bluuebunny/crossref_metadata_2025_split huggingface dataset:
Phosphorus nutrition of an obligately mycorrhizal plant treated with the fungicide benomyl in the field
Authors: MERRYWEATHER JAMES , FITTER ALASTAIR 
Published: April 2006

summaryWe controlled arbuscular mycorrhizal (AM) fungi in the routs of bluebell (Hyacinthoides non‐scripta L. Chouard ex Rothm.) in the field by immersina otherwise undisturbed colonies in a fungicide suspension. Monthly application of benomyl successfully reduced root colonization by AM fungi throughout a 2 yr experimental period. Benonlyl had lit) effect on the availability of soil phosphorus (P), but reduced the P concentration of all parts of the plant (bulb, roots, leaves and inflorescences). Unlike the vegetative parts, flowers and seed of benomyl‐treated plants had the same P concentration as untreated plants at the end of the first season. However, at the final harvest after two growing seasons flower P concentration had been reduced by treatment. H. non‐scripta appears to protect reproductive structures from P deficiency when the plant is deprived of P, suggesting that A.M plays an important role in fitness determination. This is the first demonstration that depriving a plant growing in its natural environment of mycorrhiza on a long‐term basis can reduce P acquisition. Taken with data from experiments in controlled conditions, it confirms that H. non‐scripta is an obligately mycorrhizal species.
Transmissible reproductive changes following physiological adaptation to salinity in Sorghum bicolor
Authors: AMZALLAG G. NISSIM 
Published: April 2006

summaryA 3 wk exposure to 150 mm NaCl induced adaptation to salinity in 8‐d‐old seedlings of Sorghum bicolor (L.) Moench. This treatment, defined as standard adaptation treatment, modified the expression of the reproductive traits, and the relationship between vegetative and reproductive organs, The adaptation response was accelerated when 8‐d‐old seedlings were sprayed daily with abscisic acid (ABA) for 10 d. Adaptation was also enhanced when seedlings were exposed to salinity on day 5, instead of day 8, after germination. These adaptation treatments, applied during the early vegetative development, influenced the expression of late reproductive characters. Thus besides the direct disturbing effect of NaCl, the adaptation process also has a specific influence on the expression of the sexual characters, Offspring of adapted plants were exposed to a standard adaptation treatment. The expression of the reproductive traits of the progeny was generally less perturbed than in their parents, where treatment influenced characters such as fertility, plant height and seed size of the progeny. Therefore, the adaptation process induced stabile and transmissible changes in the expression of the reproductive characters, All analogy between changes induced by salt adaptation in Sorghum plants and somaelorial variations is suggested. The evolutionary significance of the adaptation response is discussed.
Micro‐scale patterns of modern pollen deposition within three alpine plant communities*
Authors: PARDOE H. S. 
Published: April 2006

summaryFew studies have examined patterns of pollen deposition or the relationship between vegetation and pollen assemblages at the small scale. This paper examines the representation of both individual taxa and whole plant communities in modern pollen spectra. Micro‐scale variations in modern pollen deposition were studied in three alpine plant communities on Storbreen glacier foreland, southern Norway: a pioneer community; a Salix‐shrub community; and an ericaceous heath community. The relationships between vegetation and modern pollen deposition and the variability of these relationships at the local scale were investigated within 16 × 1 m2‐quadrats. The data were classified using two‐way indicator‐species analysis (TWINSPAN) and ordinated using detrended‐correspondence analysis (DCA). In addition, the pollen and vegetation data were ordinated simultaneously, using canonical correspondence analysis (CCA). The effect of removing arboreal pollen from the pollen sum was examined. The three plant communities were distinguished successfully by multivariate statistical techniques, using; both pollen data and vegetation data. However, within the communities there was high variability in pollen deposition, which was most pronounced in the Salix‐shrub community. The abundance of individual taxa in the vegetation was compared with their representation in the pollen spectra. The strongest relationships were shown by Salix Ericales, Empetrum and Lycopodium. Certain taxa showed consistent, reproducible patterns of behaviour. These patterns provided valuable evidence for separating contrasting plant communities. Comparison of modern pollen‐vegetation relationships of this kind with pollen data from Holocene and Pleistocene sites is important to improve the reconstruction of past plant communities. Statistical analyses showed that for the majority of taxa a moss polster consisting of 20 subsamples was necessary to reduce the effect of microscale variability in this environment to acceptable levels.
Late‐glacial and early Holocene vegetation of Snowdonia
Authors: INCE JOHN 
Published: April 2006

summaryDetailed pollen and lithostratigraphic analyses of lake deposits at Clogwyngarreg provide a comprehensive record of vegetational and environmental change in the lowlands of Snowdonia, north Wales during the late‐glacial and early Holocene. A radiocarbon determination suggests that the low lands were ice free by at least c. 13 500 BP. and thiit by that time open habitat herhaceous taxa, including abundant Rumex spp. were colonizing the recently deglaciated ground. The initial pioneer grassland communities Were gradually invaded by Juniperus and Betula, hut the development of birch woodland was limited. An interstadial episode, the lute‐glacial lnterstadial (Windermere Interstadial) is recognized in the sequence of plant succession that culminated m the establishment of juniper. A significant decline in Juniperus pollen frequencies and an increase in Cramineae, in the absence of an expansion in birch woodland, suggests that environmental conditions in the mid‐ to late‐late ‐glacial Interstadial were less favourable m juniper than those of the early‐middle Interstadial. Towards the top of the Interstadial organic sequence fluctuations in the Juniperus pollen curve, coupled with high Isoetes spore values and the deposition of a stone horizon, suggest local instability and re‐working prior to the deposition of Loch Lomond (Younger Dryas) Stadial mini‐rofjenic sediments. By c. 11 000 BP widespread solifluction and increasingly severe environmental conditions led to a breakup of existing plant communities and a proliferation of open habitat and disturbed ground taxa. During the Loch Lomond (Younger Dryas) Stadial, glaciers reoccupied the higher cwms of Snowdonia. Climatic amelioration, marking the Holocene at c. 10 000 yr BP, was characterized by a rapid expansion of Juniperus at Clogwyngarreg and evidence for early Holocene woodland development is presented.
Antioxidant responses to drought in sunflower and sorghum seedlings
Authors: ZHANG JINGXIAN , KIRKHAM M. B. 
Published: April 2006

summaryTo determine if antioxidant responses to drought differ between C3 and C4 plants, we grew Sorghum bicolor (C4) and Helianthus annuus (C3) under either watered or dry conditions in a growth chamber. Levels of leaf enzymatic antioxidants (ascorbate peroxidase, catalase, guaiacol peroxidase, dehydroascorbate reductase, monodehydroascorbate reductase, glutathione reductase and superoxide dismutase), nonenzymatic antioxidants (ascorbate, glutathione and carotenoids) and stress parameters (Chl and malondialdehyde [MDA]) were determined. Under watered and drought conditions, Chl contents and leaf relative water contents (RWC) were higher in sorghum than in sunflower; however, MDA levels were higher in sunflower than in sorghum. Under watered conditions, inherent levels of antioxidants were not consistently higher or lower in sorghum than in sunflower. In response to drought, levels of antioxidants, Chl and MDA showed increase, decrease or remained unchanged depending on crop, duration of drought and kind of antioxidants. Duration of drought was divided arbitrarily into three stages. At an early stage of drought (watering had stopped for 3–4 d) when soil water content (WC) and leaf RWC had decreased only in sunflower, drought generally did not affect levels of antioxidants and stress parameters. At a middle stage of drought (watering had stopped for 5–6 d) when soil WC had decreased for both sorghum and sunflower but leaf WC and RWC had decreased only in sunflower, drought changed levels of some antioxidants in sunflower and sorghum. At a late stage of drought (watering had stopped for 7–8 d) when soil WC, leaf WC and RWC had decreased in sorghum and sunflower, most parameters studied were affected by drought. Because of the differential effect of drought, levels of antioxidants were not consistently higher or lower in sorghum than in sunflower under drought. These results show that, under both drought and watered conditions, sorghum does not have consistently higher or lower antioxidant levels than sunflower, and that antioxidant responses to drought differ in C3 and C4 plants.
Ammonium assimilation by young plants of Hordeum vulgare in light and darkness: effects on respiratory oxygen consumption by roots
Authors: RIGANO C. , DI MARTINO RIGANO V. , VONA V. , CARFAGNA S. , CARILLO P. , ESPOSITO S. 
Published: April 2006

summaryBarley plants (Hordeum vutgare L.) grown for 10 d in nitrogen‐free hydroponic culture, after a rapid initial phase absorbed supplied NH4+ at a constant rate of 15.1 ±1.2 μ mol h−1 g−1f. wt in the light, arid at a rate of 13.81 ± 1.6 μ mol h−1 g−1 f. wt in darkness. Ammonium‐grown plants assimilated NH4+ at a rate of 7.5 ± 0.33 μmol h−1 g−1 f. wt and at a 50% lower rate in darkness. Nitrogen‐free grown plants showed low concentrations of free amino acids in both root and shoot tissues. Supplying NH4+ caused an immediate increase in the concentration of free amino in the root tissues of both illuminated and darkened plants over a 120 mm period. The increase in concentration of glutamine then exhibited a lag period of 120 min, after which it resumed, but to a very small extent. Glutamine also accumulated in shoot tissue of illuminated plants at increasing rates, attaining a concentration which, 8 h after NH4+ supply, was 1.61‐fold greater than that attained in the roots. In shoots of darkened plants, by contrast, the concentration of glutamine increased slowly and was always smaller than that in the root tissue. Overall formation of glutamine (in shoots and roots) occurred at decreasing rates during the first 4 h, and then at increasing rates. The increase was more pronounced in illuminated plants than in darkened plants, liven 24 h after NH4+ was supplied, glutamine content in root tissue was lower than that in shoot tissue. However, 48 h later, the concentrations of glutamine in root and shoot were similar, attaining values that were almost 47‐fold (in root) and 134‐fold (in shoot) greater than initial values. Significant levels of asparagine were detected in the root and in the shoot 24 h after adding NH4+. These increased further during the succeeding period. Ammonium supply caused a transitory drop in the concentration of ATP in root tissue, along with noticeable transitory variations in glucose‐6‐P concentration. A permanent decrease in free glucose concentration was also detected. Addition of NH4+ caused 2‐ and 1.43‐fold increases in respiratory oxygen consumption by roots of illuminated and darkened plants, respectively. Both in the light and in the dark, the root tissue accumulated methylammonium up to a concentration of 55–67 μmol h−1 g−1f. wt. Methylammonium was never found in shoot tissue of either illuminated or darkened plants. Methylammonium stimulated respiration of root barley plants by a factor of 1.2. Regulatory aspects of NH4+ metabolism are discussed.
The phosphorus requirement of N2‐fixing and urea‐fed Acacia mangium
Authors: RIBET JÉRǑME , DREVON JEAN‐JACQUES 
Published: April 2006

summaryThe fast‐growing leguminous tree Acacia mangium Willd, was grown for at least 22 wk in aerated solution culture either under N2‐fixing conditions or with 2 mmol urea per plant per wk. Inorganic phosphorus was supplied at between 1 and 100 μmol P1 per plant per wk: the latter was determined to be the optimum P supply for growth. The external P requirement for growth and the efficiency of utilization of internal P were similar for both N sources. However, shoot growth and the concentrations of N and P in leaves were decreased by P deficiency to a slightly higher extent in N2‐fixing plants than in urea‐fed plants. Even though P deficiency limited nodule growth more drastically than it did shoot growth, the fraction of P allocated to both nodules and nodule nitrogenase activity (acetylene reduction) increased with P deficiency. It is concluded that this increase in nitrogenase activity reflects a higher N requirement per unit nodule mass in P‐deficient plants and that, once nodules are fully functional the efficiency of utilization of internal P in N2‐fixing A. mangium is high compared with that of other N2‐fixing legumes.
Effects of elevated carbon dioxide and arbuscular mycorrhizal infection onTrifolium repens
Authors: JONGEN MARJAN , FAY PETER , JONES MICHAEL B. 
Published: April 2006

summaryTrifolium repensL. cv. aran was grown for 58 d at ambient (350 μol mol−1) and elevated (700 μol mol−1) atmospheric CO2, wish and without the arbuscular mycorrhizal fungusGlomus mosseae(Nicol. & Gerd.) Gerd. & Trappe cv. YV. Plant biomass, mycorrhizal infection, non‐structural carbohydrates, C, N and P content were examined. Elevated CO2(a) significantly increased above‐ and below‐ground biomass, (b) decreased specific leaf area and specific root length, (c) decreased tissue %N and increased the C:N ratio, and (d) significantly increased total non‐structural carbohydrates. InoculatingT. ripenswithGlomus mosseae(a) significantly increased above‐ and below‐ground biomass. (b) increased the total root length and total leaf area, and (c) significantly decreased tissue of Evidence of an increased influence of mycorrhiza on the P nutrition ofT. repensat elevated CO2was found in the 22%, increase in leaf total P (P< 005) of mycorrhizal plants grown at elevated CO2compared with non‐mycorrhizal plants. No significant interactions were found between CO2and mycorrhiza treatments.The proportion ofT. repensroot length colonized byGlomus mosseae wasnot affected byCO2concentration. The percentage mycorrhizal infection was 29% at ambient CO2and 35%, et al elevated CO2. However, exposure to elevated CO2significantly increased the total mycorrhizal foot length from 3.4 to 6.1 m per plant.The results show little evidence that the role of arbuscular mycorrhiza in the growth and nutrition ofT. repenswould increase if atmospheric CO2were to increase as predicted.
Phosphodiesterase as mycorrhizal P sources
Authors: LEAKE J. R. , MILES W. 
Published: April 2006

summaryThese results provide the first account of the breakdown and utilization of DNA by an ericoid mycorrhizal fungus, and of its phosphodiesterase activity in vitro. Hymenoscyphus ericae (Read) Korf & Kernan grew well on DNA as a sole source of phosphorus (P), achieving greater mycelium dry weight than on an equivalent concentration of P supplied as orthophosphate. Some characteristics of the production and activity of extracellular (culture filtrate) and cell‐wall bound phosphodiesterase in H. ericae are reported. At least part of the phosphodiesterase activity is attributed to the exonuclease F nucleotide diesterase on the basis of its high affinity for a specific substrate of this enzyme, The pH optima for extra‐cellular and cell‐wall‐bound diesterase are acidic (pH 4.0–5.5), with considerable activity maintained in the pH range typical of organic soils under ericaceous plants (pH 3.0–4.5). The production of phosphodiesterase was not substrate‐induced, since highest specific activity for wall‐bound enzyme was found in culture grown without organic or inorganic P. The results are discussed in relation to the ecology and biology of acid organic soils on which ericaceous plants are dominant.
Phosphodiesters as mycorrhizal P sources
Authors: MYERS M. D. , LEAKE J. R. 
Published: April 2006

summaryMycorrhizal plants of Vaccinium mocrocarpon Aiton used nuclei from salmon sperm as a sole source of phosphorus (P) and achieved similar yields, P content and P concentration to plants crown with orthophosphate. Mycorrhizal infection significantly increased the effectiveness of utilization of both inorganic and organic (nuclei) sources of P by Vaccinium but in the case of the organic source this involved providing access to P which was completely unavailable to the uninfected plants. The results provide further support for the view that ericoid mycorrhizas have a crucial role in direct recycling of nutrients from organic matter, independent of the mineralizing activities of saprotrophic micro‐organisms.
The physiology of basidiomycete linear organs
Authors: GRAY S. N. , DIGHTON J. , JENNINGS D. H. 
Published: April 2006

summaryAutoradiography and quantitative image analysis were used to measure 137Cs distribution and translocation through mycelia of A. gallica Marxmuller & Romagn. and A. ostoyae (Romagn.) Herink growing in small microcosms in the laboratory. Rhizomorphs of A. gallica were labelled with 134Cs in the field, and the translation of radiolabel measured after excavation and destructive harvesting. The flux of radiocaesium through rhizomorphs was estimated to be greater than through undifferentiated hyphae, and greater through rhizomorphs growing in the field than through rhizomorphs grown across homogeneous media in the laboratory'. Differentiation within mycelia resulting in melanization or rhizomorph formation cave rise to increased heterogeneity in the 137Cs distribution through laboratory microcosms compared with that through microcosms containing undifferentiated mycelia. Radiocaesium leaked from undifferentiated hyphae into the surrounding medium, but melanized regions of the mycelium appeared to be conservative for radiocaesium. These findings provide further evidence for the importance of filamentous fungi in determining the distribution and rate of release of radiocaesium currently present in the environment as a result of weapons testing and the accident at the Chernobyl nuclear reactor.
Ion compartmentation in the red algaCaloglossa leprieuriiin response to salinity changes: freeze‐substitution and X‐ray microanalysis
Authors: MOSTAERT ANIKAS S. , ORLOVICH DAVID A. , KING ROBERT J. 
Published: April 2006

summaryThe elemental content of cell compartments in the euryhaline red macroalgaCaloglossa leprieurii(Montague) J. Agardh subjected to different salinities, was determined by X‐ray microanalysis of freeze‐substituted thin sections. Duty are given for three compartments; cell wall, vacuole and cytoplasm. The most abundant elements detected were potassium, sodium and chlorine, with a Sulphur peak in the cell wall indicating the presence of sulphated polysaccharides. With salinity upshock the cytoplasm is maintained low in K, Na and Cl, whereas in the vacuoles they increased. High levels of K and Na located in the cell wall reflect cation binding to negatively charged polysaccharides. Hyposaline shock resulted in decreased K, Na and Cl levels in all compartments, though K was retained in the cytoplasm. Results are discussed with regard to the role of ion compartmentation in the salt tolerance of this alga, and the cation exchange properties of the cell wall are emphasized.
Cation ratios inCladonia portentosaas indices of precipitation acidity in the British Isles
Authors: HYVÄRINEN M. , CRITTENDEN P. D. 
Published: April 2006

summaryThe relationship between rainfall chemistry and the concentrations of potassium, calcium and magnesium in the apices (top 5 mm) of the cushion‐forming; lichenCladonia portentosa(Dufour) Coem was investigated. Lichen samples, together with underlying topsoil, were collected from heathlands in close proximity to rain gauges in the UK Acid Deposition Monitoring Network, located in rural areas of the British Isles, which provide wet deposition data based on weekly bulk samples. The ratios K+: Mg2+and extracellular Mg2+: intracellular Mg2+in the lichen apices were strongly correlated with H+concentration in precipitation. It is suggested that shifts in these ratios occur owing to enhanced displacement of extracellular Mg2+by elevated H+concentration in acid rain. By contrast, there was no indication of any relationship between total acid deposition and lichen chemistry. The concentration of Mg2+in the lichen was weakly correlated with that in soil, whereas lichen Ca2+content was not correlated with either precipitation or soil chemistry. It is concluded that these ratios describing changes in lichen Mg2+content provide good biomarkers for wet‐deposited acidity.
Molecular genetics of cellular differentiation in leaves
Authors: HALL LISA N. , LANGDALE JANE A. 
Published: April 2006

summaryLeaves of green plants vary widely in morphology. However, the underlying cell types and structures observed in leaves of different species are remarkably similar. Although we can adequately describe leaf development in morphological terms we cannot yet explain interactions at the cellular level. In recent years molecular genetics has been used extensively to address a variety of developmental questions. The isolation of a wide variety of mutants disrupted in numerous aspects of leaf ontogeny has led to the cloning of genes involved in various developmental processes. In this review we consider advances that have been made in understanding shoot apical meristem organization, leaf initiation and the development of leaf form. In particular we concentrate on progress, that has been made in understanding cellular differentiation in the epidermis, and within the interior of the leaf, namely the photosynthetic cells and the vasculature.

CONTENTS

Summary
533

I.
Introduction
533

II.
Shoot growth
533

III.
Leaf initiation
534

IV.
Development of leaf form
536

V.
Cellular differentiation
537

VI.
Perspectives
548

VII.
Acknowledgements
549

VIII.
References
549