bluuebunny/crossref_metadata_2025_split huggingface dataset:
Quantification of frost damage in plant tissues by rates of electrolyte leakage
Authors: MURRAY M. B. , CAPE J. N. , FOWLER D. 
Published: April 2006

SUMMARYA method for assessing frost hardiness of plant tissues [using shoots of Picea rubens Sarg. syn P. rubra (Du Roi) Link] has been developed based upon the rate of electrolyte leakage from shoots immersed in distilled water after exposure to a range of freezing treatments. The relationship between conductivity (the electrolyte concentration in solution) and time has been shown to follow an asymptotic curve, which may be represented by a first‐order equation: Ct–Co= Cauto–Co– C‐kt) where C1 is the conductivity at time t, Co is the initial conductivity, Cautois the conductivity after autoclaving and k is the first‐order rate constant (units time‐1). The rate of electrolyte leakage (k) varies directly with the extent of tissue damage. In P. rebens a rate of 0‐4%, h‐1 distinguished between shoots which eventually died, and shoots which remained alive. A minimum of 3 conductivity measurements (after 1 day, 5 days and after autoclaving) is required for a reliable estimate of k. This objective, quantitative method of assessing frost hardiness may therefore be used directly to estimate LT50 values within a population.
Interpretation of the pollen stratigraphy of Late Devensian lateglacial and early Flandrian sediments at Llyn Gwernan, near Cader Idris, North Wales
Authors: LOWE J. J. , LOWE S. 
Published: April 2006

SUMMARYPollen‐stratigraphic information is presented for two profiles from a high resolution Devensian lateglacial succession at Llyn Gwernan, North Wales. Pollen concentration and preservation data are available for one of these profiles and two series of radiocarbon dates, one based on‘conventional’radiometric counting and one on accelerator mass spectrometry measures, provide age estimates for the succession. The data indicate the following sequence of events at Llyn Gwernan: deglaciation of the area about or shortly before 14200 n. p.; cold, dry climatic conditions from 14200 to 13 200 n. p.; generally stable environmental conditions from 13 200 to 12 100 B.P.; steady deterioration of climate between 12100 and 11 160 B.I.; harsh climatic conditions between 11 160 and 10200–10000 B.P. This interpretation broadly supports that previously proposed for N. Wales on the basis of coleopteran evidence. Implications of some of the differences in pollen stratigraphy between the two Llyn Gwernan profiles and possible evidence for two minor climatic oscillations during the lateglacial interstadial are discussed.
Two pollen diagrams from the same site
Authors: TURNER JUDITH , INNES J. B. , SIMMONS I. G. 
Published: April 2006

SUMMARYTwo pollen diagrams from within one metre of each other at a blanket peat site on the North York Moors are similar, and fully justify the usual practice of preparing only one diagram. There are however minor differences. These indicate the degree of random variation that can occur and should be borne in mind when interpreting pollen diagrams from blanket peat.
Pollen analysis of a Quaternary peat sequence on Gough Island, South Atlantic
Authors: BENNETT K. D. , GRIBNITZ K.‐H. , KENT L. E. 
Published: April 2006

SUMMARYA peat sequence on Gough Island, South Atlantic, is described. The deposit is at least 43 000 years old, and may be early Quaternary in age. Pollen analyses suggest a flora and vegetation on Cough Island similar to those of today, supporting conclusions based on pre‐Holocene pollen samples from islands in the Tristan da Cunha group. The present flora has probably been on Cough Island continuously for at least the last 40000 years, and is not a Holocene immigrant flora.
Instability in the root meristem of Zea mays L. during growth
Authors: CLOWES F. A. L. , WADEKAR R. 
Published: April 2006

SUMMARYPrimary roots of Zea mays L., when grown to 100 mm long, may display instability in the architecture of their meristems. This occurs over the whole temperature range from 15 to 35 °C, but most frequently at the two extremes of the range and is associated with abnormally low ratios between rates of mitosis in the proximal tier of the cap cells and rates in the cells of the Quiescent centre. Anomalous meristems show either proliferation of the number of cell layers between stelar pole and cap boundary or protrusions of cells derived from the quiescent centre into the cap where they can spread to form new sets of cap initials. The process can be repeated, but there is no evidence to suggest that the originally closed meristem ever operates as an open meristem with only transiently quiescent cells distal to the stelar pole.
Absence of nuclear DNA synthesis in vesicular–arbuscular mycorrhizal fungi during in vitro development
Authors: BURGGRAAF A. J. P. , BERINGER J. E. 
Published: April 2006

SUMMARYA study of the in vitro viability of VA mycorrhizal propagules [Glomus caledonium (Nicol. & Gerd.), Gigaspora margarita (Becher & Hall)], indicated that none could be used for continuous in vitro cultivation. Large numbers of nuclei (at least 20000 for G. margarita) were found in the chlamydospores. Nuclear division could not be demonstrated in vitro, during or after spore germination using various cell cycle inhibitors, or by direct isotope labelling of nuclear DNA. Manipulation of secondary messengers (cAMP, calcium) and the microtubule or micro‐filament system did not increase the in vitro growth of the tested VA mycorrhizal strains.
Responses of the non7hyphen;mycotrophic plant Salsola kali to invasion by vesicular–arbuscular mycorrhizal fungi
Authors: ALLEN MICHAEL F. , ALLEN EDITH B. , FRIESE CARL F. 
Published: April 2006

SUMMARYVesicular–arbuscular mycorrhizal fungi reduced the growth and survival of the non‐mycotrophic weed, Salsola kali (Chenopodiaceae) in field and greenhouse experiments. To determine the mechanisms by which mycorrhizal fungi can affect a non‐mycotrophic plant, we mapped the root responses of S. kali and the mycotrophic grass Agropyron dasystachyum to invasion by a mixture of Glomus spp. and by Gigaspora margarita. The fungi invaded the roots of both species within 10 days following seed germination. In A. dasystachyum normal mycorrhizal development occurred and no root browning or autofluorescence was observed, indicating a compatible reaction. In S. kali, the fungi initially invaded the roots and formed arbuscules and peletons. The roots reacted to invasion by autofluorescing bright yellow, suggesting lignification. With 1 or 2 days following root penetration by the fungus, the invaded root segment turned brown and, with the exception of some vesicles, the fungus disappeared from the root. The fungus sometimes then reinvaded new root segments farther down the root.These observations suggest that there is an incompatible reaction beween this non‐mycotrophic annual and VA mycorrhizal fungi whereby the plant actively rejects infection. This response could form the basis for initiating studies on the genetics of mutualistic versus parasitic symbioses.
Cotton root growth as influenced by phosphorus nutrition and vesicular–arbuscular mycorrhizas
Authors: PRICE N. S. , RONCADORI R. W. , HUSSEY R. S. 
Published: April 2006

SUMMARYCotton, Gossypium hirsutum L., was grown in the greenhouse in sand‐nutrient culture at five phosphorus (P) concentrations, and root systems were examined after 10 and 20 days. Extension rates of primary laterals and numbers of secondary laterals increased with increasing P. Cotton was grown for 6 weeks in environment cabinets in soils of three P concentrations with and without mycorrhizas. Increased P and mycorrhizas both stimulated plant growth (f. wt shoot d. wt), but however specific root length (cm root g' root f. wt) of mycorrhizal plants was reduced.
Use of cryo‐techniques with scanning electron microscopy to study infection of mature red raspberry fruits by Botrytis cinerea
Authors: WILLIAMSON B. , DUNCAN G. H. 
Published: April 2006

SUMMARYScanning electron microscopy (SEM) was used to study the infection of the mesocarp cells of ripe drupelets of the compound fruit of red raspberry (Rubus idaeus L.) by Botrytis cinerea Pers.: Fr. 24 h after the fruit had been wounded and inoculated with dry conidia. Frozen fully hydrated specimens showed that conidia had germinated in juice at the point of inoculation and in partially freeze‐dried specimens hyphae were visible in some cells. However, structural detail was largely obscured by ice segregation zones in the closely packed large columnar, poyhedral cells of the fruit. These artifacts were removed in specimens which had been cryotrimmed and fully freeze‐dried. In such specimens there were four distinct zones around the inoculation wound. Intercellular and intracellular hyphae were visible in the innermost area (zone 1); the walls of some infected cells were swollen, eroded and porous. In zone 2, an area of cells immediately beyond the hyphae, little structure was retained but in zone 3 cell walls were well preserved and showed lamellar or reticulate material in the intercellular spaces. The outer zone (zone 4) consisted of apparently healthy cells.
Interactions between infection by endophytic fungi and nutrient limitation in the grasses Lolium perenne and Festuca arundinacea
Authors: CHEPLICK G. P. , CLAY K. , MARKS S. 
Published: April 2006

SUMMARYAlthough grasses infected by fungal endophytes often exhibit increased growth relative to uninfected plants, the results of infection may be manifested as decreased growth in plants growing under stressful conditions. A preliminary experiment compared perennial ryegrass (Lolium perenne L.) infected by Acremonium lolii Latch, Christensen & Samuels with uninfected plants grown at three soil moistures and three nutrient concentrations. Total biomass, tiller number, and relative tillering rate were significantly affected by nutrient concentration and moisture. Although major differences between infected and uninfected plants were not apparent, relative growth rates of infected plants were significantly greater than uninfected plants in three of nine treatment combinations. Interactions between infection and nutrient limitation were examined in seedlings and adults of perennial ryegrass and tall fescue (Festuca arundinacea Schreb., infected by A. coenophialum Morgan‐Jones and Gams). A significant nutrient × infection interaction for tall fescue seedlings indicated that, compared to uninfected seedlings, infected seedlings had greater biomass at the high nutrient level but a significantly lower biomass at the low nutrient level, suggesting a metabolic cost to the host due to competition with the fungus for nutrients or photosynthate. Infected perennial ryegrass seedlings had significantly more biomass at high and intermediate nutrient levels, but not at low nutrient levels. Although infection did not significantly affect total biomass in perennial ryegrass adults, in tall fescue adults the benefits of endophyte infection to host plants (recorded as greater biomass) became increasingly greater with increasing nutrient availability.
Pollen assemblage–plant community relationships on the Storbreen glacier foreland, Jotunheimen Mountains, southern Norway
Authors: CASELDINE C. J. 
Published: April 2006

SUMMARYPresent‐day pollen assemblages from 38 sites within differing but closely juxtaposed plant communities from the Storbreen glacier foreland in southern Norway, provide evidence for the degree to which these plant communities can be characterized by distinctive pollen assemblages. Multivariate statistical analyses of the data demonstrate a broad, tripartite division in the pollen record which reflects the three major vegetation types: (i) Pioneer Poa alpina–Trisetum spicatum community; (ii) Snowbed Salix herbacea‐dominated community; (iii) Dwarf‐shrub heath community. Occasional overrepresentation of Salix, Oxyria and Cyperaceae pollen leads to assemblages that are difficult to characterize and remain outside all major groups. Four general pollen indices are derived, each of which provide maximum limiting estimates for the proportion of pollen derived from different potential source areas. Combined with isopollen mapping the indices suggest that in pioneer communities between 20–40% of pollen collected within the community could have derived locally i.e. within the 16 m2 quadrat, whereas in the dwarf‐shrub heath this figure rises to over 60%. The remaining pollen largely originates from long distance transport, i.e. < 1 km, with little movement of foreland‐derived pollen across the foreland itself. Thus the ‘extra‐local’ component appears to play a relatively insignificant role within the area of study. The ability to separate such local and long‐distance elements will prove of particular value in the reconstruction of the history of plant communities beyond the tree‐line.
Superoxide dismutase activation in response to lime‐induced chlorosis
Authors: OSTROVSKAYA L. K. , TRUCH V. V. , MIKHAILIK O. M. 
Published: April 2006

SummaryAlterations in superoxide dismutase (SOD) activity were studied on chlorotic grapevines (Vitis vinifera L.) grown under natural conditions on soil containing 30–35% CaCO3, and in lupins (Lupinus luteus L.) grown in a greenhouse with addition of 20% CaCO3 to the soil. In both series of experiments SOD activity in leaves of chlorotic plants was from 20 to 30%, higher. The efficiency and absolute rate of superoxide anion radical formation were found to rise as a result of iron deficiency in the lupin leaves. Increased SOD activity and greater amounts of enzyme isoforms were observed in the leaves of grapevine cultivars resistant to lime‐induced chlorosis as compared to less resistant cultivars. The present investigation suggests that initiation of lime‐induced chlorosis is determined not only by reduced chlorophyll biosynthesis but also by other consequencies of iron deficiency in tissues, particularly by the high rate of formation of superoxide and other activated oxygen species, causing destructive changes in the photosynthetic apparatus. The increased SOD activity may be regarded as a protective mechanism against the formation of superoxide.
On host regulation of the vesicular—arbuscular mycorrhizal symbiosis
Authors: KOIDE ROGER T. , LI MINGGUANG 
Published: April 2006

SummaryWe investigated mycorrhizal infections caused by Glomus elunicalum Becker & Gerd. in sunflower (Helianthus annuus L.) plants given small concentrations of phosphate. In pure sand given no additional phosphate, infection was only poorly developed. As phosphate availability was increased, the extent of infection also initially increased. We hypothesized that the extent of infection should be regulated by the nutritional status of the shoot. However, by performing a split‐root experiment, we found that the root rather than the shoot was responsible for this regulation.
A technique for dual vesicular–arbuscular endomycorrhizal/ectomycorrhizal infection of Eucalyptus in vitro
Authors: BOUDARGA KHADIJA , LAPEYRIE FRÉDERIÉ , DEXHEIMER JEAN 
Published: April 2006

SummaryA few species of plant, including Eucalyptus, bear simultaneously on their root system and even on the same root apex, more than one symbiotic microorganism. The development of techniques allowing mixed inoculations is an essential prerequisite for the study of interactions between different symbionts. A simple in vitro technique for rapid synthesis of dual vesicular‐arbuscular endomycorrhiza/ectomycorrhiza on a single root apex of Eucalyptus seedlings is described. This technique was derived from the paper‐sandwich technique for synthesis of ectomycorrhizas, and was modified to render it compatible with endomycorrhizal infection. Electron microscopy observations of dual endomycorrhiza/ectomycorrhiza showed both symbioses coexisting on the same apex, with no obvious sign of antagonism.
Growth and phosphorus acquisition of karri (Eucalyptus diversicolor F. Muell.) seedlings inoculated with ectomycorrhizal fungi in relation to phosphorus supply
Authors: BOUGHER N. L. , GROVE T. S. , MALAJCZUK N. 
Published: April 2006

SummaryGrowth and phosphorus acquisition of pot‐grown seedlings of karri (Eucalyptus diversicolor F. Muell.) were examined following inoculation with four ectomycorrhizal fungi –Descolea maculata Bougher (two isolates), Pisolithus tinctorius (Pers.) Coker & Couch, and Laccaria laccata (Scop, ex Fr.) Berk. & Br. Seedlings were raised in steam‐sterilized sand to which 13 rates of phosphorus (0.100 mg P kg−1 soil) were applied.All fungi except P. tinctorius produced a plant growth response. L. laccata produced the largest growth response. Responses were greatest at low rates of application of P to soil. There was no effect of the fungi on growth at levels of P application above 28 mg P kg−1 soil. A threshold effect (no increase in growth with increasing additions of P) characteristic of non‐mycorrhizal seedlings was eliminated by mycorrhizal infection.Mycorrhizal inoculation increased P content of plant tissues at sub‐optimal levels of P supply. The effect of mycorrhizas on seedling P status diminished with increasing soil P. One isolate of D. maculata often had greater rates of P accumulation and produced higher concentrations of P in plant tissues than L. laccata, but did not produce greater plant biomass.Frequency of infection for all fungi was low in soils with no additional P, and greatest with the addition of 2 mg P kg−1 soil (L. laccata and D. maculata isolate A), or 4 mg P kg−1 soil (D. maculata isolate B). Infection was reduced with increasing soil P, and not evident at 36 mg P kg−1 soil or higher levels of soil P. L. laccata had higher infection frequency and mycorrhizal root length at all levels of soil P than the D. maculata isolates.Two fungi produced basidiomes. This occurred at levels of soil P application ranging from 4 to 28 mg P kg−1 soil for D. maculata (isolate B), and at 4 to 28 mg P kg−1 soil for L. laccata.
Nitrate nutrition of maritime pine (Pinus pinaster Soland in Ait.) ectomycorrhizal with Hebeloma cylindrosporum Romagn.
Authors: SCHEROMM P. , PLASSARD C. , SALSAC L. 
Published: April 2006

SummaryIn maritime pine seedlings (Pinus pinaster Soland in Ait.), nitrate absorption and reduction capacities were estimated by the incorporation of 15N‐labelled nitrogen. This method allowed us to work on the whole plant Without perturbing plant behaviour. For this purpose, xylem and phloem transports were quantified. After 48 h i nitrate nutrition, mycorrhizal symbiosis with Hebeloma cylindrosporum Romagn. modified neither nitrate accumulation nor absorption and reduction capacities of this anion. Xylem transport of reduced nitrogen was similar in mycorrhizal and non‐mycorrhizal seedlings. Only phloem transport was modified by mycorrhizal symbiosis. The intensity of the phloem transport in mycorrhizal pines was approximately twice that in non‐mycorrhizal plants.
Developmental changes in Sitka spruce as indices of physiological age
Authors: STEELE M. J. , YEOMAN M. M. , COUTTS M. P. 
Published: April 2006

SummaryAdventitious rooting ability is considered a good indicator of juvenility in trees and has often been used to assess explants subjected to treatments to alter developmental stage. However, rooting assessments are not always practical and the callusing of needles in vitro was investigated as an alternative bioassay of physiological age. Shoots were sampled from the uppermost whorl of Sitka spruce trees aged 1, 3, 4, 6, 11, 16, 21, 35 and 39 years and from the lowest whorls of 3‐ and 4‐year‐old trees. Needles were sampled for measurement of length, width, length/width ratio, projected and total surface areas, dry weight and specific leaf area. For explants of uppermost whorl origin, there were decreases in the rooting ability of cuttings and the callusing response of needles with increasing age of tree. Associated with the loss in callusing ability was an increase in the production of a black exudate. The changes with age for rooiing, callusing and exudation could each be adequately described by the Gompertz growth function which showed their rates of change to be similar. The observed changes are closely associated with changes in needle area, weight and specific leaf area. Euclidean distances (using the mean values of selected characteristics for each age class) were computed as a measure of physiological age. The shoots and needles of basal shoots are more juvenile in character than those taken from the uppermost whorls of the same trees.
The role of iron in nodulation and nitrogen fixation in Lupinus angustifolius L
Authors: TANG CAIXIAN , ROBSON ALAN D. , DILWORTH MICHAEL J. 
Published: April 2006

SUMMARYThe effects of iron concentration in solution on nodulation and symbiotic N2 fixation in lupins (Lupinus angustifolius L. ev. Yandee) were studied in solution culture in the glasshouse by comparing plants supplied with NH4NO3 with those reliant on N2 fixation.At very low iron supply, adding NH4NO2 did not increase shoot growth. Under moderate iron deficiency, where plants were pale green, adding NH4NO3 increased shoot growth, implying that moderate iron deficiency was, operationally, nitrogen deficiency. Higher iron concentrations in solution were required for maximum growth of plants reliant on symbiotic N2 fixation than for those supplied with NH4NO3Iron deficiency depressed nodule initiation earlier than host plant growth, resulting in decreased nodule number and mass. Alleviating iron deficiency enhanced leghaemoglobin production in nodules and increased nitrogen concentrations in the shoots. Iron concentration in the youngest fully expanded leaves provided a good indication of the severity of iron deficiency‐caused chlorosis.The results suggest that iron is involved in symbiotic N2 fixation through effects on both nodule initiation and nodule function, and that the symbiosis has a higher iron requirement than that needed for host plant growth.
The effect of zinc contamination from electricity pylons. Contrasting patterns of evolution in five grass species
Authors: AL‐HIYALY S. A. K. , MCNEILLY T. , BRADSHAW A. D. 
Published: April 2006

SUMMARYSamples of 8–35 individuals of Agrostis capillaris, A. stolonifera, Anthoxanthum odoratum, Deschampsia cespitosa and Festuca ovina were collected from zinc‐contaminated soils beneath electricity pylons erected in North Wales and Lancashire between 1956 and 1970. Their zinc tolerance was assessed, as was that of two individuals of the same species collected from adjacent uncontaminated soils. Five soil samples from beneath each pylon were collected for evaluating total and extractable soil zinc, soil pH, and soil organic matter.Some degree of zinc tolerance was detected in all five species, suggesting that evolution of tolerance has taken place relatively rapidly, particularly in A. capillaris, D. cespitosa, and Anthoxanthum odoratum. However, tolerant individuals of all species were not found beneath all pylons even when the species was present in the surrounding vegetation. This confirms and extends to other species previous findings in A. capillaris, that the gene or genes necessary for the evolution of tolerance are not universally present within species.