bluuebunny/crossref_metadata_2025_split huggingface dataset:
Symbiotic exchange of carbon and phosphorus between cucumber and three arbuscular mycorrhizal fungi
Authors: PEARSON J. N. , JAKOBSEN I. 
Published: April 2006

SUMMARYCucumber (Cucumis sativus L.) was grown in an irradiated soil:sand mixture in PVC tubes containing a root compartment, a hyphal compartment and a hyphal 32P‐labelling compartment. The soil was inoculated with either Scutellospora calospora (Nicol. & Gerd.) Walker & Sanders, Glomus sp. or Glomus caledonium (Nicol. & Gerd.) Trappe & Gerdemann or left uninoculated.At 23 d from sowing 20 μCi of an aqueous solution of carrier‐free 32P was pipetted into the hyphal labelling compartment. Just 24 h later the plants were labelled with 14CO2 for 16 h. At harvest the plants were analysed for mycorrhizal colonization and distribution of 14C and 32P.Hyphae of G. caledonium proved to have the most rapid 32P uptake and transfer system of the three fungi studied. The host was provided with an order of magnitude more 32P than supplied by either Glomus sp. or S. calospora. The S. calospora‐colonized plants contained the least 32P counts of the three mycorrhizal treatments. 75% of the total 32P in the plant was present in the shoots of the plants colonized by G. caledonium; the corresponding figures for the shoots of S. calospora and Glomus sp. were 45 and 25%, respectively.The proportion of assimilated 14C allocated to below‐ground events was 35, 32 and 25 with S. calospora, Glomus sp. and G. caledonium, respectively. The specific incorporation of 14C into roots colonized by Glomus sp. was 1.8 and 3.1 times as high as into roots colonized by G. caledonium and S. calospora, respectively.In contrast, the specific root respiration (Bq mg−1 d. wt) was similar in the mycorrhizal treatments. The 14C flow into external hyphae was approximately 0.8% of the total assimilated 14C for all three fungi.Based on these results, mycorrhizal efficiency was calculated as hyphal 14C use per unit 32P transported, below‐ground 14C use per unit 32P transported, 32P transported per metre of hyphae and hyphal 14C use per metre of hyphae.
Nomenclature and diagrammatic representation of oligomeric fructans — a paper for discussion
Authors: LEWIS D. H. 
Published: April 2006

SUMMARYAs proposed at the Second International Symposium on Fructan, a paper for discussion has been prepared which suggests alternative schemes based on that by A. L. Waterhouse circulated at the Symposium. This scheme has itself been modified in collaboration with N. J. Chatterton and published together with a glossary of terms. This glossary, also slightly modified, is reproduced here. The principal alternative (and additional) proposals have been made by N. C. Carpita, C. J. Pollock and D. H. Lewis, and compiled and edited by the last of this trio.
Influence of acidic mist on frost hardiness and nutrient concentrations in red spruce seedlings
Authors: SHEPPARD LUCY J. , CAPE J. N. , LEITH I. D. 
Published: April 2006

SUMMARYTwo‐year‐old red spruce (Picea rubensSarg.) was grown in replicated open‐top chambers supplied with charcoal‐filtered air near Edinburgh, Scotland. Between May and November 1989, plants were exposed to four mist treatments, three containing sulphuric acid and ammonium nitrate in equimolar concentrations at 0.005 mol m−3(pH 5) or 1.0 mol m−3(pH 27), and a fourth treatment with sulphuric acid alone at 1.0 mol m3(equivalent to 2 mm precipitation). Two dose rates were used for the pH 2.7 treatment equivalent to 2 and 8 mm of rain per week. Three subtreatments (soil surface exposed to mist, addition of extra sulphuric acid to the soil surface, exclusion of mist from the soil) were included in each chamber. Frost hardiness was assessed by measuring rates of electrolyte leakage after controlled freezing of detached shoots.At the end of October, frost hardiness, expressed as the lethal temperature for 50% of shoots (LT50), was decreased by 8 °C in the 8 mm wk−1treatment at pH 27, compared to pH 5. The 2 mm wk−1treatment at pH 2.7 had no effect on frost hardiness either when ammonium nitrate was present or absent (i.e. sulphuric acid only). Excluding mist from the soil, and adding extra sulphuric acid, bothincreasedfrost hardiness by about 3 °C when compared with uncovered soil. Excluding mist from the soil increased the amount of foliage initiated and produced inside the chambers but neither subtreatment, excluding the mist nor providing additional sulphuric acid to the soil affected foliar nutrient concentrations. Mist of pH 27 as sulphuric acid alone and in combination with ammonium nitrate both enhanced N uptake.Several observations concerning the effect of acidic mist on frost hardiness were confirmed by this study: (i) preventing mist from reaching the soil/roots, improving conditions for root growth can ameliorate the effects of acidic mist on shoot growth and frost hardiness; (ii) the effect was determined by the ion dose but not by the ion concentration in the mist; (iii) the effect was primarily mediated through foliar absorption; (iv) the presence of high foliar nitrogen concentrations did not increase frost hardiness when foliar sulphur concentrations were also high; (v) low N concentrations were more important for frost hardiness than high foliar N concentrations.
Light environment alters response to ozone stress in seedlings of Acer saccharum Marsh, and hybrid Populus L.
Authors: TJOELKER M. G. , VOLIN J. C. , OLEKSYN J. , REICH P. B. 
Published: April 2006

SUMMARYHybrid poplar (Populus tristis Fisch. ×P. balsamifera L., cv. Tristis) and sugar maple (Acer saccharum Marsh.) seedlings were grown under contrasting light and ozone treatments to investigate the role of the light environment in their response to chronic ozone stress. In consecutive growth chamber experiments, cuttings of shade‐intolerant poplar and 3‐yr‐old seedlings of shade‐tolerant sugar maple were grown in pots for 6 and 10 wk, respectively, under shaded, low light irradiance (c. 2.5 mol m−2 d−1 PPFD or 7% of full sunlight) and six‐fold greater irradiance (c. 16.6 mol m−2 d−1 PPFD or 45% of full sunlight) in combination with low (< 10 nl 1−1) and elevated levels of ozone (c. 99–115 nl 1−1). In unshaded poplar plants, ozone exposure reduced root dry mass by 33% at final harvest, while shaded plants had no such response. By comparison, sugar maple root dry mass was reduced by ozone in shaded plants by 10%, but was unaffected by ozone in unshaded plants. In poplar, leaf area: plant dry mass ratios were unaffected by ozone, whereas in sugar maple ozone‐exposed plants had a 24% lower leaf area: plant dry mass ratio in the shaded treatment. In shade‐grown sugar maple, ozone doubled dark respiration rates of leaves, but in unshaded seedlings ozone had no effect on respiration. In comparison, in poplar plants ozone exposure resulted in greater increases in dark respiration under unshaded than shaded conditions. In unshaded plants, ozone treatment resulted in lower in situ net photosynthesis in poplar, but not in sugar maple. Overall, shade‐grown sugar maple appeared more sensitive to ozone stress than unshaded plants in terms of lower leaf area: plant dry mass ratio and root growth and higher leaf respiration. In poplar on the other hand, root growth, leaf respiration and photosynthesis were more affected by ozone in unshaded than in shaded plants. These findings suggest that shade‐grown sugar maple and unshaded poplar may experience greater reductions in carbon gain and growth under elevated levels of ozone than plants under the opposite light conditions.
Light environment alters response to ozone stress in seedlings ofAcer saccharumMarsh, and hybridPopulusL.
Authors: VOLIN J. C. , TJOELKER M. G. , OLEKSYN J. , REICH P. B. 
Published: April 2006

SUMMARYDiagnostic gas exchange measurements and foliar chemical assays were conducted on hybrid poplar (Populus tristisFisch. ×P. balsamiferaL. cv. Tristis) and sugar maple (Acer saccharumMarsh.) seedlings grown under contrasting light and ozone treatments. Seedlings were grown in low irradiance (c. 2.5 mol m−2d−1) and six‐fold greater irradiance (c. 16.6 mol m−2d−1) in combination with low (< 10 nl I−l) and elevated (99–115 nl 1−1) ozone. Analysis of light response curves showed ozone‐induced reductions in photosynthetic capacity and quantum yield for unshaded poplar and shaded sugar maple, but not the contrasting light treatments. Photosynthesis at saturating CO2concentrations was decreased in the elevated ozone treatment in both the unshaded and shaded poplar and in shaded sugar maple. Poplar had significant reductions in chlorophyll concentration due to ozone exposure in both unshaded and shaded treatments. Older leaves of unshaded poplar plants had significantly greater reductions in chlorophyll levels due to ozone than older leaves of shaded plants. In maple, only shade‐grown leaves had significant decreases in chlorophyll concentration due to ozone exposure. The diagnostic gas exchange measurements in conjunction with chlorophyll measurements indicate that in hybrid poplar, unshaded leaves may be more sensitive to ozone than shade leaves, while in sugar maple, shade leaves are more sensitive to ozone. For hybrid poplar a decrease in photosynthetic capacity, quantum yield and chlorophyll concentration in the unshaded, moderately high light environment due to elevated ozone is consistent with prior studies. The results indicating that sugar maple seedlings may be more detrimentally affected by elevated ozone in the lower light environment may have serious implications for this and other shade‐adapted species with respect to their performance in an understorey environment.
Light environment alters response to ozone stress in seedlings of Acer saccharum Marsh, and hybrid Populus L.
Authors: LINDROTH R. L. , REICH P. B. , TJOELKER M. G. , VOLIN J. C. , OLEKSYN J. 
Published: April 2006

SUMMARYBoth light conditions and ozone fumigation alter the chemical composition of tree foliage and are thus likely to influence tree‐insect interactions. We investigated the direct and interactive effects of light environment and ozone exposure on the performance of gypsy moth (Lymantria dispar L.) larvae reared on hybrid poplar (Populus tristis Fisch. ×P. balsamifera L. cv. Tristis) and sugar maple (Acer saccharum Marsh). We used a split‐plot experimental design (light nested within ozone) and fourth‐instar bioassays to calculate standard indices of insect growth and feeding performance. For insects fed poplar, consumption, growth and processing efficiencies were affected more by light environment than by ozone. Larvae ate and grew less on high‐light foliage, responses attributable to higher levels of phenolic glycosides in those leaves. For insects fed maple, no significant effects of light, ozone, or light x ozone were observed. These results demonstrate that light environment and ozone pollution can alter the dynamics of interactions between trees and associated insects and that responses are species‐specific.
Ozone effects on root‐disease susceptibility and defence responses in mycorrhizal and non‐mycorrhizal seedlings of Scots pine (Pinus sylvestris L.)
Authors: BONELLO PIERLUIGI , HELLER WERNER , SANDERMANN HEINRICH 
Published: April 2006

SUMMARYInteractions between ozone and biotic stress caused by a pathogen, Heterobasidion annosum (Fr.) Bref., in mycorrhizal [Hegeloma crustuliniforme (Bull, ex St. Am.) Quel.] and non‐mycorrhizal Scots pine seedlings were investigated using a semi‐axenic model system.Ozone exposure (200 nl 1−1, 8 h d−1 for 28 d) increased disease incidence significantly, but mycorrhizal infection completely prevented this negative effect. The presence of the pathogen on the root systems was necessary for the induction of changes in the soluble and wall‐bound secondary compounds of roots and needles; ozone alone did not induce such changes. Mycorrhizal infection appeared to have a dampening effect on the induction of these compounds. H. annosum induced a significant accumulation of the two pine stilbenes both locally and systemically in the more susceptible seedlings. In these seedlings ozone had a significant positive effect on the accumulation of both stilbenes in the roots, but it reduced pinosylvin and had no effect on pinosylvin 3‐methyl ether in the needles. The catechin content of the roots decreased in the same infected seedlings, but to a larger degree upon ozone treatment. One compound of as yet unknown structure accumulated gradually in the infected roots over the experimental period, and could thus be associated with resistance. Its accumulation was little affected by ozone treatment. Among the root cell wall‐bound phenolics analyzed, only lignin‐like material showed significant changes. The presence of the pathogen was again necessary for induction, but ozone had an inhibitory effect on this response.Pure pinosylvin applied through the hypocotyls of excised seedlings was shown to be phytotoxic, with the needles displaying discoloration and wilting as observed after pathogenic inoculation, and being characterized by a lower chlorophyll content and increased transpiration. Accumulation of pinosylvin in the needles was detected at amounts comparable to those found in the main experiment.
Nitrogen relations of the sorghum‐Striga hermonthica host‐parasite association: germination, attachment and early growth
Authors: CECHIN I. , PRESS M. C. 
Published: April 2006

SUMMARYThe probability of the parasitic angiosperm Striga hermonthica achieving a successful union with its sorghum host is in part dependent on the concentration of ammonium nitrate in the growth medium. Germination rates were higher with 1 mM than with 3 mM ammonium nitrate. Ammonium nitrate did not influence either the stability of active components of host root exudate, or their perception by the parasite's seed. High concentrations of ammonium nitrate did not significantly reduce the leakage of potassium ions from sorghum roots (although patterns of exudation may differ between groups of compounds). Thus, it appears that ammonium nitrate reduced either the production of stimulatory compounds, or their specific leakage from host roots. Subsequent attachment of the parasite radicle and early growth of the plant were also lower at higher concentration of ammonium nitrate, and possible reasons for these observations are discussed.
Responses to salinity of grapevine plants with split root systems
Authors: SHANI U. , WAISEL Y. , ESHEL A. , XUE S. , ZIV G. 
Published: April 2006

SUMMARYGrape yield, shoot and root vigour and water use by grapevine plants with split root systems were investigated. Some plants had both root parts continuously irrigated either with fresh or with saline water. Some plants got a dual treatment; one portion got fresh water and the other saline water. The irrigation water of a third group was changed during the experiment from fresh to saline water or vice versa.Fruit yield and root and shoot viability were positively correlated with the actual water use.Water ascent along the stem of the grapevines was found to be sectorial. Most of the water was supplied by the freshwater roots. Only small quantities of water were supplied by salt‐affected roots to their respective twigs.Changes in the water quality of the root medium induced a dual effect: (a) a fast response, caused by the direct change in the ambient w7ater potential; and (b) a long‐term response that developed over several weeks. The latter response was induced by the development of new roots, or by death of others, upon a change in the quality of the irrigation water.The commonly used grapevine plants of the Arava valley are negatively affected by NaCl already at concentrations below 100 mM. Under such conditions, shoot growth and fruit yield were seriously inhibited, even when one part only of the root system was exposed to saline water.
The functional ecology of Empodisma minus (Hook, f.) Johnson & Cutler in New Zealand ombrotrophic mires
Authors: AGNEW A. D. Q. , RAPSON G. L. , SYKES M. T. , BASTOW WILSON J. 
Published: April 2006

SUMMARYMires dominated by restionaceous rushes occur in valley and basin sites around New Zealand. The main restiad species is Empodisma minus which produces a surface mat of negative geotropic roots which eventually form a principal part of the underlying peat. Comparison of the peat chemistry of four such mires with a minerotrophic mire w*as consistent with their suspected ombrotrophic status. The base‐exchange capacity achieved (704 + 23.3 mequiv m−2 of the surface) by the superficial roots of Empodisma is at least as great as that of the New Zealand Sphagnum cristatum which is not dominant in ombrotrophic conditions. The widespread development of a hummock and hollow microtopography may be associated with higher rainfall regimes and the propensity of Empodisma for directing most incoming rainfall (on which its nutrient economy depends) down its wiry stems.
Gene expression under temperature stress*
Authors: HOWARTH CATHERINE J. , OUGHAM HELEN J. 
Published: April 2006

SUMMARYIn this review, changes in plant gene expression in response to environmental stresses are discussed using the examples of high and low temperature treatments. While some changes may contribute to acclimatory processes which improve plant survival or performance under stress, others may be ‘shock’ responses indicative of sensitivity. The heat‐shock response, which is almost ubiquitous among eukaryotic organisms, is characterized by repression of normal cellular protein synthesis mediated at both the transcriptional and the translational level, and induction of heat‐shock protein (HSP) synthesis. There is a correlation between HSP synthesis and induced thermotolerance in plants, but the evidence for a causal relationship is not conclusive. The possible biochemical functions of some of the HSPs are now becoming apparent; they are believed to play an important role in preventing accumulation of damaged proteins in the cell during heat shock. Although no other environmental stress elicits the full heat‐shock response, certain treatments do induce synthesis of subsets of the HSPs, and the reasons for this are considered. Alterations in gene expression in response to low temperatures are more diverse and usually less dramatic than the heat‐shock response, with which they share little, if any, homology. Biochemical adjustments during cold treatment are discussed, with particular reference to those which contribute to acclimation. Several genes whose expression is induced by cold have been cloned and characterized, and in some cases it is possible to attributein vivofunctions to them; they include enzymes of lipid, carbohydrate and protein metabolism, structural proteins and putative cryoprotectants. The use of transgenic plants is further facilitating an investigation of the biochemical factors which are important in cold acclimation. Drought, osmotic stress and abscisic acid induce expression of many of the same genes as does cold treatment; it seems likely that some of the products of these genes contribute to increased freezing tolerance by protecting against intracellular dehydration.ContentsSummary1I.Introduction1II.High temperature stress3III.Low temperature stress10IV.Concluding remarks20Acknowledgements21References21
Flooding resistance and shoot elongation in relation to developmental stage and environmental conditions in Rumex maritimus L. and Rumex palustris Sm.
Authors: Van der SMAN A. J. M. , BLOM C. W. P. M. , BARENDSE G. W. M. 
Published: April 2006

SUMMARYThe flooding resistance of Rumex maritimus L. and Rumex palustris Sm., two species from frequently flooded areas of river forelands, was studied in two large‐scale outdoor experiments. Plants were raised in cohorts and in several stages of development subjected to four weeks of submergence in early summer or in midsummer.The role of under‐water shoot elongation in raising foliage above the water line was not equally important in both species. In R. maritimus, survival following either early‐ or midsummer flooding was restricted mainly to plants which emerged from the water surface by elongating their main shoot. R. palustris was better able to survive submergence, especially under early‐summer conditions.As a consequence of survival being restricted to plants in the stem elongation stage, flooded plants of R. maritimus all reproduced in the first growing season and seed output correlated positively with stem length immediately after flooding. This was also the case for R. palustris flooded at midsummer. However, for plants of R. palustris which were flooded in early summer and remained below the water line, flowering was delayed or even postponed to the following season.Variation in seed weight was much larger in R. maritimus than in R. palustris and more clearly related to cohort and treatment effects.Differences between both species in Hooding resistance did not seem to be primarily caused by different abilities of shoot elongation, but by differences in submergence tolerance in relation to life‐history characteristics.
H+ exchange and nutrient uptake by roots of the emergent hydrophytes, Cyperus involucratus Rottb., Eleocharis sphacelata R. Br. and Juncus ingens N. A. Wakef.
Authors: SORRELL BRIAN K. , ORR PHILIP T. 
Published: April 2006

SUMMARYWe immersed the root systems of three emergent aquatic monocots (Cyperus involucratus Rottb., Eleocharis sphacelata R. Br. (both Cyperaceae), and Juncus ingens N. A. Wakef. (Juncaceae)) in nutrient agar gels with pH indicators and pH microelectrodes to study H+ exchange by root systems. For all three species, the pH changed at the tips of the adventitious roots and around young laterals. Older, lignified surfaces had little effect on pH. The pH changes around the laterals were affected by the form of nitrogen in the nutrient gel When NO3− was supplied as the N source, there was a small pH increase, whereas NH4+ enhanced H+ release, causing the pH adjacent to the laterals to decrease below 4.5. In contrast, root tips acidified the media, irrespective of the nutrient composition. H+ exchange was quantified from titrimetric assays of H+ exchange in nutrient solutions. There was a net H+ efflux from the roots of all three species into complete nutrient solutions with NH4+ as the N source, ranging from 246 μmol H+ h−1 g−1 d. wt for C. involucratus, to 32 μmol H+ h−1 g−1 d. wt for J. ingens. The H+ efflux into similar nutrient solutions with NO3− as the N source ranged from −89 μmol H+ h−1 g−1 d. wt for C. involucratus to −0.8μmol H+ h−1 d. wt for J. ingens. By assuming that H+ exchange was mainly located in the laterals, rates of H+ excretion as high as 542 μmol H+ h−1 g−1 d. wt can be calculated for C. involucratus in NH4+ solutions. Rates of H+ excretion by C. involucratus were scarcely affected by solutions of most Other ions. The NH4+‐induced H+ release was dramatically reduced by H+ pump inhibitors, attaining only 18% of control rates with 50 μM diethylstilbestrol and 38% of control rates with 5 μM dicyclohexylcarbodiimide.