bluuebunny/crossref_metadata_2025_split huggingface dataset:
An analysis of the balance between root and shoot activity in Lolium perenne cv. Melvina. Effects of CO2 concentration and air temperature
Authors: NIJS IVAN , IMPENS IVAN 
Published: March 2003

SUMMARYThis study investigated the mechanisms which control the partitioning between roots and shoots in plants subjected to changes in environment. Two types of analyses were used: firstly, an examination of the cost and revenue associated with investment in different plant parts, and secondly, a test of the principle of functional equilibrium between roots and shoots, i.e. whether root dry matter × root specific activity balances shoot dry matter × shoot specific activity. Measurements were made on individual plants of Lolium perenne in sunlit controlled environments, grown from germination to canopy closure under optimal nitrogen supply. At the final harvest, increased air temperature (+ 4 °C above ambient) reduced whole‐plant dry matter by 12% relative to the control, whereas elevated CO., mole fraction (700 μmol mol −1) led to a 38 % gain. The combined treatment yielded an intermediate result (+ 19%). Plants grown at + 4°C maintained balanced activity between roots and shoots throughout the experimental period, irrespective of CO2 concentration. This required enhanced allocation to roots in young plants to compensate for a strong negative effect of higher temperature on root specific activity, which suggests that plants conserve balanced activity by adjusting dry matter partitioning. The extra cost involved with the adjustment at +4°C significantly enhanced the cost:revenue ratio of plant investment. In ambient temperature, the balance between roots and shoots departed from equilibrium, slightly at ambient but substantially at elevated CO2: the plants accumulated excess carbon relative to nitrogen, and this imbalance increased with plant age. At elevated CO2, the cost: revenue ratio increased in young plants but this was later reversed owing to loss of root specific activity, which explains the gradually declining CO2, stimulation with time. The strategies in equilibrating root and shoot functioning observed in the different treatments are discussed in the light of whole plant performance.
Environmental factors and genotypic changes in lipids contribute to the winter hardiness of Norway spruce (Picea abies)
Authors: WELLBURN ALAN R. 
Published: March 2003

SUMMARYLipids were extracted from needles of Norway spruce plants of different provenances. The plants, seeds of which were originally collected from all over Europe, were grown at two sites in England at the same longitude but one 350 km north of the other. Significant correlations were observed between monogalactosyl diglyceride (MGDG) and digalactosyl diglyceride (DGDG) ratios on the one hand and, on the other, the lowest extreme winter temperature at the original site of seed collection (EWTS).In the case of lipid changes, however, environmental differences due to site were more important than the inherent genotypic characteristics of the planted trees while provenances with the lowest EWTS values had more MGDG than DGDG. This implies that existing winter hardiness under mild climatic conditions does not come from changes in this ratio although DGDG formation from MGDG is known to be an important feature of winter hardening in Norway spruce elsewhere in Europe. However, closer analysis of the fatty acids in lipids from provenances at individual sites did reveal significant correlations between those provenances with low EWTS values and certain molar amounts or ratios of fatty acids in DGDG, some of which could be traced to genotypic expression. These partly involved the unusual Δ5 desaturations which are mainly confined to the fatty acids of those conifers like Norway spruce that harden to very low temperatures.
The influence of nitrogen fertilization on the carbon economy of Paxillus involutus in ectomycorrhizal association with Betula pendula
Authors: EK H. 
Published: March 2003

SUMMARYMycorrhizal mycelium was allowed to grow into a compartment from which roots were excluded. Ammonium or nitrate was supplied exclusively to the fungus and the respiration rate before and after nitrogen addition was measured. Mycelial respiration in the fungal compartment represented 11–29%, of total fungal and root respiration. The mycelium in the fungal compartment received 20–29% of shoot net assimilation, and 43–64%, of the carbon allocated to the mycelium was respired. The nitrogen‐induced respiration increase ranged, in the fungal compartment, from 54 to 180%.
Responses to water stress in an ABA‐unresponsive hybrid poplar (Populus koreana×trichocarpa cv. Peace) III. Consequences for photosynthetic carbon assimilation
Authors: RIDOLFI MICHÉLE , DREYER ERWIN 
Published: March 2003

SUMMARYNet CO2 assimilation rates and chlorophyll a fluorescence were measured on leaves of an ABA‐unresponsive poplar (Populus trichocarpa×koreana cv. Peace) during a period of drought. Stomata of fully expanded leaves of ‘Peace’ partly closed during drought, while those of Populus euramericana cv. Robusta closed almost completely. The measured data were used to calculate total light‐driven electron flows and to derive an estimate of a CO., mole fraction in the chloroplasts. Two major results were obtained, (i) In well watered plants, photosynthesis operated at lower CO2 mole fractions in the chloroplasts of cv. Peace than in those of cv. Robusta, whereas CO2 mole fractions in the sub stomatal spaces were of the same order of magnitude. We concluded that a higher resistance to CO2 influx in the mesophyll contributed to the lower net assimilation rates in ‘Peace’, (ii) Drought induced an important decrease in CO2 availability in ‘Robusta’ but not in ‘Peace’. This suggested that reduced CO2 influx was a major cause of the limitation of net CO2 assimilation during drought in ‘Robusta’, but not in ‘Peace’, where drought probably reversibly reduced the apparent carboxylation efficiency of Rubisco. Measurements of O2evolution under saturating CO2 supported this view, as photosynthesis decreased in draughted plants of ‘Peace’ but not of ‘Robusta’. Moreover, estimates of the 13C/12C isotope ratio in the leaves of both cultivars showed drought‐related decreases in discrimination, which, in the case of ‘Peace’, could only be explained by changes in activity of the photosynthetic carbon reduction cycle.
Xerophytic implications of increased sclerophylly: interactions with water and light in Hakea psilorrhyncha seedlings
Authors: GROOM PHILIP. K. , LAMONT BYRON B. 
Published: March 2003

SUMMARY Hakea psilorrhyncha R. M. Barker seedlings were subjected to a two‐way interaction experiment with two levels of water availability and two levels of light. Physiological drought was imposed by adding 6000 MW polyethylene glycol (PEG), at an osmotic potential of − 0.56 MPa, in a continuous‐flow drip irrigation system. Unstressed plants (‐PEG) were watered with distilled water (osmotic potential of −0.01 MPa). Seedlings were grown under natural light (120–500 μmol m−2 s−1 sunlight at midday + L) or shaded (< 150 μMmol m−2 s−1 sunlight at midday; – L. Plant morphology tissue water relations and carbon isotope composition ($13C) were measured after 12 wk growth. The smallest leaves had the highest mass per unit area (LMA, an index of sclerophylly) and were present in the + PEG+ L treatment, whereas the largest, thickest leaves had the lowest density and were produced in the – PEG + L treatment. Plants in shade were smaller and less sclerophyllous. There was a linear decrease in osmotic potential at full turgor and turgor loss point, and an increase in elastic modulus and $13PC, as level of sclerophylly increased, with ‐PEG‐L leaves at one extreme and +PEG + L at the other. We conclude that high levels of sclerophylly induced by low water availability and high light intensity are associated with substantial drought tolerance in H. psilorrhyncha.
Spontaneous hybridization of the putative ancestors of the allotetraploid Poa annua
Authors: DARMENCY H. , GASQUEZ J. 
Published: March 2003

summarySpontaneous hybrids between the two diploids Poa infirma Kunth and P. supina Schrader were obtained at the rate of 0.2%. No reciprocal maternal effect was observed. Almost all hybrids survived, grew normally but were sterile. Hybrids were diploid, and resembled in morphology the tetraploid P. annua L. (annual meadow grass). In their isozymes, they showed additivity of the parental patterns, and were very similar to those found in P. annua populations. The ease with which hybrids were obtained and the similarity of their morphological and isozyme pattern to P. annua suggest that the two diploid species are closely related to the allotetraploid species, and are perhaps its parent species.
Root production and turnover and carbon budgets of two contrasting grasslands under ambient and elevated atmospheric carbon dioxide concentrations
Authors: FITTER A. H. , GRAVES J. D. , WOLFENDEN J. , SELF G. K. , BROWN T. K. , BOGIE D. , MANSFIELD T. A. 
Published: March 2003

summaryMonoliths of two contrasting vegetation types, a species‐rich grassland on a brown earth soil over limestone and species‐poor community on a peaty gley, were transferred to solardomes and grown under ambient (350 μ 1−1) and elevated (600 μ11−1) CO2 for 2 yr. Shoot biomass was unaltered but root biomass increased by 40–50% under elevated CO2. Root production was increased by elevated CO2 in the peat soil, measured both as instantaneous and cumulative rates, but only the latter measure was increased in the limestone soil. Root growth was stimulated more at 6 cm depth than at 10 cm in the limestone soil. Turnover was faster under elevated CO2in the peat soil, but there was only a small effect on turnover in the limestone soil. Elevated CO2 reduced nitrogen concentration in roots and might have increased mycorrhizal colonization. Respiration rate was correlated with N concentration, and was therefore lower in roots grown at elevated CO2. Estimates of the C budget of the two communities, based upon root production and on net C uptake, suggest that C sequestration in the peat soil increases by c. 0.2 kg C m −2yr−1(= 2 t ha yr−1) under elevated CO2.
Phosphorus allocation and utilization in three grass species with contrasting response to N and P supply
Authors: RYSER PETER , VERDUYN BETTY , LAMBERS HANS 
Published: March 2003

summaryThe growth of the grass Brachypodium pinnatum (L.) Beauv. in Dutch nutrient‐poor chalk grasslands increases with enhanced nitrogen supply, whereas other grass species also require an enhanced phosphorus supply for a similar response (e.g. Dactylis glomerata L.), or are competitively suppressed at any increase in nutrient supply (e.g. Briza media L.). We investigated whether this interspecific variation in response to N and P supply is caused by differences in P productivity (PP), i.e. the instantaneous rate of biomass production per unit of P present in the plant. We hypothesized that PP is highest in Brachypodium pinnatum, in contrast to N productivity which is known to be the highest in Dactylis glomerata. Phosphorus productivity and its components were studied using a growth analysis with four exponential P addition rates of 0.03, 0.06, 009 and 0.11/0.15 mg P mg−1P d−1.Although Brachypodium pinnatum allocated more P to its leaf blades, it had a lower P productivity at high N and low P supply than did Dactylis glomerata. This was associated with a higher productivity per unit leaf P in Dactylis glomerata. Across all species and treatments, leaf PP showed a distinct negative correlation with P concentration per leaf area, regardless whether the variation in area‐based leaf P concentration was caused by variation in leaf thickness, leaf tissue mass density or mass‐based P concentration. A possible explanation for this would be a positive correlation between leaf chlorophyll concentration and P concentration, leading at high concentrations to shading within the leaf and to a low photosynthetic rate per unit leaf P. We conclude that a high pp is determined by the ability of a plant to distribute its P over a large leaf area, rather than by greater allocation of P to the leaves. Interspecific relationships for P productivity are similar to those known for N productivity.
Performance of the thistle gall fly, Urophora cardui, in relation to host plant nitrogen and mycorrhizal colonization
Authors: GANGE ALAN C , NICE HELEN E. 
Published: March 2003

summaryMany hypotheses have been developed to explain the adaptive nature of insect galls. One of these, the nutrition hypothesis, states that gall formers have advantages over other insects because gall tissue provides a better (higher quality) food source than unmodified tissue. However, this has rarely been experimentally tested. In a test of this hypothesis, we grew plants of Cirsium arvense (L.) Scop. in a factorial design with two main treatments: the addition of nitrogen (to enhance foliar N levels) and of fungicide (to reduce colonization of roots by arbuscular mycorrhizal fungi). Mycorrhizal fungi have been shown previously to reduce the N concentration of host plants. Plants were exposed to adult gall flies, Urophora cardui L., and maintained through one season to allow maturation of galls.Reduction of the percentage mycorrhizal colonization by fungicide resulted in an elevation of total stem N comparable to that achieved by N addition, but gall N concentration remained unchanged in all treatments. Nitrogen application elevated stem N levels when mycorrhizal fungi were present, but application of both compounds together did not result in any increase over either single treatment. Fungicide application resulted in larger galls, which contained more larval chambers, with more live, and heavier, larvae. However, the main effects of N were not significant, as N addition only increased fly performance on plants where mycorrhizas were not reduced.It is suggested that U. cardui gall inhabitants can manipulate N at an optimal level and thus might conform to a modified version of the nutrition hypothesis. Mycorrhizal colonization might reduce gall fly performance by delaying the appearance, or impairing the quality, of secondary nutritive tissue in the gall. Future tests of the nutrition hypothesis should include a consideration of the plant's mycorrhizal status.
Genetic structure of a natural population of the ectomycorrhizal fungus Suillus pungens
Authors: BONELLO PIERLUIGI , BRUNS THOMAS D. , GARDES MONIQUE 
Published: March 2003

Sequence‐based markers were developed to study the genetic structure and reproductive biology of the ectomycorrhizal fungus Suillus pungens Thiers & Smith in a Bishop pine (Pinus muricata D. Don) forest. Six different basidiome genotypes were found in a 1200 m2 area. Five of the six genotypes were represented by single basidiomes. The remaining genotype comprised 13 basidiomes and covered an area of at least 300 m2, with maximum measured dimensions of 40 m and 14 m. This is the largest genet of an ectomycorrhizal fungus described to date, and is likely the result of vegetative growth, because analysis of single spore isolates eliminates the possibility of genetic identity resulting from either apomixis or fortuitously indistinguishable recombinant genotypes. Genetic analysis also shows that although out‐crossing appears to predominate in the population, at least a low percentage (1·4%) of spores are secondarily homothallic.The combination of extensive vegetative growth and abundant fruiting suggests S. pungens utilizes more carbon than might be expected for a species which accounts for <3% of the total ectomycorrhizal abundance at the site. Additional carbon might come from either more efficient host–fungus transfer, pooling of carbon from the roots of different host plants, or saprophytism.
The response of Norway spruce seedlings to simulated acid mist
Authors: SHEPPARD LUCY J. , LEITH IAN D. , MURRAY MAUREEN B. , CAPE J. NEIL , KENNEDY VALERIE H. 
Published: March 2003

Four pot experiments are reported in which Norway spruce (Picea abies (L.) Karst) seedlings, of different nutrient status, were treated with acid mist for one growing season in open‐top chambers (OTCs). Combinations of H+, SO42−, NH4+ and NO3− were applied at different frequencies of application and supplying different doses of S and N kg ha−1. Plant growth, visible injury, frost hardiness and nutrient status were observed. These experiments were undertaken to improve our understanding of the interaction of environmental factors such as nutrition and mist‐exposure frequency on seedling response to N and S deposition.Both acidity (pH 2·7) and SO42− ions were necessary to induce visible injury. Mist containing SO42−, H+ and to a lesser extent NH4+ significantly reduced winter frost hardiness. Increasing the misting frequency, and to a lesser extent the overall dose, increased the likelihood of acid mist causing visible injury and reducing frost hardiness. Post‐planting stress, low N status and needle juvenility increased the likelihood of acid mist causing visible injury. Increased plant vitality, adequate N status and growth rate reduced the likelihood of acid‐mist‐induced reductions in frost hardiness.Principles underlying the responses of spruce seedlings treated in controlled conditions to acid mist are discussed.
Ozone and forest trees
Authors: BROADMEADOW MARK 
Published: March 2003

Current estimates of forest yield losses attributable to ozone pollution amount to c. 10% over Europe as a whole. This figure is derived from a synthesis of all European studies using trees for which AOT40 exposure values are available. However, the choice of 40 nl l−1 as the threshold concentration for demonstrable effects has led to debate, and this value might not be low enough to predict ozone effects in Scandinavia, where concentrations are lower than in southern Europe, and chronic injury resulting from cumulative exposure is observed. This ‘level I’ approach provides a useful means for mapping physiologically effective concentrations but has significant shortcomings in that it is unable to take environmental conditions into account. In order to produce a mechanism capable of predicting yield losses resulting from ozone pollution at specific sites and for individual species, the effective ozone dose, a product of conductance and concentration, must be calculated. Process‐based models relating the environment (temperature, humidity/saturation deficit, incident light and soil moisture content) to conductance are available for a number of species (oak, Scots pine, Norway spruce, Sitka spruce, beech and poplar). Effective ozone doses could therefore be calculated, and the relationships between effective dose and yield loss could be determined by revisiting existing data for which only concentrations or AOT40 values are available at present. Yield loss must be the growth parameter with which ozone damage is expressed, since visible injury does not necessarily represent severe injury to the plant, whilst visibly unaffected plants may be significantly compromised in terms of biomass accumulation. For conifers, premature needle drop, although indicative of ozone pollution, might not represent a significant reduction in growth since older needles are, functionally, relatively unimportant.When revisiting old experiments the question should also be asked ‘what is an appropriate control treatment’. It is unrealistic to expect ambient O3 concentrations on a global scale to return to pre‐industrialization levels, and therefore the use of a charcoal‐filtered treatment is probably unrealistic. In addition, charcoal filters will remove some of the NOx, and therefore on nutrient deficient soils (typical of many forest soils) the ‘control’ treatment might represent a reduced supply of nitrogen, making it difficult to disentangle the ozone effect per se.The stage has therefore been reached where ‘level II’ ozone exposure mapping (i.e. based on effective dose at the physiological level) is possible for a number of species. As financial considerations become increasingly important, the scientific community must aim to provide better estimates of O3‐induced yield losses so that long‐term environmental audits can be performed.
Interactions between pea root‐inhabiting fungi examined using signature fatty acids
Authors: Larsen John , Bødker Lars 
Published: March 2003

Summary

• Interactions are investigated between the arbuscular mycorrhizal fungus, Glomus mosseae, and the root pathogen, Aphanomyces euteiches, on pea (Pisum sativum) roots, as arbuscular mycorrhiza are known to suppress a broad range of root pathogens.

•  Phospholipid (PLFA) and neutral lipid (NLFA) fatty acids were used as indicators of biomass and energy reserves, respectively, of A. euteiches and G. mosseae in inoculated roots of pot‐grown pea seedlings.

• Symbiosis between pea and G. mosseae had no effect on the severity of disease caused by A. euteiches, which decreased pea shoot and root dry weight. However, the presence of G. mosseae in pea roots reduced both biomass and energy reserves of A. euteiches, indicated by a reduction in PLFA 14 : 0 and both NLFAs 14 : 0 and 14 : 1ω9. Similarly, a reduction in PLFA and NLFA 16 : 1ω5 indicated reduced biomass and energy reserves of G. mosseae in A. euteiches‐infected roots.

•  Signature fatty acids can be used to quantify biomass and energy reserves of G. mosseae and A. euteiches simultaneously, in pea root; this appears to be a promising method for studying interactions between arbuscular mycorrhizal fungi and root pathogens in planta.
Rice carbon balance under elevated CO2
Authors: Sakai Hidemitsu , Yagi Kazuyuki , Kobayashi Kazuhiko , Kawashima Shigeto 
Published: March 2003

Summary

Season‐long effects of elevated CO2 concentration ([CO2]) on the carbon balance of the rice (Oryza sativa) canopy are reported here.
The experiment was conducted in six sunlit, semiclosed growth chambers for an entire growing season. Rice plants (cv. Nipponbare) were grown at 350 µmol mol−1[CO2] (ambient) in three chambers, or at 650 µmol mol−1 (elevated) in the other three chambers. Canopy net photosynthesis and night‐time respiration were determined in the chambers by mass balance.
Both canopy gross photosynthesis and total respiration, through the entire growing season, were increased by the CO2 enrichment. But CO2‐induced variations in canopy carbon gain were mainly caused by changes in canopy photosynthesis. The enhancement of daily canopy gross photosynthesis by elevated [CO2] was 33.4% for the first 3 week, but it declined gradually and disappeared by heading. Enhancement of daily net carbon gain also decreased as rice plants grew.
These results show that the increase in rice biomass by elevated [CO2] results more from the increase in carbon gain at early rather than later stages of growth.