bluuebunny/crossref_metadata_2025_split huggingface dataset:
Contrasting effects of elevated CO2 and water deficit on two native herbs
Authors: FERRIS RACHEL , TAYLOR GAIL 
Published: April 2006

summaryThis study investigated the effects of carbon dioxide (CO)2 enrichment and soil water deficit on the water use efficiency (WUE) and growth of Sanguisorba minor Scop, (salad burnet I and Anthyllis vulneraria L. (kidney vetch), growing in controlled environments. Instantaneous WL E (IWUE) increased in both species in elevated CO2, with a higher average increase in unwatered (UW) A. vulneraria over the drying cycle. Total plant WUE of A. vulneraria increased in elevated CO, and under water deficit: the UW plants in elevated CO., had higher WUE and reduced water loss. By contrast, thee was only an effect of water supply on S. minor: total plant WUE increased and water loss decreased in the UV plants in both CO2, treatments. Total apparent root length (ARL) of both species increased with CO2, enrichment and in UW S. minor total ARL was increased. By contrast, for A. vulneraria, total ARL of UV plants increased in ambient CO2, but decreased in elevated CO2 as compared with well‐watered (WW) plants. Shoot dry weight (SDW) and root dry weight increased in both species (WW and UW) with CO2. enrichment. For UW S. minor, SDW decreased relative to WW plants in both CO2 treatments. By contrast, ANOVA showed no significant effect of water supply on SDW of A. vulneraria. Leafier length increased in both species in elevated CO2, and decreased following drought. Cell wall tensiometric extensibility (%P) increased in expanding leaves of S. minor in elevated CO., and for both species %P decreased in the UW plants as compared with those WW. Leaf water potential (f) of both species was lower in growing leaves of WAV plants in elevated CO2 Water deficit reduced the Ψ of growing leaves in both CO2, treatments. The different responses of these species suggest that in a drier, enriched CO2, environment survival in a community might depend on their ability to maintain growth at the same time as conserving water.
Chemical changes in selected wetland plant species with increasing Fe supply, with specific reference to root precipitates and Fe tolerance
Authors: SNOWDEN R. E. D. , WHEELER B. D. 
Published: April 2006

summaryA range of wetland plant species (44) was screened in solution culture experiments for sensitivity to large concentrations of supplied Fe. Two distinct root precipitates were observed (see ‘Appendix’ for a tabulated summary of symptoms). Energy dispersive spectroscopy showed that an ochreous precipitate was probably a hydrated ferric oxide whilst a pale yellow or yellow‐grey one was an Fe‐P solid, possibly a ferric phosphate. Ochre precipitates were found almost exclusively cm the roots of Fe‐tolerant species and were particularly intense on the most tolerant ones, Monocotyledonous species (generally more Fe‐tolerant than dicotyledonous species and with higher root porosities), tended to produce ochre most freely. The Fe‐P precipitate was frequently found on roots of the less tolerant species and was particularly abundant on the most sensitive ones. Blackening of roots (with flaccidity I, another common response of roots of Fe‐sensitive plants exposed to large Fe concentrations, was not a result of any obvious external precipitate. There was no evidence that differential pH changes induced by roots helped to determine either Fe tolerance or the nature of the root precipitate observed. Roots of all species tested caused the pH of an agar medium to rise. Elevated Ft‐ supply resulted in greater external acid phosphatase activity in roots of two test species. The increase corresponded with the species' mean relative growth rate (RGR) (and presumed P requirement), and with me fertility of sites in which it grows. Chemical analyses of shoots and roots of four species of differing Fe tolerance showed that, with increasing Fe supply, mean shoot Fe concentrations increased significantly whereas for most other elements (except Na and Zn) a significant reduction in concentrations in the shoot was observed. Mean root concentrations of most elements also fell significantly with increasing Fe supply, though for three of the four test species there was a significant increase in root P concentrations. It is clear that only some wetland plant species form ochreous root precipitates when grown in Fe‐rich conditions, and have an effective Fe‐exclusion mechanism. Growth of those species that lack this capacity is affected adversely by high Fe concentrations. This might be owing both to direct effects of Fe uptake and to indirect effects, particularly of Fe upon P metabolism. No evidence was found to suggest chat the Fe‐tolerant species examined could accommodate higher tissue Fe concentrations than the Fe‐sensitive species.
Resource partitioning to growth, storage and defence in nitrogen‐fertilized Scots pine and susceptibility of the seedlings to the tarnished plant bug Lygus rugulipennis
Authors: HOLOPAINEN JARMO K. , RIKALA RISTO , KAINULAINEN PIRJO , OKSANEN JARI 
Published: April 2006

summaryWe tested how variable nitrogen availability affects the above‐and below‐ground growth of first‐year Scots pine (Pinus sylvestris L.) seedlings and carbon allocation to defensive allelochemicals and storage. Concentrations of free ammo acids were considered as indicators of nutritive quality. Suitability of seedlings for polyphagous Lygus rugulipennis Popp. (Heteroptera: Miridae) was tested with oviposition preference and nymphal growth experiments. At the end of the growing season, needle length increased while root hiomass decreased with elevated N fertilization, but shoot length was not affected. Concentration of starch in needles and roots, representing carbon storage, was not significantly affected by N fertilization, although there was a decrease in the starch concentration of needles when nitrogen input increased. Nitrogen fertilization significantly increased the pool of total and non‐essential ammo acids in the shoots. Arginine, proline and glutamine were the individual ammo acids most affected by elevated N. Of the carbon‐based defence compounds, total resin acid concentrations in shoots were significantly reduced with elevated nitrogen in 9‐wk‐old seedlings. Palustric acid and neoabietic acid were the most affected individual) resin acids, where as foliar monoterpenes were not influenced by N availability. Total phenolics in shoot and root showed variable response. The increasing effect of nitrogen on the oviposition rate of Lygus females was almost linear. Mean relative growth rate of the nymphs was significantly affected by the level of N fertilization. but the mortality of nymphs was high in all treatments. The results suggest that in nitrogen‐rich environments the needle growth of small Scots pine seedlings is improved, but their Susceptibility to insect attack is increased and they remain less defended as predicted by the carbon/nutrient balance hypothesis. Total phenolics and resin acids, representing phenylalanine and mevalonic acid pathways, respectively, were both reduced by increased nitrogen availability. Together with the simultaneous increase of foliar free nitrogen in the form amino acids, the nutritive value of seedlings is ameliorated and this might explain susceptibility of nursery‐grown. N fertilized seedlings to polyphagous Lygus bugs.
Auxin action and auxin‐binding proteins
Authors: NAPIER RICHARD M. , VENIS MICHAEL A. 
Published: April 2006

SUMMARYThe plant growth regulator auxin mediates an enormous range of developmental and growth responses, some of which are manifest rapidly and others manifest only after considerable lag periods. The protein that perceives auxin, the auxin receptor, has been sought by many laboratories and the search has identified a good number of candidates. However, a receptor must not only bind auxin, but also transduce the auxin stimulus into the responses we recognize. Finding evidence for this second condition has always proved very demanding. A key requisite is a convenient assay for auxin activity and preferably one involving a rapid response because this is likely to be linked directly to the perception event. For one auxin‐binding protein (ABP1) there is growing evidence that it is a functional auxin receptor. The assays used in this work have been rapid auxin‐induced changes in protoplast electrophysiology. There are many other responses induced rapidly by auxin for which a link to ABP1 has yet to be established. We have reviewed the whole range of rapid auxin‐mediated responses and by doing so we hope to have provided a comprehensive picture of the many events to which a receptor (or receptors) must connect. Against this framework we match the known properties of all putative receptors, including ABP1. Not only have we tried to identify auxin‐binding proteins unlikely to be receptors, but we also highlight the remaining gaps in our understanding of the more likely receptor candidates.

Contents

Summary
167

I.
Introduction
168

II.
Gene activation
168

III.
Mutants
179

IV.
Auxin‐induced elongation growth
179

V.
Other auxin‐binding proteins
191

VI.
Auxins and signal transduction
192

VII.
Overview
194

Acknowledgements
195

References
195
Interacting effects of soil fertility and atmospheric CO2 on leaf area growth and carbon gain physiology in Populus×euramericana (Dode) Guinier
Authors: CURTIS PETER S. , VOGEL CHRISTOPH S. , PREGITZER KURT S. , ZAK DONALD R. , TEERI JAMES A. 
Published: April 2006

SUMMARYTwo important processes which may limit productivity gains in forest ecosystems with rising atmospheric CO2are reduction in photosynthetic capacity following prolonged exposure to high CO2 and diminution of positive growth responses when soil nutrients, particularly N, are limiting. To examine the interacting effects of soil fertility and CO2 enrichment on photosynthesis and growth in trees we grew hybrid poplar (Populus × euramericana) for 158 d in the field at ambient and twice ambient CO2 and in soil with low or high N availability. We measured the timing and rate of canopy development, the seasonal dynamics of leaf level photosynthetic capacity, respiration, and N and carbohydrate concentration, and final above‐ and belowground dry weight.Single leaf net CO2 assimilation (A) increased at elevated CO2 over the majority of the growing season in both fertility treatments. At high fertility, the maximum size of individual leaves, total leaf number, and seasonal leaf area duration (LAD) also increased at elevated CO2, leading to a 49% increase in total dry weight. In contrast, at low fertility leaf area growth was unaffected by CO2 treatment. Total dry weight nonetheless increased 25% due to CO2 effects on A. Photosynthetic capacity (A at constant internal p(CO2), ((C1)) was reduced in high CO2 plants after 100 d growth at low fertility and 135 d growth at high fertility. Analysis of A responses to changing C1 indicated that this negative adjustment of photosynthesis was due to a reduction in the maximum rate of CO2 fixation by Rubisco. Maximum rate of electron transport and phosphate regeneration capacity were either unaffected or declined at elevated CO2. Carbon dioxide effects on leaf respiration were most pronounced at high fertility, with increased respiration mid‐season and no change (area basis) or reduced (mass basis) respiration late‐season in elevated compared to ambient CO2 plants. This temporal variation correlated with changes in leaf N concentration and leaf mass per area. Our results demonstrate the importance of considering both structural and physiological pathways of net C gain in predicting tree responses to rising CO2 under conditions of suboptimal soil fertility.
Submerged batch culture of the psychrophile Monographella nivalis in a defined medium; growth, carbohydrate utilization and responses to temperature
Authors: CAIRNS ANDREW J. , HOWARTH CATHERINE J. , POLLOCK CHRISTOPHER J. 
Published: April 2006

SUMMARYAn asporogenous strain of the pink snow mould fungus, Monographella nivalis (Schaffnit) E. Müller, anamorph Gerlachia nivalis (Ces. ex Sac.) W. Gams & E. Müller (Syn. Fusarium nivale Ces. ex Sacc.), grew at 5 °C on a denned salts medium plus vitamins and utilized a variety of simple and polymeric carbohydrates as the sole carbon and energy source. Mycelium was grown at temperatures between 3 and 15 °C in aerated submerged fermentation culture in chemically defined medium plus sucrose. Optimum growth rates of 0·035–0·033 h‐1 occurred between 9 and 12 °C. Growth in a simple medium showed that all biochemical and physiological processes necessary for growth were functional at 3 °C. The growth performance of the organism at low temperatures was no better than would be expected from extrapolation of mesophilic growth responses to temperature. The optimum growth temperature of 9–12°C showed that some biochemical or physiological process was impaired above 12 °C.Uptake and incorporation of 35S‐methionine by mycelium at different temperatures showed that general protein synthesis increased up to 25 °C, and hence was not responsible per se for the sensitivity to temperatures above 12 °C. Heat shock proteins were synthesized at the relatively low temperature of 25 °C, consistent with the low temperature optimum for growth. When grown with sucrose as the sole carbon source, the mycelium catalyzed the extracellular hydrolysis of sucrose, releasing glucose and fructose together with a small amount of fructan trisaccharides and a trace of tetra‐ and penta‐saccharides. Fructan accumulation was transient, corresponding with maximal rates of sucrose hydrolysis. Most biomass formation occurred in the absence of fructan in the culture, hence fructan was not necessary for growth at low temperature and did not appear to function as a cryoprotectant. Invertase activity was mostly (60–70%) bound to mycelium; the remainder was free in the culture supernatant. The regulation of invertase expression appeared to be by sucrose‐induction, rather than by end‐product repression. Rates of sucrose hydrolysis in culture were temperature‐sensitive and were markedly depressed above 12 °C, indicating inhibition of invertase formation.
Colonization of wheat (Triticum vulgare L.) by N2‐fixing cyanobacteria
Authors: GANTAR M. , KERBY N. W. , ROWELL P. , OBREHT Z. , SCRIMGEOUR C. 
Published: April 2006

SUMMARYTwo cyanobacterial soil isolates, Nostoc 2S9B and Anabaena C5, that had previously been shown to form different types of association with the roots of wheat plants grown in liquid culture, were tested for heterotrophic nitrogenase activity and the ability to colonize the roots of plants grown in sand. Nostoc 2S9B showed substantial nitrogenase activity when associated with the roots of plants grown in liquid culture in medium free of combined N, even with the roots maintained and with assays performed in the dark (29 % of the rate shown by root‐associated Nostoc 2S9B grown and assayed in the light). When grown heterotrophically in the dark, at the expense of fructose, free‐living Nostoc 2S9B showed a similar nitrogenase activity to root‐associated Nostoc 2S9B in the dark. In contrast, Anabaena C5 showed no nitrogenase activity in the dark, under these conditions.When three different wheat cultivars were grown in sand that had previously been surface‐inoculated with Nostoc 2S9B or with the cultured symbiotic cyanobacterium Nostoc LBG1, isolated from the bryophyte Anthoceros, there was colonization of the plant roots; there was no colonization of roots by Anabaena C5 under these conditions. Some increases in plant biomass and nitrogen content were observed, but these were dependent on the wheat cultivar and cyanobacterial inoculum used.Wheat plants grown in sand that had been pre‐inoculated with Nostoc 2S9B, Nostoc LBG1 or Anabaena C5 in medium free of combined N had lower δ15N values in both roots and shoots than plants grown under identical conditions without a cyanobacterial inoculum. The observed 15N/14N fractionation indicates that N2 fixed by the cyanobacteria contributed to the nitrogen economy of the wheat plants, irrespective of whether they were closely associated with the plant roots.
Characterization of abscission zones in the flowers and fruits of peach [Prunus persica (L.) Batsch]
Authors: ZANCHIN A. , MARCATO C. , TRAINOTTI L. , CASADORO G. , RASCIO N. 
Published: April 2006

SUMMARYCell wall hydrolases, their mRNAs, and ultrastructural details of cell wall digestion have been studied in peach abscission zones (AZ) located at the base of flower bud (AZ1) and the base of flower receptacle (AZ2), respectively.Induction of abscission was obtained by treatment of explants with exogenous ethylene. Cell separation patterns of the two examined abscission zones have been compared with those of other already known AZs of peach, i.e. the AZs located between fruit and peduncle and the leaf AZ. Analyses have shown similarities in response to ethylene treatment between AZ1 and leaf AZ and between AZ2 and AZs, respectively. Results have been discussed considering the precise position of AZ1 and AZ2 on the flower bud. The timing of functional differentiation, evaluated as the cells’ability to respond to induction by ethylene treatments, showed that AZ1 and AZ2 became functional after bud breaking and bud scale shedding. Later on, they lost their functionality at about 6–7 wk from anthesis. AZ3 became functional very precociously and could be activated 1 wk after anthesis in the fertilized flowers. In the latter zone the cells could also undergo a morphological predifferentiation, even though it occurred a long time after the acquisition of the ethylene responsiveness. This finding shows that morphological differentiation is not necessarily a prerequisite for those cells to become competent to respond to the abscission inducing stimuli.
Ectomycorrhizal fungal succession in jack pine stands following wildfire
Authors: VISSER SUZANNE 
Published: April 2006

SUMMARYA study was conducted to determine if ectomycorrhizal fungi in an age sequence of jack pine (Pinus banksiana Lamb.) stands which had regenerated following wildfire disturbance followed a successional pattern. Ectomycorrhizal development and number of symbionts were assessed in the forest floor and 0‐20 cm deep mineral soil in 6, 41, 65 and 122‐yr‐old stands by conducting a macrofungal fruit body survey and examining pine root tips microscopically for mycorrhizal status and types of fungi forming the symbiosis. The majority of roots were located in the mineral soil with no substantial invasion of the forest floor except in the 122‐yr‐old stand. Over 90 % of the jack pine root tips were mycorrhizal and the majority of fruit bodies were produced by ectomycorrhizal species, regardless of stand age. There was no decrease in ectomycorrhizal colonization of roots with stand age. Both fruit body and root assessments revealed a distinct sequence of mycorrhizal fungi with stand age consisting of early‐stage fungi [Coltricia perennis (L:Fr.) Murr., Thelephora spp., E‐strain]; multi‐stage fungi [Suillus brevipes (Pk.) Kuntze, Inocybe spp., Cenococcum geophilum Fr., Mycelium radicis atrovirens Melin] and late‐stage fungi [Cortinarius spp., Lactarius spp., Russula spp., Tricholoma spp., Hygrophorus spp., Hydnellum peckii Banker, Suillus tomentosus (Kauff.) Sing., Snell & Dick, Piloderma byssinum (Karst.) Jül. and Sarcodon scabrosus (Fr.) Karst.]. Many of the basidiomycete species fruiting above ground were detected also on the roots below ground. Fruit bodies of SO species of ectomycorrhizal fungi were recorded while 39 distinct mycorrhizal types were identified on the roots. There was a significant increase in mycorrhizal species richness between the 6 and 41‐yr‐old stands and this was primarily the result of partial replacement of Suillus brevipes on the 6‐yr‐old trees by late‐stage fungi in the older stands. Very few species present in the 6‐yr‐old stand were completely replaced in the older stands; rather, the multi‐stage species present in the young stand were joined by late‐stage species in the mature stands. The species abundance distribution of fungi on the roots in the 6‐yr‐old stand was best described by a geometric series which is typical of an early successional community while the distributions in the three oldest stands conformed to a lognormal series which is indicative of a stable, species rich community. Both the composition and structure of the ectomycorrhizal community had stabilized 41 yr after wildfire.
Differential toxicity of heavy metals is partly related to a loss of preferential extraplasmic compartmentation: a comparison of Cd‐, Mo‐, Ni‐ and Zn‐stress
Authors: BRUNE ANDREAS , URBACH WOLFGANG , DIETZ KARL‐JOSEF 
Published: April 2006

SUMMARYBarley was grown at inhibitory concentrations of cadmium, molybdenum, nickel and zinc. Primary leaves were analyzed for cellular and sub cellular compartmentation of the heavy metals. Epidermis and mesophyll protoplasts, mesophyll vacuoles and chloroplasts were isolated and apoplasmic washing fluid prepared, and the heavy metal contents of the various fractions determined. Efflux experiments showed that heavy metals were not lost from the preparations within the time span of the experiment. The different heavy metals were subjected to distinct distribution mechanisms within the leaves: (1) On a relative basis, the order of preferred epidermal accumulation was Cd = Zn > Mo > Ni (P < 0.01). (2) Within the mesophyll, Mo showed the highest degree of vacuolar compartmentation, whereas Ni was compartmentalized into the cytoplasm including chloroplasts to almost 80%. (3) The low degree of vacuolar compartmentation was correlated with the development of damage in the leaves, as visualized by chlorosis and decreased quantum yield efficiency. (4) Damage was inversely correlated with apoplasmic compartmentation. (5) Interestingly, sulfhydryl contents of stressed leaves were neither positively nor negatively correlated with toxicity of the heavy metals: maximum induction was seen in the presence of Cd, followed by Zn, and no changes under Ni and Mo‐stress. Increases in leaf SH‐contents were small as compared with induction in the roots.
Acid invertase in mycorrhizal and non‐mycorrhizal roots of Norway spruce (Picea abies [L.] Karst.) seedlings
Authors: SCHAEFFER CHRISTOPH , WALLENDA THOMAS , GUTTENBERGER MARTIN , HAMPP RÜDIGER 
Published: April 2006

SUMMARYSucrolytic enyzme activities and concentrations of hexoses typically increase in plant/microbe symbioses. However, there is little information on ectomycorrhizal associations. We measured invertase activity and soluble sugar contents in roots of mycorrhizal and non‐mycorrhizal Norway spruce [Picea abies (L.) Karst.] seedlings. We used two ectomycorrhizal fungi, a basidiomycete [Amanita muscaria (L. ex Fr.) Hooker] and an ascomycete (Cenococcum geophilum Fr.). Mycorrhizas and non‐mycorrhizal short roots, as well as other parts of the root system, were investigated at different developmental stages by micro‐analytical methods.Neither sucrose nor invertase could be detected in fungal mycelia. In vitro measurable invertase activity and the sucrose, glucose and fructose content were reduced in both types of mycorrhizas compared with the non‐mycorrhizal short roots. Correction of data for the fungal component in the mycorrhizas, indicated that there were no differences in plant‐specific amounts of sucrose and acid invertase activity in mycorrhizal and non‐mycorrhizal roots. However, amounts of glucose and fructose, which are present in both partners, were clearly reduced in the mycorrhizas. As high fructose levels inhibit acid invertase, a reduction in the amount of fructose in the symbiotic tissue could favour in vivo acid invertase activity. Our results indicate that the situation in ectomycorrhizas may be different from those in other biotrophic interactions.