bluuebunny/crossref_metadata_2025 huggingface dataset:
The profusion of dark septate endophytic fungi in non‐ectomycorrhizal fine roots of forest trees and shrubs
Authors: AHLICH KARIN , SIEBER THOMAS N.
Published: April 2006

summary

Endophytic fungi were isolated from surface‐sterilized non‐ectomycorrhizal fine roots of 14 shrub and forest tree species of the northern temperate zone. With the exception of three host species, between 70 and 100% of the roots of each host yielded endophytic fungi. Species diversity was tow. Thirty‐five taxa were found, nine of them in more than 1% of the 421 tree/shrub individuals examined. Dark septate endophytes (DSE; Mycelium radicis atrovirens‐complex dominated the fungal assemblages of coniferous and ericaceous hosts. About one fifth of the DSE sporulated after 1 yr of incubation at 4 °C and in darkness, and could be identified as Phiolocephala fortinii. could be isolated from a wide range of hosts and sites (Abies alba, Calltheria vulgaria, Fagus sylvatica, Picea abies, Pinus sylvestris and vaccinium murtillus in in Switzerland; Alnus rubra and Gaultheria Gaulteria shallon in Canada; Picea abies and Picea sylvestris in Germany. Pilots sylvestris in Finland). Thus, P. fortinii seems to be neither host‐ nor site‐specific. Four morphological types were recognized among the DSE‐isolates. Type 1 was distinctly different because its aerial mycelium was very sparse or absent. In contrast to other types, type 1 never sporulated. Thus, type I isolates probably belong to a separate taxon. Most isolates were of type 2. About one quarter of the type 2, type 3 and type 4 isolates sporulated and could fee identified as P. fortinii. Types 3 and 4 are supposed to be variants at type 2. The relative proportion of each type seemed to depend on the site, but a clear pattern of host or site preference could not be recognized. Differences between types in micromorphology of colonies grown on water afiar overlaid with cellophane sheets were minimal and therefore cannot he used for routine differentiation. The features of the DSE observed in root squashes corresponded well with those detected in synthesis experiments or pathogenicity vests with P. fortinii in other studies. In this study DSE were, never seen in roof tissues proximal to the innermost phellogen. Cryptosporiopsis radicicola was isolated most frequently form roots of F. sylvatica but constituted only;i minor component of the fungal assemblages of A. alba. Pic. abies. and Pin. sylvestris.
The dynamics of ectomycorrhizal infection of Shorea leprosula seedlings in Malaysian rain forests
Authors: SEE LEE SU , ALEXANDER I. J.
Published: April 2006

summary

The development of mycorrhizal infection on seedlings of the dipterocarp. Shorea leprosula (Miq.). was followed for 7 months after germination at three sites in West Malaysia. Arbuscular mycorrhizal infection was not observed, Seedling roots had well‐developed ectomycorrhizal sheaths, but no Hartig net, 20 d after germination, i.e. before the leaves had formed. By 2 months a range of ectomycorrhizal types with well‐developed Hartig nets were present. Twenty‐three types were recognized, of which 15 were common to alt three sites, and 20 to two sites. Individual seedlings never had more than five types and normally had line or two types only. The majority of ectomycorrhizas were formed by relatively few fungi and the six most abundant types at each site accounted for 77–92%, of the mycorrhizas. On the basis of the frequency of types (i.e. number of seedlings having mycorrhizas of a given type), and the number of times that a type contributed more than 40% of the mycorrhizas on a given seedling it was possible to recognize group of 12 dominant types. At each site new types were encountered at each harvest, and the number of types per harvest also increased. As well as fungi entering the mycorrhizal community as time progressed there was clear evidence that some fungi were lost or declined in relative abundance. Over the study period the level of infection fell at the two sites at which it was initially greatest. Although the community of mycorrhizal fungi was broadly similar at all three sites, overall level of infection, total number of types and number of types per seedling were highest at the site which appeared to have experienced the least disturbance and at which there were the greatest number of adult S. Ieprosula trees.
Effects of elevated CO2 and nutrient supply on the seasonal growth and morphology of Agrostis capillaris
Authors: NEWBERY R. M. , WOLFENDEN J.
Published: April 2006

summary

Responses to elevated CO2 have been studied using an upland grass species, Agrostis capillaris L. The plants were grown in sand culture with a range of N, P and K concentrations, in ‘Solardome’ growth chambers with either ambient air or a CO2 concentration of 250μmol CO2 mol−1 above ambient The interactive effects of high CO2 and nutrient supply (in plant growth and morphology were monitored throughout the growing season.

A. capillaris exhibited positive growth responses to enhanced CO2 even at limiting supplies of N and P. Moreover, greater shoot mass at elevated CO2 was attributed to disproportionate increases in leaf and tiller number, resulting in an increase in the average leaf number per tiller. However, total leaf area remained unaffected, indicating that leaf size was reduced. There was no evidence of any acclimation in the growth response of A. capillaris to additional CO2, even in N and P‐stressed plants. On the contrary, a stimulation in leaf production was observed later in the growing season.

A consistent interaction was observed between N and P concentrations, whereby the response to one element was greater at higher concentrations of the other. In addition, there were indications of competition among the three elements for uptake at the root. These findings indicate the importance of multifactorial nutrient experiments in developing an understanding of the complex relationships during CO2 enrichment.
Photosynthesis and nutrient‐use efficiency of barley in response to low arbuscular mycorrhizal colonization and addition of phosphorus
Authors: FAY P. , MITCHELL D. T. , OSBORNE B. A.
Published: April 2006

summary

The effects of arbuscular mycorrhizal infection by Glomus mosseae (Nicol. & Gerd.) Gerd. & Trappe on growth and photosynthesis of barley (Hordeum vulgare L. cv. Manitou) were investigated in sand culture at five levels of calcium phosphate (50, 100, 200, 400 and 800 mg P kg−1). Mycorrhizal infection was low and varied with P supply, declining from 3.3% at 50 mg P kg−1 to 1.5% at the highest P concentration. In general, there were small differences in biomass between mycorrhizal (+AM) and non‐mycorrhizal (‐AM) barley but a significant reduction in dry mass of senesced leaves occurred in the +AM plants. Leaf P concentrations increased with P application, but did not differ between + AM and ‐AM plants. Although there were no differences in dry mass between + AM and ‐AM plants at 50 mg P kg−1, it was at this lowest P supply that +AM plants had higher rates of photosynthesis and greater P‐use and N‐use efficiencies. The mycorrhizal enhancement of maximum photosynthetic rate at the lowest P level was associated with a higher stomatal conductance, but was not related to increased leaf P or to changes in photon yield or the ratio of variable (FV) to maximum (FM) chlorophyll fluorescence.
Effects of Ascochyta caulina on photosynthesis of leaves of Chenopodium album
Authors: KEMPENAAR C. , HORSTEN P. J. F. M. , SCHEEPENS P. C.
Published: April 2006

summary

The effect of leaf necrosis caused by Ascochyta caulina (P. Karst.) v.d. Aa & v Kest. on photosynthesis of leaves of Chenopodium album L. was studied in growth chambers. Fully expanded leaves of young plants were sprayed with a suspension of pycnidiospores, or with a spore‐free control solution. Subsequently, leaves were exposed to high humidity for 6, 18, or 24 h to promote different levels of necrosis. Individual leaves were assessed for proportion of necrotic leaf area and net photosynthetic rate (npr) 3, 4 and 7 d after treatment. The npr of leaves decreased with increasing proportion of necrotic leaf area. The relationship between the two was linear in five of six regression analyses carried out. The observed linearity indicates that necrotic leaf tissue hardly affected the surrounding healthy leaf tissue. The proportion of necrotic leaf area that caused a npr of zero was on average 0.4, ranging from 0.2 to 0.5.
Catechin, proanthocyanidin and lignin contents of loblolly pine (Pinus taeda) needles after chronic exposure to ozone
Authors: BOOKER FITZGERALD L. , ANTTONEN SEIJA , HEAGLE ALLEN S.
Published: April 2006

summary

Concentrations of soluble and bound phenolic compounds were measured in needles of 3‐yr‐old loblolly pine (Pinus taedaL.) trees exposed from May to November 1993 to a range of ozone (O3) concentrations in open‐top field chambers, The treatments were charcoal‐filtered air (CF). non‐filtered air (NF), and NF air with O2added at 1.5 times (NF 1.5) and 2(1 times (NF 2.0) the ambient O., concentration for 12 h daily. Average daily (0800–2000 hours) O3concentrations in the CF. NF. NF 1.5 and NF 20 treatments were. 29. 47, 76 and 98 nl 1−1. respectively, for the 140 d treatment period. At the end of the treatment period, total phenolic and proanthocyanidin concentrations in the previous year's needles were 25–29% higher in the NF 2.0 treatment compared with the lower O3treatments. Catechin concentration increased in the previous year's needles by as much as 81 % between the NF 2.0 treatment and the lower O3treatments. Catechin is an effective antioxidant, and elevated levels might confer some protection against O3injury. No significant differences in total phenolics and proanthocyanidins in the previous year's needles were detected among the remaining treatments, or among any O3treatment for the current year's needles. Lignin content in needles of both years was not significantly affected by O3exposure. Chances in the phenolic content of older needles in response to elevated O3could alter plant‐pathogen interactions and slow down microbiol decomposition, which could contribute to a decline in site soil quality.
The effects of different ozone exposures on three contrasting populations of Plantago major
Authors: PEARSON S. , DAVISON A. W. , REILING K. , ASHENDEN T. , OLLERENSHAW J. H.
Published: April 2006

summary

Plantago major grows throughout Britain in a range of ozone climates. Because populations have been shown to differ in ozone resistance, the aim of the experiment was to compare the reaction of populations from contrasting ozone climates to different types of ozone exposure. Three populations were grown under controlled conditions in five different ozone treatments (including controls for 10 wk. Development, growth, stomatal conductance and seed production were recorded. Populations were from the south coast of England (Lullington), near a mountain summit (Great Dun Fell) and lowland Scotland (Bush). Ozone treatments were: charcoal and Purafil filtered air (CF); 35 nl l−1 for 24 h every day: 70 nl l−1 h for 7 h everyday: CF then three episodes each week of 70 nl l−1 for 7 h; and 35 nl l−1 continuously plus three 7 h episodes each week of 70 nl l−1.

The different ozone treatments resulted in different responses in each population. Ozone promoted senescence in the Great Dun Fell population but not in the others; it reduced root growth more in the Lullington population than in the others but those from Lullington and Great Dun Fell maintained seed production to a much greater extent than the Bush population. The reproductive effort (number of seeds g−1 of vegetative weight) actually increased in ozone in the Lullington and Great Dun Fell populations. It is suggested that this might he a general stress response rather than being specifically related to ozone. Effects on stomatal conductance were similar to those previously reported and the converse of effects on seed production.

The relative responses of the populations varied according to the ozone treatment. Continuous exposure to 35 n1 l−l reduced leaf size only in the Great Dun Fell population, but seed output was reduced in the Bush population. In some cases, giving 3–d episodes of 70 n1 l−1 had a greater effect than giving the dose every day but the effects varied with the population. This greater effect was considered to be a result of the time it takes for a plant to develop maximum anti‐oxidant defence, which is lost when the ozone decreases after the episode. A plant exposed to episodes might have to re‐induce defence with each exposure.

Although it is reported frequently that ozone favours allocation of resources to the shoot over the root, it is concluded that this is an over‐simplification of the response. Even within a species there is a complex suite of responses that varies with the population and with ozone exposure. Describing a population as resistant or sensitive is also an over‐simplification.
Effects of emissions from copper‐nickel smelters on the frost hardiness of Finns sylvestris needles in the subarctic region
Authors: SUTINEN MARJA‐LIISA , RAITIO HANNU , NIVALA VESA , OLLIKAINEN RISTO , RITARI AULIS
Published: April 2006

summary

It has been proposed that freezing injuries play an important role in the forest decline phenomenon. In this study, the effect of emissions from the copper‐nickel smelters in Monchegorsk and Nikel‐Zapolyarnyi in the Kola Peninsula, south‐west Russia, on seasonal changes in the frost hardiness of Pinus sylvestris L. needles were studied. The frost hardiness of current‐year needles during autumn, winter, spring and early summer in 1991–1993 was estimated by the electrolyte leakage method and by visual estimation of the proportion of damaged needles at nine sites in Finnish Lapland, at five sites in the vicinity of Monchegorsk and at two sites in Norway, in the vicinity of Nikel. The foliar S, Cu, and Ni concentrations also analysed. There were no significant differences at any time of the year between the frost hardiness of pine needles at the sites in Norway and Finnish Lapland. However, in the winter, the degree of visual damage at −45 °C, the temperature close to the lowest recorded temperature in this area, was slightly higher at the sites near to Nikel than at the sites in Finnish Lapland. In the Kola Peninsula the frost hardiness was consistently lower at the sites located 10 km to the south and 36 km to the south‐west of Monchegorsk than at the other sites (48–110 km to the south‐west). The differences were greatest in early June, 1991, when frost hardiness was −2 °C and −8°C at the sites closest to Monchegorsk. At the same time, the frost hardiness at the other sites was e.−20 °C. There were slight differences between years, but the trends were the same. A clearly increasing gradient in the S, Cu and Ni concentrations was observed on moving towards the emission point source at Monchegorsk. Highly elevated concentrations were found within 40 km of the smelter. The results suggest that air pollutants from the copper‐nickel smelter have predisposed the pines to freezing injuries, rhus contributing to forest decline in the Kola Peninsula.
The metabolism of fructans in roots ofCichorium intybusduring growth, storage and forcing
Authors: VAN DEN ENDE WIM , MINTIENS ANNEMIEKE , SPELEERS HILDE , ONUOHA AMABILIS A. , VAN LAERE ANDRÉ
Published: April 2006

summary

During the 1993 growing season samples from field‐grown roots of chicory(Cicborium intybusL. var.folinsumev. Flash) were analysed by ion‐exchange HPLC (Dionex). We measured the concentrations (μmol g−1f. wt) of glucose, frurtose, sucrose, 1‐kestosc and 1,1 nystose. The concentrations of the higher fructans were relative (units g−1f. wt). The data showed a significant increase in the concentration of fructans with a high degree of polymerization (DP) during July, August und September and a decrease of the glucose concentration. The Concentrations of sucrose, fructose and oligomeric fructans remained roughly constant over the same period. However, in early October, important changes occurred over a very short period. These changes included: (1) a significant increase in fructose concentration; (2) an increase in the concentration of fructans with a low DP; (3) a decrease in fructans with a high DP; (4) an appearance of alternative peaks (probably representing fructans without terminal glucose); and (5) an increase in sucrose concentration. These changes werenotaffected by a short‐day treatment starting on 6 September. Forcing of the roots for endive production was accompanied by further breakdown, mainly of the larger fructans. Activity of SST (sucrose: sucrose fructosyl transferase) decreased slowly throughout the growing season lo essentially disappear by October. Neutral invertase activity increased more gradually. SST activity decreased very rapidly during cold storage and forcing.
Effects of sulphur dioxide and ozone on lichen colonization of conifers in the Liphook Forest Fumigation Project
Authors: BATES J. W. , MCNEE P. J. , MCLEOD A. R.
Published: April 2006

summary

In the Liphook Forest Fumigation Project the conifersPicea abies(L.)Karst.,P, sitchensis(Bong‐) Carr. andPinus sylvestrisL. were grown from the seedling stage and subjected, by open‐air fumigation, to three regimes of SO2(ambient, 4 ppb (parts in 109by volume); low, 12 ppb; high, 20 ppb) and two regimes of O3(ambient, 25 ppb; high, 30 ppb) in factorial combination, between 1987 and 1990. We determined the abundance of three lichens,Evernia prunastri(L.) Ach.,Hypogymnia physodes(L.) Nyl. andLecanora canizaeoidesNyl. ex Crombie, which colonized the trunks and branches of the saplings, at the end of the experiment between May‐July 1991. All three species showed a marked preference forP. abiesand were scarcest onP, sylvestriswhich had the most acidic hark.E. prunastriwas the rarest of the three lichens and only colonized plots exposed to ambient SO2(4 ppb). Diminutive thalli ofH. physodeswere relatively numerous in the ambient SO2, plots, much scarcer in those receiving low SO2(12 ppb) and rare in those with high SO2(20 ppbl. Coverage byL. conizaeoideswasverylow in the ambient SO2, plots but appreciable in the low and high SO2treatment plots. The results indicate directly beneficial effect of SO2onL. conizaeoidescolonization rather than an indirect benefit through competitor release. The O3treatment (1.3 times ambient during Spring‐Autumn) did not influence the abundance of the lichens. All three lichen species appeared to be more sensitive (positive and negative effects) to SO2, than mapping studies have suggested. Possible reasons for the high SO2‐sensitivity of the lichens are discussed. These include the high acidity of conifer bark and the fact that growth from diaspores and development of immature thalli is involved rather than survival of established populations.
Stomatal uptake of SO2, NOx and O3 by spruce crowns (Picea abies) and canopy damage in Central Europe
Authors: SLOVIK STEFAN , SIEGMUND ALFRED , FÜHRER HANS‐WERNER , HEBER ULRICH
Published: April 2006

summary

The stomatal uptake of SO2, NO2 and O3 by Norway spruce canopies (Picea abies (L.) Karst.) has been integrated at six sites in central Germany (Königstein in the Taunus mountains. Witzenhausen, Grebenau, Frankenberg, Fürth in the Odenwald mountains and Biebergemünd in the Spessart mountains), Results are based on 788000 half‐hourly available sets of field data on air pollution and site meteorology measured since 1984 (45 site years). Data on stomatal water conductance are available from statistical response functions obtained in the field at all times of day and seasons of the year. From this, stomatal conductance was calculated fur different atmospheric tract gases. Statistical response functions are presented which allow the separate estimation of annual stomatal net uptake of trace gases in the field if only (i) measured annual means of SO2, NO2, and O3, pollution and (ii) the length of the trunk growth period (defined by temperature) are known. The following specific annual doses of stomatal trace‐gas net uptake in the field (μmol m−2total needle surface d−1annual trunk growth period/(nPa Pa−1) annual mean of trace gas concentration) are obtained; SO2: (0.157 ± 0.011) μmol m−2d−1/(nPa SO2, Pa−1), NOx: (0.4774 ± 0.034) μmol m−2d−1/(nPa NO2 Pa−1), O3: (0.474 ± 0.034) μmol m−2d−1/(nPa O3 Pa−1). There is an apparent NO2, compensation point at 7 nPa Pa−1in the field if NOx (=NO2, + NO) fluxes are integrated; the individual NO2, compensation point equals c 3.2 nPa Pa−1. Additionally, a statistical response function is presented, which estimates actual stomatal water transpiration rates in the field on the basis of measured water vapour pressure differences. VPD (mPa Pa−1). Complex canopy effects were calculated on the basis of available data using an effective leaf area which is 0×32 times the morphological leaf area index. Results are consistent (i) with available water balance data, (ii) with observed SO2‐dependent sulphate accumulation rates in spruce needles and (iii) with observed epicuticular SO2, deposition rates. Pollution data are compared with observed damage of spruce canopies in the field. There was a statistically significant correlation between observed damage to spruce canopies.
Identification of pollen components regulating pollination‐specific responses in the stigmatic papillae of Brassica oleracea
Authors: ELLEMAN C. J. , DICKINSON H. G.
Published: April 2006

summary

When components of the mature pollen grain of Brassica oleracea are applied to the cuticularised surfaces of the stigmatic papilla, a number of changes can take place in the architecture of the subjacent cell wall. Treatment of the papillar surface with isolated pollen coating evokes a rapid and extensive expansion of the outer of the two stigmatic wall layers. This response occurs within 4 h but is restricted to those regions where no callose is formed and where the coating exhibits a characteristic increase in electron opacity. This study establishes that the coating alone is responsible for initiating the expansion of the outer wall, which is considered to be an essential step preceding penetration of the stigma surface by the pollen tube. Vesicle‐like inclusions, some staining intensely, occasionally occur in regions of the wall expanded by isolated coating, sometimes fusing to form a subcuticular ‘boundary layer’. These structures are not observed under compatible grains in vivo and their presence is regarded as artefaetual. However, close examination of the plasma membrane at sites beneath areas of expanded cell wall reveals membrane‐bound structures resembling the vesicles being generated by the cytoplasm and moving into the apoplast. These data indicate that signals from the coating initiate the loosening of the wall matrix by stimulating an unusual form of localized secretion which appears to be an essential prerequisite for stigmatic penetration.

Isolated pollen coating contaminated with fragments of the grain itself engender a very different response, including the formation of densely‐staining vesicles accompanied by extensive accumulations of callose; wall expansion never occurs under these circumstances. Self‐pollinations in B. oleracea are frequently accompanied by the synthesis of stigmatic callose, the presence of which has, in the past, been interpreted as forming a structural barrier to incompatible pollen tubes. However, callose elicited both by self‐pollinations and coating supplemented by killed grains is independent of protein synthesis and occurs in the presence of the phosphatase inhibitor, okadaic acid. Since both these inhibitors also overcome self‐incompatibility (SI) in B. oleracea, these data strongly suggest that callose synthesis is unrelated to the operation of SI, and it is proposed that callose, when formed, is elicited by molecules released from the necrotic pollen protoplast. Interestingly, isolated pollen coating of self‐ and cross‐genotypes does not readily elicit callose.

The significance of these changes in the stigmatic wall is discussed in the perspective of current views on pollination and self‐incompatibility in Brassica.
The effects of dry O3, SO2 and NO2 on reconstituted epicuticular wax tubules
Authors: JETTER REINHARD , RIEDERER MARKUS , LENDZIAN KLAUS J.
Published: April 2006

summary

Epicuticular wax tubules were reconstituted in vitro by recrystallizing nonacosan‐10‐ol from the soluble cuticular lipids of Picea pungens Engelm. on a glass support. Fumigation of these preparations for 100 h with dry O3 (1.8 %), SO2 (100%) or for 1500 h with NO2 (0.1 %) did not change their composition or crystal habit. Exposure of reconstituted wax tubules to 1 % of dry NO2 yielded planar crystals of nonacosan‐10‐one after 100 h. Further exposure (264 h) resulted in the complete degradation of aggregates and the formation of nonadecanoic and eicosanoic acids. The same oxidation steps and the accompanying changes of crystal shapes could be induced by fumigation of nonacosan‐10‐ol tubules with 100% of dry NO2 for 0.25–1 hand for 2 h, respectively. The oxidation of nonacosan‐10‐ol depended on the doses applied. At ambient concentrations, equivalent doses would accumulate only over thousands of years. Oxidative transformations alone can therefore not account for the in vivo degradation of wax tubules on conifer needles.
Variation in seed production and germinability in common reed (Phragmites australis) in Britain and France with respect to climate
Authors: McKEE JUNO , RICHARDS A. J.
Published: April 2006

summary

Northern populations of Phragmites australis (Cav.) Trin. ex Steud. (common reed) often flower so late that the ability to produce viable seeds before winter dieback can be limited. If climate changes as predicted, the reed may become able to set seed further north in its range. This would have implications for the ability of reed to colonize new sites as well as for the distribution of animals which eat reed seeds in winter.

A survey of 34 British populations in 1993 and 1994 showed that seed production is highly variable between sites, ranging from 0 to 100%. Southern and western populations tended to show the highest seed sets, although some southern populations were infertile and some northern sites set seed. Average seed weight tended to be higher in sites which showed good seed set. Seeds from sites with high average seed weight tended to germinate more readily.

The seed‐setting capability of populations was successfully associated with climatic conditions at the time of flowering. However, seed weight was not found to relate to climate, but depended on seed production and overall plant height. Logistic regression modelling indicated that the best seed sets should occur in P. australis when: (i) August rainfall is low; (ii) the combined rainfalls of September and October are high; and (iii) the combined temperatures of these months are high. The model accounts for approximately one third of the variation in observed seed sets between sites, indicating that other, unmeasured, factors might also play a part in determining seed set in P. australis.

At three northern populations which were studied in more detail, a number of genotypes coexisted, and legitimate pollen germination and pollen‐tube growth was observed in each case. As no seed set occurred in two of these, self‐incompatibility cannot explain poor seed setting.
The differential effects of cell wall‐associated phenolics, cell walls, and cytosolic phenolics of host and non‐host roots on the growth of two species of AM fungi
Authors: DOUDS D. D. , NAGAHASHI G. , ABNEY G. D.
Published: April 2006

summary

Experiments were conducted to test the hypothesis that cellular compounds, especially wall‐associated compounds, released during emergence of secondary roots, stimulate the growth of arbuscular mycorrhizal (AM) fungi. Purified cell walls, crude cell‐wall extracts, crude cytoplasmic extracts, and phenolic compounds previously identified as cell wall‐associated, from Ri T‐DNA‐transformed roots of host (Daucus carota L.) and non‐host (Beta vulgaris L.) were incorporated into growth medium and tested for their effects upon growth of the AM fungi Gigaspora gigantea (Nicol. & Gerd.) Gerdemann and Trappe and Gigaspora margarita Becker and Hall. Purified cell walls of both plants had little effect on G. gigantea but non‐host cell walls inhibited the growth of G. margarita. Ferulic acid, a major constituent of non‐host root, depressed the growth of both fungi. Nothing tested which was unique to the non‐host root affected hyphal growth to the point that contact would be prohibited. Caffeic acid, found in D. carota cytoplasm, also depressed growth of both fungi. Para‐hydroxybenzoic acid, a constituent of D. carota roots, stimulated growth of G. margarita hyphae, but did not affect hyphal growth of G. gigantea. Vanillic acid, unique to D. carota root cell‐wall extracts, stimulated hyphal growth and branching of both fungi, and should increase the probability of contact between fungus and host root.
The development of a CO2‐concentrating mechanism in Emiliania huxleyi
Authors: NIMER N. A. , MERRETT M. J.
Published: April 2006

summary

The development of an inorganic carbon concentrating mechanism (CCM) in relation to the expression of extracellular carbonic anhydrase (CAext) in cells from the stationary phase of Emiliania huxleyi cultures was investigated. Unlike exponential phase cells, those in the stationary phase showed a high affinity for CO2: the K0.5[CO2] (i.e. the CO2 concentration required for half‐maximal rate of photosynthesis) was 1.6μM at pH 8.3. Measurement of the internal inorganic carbon concentration by the silicone oil centrifugation technique showed that, with 1 mM external dissolved inorganic carbon (DIC), the intracellular inorganic carbon concentration was sixfold greater at pH 7.5 and twofold greater at pH 8.3, than the external concentration. The potent CAext inhibitor, dextran‐bound sulphonamide (DBS), gave an 80% inhibition of DIC‐dependent photosynthetic oxygen evolution. Similarly, DBS decreased the intracellular DIC concentration and inhibited photosynthetic 14CO2 fixation. The lipid‐permeable CA inhibitor, ethoxyzolamide (EZ), increased the intracellular DIC concentration but inhibited photosynthetic 14CO2 fixation. The observed intracellular DIC concentrations indicated that the stationary phase cells have the capacity to transport CO2 actively against a concentration gradient.
Response ofEriophorum vaginatumto CO2enrichment at different soil temperatures: effects on growth, root respiration and PO43−uptake kinetics
Authors: BASSIRIRAD H. , TISSUE D. T. , REYNOLDS J. F. , CHAPIN F. S.
Published: April 2006

summary

In a phytotron experiment, we examined responses of a tussock sedge,Eriophorum vaginatumL., to changes in atmospheric CO2, concentration and soil temperature. We were particularly interested in phosphorus (P) acquisition and below ground plant characteristics that regulated its uptake in response to CO2, enrichment. Plants were grown at two CO2, partial pressures, 35 and 70 Pa, three soil temperature regimes, 5, 15 and 25 °C and a constant ambient air temperature of 15 °C. Elevated CO2, increased total plant biomass production, but decreased tissue P concentration. Although high CO2, enhanced root carbohydrate concentration, it inhibited root respiration with no significant effect on root PO43−absorption capacity or root:shoot ratio. Surprisingly, there were no significant interactions between CO2, and soil temperature. The inability ofEriophorumto exhibit root–level compensatory adjustments, e.g. increased root: shoot ratio or PO43−absorption capacity, was largely responsible for the observed decline in tissue P concentration under elevated CO2, conditions. This could ultimately limit long–term growth responses ofEriophorumto CO2enrichment in the field where P availability is limiting. We found that uptake of PO43−in response to elevated CO2was independent of changes in root respiration, but changes in root respiration could have important implications for ecosystem carbon budget under elevated CO2levels. Our data indicated that although root respiration on a per unit biomass basis declined in response to CO2enrichment, this effect was counterbalanced by increased root biomass, so that high CO2stimulated root respiration on a whole‐plant basis by 30%. This might help to explain why long‐term exposure to high CO2increases CO2efflux fromEriophorum‐dominated ecosystems.
Distribution of phosphorus and calcium from nodal roots of Trifolium repens: the relative importance of transport via xylem or phloem
Authors: LÖTSCHER M. , HAY M. J. M.
Published: April 2006

summary

The intra‐plant distribution of radioactive phosphorus (32P) and calcium (45Ca) exported from a single nodal root of Trifolium repens (white clover) was measured to ascertain if initial allocation of radioisotopes via the xylem was significantly altered over time by redistribution via the phloem. The radioisotopes were simultaneously supplied in a 2 h pulse which was followed by supply of non‐radioactive nutrient solution until harvest 3, 6, 9, 21 or 72 h after the start of labelling. By the end of the 3 d experimental period net export from the source root was 94 % total absorbed 45Ca but only 56 % of 32P. After movement through the stolon of the parent axis, main sinks for both nutrients were the leaf and the branch at the second node distal to the source root (64 and 30 % of total absorbed 45Ca and 32P respectively after 72 h). Very little of either radioisotope moved into branches located along the stolon of the parent axis, on the side opposite to the source root (1 and 2% of total absorbed 45Ca and 32P respectively after 72 h). This evidence, along with knowledge of the vascular architecture of the genotype, indicated that the allocation of mineral nutrients was determined chiefly by the vascular links between the source root and sink organs rather than sink size or proximity to the source root. Data indicated that some distribution of 32P occurred via the phloem but that it was quantitatively small in relation to allocation via the xylem both in the short (3 h) and medium (72 h) terms.
Effect of arbuscular mycorrhizas on uptake of nitrogen byBrachiaria arrectaandSorghum vulgarefrom soils labelled for several years with15N
Authors: IBIJBIJEN J. , URQUIAGA S. , ISMAILI M. , ALVES B. J. R. , BODDEY R. M.
Published: April 2006

summary

A pot experiment was conducted under glasshouse conditions to investigate the effect of the inoculation of arbuscular mycorrhizal (AM) fungi on the growth and N uptake of two graminaceous plants:Brachiaria arrecta(Hack. ex. Th. Dur & Schinz) Stent andSorghum vulgare(Pers.) growing in four fumigated soils which had been labelled for several years with15N. The four soils had different chemical characteristics, especially in their P availability. The levels of root colonization by AM fungi were inversely related to the P concentration in these soils. Positive responses to AM fungal inoculation were observed for all the yield parameters except in the soil with the highest P availability (40 μg P g−1soil, extractant Mehlich‐1). In the other three soils, AM fungal inoculation of both crops increased N accumulation by between 17 and 46%, but the15N enrichment of the N absorbed was significantly lower in the mycorrhizal plants than in those not colonized by mycorrhizal fungi. This suggests that some of the N absorbed from the soil by the mycorrhizal roots was derived from N sources other than the mineral N.
Effects of NO (+ NO2) pollution on growth, nitrate reductase activities and associated protein contents in glasshouse lettuce grown hydroponically in winter with CO2 enrichment
Authors: HUFTON CAROLINE A. , BESFORD ROBERT T. , WELLBURN ALAN R.
Published: April 2006

summary

Winter hydroponic growth of several lettuce cultivars under glass showed considerable inhibition (up to 47%) of growth after 6 wk exposure to concentrations of NO (+ NO2 450 nl −1 in total) typical of emissions from propane burners used for direct heating and CO2 enrichment. After a further 4 wk under similar conditions, however, these growth depressions were replaced by a swing into benefit so that, by harvest, pollutant‐exposed lettuces were bigger and had faster assimilation rates than those growing in clean CO2‐enriched air. This adaptation may partly be explained by enhanced use of NO2‐derived N by lettuce leaves, a consequence of increased nitrate reductase (NaR) activities and amounts of associated NaR proteins, despite adequate nitrate also being available in the hydroponic fluid. Rates of NaR activity in the roots, by contrast, were depressed by NO (+ NO2) pollution. NaR activities were highest in early afternoon in clean or polluted air but these daily patterns did not coincide with the content of NaR‐associated proteins determined by ELISA. Other mechanisms of modulating NaR activity must therefore be responsible.
Ultrastructure and supramolecular organization of photosynthetic membranes of some marine red algae
Authors: TSEKOS I. , REISS H.‐D. , ORFANIDIS S. , OROLOGAS N.
Published: April 2006

summary

The ultrastructure and supramolecular organization of photosynthetic membranes in four species of marine red algae (Porphyra yezoensis, Porphyra leucosticta, Erythrocladia subintegra, Pterothamnion crispum) were studied both in replicas of rapidly frozen cells and in ultrathin sections. Because the thylakoids in red algal chloroplasts are not stacked, freeze‐fractured thylakoid membranes exhibit only two types of fracture faces (EF and PF). In all four species the PF reveals numerous, tightly packed, but randomly distributed particles (density range from 3530 to 4970 particles μm−2 for Porphyra yezoensis). The particle size distribution is uniform in the two types of fracture faces with an average diameter of about 11.3–11.6 nm in all four algae.

The phycobilisomes of Porphyra yezoensis and Erythrocladia subintegra have the approximate shape of a compressed rotation ellipsoid with the following dimensions; Porphyra yezoensis, length 52.8±1.2 nm, thickness 24.4±0.6 run, height 34.6±1 nm; Erythrocladia subintegra, length 45.1±0.7 nm, thickness 23.1±0.5 nm, height 29.4±0.9 nm. In Porphyra yezoensis, Porphyra leucosticta and Erythrocladia subintegra both the phycobilisomes and EF particles are organized into rows with a spacing of 70–80 nm in Porphyra yezoensis, 65–75 nm in Porphyra leucosticta and 53.8–55 nm in Erythrocladia subintegra. EF particle complexes with four subunits were found in Porphyra yezoensis. In Pterothamnion crispum the shape of the phycobilisomes is hemiellipsoidal. The phycobilisomes seem to be organized into rows; their centre to centre periodicity is c. 60 nm. Porphyra yezoensis cells possess about 770±58 phycobilisomes μm−2 of thylakoid surface, whereas the number of EF particles is about 1270±203 μm−2 Thus, the ratio of phycobilisomes to EF particles is c. 0.6. In Erythrocladia subintegra the ratio of phycobilisomes to EF particles is about 0.7.

Of special interest is the ocurrence of a crystalline matrix in pyrenoids of Porphyra leucosticta and the absence of phycobilisomes in the intrapyrenoid thylakoids of Porphyra yezoensis and Erythrocladia subintegra.
Cell ultrastructural evidence of accelerated ageing of Norway spruce needles in industrial areas
Authors: WULFF A. , AHONEN J. , KÄRENLAMPI L.
Published: April 2006

summary

Needle mesophyll cell ultrastructure of 1st to 9th yr needles from Norway spruce (Picea abies (L.) Karst.) trees of different ages was studied at three different sites to determine the normal features of needle ageing, and the impact of air pollution on the needle ageing process. The sites included one rural area and two industrial environments, of which one contained SO2 emissions and the other SO2 and F emissions. The ultrastuctural features of needle mesophyll cells of different ages were found to be remarkably similar when young (20‐yr‐old) and mature (> 50‐yr‐old) trees were compared. Senescence‐related ultrastructural symptoms such as increase in the number and size of plastoglobuli and an increase in the large lipid accumulations were observed with increasing needle age. In addition, the occurrence of lipid bodies in the central vacuole and an increased number of dark grains in the cell wall were detected in ageing needles. No changes in chloroplast length were observed during the ageing of needles, although the width of the chloroplasts showed a tendency to increase. A poor differentiation of granal membranes and an increase in small cytoplasmic lipid bodies and irregularly‐shaped lipid material were symptoms typical of needles in the industrial areas. The ageing symptoms appeared in younger needles and were more evident in industrial areas than at the control site, suggesting an accelerated ageing process in the industrial areas.
The effect of elevated CO2 and grazing by Gastrophysa viridula on the physiology and regrowth of Rumex obtusifolius
Authors: PEARSON MARK , BROOKS GEORGINA L.
Published: April 2006

summary

Plants of Rumex obtusifolius L. were grown in Solardomes under ambient and elevated (+ 250 μmol mol−1) mole fractions of CO2 and were exposed to two levels of herbivory by Gastrophysa viridula Degeer larvae. The herbivory treatment lasted 1 month, thereafter half of the plants were harvested and over the following month during a period of regrowth physiological measurements were made on the remaining plants. At the termination of the herbivory treatment uninfested plants showed no damage, whereas the low and high herbivore treatments caused 20–40% and 50–70% loss of leaf area as a proportion of total leaf area, respectively. The CO2 treatment did not affect the degree of defoliation. Total leaf area was not significantly affected by either CO2 or herbivory. Uninfested plants grown in elevated concentrations of CO2 showed increased growth, root‐to‐shoot ratios (RS), rates of photosynthesis and reduced stomatal conductance compared with uninfested plants grown in ambient CO2. A/C1 analysis revealed that plants grown in elevated CO2 showed reductions in Vcmax. For plants grown in ambient CO2 the high herbivory treatment led to increased rates of photosynthesis and decreased rates of dark respiration per unit leaf area, and caused increases in stomatal conductance and RS. For plants grown in elevated CO2 the high herbivory treatment increased plant biomass and RS. The increases in RS in response to elevated CO2 and herbivory appeared to be additive. Defoliation did not reduce the degree of photosynthetic down‐regulation caused by growth in elevated concentrations of CO2, but appeared to reduce the rate of ontogenic decline in photosynthesis in ambient CO2.
Interactions between the parasitic angiosperm Orobanche aegyptiaca and its tomato host: growth and biomass allocation
Authors: BARKER E. R. , PRESS M. C. , SCHOLES J. D. , QUICK W. P.
Published: April 2006

summary

The influence of the parasitic angiosperm Orobanche aegyptiaca on the growth and shoot/root allometry of tomato plants was studied in two experiments. In the first, the density of infection was manipulated, with host and parasite biomass being measured 56 d after planting (d.a.p.). In the second, multiple harvests were made from 14 to 91 d.a.p. at one level of infection (20 mg seed dm−3). The first experiment demonstrated an approximately linear reduction in host biomass up to 10 mg seed dm−3 soil, beyond which there was no further reduction. The parasite also depressed shoot/root ratio, which changed prior to any decrease in total biomass. These trends were maintained in the second experiment, becoming more pronounced with time. Significant reductions were observed in host biomass compared with that of uninfected controls from 42 d.a.p., following the emergence of the parasite above ground, and corresponded with the onset of lower relative growth rates (RGRs) in the infected plants. Infection also influenced components of RGR: there was a stimulation of leaf area ratio (LAR) and a depression of unit leaf rate (ULR). The data are discussed with respect to the influence of other parasitic weeds on host growth.
Carbohydrate metabolism in source leaves of barley grown in 700 μmol mol−1 CO2and infected with powdery mildew
Authors: HIBBERD J. M. , WHITBREAD R. , FARRAR J. F.
Published: April 2006

summary

Soluble carbohydrate accumulated faster in second leaf blades of barley when plants were grown in 700 μmol mol−1 CO2 rather than 350 μmol mol−1 CO2. Infection of the second leaf blade by powdery mildew had no effect on the concentration of soluble carbohydrate until 6 d after inoculation when it was lower than in controls. The accumulation of soluble carbohydrate in the second leaf of uninfected plants grown in 700 μmol mol−1 CO2 was due largely to earlier and faster accumulation of fructan. TLC showed that the series of fructan was not different in plants grown in 700 μmol μmol−1 CO2 relative to plants grown in 350 μmol mol−1 CO2, neither did infection by powdery mildew affect the series of fructan present in the second leaf blade. The rate constant for phloem loading obtained by compartmental analysis of 14C efflux from the leaf blade was not reduced in plants grown in 700 μmol mol−1 CO2, indicating that carbohydrate accumulation was not caused by reduced ability of the leaf to export carbon.
Effects of mycorrhizal colonization byPaxillus involutuson uptake of Ca and P byPicea abiesandBetula pendulagrown in unlimed and limed peat
Authors: ANDERSSON SOLBRITT , JENSÉN PAUL , SÖDERSTRÖM BENGT
Published: April 2006

summary

Uptake of P(32P) and Ca(45Ca) by seedlings ofPicea abies(L.) Karst andBetula pendulaRoth, non‐mycorrhizal or mycorrhizal withPaxillus involutus(Batsch: Fr) Fr. was studied. Seedlings were grown in unamended peat (pH 4.0) or in peat limed (CaO) to pH 5.1 or 6.1. A double‐labelled (32P and45Ca) complete nutrient solution was added to the peat 7 wk after planting. An 8 d period was allowed for uptake of the isotopes before the seedlings were harvested.

Mycorrhizal colonization clearly increased the uptake of P(32P) in the unlimed substrate and in the substrate limed to a pH of 5.1. At the highest lime rate, the uptake of P(32P) was greatly reduced in both mycorrhizal and non‐mycorrhizal seedlings. The difference in P uptake between mycorrhizal and non‐mycorrhizal seedlings was small at this lime rate. The mycorrhizal colonization of the roots was not affected by liming. How‐ever, it is possible that the mycelial growth into the substrate was inhibited. The reduction in uptake could thus be an effect of a lower availability of P in combination with a decreased fungal uptake surface at the highest lime rate.

The mycorrhizal effect on uptake of Ca was much smaller than its effect on uptake of P. Mycorrhizal colonization increased the Ca(45Ca) uptake in the unlimed treatment, where the Ca content in the substrate was very small. In the limed substrates the uptake of Ca was as high or higher in the non‐mycorrhizal than in the mycorrhizal seedlings.