bluuebunny/crossref_metadata_2025_split huggingface dataset:
Responses of potato plants to sulphur dioxide, water stress and their combination
Authors: QIFU MA , MURRAY FRANK 
Published: April 2006

summaryThe effects of SO2, and water stress, singly and in combination on potato plants (Solanum tuberosum L. cv. Russet Burbank) were studied by exposing them to one of three SO2 concentrations (2, 110 and 300 nl 1−1) and one of two levels of soil moisture (well‐watered and water‐stressed). Visible leaf injury attributable to SO2 toxicity was observed after 6 weeks of fumigation with 300 nl 1−1 SO2 and 9 weeks of fumigation with 110 nl 1−1 SO2. Leaf, stem and tuber growth were significantly reduced by 300 nl 1−1 SO2 and water stress. Exposure to 300 nl 1−1 SO2 under well‐watered conditions induced an increase of the shoot: root (including tuber) ratios but not for the ratios (excluding tuber) early in the season, indicating a strong effect of the treatment on tuber growth. With progress of the season, water stress usually reduced both ratios.SO2−induced growth reductions in well‐watered plants were mostly significant, but usually not in water‐stressed plants, indicating a protective function of soil water stress in the response of plants to SO2. This could be caused by reduced SO2 uptake in water‐stressed plants, as the well‐watered plants showed much higher leaf sulphur concentrations than did the water‐stressed plants at the same SO2 concentrations.
Simulated acid rain and the reproduction of mountain birch [Betula pubescens ssp. tortuosa (Ledeb.) Nyman]: a cautionary tale
Authors: NEUVONEN S. , NYYSSÖNEN T. , RANTA H. , KIILUNEN S. 
Published: April 2006

summaryLaboratory experiments showed that mountain birch pollen u as sensitive to the acidity of the incubation solution : the percentage of pollen germination was significantly reduced (compared to control, pH 5.6) at pH 4.0 and the length of the longest germ tube was reduced by nearly 50% at pH 4.6. On the other hand, the pollen germination percentage was not significantly affected by treating the male catkins of mountain birch with acid spray down to pH 3.0. Furthermore, a field experiment with simulated acid rain did not show any significant treatment effects either on the number or size of female catkins or on the seed germination capability of mountain birch. There are several mechanisms which may compensate and buffer the effects of acidity on the reproduction of trees.
Seasonal changes in the pigments, carbohydrates and growth of red spruce as affected by exposure to ozone for two growing seasons
Authors: AMUNDSON R. G. , ALSCHER R. G. , FELLOWS S. , RUBIN G. , FINCHER J. , VAN LEUKEN P. , WEINSTEIN L. H. 
Published: April 2006

summaryThree‐year‐old red spruce seedlings were exposed to various concentrations of ozone, from 0.4 to 3 times ambient, for two consecutive growing seasons in open‐top chambers in Ithaca, NY, USA. Exposures, which varied with changes in daylength, were from 30 May to 14 December 1987 and 1 June to 1 December 1988. Seedling biomass, foliar pigments and carbohydrate content of roots and shoots were assessed once or twice per month. Tree biomass increased through the summer and declined slightly in late autumn, regardless of ozone treatment. Biomass and contents of sugar and starch of 1988 fixed growth declined linearly with exposure to increasing levels of ozone. Rates of decline in total shoot biomass and old shoot biomass increased linearly with exposure to increasing concentrations of ozone, but tree height was not affected. Seasonal means of starch content of roots decreased linearly with increasing doses of ozone, but in contrast seasonal mean sugar content and rate of sugar accumulation of roots increased linearly. Chlorophyll a and chlorophyll b contents were not affected by ozone.These data are consistent with the concept that ozone stress is cumulative, since effects on biomass and carbohydrate content of roots and shoots were not detected after the first year of exposure, but were detected after the second year of treatments. Furthermore, biomass was reduced by ozone only in tissues that were initiated during the first year of exposures and developed during the second year of exposures (1988 fixed growth).
Sensitivity of frost resistance and growth in citrus and avocado to chronic ozone exposure
Authors: EISSENSTAT D. M. , SYVERTSEN J. P. , DEAN T. J. , YELENOSKY G. , JOHNSON J. D. 
Published: April 2006

summaryThe effects of elevated levels of ozone on growth and frost resistance were studied using broadleaf‐evergreen citrus and avocado trees. ‘Ruby Red’ grapefruit (Citrus parodist L.) trees on either Volkamer lemon (Citrus volkanieriana Ten. & Pasq.) or sour orange (Citrus aurantium L.) rootstocks and ‘Simmonds’ or ‘Pancho’ avocado trees (Persea americana Mill.) on the rootstock ‘Waldin’ were exposed to ozone in open‐top chambers for 4 months in 1988 and for 8 months in a second experiment in 1989. The ambient ozone concentration, averaged over a 12 h day, was 30‐1 nl 1−1 in 1988 and 39‐1 nl 1−1 in 1989 during the exposure period. Citrus tree growth, estimated by total leaf mass, was unaffected by ozone concentrations of 3 × ambient in either year but the growth of avocado in 1989 was reduced 20 and 61 % by ozone concentrations at 2 × and 3 × ambient, respectively. Frost resistance, estimated by electrolyte leakage from leaf disks and from survival of leaves, stems and whole plants following exposure to freezing temperatures, was often diminished in avocado and citrus at 3 × ambient ozone, but occasionally was increased at 2 × ambient. The effects of chronic ozone exposure on frost resistance were generally subtle; 3 x ambient ozone exposure in 1989 compared to 0.3 × only caused the temperature for 50% electrolyte leakage (LT30) to increase less than 1 °C (− 5.3 to −4.8 °C) in citrus and about 2 °C (− 8.0 to −5.8 °C) in avocado. Nevertheless, the tests for frost resistance on whole plants indicated that these differences could have a substantial impact on stem and plant survival if the frost was at a critical temperature. The likelihood that chronic ozone exposure currently affects citrus frost resistance in Florida appears slight.
Late‐ and post‐glacial vegetational change at Black Loch, Fife, eastern Scotland – a multiple core approach
Authors: WHITTINGTON GRAEME , EDWARDS KEVIN J. , CUNDILL PETER R. 
Published: April 2006

summaryPercentage and absolute (concentration and ‘influx’) pollen diagrams are presented from four locations within a small lake (Black Loch) in eastern Scotland. Two lake marginal cores extend back to lateglacial times but material recovered from the more central cores provides data over only the last c. 3500 years. Two cores are radiocarbon dated (a total of 25 dates) and provide a chronological framework for catchment events. The differences in pollen histories between cores serve to exemplify the dangers of reliance upon single profiles, but the similarities are sufficiently strong to enable useful comparisons to be made and to permit a comprehensive reconstruction of vegetational history for the site. Of particular note is the apparent early arrival of Corylus (c. 8600 BP) and Alnus (c. 7300 BP), the local presence of Pinus and the existence of multiple elm declines. Human impacts upon the vegetational landscape are demonstrable from at least Neolithic times onwards and the presence of Cannabis sativa pollen is strong from c. 985 BP. The planting of woodland on Sanded estates over the last few centuries is clearly represented.
A 12 500 year record of vegetational history at Sluggan Bog, Co. Antrim, N. Ireland (incorporating a pollen zone scheme for the non‐specialist)
Authors: SMITH A. G. , GODDARD I. C. 
Published: April 2006

summaryA radiocarbon‐dated pollen diagram from a typical lowland raised bog in County Antrim is presented, together with a limited stratigraphic study. The record of vegetational development described is unusually complete for the last 12 FDD years. The pollen diagram is divided into ten pollen zones which it is hoped will be useful to the non‐specialist. A visual summary is given in Figure 5.Deposits of the Midlandian late‐glacial are contained in a small basin beneath the reedswamp and later Sphagnum peats of the mire. Birch woodland developed early in the sequence (approx, 12 350 BP) in the Belling interstadial period. Declines of this woodland occurred at approx. 12 200 BP and 11 700 BP. The probability that the 12200 BP decline represents the end of the thermal maximum of the late‐glacial interstadial is discussed. In the period equivalent to the classical Allerod interstadial, the vegetation appears to have been essentially treeless. A summary comparison of Irish Late‐glacial pollen assemblage zones is given. All radiocarbon dates are conventional, without calibration.The birch woods of the early post‐glacial (early Littletonian) were subject to a set‐back at approx. 9400 BP that lasted some 200 years during which time there appears to have been a reversion to the unstable soils characteristic of earlier times. The possibility of an early post‐glacial climatic oscillation is discussed.In the zonation scheme, attention is drawn to the decline of hazel pollen at approx. 8600 bp which appears to represent a turning point in woodland development. The mire surface was invaded by pines in the Late Boreal period. The decline of the pine pollen curve at the Boreal‐Atlantic transition (our S: V1‐S: VII pollen zone boundary, dated to approx. 7000 DP) is discussed in relation to evidence of burning and possible human activity.Neolithic forest clearance activity on a minor scale is attested at the elm decline which at Sluggan falls rather late in the usual range for this horizon, at approx. 4900 bp. Major episodes of forest clearance took place in the Bronze Age. Thereafter woodland largely regenerated before further clearance starting in the seventh century AD which must have become substantial by Viking times. The local woodlands appear to have recovered again, however, and despite some further clearance in the Late Anglo‐Norman period persisted substantially until relatively recent times.The possibility of climatic influences on the later vegetational history is discussed, particularly in relation to declines of the pollen curves of elm at approx. 4200 BP and AC 300, and of pine at approx. 3800 BP.
Tuberculate mycorrhizas of Castanopsis horneensis King and Engelhardtia roxburghiana Wall
Authors: HAUG I. , WEBER R. , OBERWINKLER F. , TSCHEN J. 
Published: April 2006

summaryTuberculate mycorrhizas of Castanopsis borneensis King (Fagaceae) and Engelhardtia roxburghiana Wall. (Juglandaceae) were studied by light and electron microscopy. The tubercles of both trees showed similar structure and morphology. The fungal partner is an unidentified basidiomycete. Beside normally developed mycorrhizas in each tubercle some heavily‐infected roots were found. These roots are characterized by a very thick hyphal mantle around a dead root tip and a circle‐like ingrowth of the fungus up to the vascular tissue – the strangulation zone. All cells distal to the strangulation zone were dead, but basipetal to it, normal cortical tissue with an epidermal Hartig net was present. The outer cortex in this region showed wall ingrowths along the inner tangential walls and an accumulation of ER and mitochondria. The formation and function of the heavily‐infected roots is discussed.
Mineral nutrition and mycorrhizal infection of seedling oak and birch
Authors: NEWTON A. C. 
Published: April 2006

summaryIn order to assess the factors influencing the extent and composition of ectomycorrhizal infection, and the consequences for seedling growth, seedlings of oak (Quercus robur L.) and birch (Betula pendula Roth.) were established in both field plots and pots of soil from two forested sites (Thetford Chase and Leith Hill). Seedlings were harvested after one growing season, and analysed for ectomycorrhizal infection.When a single root system of pot‐grown oak was analysed in detail seven mycorrhizal types were differentiated. The relative abundance of these types varied depending on whether infection was assessed by counting branched mycorrhizas, or individual mycorrhizal tips. This reflected variation in the pattern of branching of the different mycorrhizal types. Of the 41 mycorrhizal types differentiated in the entire survey of 1800 seedlings, five were consistently recorded as unbranched, and six were found to produce second‐order branches. Different mycorrhizal types displayed contrasting patterns of abundance, both with respect to site and host species. For example, 21 types were recorded infecting oak, whereas only 15 were found on birch; only three types were found infecting both oak and birch on both sites.In this survey, seedlings tended to be dominated by between one and three mycorrhizal types. Two types were particularly dominant: those formed by Scleroderma citrinum (Pers.) and Paxillus involutus (Batsch) Fr., which accounted for up to 61 and 92 % of the mycorrhizas of oak and birch respectively. These fungi were exceptional amongst those encountered in the present analysis, in producing both highly branched mycorrhizas and mycelial strands.The relationship between ectomycorrhizal infection and seedling growth was assessed by correlation. Total seedling dry mass was in general found to be positively correlated with the total number of ectomycorrhizal tips, but poorly correlated with the extent of ectomycorrhizal infection, except where seedling growth had previously been shown to be limited by phosphate availability (i.e. in the case of pot‐grown birch on soil from Leith Hill). Seedling dry mass was also in general poorly correlated with number of mycorrhizal types, with two exceptions (i.e. field‐grown oak and pot‐grown birch on soil from Thetford Chase).These results are discussed in the context of the role of ectomycorrhizal infection during seedling establishment, and implications for the methodologies utilized in assessing mycorrhizal infection are highlighted.
Enzymatic studies on the metabolism of vesicular—arbuscular mycorrhizas
Authors: GIANINAZZI‐PEARSON V. , SMITH S. E. , GIANINAZZI S. , SMITH F. A. 
Published: April 2006

summaryCytochemical methods were used to localize ATPase activity in different phases of development of the vesicular‐arbuscular mycorrhizal association between Allium cepa L. and Glomus intraradices Schenck & Smith. In the absence of inhibitors the pattern of lead deposition (indicative of ATPase activity) at the arbuscular interface was similar to that previously published, whether material was prefixed in glutaraldehyde or formaldehyde. Considerable activity was detected along both plant and fungal plasma membranes and in the interfacial matrix associated with young arbuscules; this decreased with senescence of arbuscules. The fungal plasma membranes of external and intercellular hyphae also showed ATPase activity, but the peripheral plant membranes interfacing with these stages of fungal development showed little or none. The only precipitates observed in the absence of ATP were in the fungal vacuoles.Inhibitors of plasma membrane H+‐ATPase (DES, SW26 and vanadate) greatly reduced the lead precipitate due to ATPase activity on the fungal and plant membranes and completely inhibited its formation in the interfacial matrix. Vanadate has been reported to inhibit ATPases other than the H+‐ATPase, and the other inhibitors may also be less specific than previously believed. Molybdate, which inhibits non‐specific phosphatase activity but not the H+‐ATPase, completely inhibited the interfacial activity but consistently left a fine precipitate along the plant membrane surrounding arbuscular hyphae and on the plasma membrane of intercellular and arbuscular trunk hyphae. Fine arbuscular branches often completely lacked activity after treatment with molybdate. EDTA, which chelates Mg2+necessary for Mg2+‐ATPase activity, and low temperature prevented the formation of membrane‐associated lead deposition in the presence of ATP, although scattered precipitates were formed over the plant and fungal cytoplasm.Incubation with β‐glycerophosphate of material prefixed with either glutaraldehyde or formaldehyde gave a picture different from that with ATP. Precipitates were heavy along the peripheral host plasma membrane and tonoplast but no or only light enzyme reactions were detected in the interfacial matrix and along the adjacent plant membrane surrounding young arbuscules, increasing in cells where arbuscular senescence was occurring. These enzyme activities were completely inhibited by molybdate but not by DES.The present observations strongly suggest that plasma membrane H+‐ATPase is a component of the ATP‐hydrolysing activities in host‐fungus interfaces of VA mycorrhiza. Interpretation of the localization of ATPase activities using cytochemical methods is discussed, together with possible changes in the distribution of the enzymes following mycorrhizal infection and their role in nutrient transfer between the symbionts.
Influence of nitrogen on accumulation of isosojagol (a newly detected coumestan in soybean) and associated isoflavonoids in roots and nodules of mycorrhizal and non‐mycorrhizal soybean
Authors: MORANDI D. , LE QUERE J. L. 
Published: April 2006

summaryA newly detected coumestan was found to accumulate in roots of soybean (Glycine max. L., var. Amsoy 71), after infection by a vesicular arbuscular (VA) mycorrhizal fungus (Glomus intraradices, Schenck & Smith) and very strongly in nodules after nitrogen application. This coumestan was identified as a 3,9 dihydroxy 10 (γ,γ‐dimethylallyl) coumestan called isosojagol. Three other associated isoflavonoids were analysed: glyceollin I, coumestrol and daidzein. Nitrogen application decreased the concentration of these three compounds in roots, particularly in non‐mycorrhizal soybeans, whilst their concentration in nodules was not significantly affected. VA mycorrhizal infection decreased the accumulation of all the compounds analysed in nodules, although the fungus was never observed inside the nodule, but increased their accumulation in roots.
Mobilization of nitrogen in swards of Trifolium subterraneum L. during regrowth after defoliation
Authors: CULVENOR R. A. , SIMPSON R. J. 
Published: April 2006

summaryThe net mobilization of nitrogen compounds (total N, soluble protein, amino N, membrane‐bound protein) from different plant parts after defoliation, and the extent to which mobilized nitrogen contributed to new leaf growth, were studied in small swards of Trifolium subterraneum L. cv. Seaton Park (subterranean clover) either completely dependent on nitrogen fixation (‐N treatment) or receiving abundant nitrate at defoliation (+ N treatment).Net mobilization of nitrogen from nodulated roots (75 % of mobilized nitrogen) and branches (25 % of mobilized nitrogen) accounted for most of the nitrogen in new leaf growth for up to 5 d in – N swards and for at least 2 d in +N swards. In – N swards, nodules degenerating as a result of defoliation were a major source of mobilized nitrogen for 2 d (50 % of mobilized nitrogen), after which the fine roots became the largest net contributor of mobilized nitrogen. Overall, a net 17% of the nitrogen present in residual organs was mobilized.Soluble protein was the major form of mobilized nitrogen for which assays were performed, accounting for 50 % of the decline in total N in the – N treatment. The relative loss of soluble protein from sward components declined in the order, nodules (47 % over 5 d), fine roots (44 % over 9 d), branches (38 % over 9 d) and taproots (37 % over 5 d). The amino N pool increased sharply in size for two days after defoliation, possibly indicating breakdown of soluble protein in excess of the nitrogen demand for regrowth or to provide a respiratory substrate.It was concluded that, in plants of adequate nitrogen status, leaf growth was unlikely to be nitrogen‐limited during the first few days after defoliation.
Some aspects of the kinetics of cadmium and thallium uptake by fronds of Lemna minor L.
Authors: KWAN K. H. M. , SMITH S. 
Published: April 2006

summaryA study of influx and accumulation of Tl and Cd by Lemna minor has revealed a number of contrasting features which arise from the basic physicochemical properties of the two elements. Short‐term influx of Cd over a range of concentration (0·1–10 üM) followed a linear trend while that of Tl over the same range produced a profile with a plateau at the higher concentrations, indicating saturation of the absorption mechanisms. Application of Ca and K antagonists aiming to indicate the nature of the absorption mechanisms did not reveal any consistent trends. Long‐term exposure of the plant to Cd and Tl produced steady‐state concentrations after 250 and 140 h respectively, by which stage Lemna had accumulated nearly twice as much Cd than Tl. It appears that a significant amount of Cd is probably in the Donnan free‐space and strongly bound to cell constituents from which the element is depurated slowly and continuously in Cd‐free medium. It is concluded that Tl is tenaciously held in the plant tissues, perhaps in the cell vacuole, as 80 % of the steady‐state concentration is retained by the plant even after 140 h in Tl‐free medium. The influence of several external physical and chemical factors further emphasizes the contrasting nature of the two elements; Tl uptake is almost entirely an active process and ion activity of Tl is relatively unaffected by changes in pH and ligand concentration. Cd uptake involves both active and passive components, ion activity is markedly reduced at low H+ion concentrations and in the presence of ligands, such as EDTA. Inhibition of uptake was found for both elements in the presence of competing ions.
Stomatal responses to abscisic acid in three lupin species
Authors: HENSON I. E. , TURNER N. C. 
Published: April 2006

summaryStomatal responses to exogenous abscisic acid (ABA), supplied to detached leaves via the transpiration stream, were examined in Lupinus augustifolius L., L. cosentinii Guss, and L. luteus L. Stomatal closure, indicated by reduced leaf conductance, was induced by ABA in all three species. This confirmed previous work with L. cosentinii, but contrasts with a report of stomatal insensitivity to ABA in L. luteus. Possible reasons for this are discussed.In all the lupin species, the abaxial leaf surface was more responsive to exogenous ABA than the adaxial surface. Comparable differences were also evident in stomatal closure in response to water deficits. ABA concentrations in abaxial and adaxial epidermal strips were found to be similar and to increase when plants were subjected to water deficits or fed ABA through the petiole. Differences in stomatal density on the two surfaces were consistent with differences in conductance observed between the surfaces of turgid leaves with low ABA levels, whilst the differential sensitivity of the two surfaces to ABA and water deficits may be related to differing amounts of ABA available per stomatal complex. The greater availability of ABA per stomatal complex on the abaxial compared to the adaxial epidermis when the lupins were subjected to water deficits or to exogenous ABA is consistent with the greater sensitivity to water deficits and ABA in abaxial compared to adaxial stomata.