were increased in a factorial field study in Swedish Lapland. After 3 yr of treatment, total moss caver on fertilized plots was found to be less than 50% of that on unfertilized plots.H. splendensmade a smaller contribution to total cover, and also had fewer shoots on the fertilizer treated plots. The relative contribution ofP. communeto the bryophyte community was greater on the fertilized plots, although total shoot numbers ofP. communewere not greater. There was, however, a larger number of dead shoots ofP. communeon the fertilized plots. Total moss cover, relative contribution to moss cover by P.communeandH. splendens, and the numbers of shoots of these two species, were unresponsive to both the temperature and water treatments. The growth of the current year's segment ofH. splendenswas retarded by both the fertilizer and temperature treatments. Furthermore, the dry weight of the physiologically active shoot was found to be significantly altered by all three treatments. The current year's growth ofP. communeshowed increases in d. wt and morphological parameters in response to the fertilizer treatment. There were also interactive effects of both the fertilizer and temperature treatments with the water treatment on the current year's stem length increment.
Nuclear differentiation in the filamentous caulonema of the moss Funaria hygrometrica
Authors: KINGHAM KEITH I. , DUCKETT JEFFREY G. , GLYN MATTHEW C. P. , LEITCH ANDREW R. 
Published: April 2006

summaryNuclei from different cell types in plants and animals show many features of differentiation; they differ in shape, volume, structure, ultrastructure and in the distribution of nuclear components. Using the filamentous caulonema of the moss Funaria hygrometrica Hedw. this study records the changes in cytoplasmic organization alongside the reorganization of the interphase nucleus, Events taking place in the meristematic cells at or near the lip of the advancing caulonemal filaments (e.g. acquisition of polarity, tip growth, nuclear and cell division, side branch initiation] are associated with haploid nuclei (1C DXA amount 0.5 pg) that are spherical or slightly oval, with no blocks of condensed chromatin, and a large central nucleolus with a large granular component. Maturation of the caulonemal cells involves wall thickening and pigmentation concomitant with suspension of elongate plastids in linear arrays along endoplasmic strands. Many cells become highly polarized with the majority of the organelles at their apical ends. These eytoplasmic changes are associated with endoreduplication of the genome to about 8C, endoreduplication occurs by amplification of the 1C genome to give nuclei with IC‐SC DNA amounts. There is no evidence of differential amplification of the genome. The amplification in the copy number of ribosomal RNA genes is associated with the heterochromatinisation of the genes within the nucleolus. At the same time the nucleolus reduces in volume owing to a diminution of the granular component and all components of the nucleolus become spatial separate. There is an increased nuclear volume associated with endoreduplication and the nucleus elongates causing an increase in the surface area of the nuclear envelope. These major nuclear reorganizations are associated with a stable distribution of the ‘D’ polypeptide involved in pre‐mRNA splicing. Scrutiny of published data suggests that similar differentiation events might be encountered commonly in other organisms. The changing nuclear morphology probably reflects the changing activity of the nucleus and the cell. It might be that nuclear reorganization changes the balance of genes or gene products and the spatial distribution of the component pans to enable the new nuclear functions. These results suggest that nuclear differentiation is a fundamental feature of cell differentiation.
Biochemistry and molecular biology of lignification
Authors: BOUDET A. M. , LAPIERRE C. , GRIMA‐PETTENATI J. 
Published: April 2006

SUMMARYLignins, which result from the dehydrogenative polymerization of cinnamyl alcohols, are complex heteropolymers deposited in the walls of specific cells of higher plants. Lignins have probably been associated to land colonization by plants but several aspects concerning their biosynthesis, structure and function are still only partially understood. This review focuses on the modern physicochemical methods of structural analysis of lignins, and on the new approaches of molecular biology and genetic engineering applied to lignification.The principles, advantages and limitations of three important analytical tools for studying lignin structure are presented. They include carbon 13 nuclear magnetic resonance, analytical pyrolysis and thioacidolysis. The use of these methods is illustrated by several examples concerning the characterization of grass lignins,‘lignin‐like’materials in protection barriers of plants and lignins produced by cell suspension cultures.Our present limited knowledge of the spatio temporal deposition of lignins during cell wall differentiation including the nature of the wall components associated to lignin deposition and of the cross‐links between the different wall polymers is briefly reviewed.Emphasis is placed on the phenylpropanoid pathway enzymes and their corresponding genes which are described in relation to their potential roles in the quantitative and qualitative control of lignification. Recent findings concerning the promoter sequence elements responsible for the vascular expression of some of these genes are presented.A section is devoted to the enzymes specifically involved in the synthesis of monolignols: cinnamoyl CoA reductase and cinnamyl alcohol dehydrogenase. The recent characterization of the corresponding cDNAs/genes offers new possibilities for a better understanding of the regulation of lignification.Finally, at the level of the synthesis, the potential involvement of peroxidases and laccases in the polymerization of monolignols is critically discussed.In addition to previously characterized naturally occurring lignin mutants, induced lignin mutants have been obtained during the last years through genetic engineering. Some examples include plants transformed by O‐methyltransferase and cinnamyl alcohol dehydrogenase antisense constructs which exhibit modified lignins.Such strategies offer promising perspectives in gaining a better understanding of lignin metabolism and functions and represent a realistic way to improve plant biomass.

Contents

Summary
203

I.
Introduction
204

II.
Main structural features of lignins
205

III.
Lignification and cell wall differentiation: spatio‐temporal deposition of lignins and inter‐relations with other wall components
213

IV.
Enzymes and genes involved in the biosynthesis and polymerization of monolignols
216

V.
Lignin mutants as a way to improve plant biomass and to explore lignin biochemistry and metabolism
226

VI.
Concluding remarks
229

Acknowledgements
230

References
230
The growth and gas exchange response of soil‐planted Norway spruce [Picea abies(L.) Karst.] and red oak (Quercus rubraL.) exposed to elevated CO2and to naturally occurring drought
Authors: DIXON MARTIN , THIEC DIDIER LE , GARREC JEAN PIERRE 
Published: April 2006

SUMMARYNorway spruce and red oak trees were planted directly into the soil and exposed to 700 μmol mol‐1CO2in open‐top chambers. There were large inter‐specific differences in response to naturally occurring drought during the second year of exposure to elevated CO2. Both species had decreased assimilation rates. CO2‐treated red oak had no loss of photosynthetic enhancement when undroughted, whereas CO2‐treated Norway spruce showed a relative increase in assimilation rates only when draughted. The effect of CO2on radial growth of both species was less marked in the second growing season, but this may have been a result of different biomass partitioning as Norway spruce shoot extension had a different pattern of growth in elevated CO2. Stomatal density and chlorophyll content were largely unaffected by the CO2treatment. A precise method for measuring Norway spruce needle surface area was also developed.
Carbon allocation and water use in juvenile Douglas fir under elevated CO2
Authors: GORISSEN A. , KUIKMAN P. J. , VAN DE BEEK H. 
Published: April 2006

SUMMARYIn this study the impact of an elevated CO2 level on allocation of assimilates and water use efficiency of Douglas fir [Pseudotsuga menziesii (Mirb.) Franco] was investigated. Juvenile Douglas firs were exposed to a long‐term treatment at 350 and 700 μ 1‐1 CO2 for 14 months and subsequently crosswise transferred to phytotrons for a short‐term treatment with 350 and 700 μ l ‐1 CO2 for 4 wk in an atmosphere continuously labelled with 14CO2. No interactive effects on total net uptake of 14CO2 between long‐term treatment and short‐term treatment were observed. The short‐term treatment with 700 μ 1‐1 CO2 increased the total net uptake of 14CO2 by 22%, compared with the 350 μ l ‐1 CO2 treatment. The long‐term pretreatment did not affect the total net uptake, suggesting that photosynthetic acclimation had not occurred. However, expressed per unit of needle mass a 14% reduction was observed in the trees pretreated at 700 μ l‐1 CO2. This was not because of a reduced sink strength of the root system. This reduced uptake per unit of needle mass after long‐term treatment may have implications for carbon storage in forest ecosystems. The results showed that an initial growth stimulation can eventually be annulled by developing physiological or morphological adaptions. 14CO2 in the root/soil respiration increased in the short‐term treatment with 700 μ l‐1 CO2, indicating a stimulated use of current carbon compounds either by roots or microorganisms. The water use efficiency during the short‐term treatment with 700 μ l‐1 CO2 increased by 32 %, but was not affected by the long‐term pretreatment. Water use per unit needle mass during the short‐term treatment was decreased both by the short‐term treatment and by the long‐term pretreatment by about 15%. Some of the observed effects appeared to be persistent, such as decreased water use per unit needle mass, whereas others, stimulation of total net 14CO2 uptake and water use efficiency, were transient.
Effect of temperature on wood decay and translocation of soil‐derived phosphorus in mycelial cord systems
Authors: WELLS J.M. , BODDY LYNNE 
Published: April 2006

SUMMARYUptake of 32P phosphorus from soil was investigated at 5–25 °C in mycelial cord systems of Phanerochaete velutina (D.C.: Pers.), Hypholoma fasciculare (Huds.: Fr.) Kummer and Phallus impudiciis (L.) Pers. which extended from 2cm3 beech (Fagus sylvatica) inocula, and which had initially developed at either 10 or 25 °C. Uptake of phosphorus from soil was opportunistic, being unaffected by the presence of additional wood resource units in mycelial cord systems. The magnitude of phosphorus uptake was dependent on species, temperature during uptake and the temperature at which cord systems developed. Phosphorus translocation to newly colonized baits, determined non‐destructively, was characterized by an initial rapid flux to a plateau in all three species. Initial rates of phosphorus translocation (up to 18·46 nmol P d‐1) generally increased with temperature whilst total translocation was species and temperature dependent. There was evidence that both P. velutina and H. fasciculare displayed temperature acclimation, since phosphorus uptake and translocation at lower temperatures was greater in cord systems which had developed initially at 10° compared with 25 °C. Mycelial extension and wood decay rates also varied with species, initial development temperature and subsequent incubation temperature, but did not correlate with the temperature profiles of phosphorus uptake and translocation. Results are discussed in relation to nutrient acquisition, conservation and cycling in basidiomycete mycelial cord systems.
A light‐ and electron‐microscopic study on a vesicular–arbuscular host‐fungus interaction in gametophytes and young sporophytes of the Gleicheniaceae (Filicales).
Authors: SCHMID ELFI , OBERWINKLER FRANZ 
Published: April 2006

SUMMARYGametophytes and primary roots of young sporophytes of the Gleicheniaceae were studied by means of light‐ and electron microscopy. An aseptate fungus invaded the gametophyte tissue through the rhizoids. The fungus spread within the thickened midrib forming intracellular hyphal coils. The latter gave rise regularly to arbuscules which were cytoplasmic in the young part of the midrib. In the older midrib, arbuscules degenerated and vesicles occurred. With arbuscular development, host cytoplasm and cell organelles increased and starch disappeared from plastids. The fungus formed globose spores inside the rhizoids. The gametophyte fungus did not transverse the gametophyte‐ sporophyte junction. Primary roots shorter than 2 mm were not infected. Primary roots longer than 2 mm showed vesicular–arbuscular mycorrhiza with a completely intracellular development of the fungus.
Clover as an indicator plant for phytotoxic ozone concentrations: visible injury in relation to species, leaf age and exposure dynamics
Authors: KARLSSON G. PIHL , SELLDÉN G. , SKÄRBY L. , PLEIJEL H. 
Published: April 2006

SUMMARYVisible ozone injury on leaves of three clover species was investigated in relation to species, leaf age and exposure dynamics. It was shown that ozone episodes in south‐west Sweden cause visible injury to subterranean clover (Trifolium subterraneum L.), white clover (Trifolium repens L.) and red clover (Trifolium pratense L.). Trifolium subterranean was most sensitive to ozone, whilst T. pratense was least sensitive. Application of the anti‐ozonant, ethylenediurea (EDU), reduced the extent of visible ozone injury, but did not give complete protection with the concentrations used. Similarly, filtration of the air reduced the extent of visible injury in T. subterraneum enclosed in open‐top chambers. EDU‐treated plants of T. subterranean accumulated more biomass than the non‐EDU treated plants after a period with rather high ozone concentrations, while the opposite occurred for T. pratense. Experiments with T. subterraneum in open‐top chambers also showed that older leaves were more sensitive to ozone than younger leaves and that a shorter period with higher ozone concentrations produced more ozone injury than a longer period with lower ozone concentrations, although the two periods had the same number of ppb‐hours.