bluuebunny/crossref_metadata_2025 huggingface dataset:
Occurrence of heavy metal tolerance and co‐tolerance in Deschampsia cespitosa (L.) Beauv. from European and Canadian populations
Authors: VON FRENCKELL‐INSAM BEATRIX A. K. , HUTCHINSON THOMAS C.
Published: April 2006

By sampling soils and plants from a variety of metal‐contaminated sites in Canada and Europe, heavy metal tolerance and co‐tolerance have been investigated in the grass Deschampsia cespitosa L. (Beauv.). Soils were analyzed for water extractable Ca, as well as for their heavy metal content (Cu, Ni, Zn, Pb, Cd, Co), electrical conductivity, pH and organic matter. Canadian plant material was collected from non‐contaminated areas, as well as sites contaminated by copper and nickel (Sudbury) and nickel and cobalt (Cobalt). European plants were sampled from reference sites and from zinc and lead contaminated locations (Bleikuhle, Pochsand/Germany).

Using cloned material the ‘in parallel’ root elongation technique was employed to determine tolerance indices to individual metals (Cu, Ni, Zn, Pb). Among the Canadian plants, patterns of tolerances matched patterns of soil contamination. Thus, at the Cobalt sites, Cu was not present in elevated amounts, and the plants did not exhibit Cu tolerance. Also, evidence suggests that the close correlation of Cu and Ni tolerance among the Sudbury plants was not the result of Cu‐Ni co‐tolerance but occurred because ions of both metals were present in elevated amounts at these sites. In addition to the tolerances expected on soil chemistry, plants taken from metal contaminated sites exhibited enhanced tolerance also to metal ions not elevated in the soils of their origin. This is interpreted as general, non‐specific, low level co‐tolerance. Thus, most Cobalt and Sudbury plants exhibited incidental tolerance at a higher level to Zn and Pb. Correlation analysis revealed very close relations both between Zn and Pb, and especially between Ni and Zn, supporting findings from previous studies. It was concluded that among the Canadian populations tested in this study, Ni tolerance conferred Zn tolerance.

Among the European plants examined, the expected tolerances to Zn and Pb were found. However, whereas some control plants from non‐contaminated sites exhibited relatively high tolerances to these metal ions, the tolerance of plants from mines was lower than expected. The Zn and Pb tolerant mine populations had no tolerance to Cu and only very low tolerance to Ni, suggesting that the enhanced Zn tolerance associated with Ni tolerance in the Canadian plants is not necessarily reversible, i.e. Zn tolerance does not necessarily confer Ni tolerance.
The demography of fine roots in response to patches of water and nitrogen
Authors: PREGITZER KURT S. , HENDRICK RONALD L. , FOGEL ROBERT
Published: April 2006

Fine root demography was quantified in response to patches of increased water and nitrogen availability in a natural, second‐growth, mixed hardwood forest in northern Michigan, USA. As expected, the addition of water and water plus nitrogen resulted in a significant overall increase in the production of new fine roots. New root production was much greater in response to water plus nitrogen when compared with water alone, and the duration of new root production was related to the length of resource addition in the water plus nitrogen treatments; the average difference in new root length between the 20vs.40 d additions of water plus nitrogen amounted to almost 600%. Roots produced in response to the additions of water and water plus nitrogen lived longer than roots in the control treatments. Thus, additions of water and water plus nitrogen influenced both the proliferation of new roots and their longevity, with both proliferation and longevity related to the type and duration of resource supply. Results suggest that root longevity and mortality may be plastic in response to changes in soil resource availability, as is well known for root proliferation.
The susceptibility of roots to infection by an arbuscular mycorrhizal fungus in relation to age and phosphorus supply
Authors: AMIJEE BY F. , STRIBLEY D. P. , LANE P. W.
Published: April 2006

An apparatus in which plant roots may be challenged uniformly with inoculum of arbuscular mycorrhizal fungi is described. Seedlings of leek (Allium porrum L.) or clover (Trifolium repens L.) were first grown non‐symbiotically in the apparatus for 21 d at three rates of phosphorus (P) addition to soil (150 (P1), 450 (P3) and 750 (P5) mg P kg−1 soil). The positions of individual root tips were recorded, and the root systems then challenged with inoculum of Glomus mosseae (Nicol & Gerd.) Gerdemann & Trappe. Roots were excised 14 d later, and the probability of occurrence of internal infection in successive 3 mm (clover) or 5 mm (leek) sections of root was estimated in first‐order laterals (clover) or main axes (leek) from the proportion of sections at each location of replicate roots that bore internal fungal structures.

Only in the region of a root proximal to the position of the root tips at inoculation could data be used to investigate change of probability of infection with cell age. Here, there were sharp declines in probability of infection with proximal distance, in both hosts and in all P treatments. The decline of probability was greater in clover: when expressed in terms of cell age at the time of challenge, there was no infection at PI in cells ≤ 10 d old in leek and none in cells ≤ 7 d old in clover.

Models of the form loge, [p1/(1 –p1)] =α+β× distance, where p1 is the estimated probability of infection and a and α are constants, were fitted to these data. The odds on infection are [p1/(1 –p1)]. For leek, β was unaltered by P addition (P3 and P5 curves were parallel to P1) but from a it could be calculated that on average the odds on successful infection at any particular distance were reduced by 37% and 70% by P3 and P5 rates of P addition respectively. In clover the curves for the three P treatments were not parallel. Addition of P appeared to reduce the odds on infection of clover much more than those of leek.

We conclude that the simplest explanation for the patterns of infection in leek is that P addition increased the time taken for soil inoculum of G. mosseae to infect roots: the mechanism in clover might be more complex.
Differential hyphal morphogenesis in arbuscular mycorrhizal fungi during pre‐infection stages
Authors: GIOVANNETTI M. , SBRANA C. , AVIO L. , CITERNESI A. S. , LOGI C.
Published: April 2006

Roots of host plants elicit a local change in morphology in the hyphae of arbuscular mycorrhizal fungi, prior to the formation of appressoria. The elicited hyphae switch from their original branching pattern and apical dominance to differentiate in a new irregular, septate branching pattern with reduced inter‐hyphal spacing. The extensive hyphal development associated with roots of host plants was shown to be due to the differential growth pattern described, and to precede the further cascade of events leading to appressorium formation and the development of a functional symbiosis.
Research on mycorrhizas: trends in the past 40 years as expressed in the ‘MYCOLIT’ database
Authors: KLIRONOMOS JOHN. , KENDRICK W. BRYCE
Published: April 2006

A detailed analysis of MYCOLIT, a comprehensive bibliographic database of mycorrhizal research containing almost 12000 references, showed some interesting trends over the past 40 yr. During the last four decades, the average number of papers published per year were 84, 110, 214 and 488, respectively. The current rate of publication is about 700 papers per year. Much research has focused on nutrient dynamics, inoculum production, mycorrhiza formation, and morphology and physiology of both vesicular‐arbuscular mycorrhizas (VAM) and ectomycorrhizas (EM). There has been a shift of attention from EM to VAM since 1970. Very little work has been done on the other kinds of mycorrhizas. Barriers to progress in some areas, such as our inability to grow the Glomales in axenic culture, have stimulated a large number of methodological papers over the past decade, while the genetics and molecular biology, especially of VAM, have been neglected. Ecological studies were more numerous than any other kind. However, there was a bias towards laboratory studies as opposed to field studies. Within field studies, researchers focused on agricultural ecosystems, while neglecting disturbed and especially natural systems. This analysis also suggests that we may know less than we think about mycorrhizas, since we have consistently based broad hypotheses and conclusions on studies of a small number of tax. Future research should be directed towards correcting the various imbalances revealed by this analysis.
Growth and stomatal responses of birch (Betula pendula Roth.) clones to ozone in open‐air and chamber fumigations
Authors: PÄÄKKÖNEN E. , PAASISALO S. , HOLOPAINEN T. , KÄRENLAMP L.
Published: April 2006

It is evident that even outside the classical high ozone areas some plant species are at risk. In this study seedlings of five birch clones (Betula pendula Roth.) were exposed to a slightly elevated ozone level in an open‐field experiment over two growing seasons. The ozone doses were 1.2 × (1991) and 15 × (1992) higher than the ambient. The clones were also fumigated with 150 nl I1 ozone for 24 d (12 h d−1) in a chamber experiment. They were found to differ in their susceptibility to ozone: ozone fumigation decreased the height growth and leaf biomass, and increased the amount of advanced visible injury in leaves of the most sensitive clone, but did not affect the height growth or amount of visible injury of the most tolerant clone. The other three clones were intermediate with respect to their sensitivity to ozone. In all clones, elevated O3 concentrations increased diffusive resistance to water vapour but increased the stomatal density in the emerging leaves. The appearance of autumn colouring was accelerated in the field experiments. The results support the conclusion that birch populations in Finland can be negatively affected by ozone. The effect is most likely in sensitive birch individuals during ozone episodes.
Developmental biology of lichens
Authors: HONEGGER ROSMARIE
Published: April 2006

Lichen‐forming fungi are a large, taxonomically diverse group of nutritional specialists which acquire fixed carbon from a population of minute green algal or cyanobacterial cells. Mycobionts of foliose or fruticose lichens differ from the rest of the fungi by expressing morphologically and anatomically complex symbiotic phenotypes. The extracellularly located photobiont cell population of these macrolichens is housed and controlled by the quantitatively predominant fungal partner which competes for space above ground, secures adequate illumination and facilitates gas exchange. This review summarizes data on the ontogeny, functional morphology, growth patterns and internal thalline differentiation of macrolichens.

Contents

Summary
659

I.
Introduction
659

II.
Establishment of the lichen symbiosis
662

III.
Growth and cell turnover
669

IV.
Outlook
674

Acknowledgements
674

References
674
Immobilization of pectin, xyloglucan and other soluble plant polysaccharides on blotting membranes
Authors: JEFFREE CHRISTOPHER E.
Published: April 2006

Soluble polysaccharides, of natural and synthetic origins, are immobilized by nylon, nitrocellulose, and polyvinylidene difluoride blotting membranes. Retention of an acid and a neutral polysaccharide, measured using radioactive pectin and xyloglucan‐rich hemicellulose, exceeded 90% on some blotting membranes eluted in aqueous media. The two polysaccharides displayed different binding characteristics.

Several polyanionic uronic acid polysaccharides, bound strongly to nylon 66 (Hybond N, Amersham) and to positively charge‐modified or cationic nylon blotting membranes (Hybond N +, Amersham), but much less strongly to paper, nitrocellulose or polyvinylidene difluoride. Fragments of pectin, including Rhamnogalacturonan I and Rhamnogalacturonan II, and galacturonic acid oligosaccharides as small as the dimer also bind to nylon membranes, and can be detected using cationic dyes or by means of their radioactivity. Xyloglucan‐rich hemicellulose in general binds more strongly than pectin to the same substrates. Of the substrates tested charge‐modified nylon gave best retention of pectin, and paper gave best retention of xyloglucan during washes in water and solutions of salts, acids and bases.

The influence of pH and solutions of mono, di‐ and trivalent salts on the retention of some pectic polysaccharides by nylon was investigated. A large proportion, in excess of 70% of pectin applied to charge‐modified nylon, remained tightly bound at all salt concentrations up to 2 M.

Soluble acid polysaccharides immobilized on blotting membranes could be detected by staining with cationic dyes, such as ruthenium red, alcian blue 8GX, and coriphosphine O, providing facile detection and a simple means of characterizing the cytochemical specificity of their staining reactions. Immobilized neutral polysaccharides, which do not react with cationic dyes, could usually be detected by the periodate‐Schiff reaction, or, if labelled with radionuclides, by autoradiography or scintillation counting.

Soluble polysaccharides, like proteins and nucleic acids, may therefore be immobilized on blotting membranes for investigation with cytochemical, immunocytochemical, and other molecular probing and detection procedures. Quantitative binding data showed marked differences in the affinity of different polysaccharides for blotting substrates. Detailed characterization of the binding behaviour is therefore a prerequisite for optimization and rational application of polysaccharide blotting.
Growth and photosynthetic acclimation by Ranunculus aquatilis L. in response to inorganic carbon availability
Authors: MADSEN TOM VINDÆK
Published: April 2006

Relative growth rates of Ranunculus aquatilis L. were measured in the laboratory at dissolved inorganic carbon (DIC) concentrations between 0.2 and 5.2 mM at air‐equilibrium CO2 (16 μM) and also at 0.55 mm DIC with elevated CO2 (350 μM). For plants grown at air‐equilibrium CO2, growth was limited by inorganic carbon below 1.6 mM DIC and the apparent half saturation constant was 0.5 mM. The growth rate at elevated CO2 was 50% higher than the carbon saturated rates obtained at high DIC concentrations and air‐equibrium CO2, where HCO3− is dominant. This difference is suggested to be caused by differences in uptake mechanisms for CO2 and HCO3− Uptake of CO2 is a diffusive process, whereas HCOa− use is an active process which involves uptake/transport systems in the cell membranes.

The plants acclimated to the DIC regime for growth by reductions in carboxylation efficiency and bicarbonate affinity, but enhanced photosynthetic capacity at elevated DIC. Within the range of concentrations used, the acclimation to CO2 and HCO3− was quantitatively similar, except for the HCO3− uptake capacity which increased at high DIC and air‐equilibrium CO2 but declined at elevated CO2. Dark respiration was unaffected by inorganic carbon per se, but increased with growth rate. Maintenance respiration was constant among treatments. It is concluded that inorganic carbon, apart from being the primary substrate for photosynthesis, has secondary growth regulatory effects which affect the photosynthetic apparatus of the plants.
Relations between carbon and nitrogen during growth of Nannochloropsis oculata (Droop) Hibberd under continuous illumination
Authors: FLYNN K. J. , DAVIDSON K. , CUNNINGHAM A.
Published: April 2006

Growth of the marine eustigmatophyte Nannochloropsis oculata (Droop) Hibberd was Followed through two periods of batch growth from stationary phase until cessation of net C‐fixation. Growth continued for two generations after exhaustion of the N‐source (100μM NH4+), with an increase in the cell C/N mass ratio from 6 to 28. N‐deprived cells had a larger mean volume (130%) than N‐replete cells. Intracellular concentrations of carotenoids and Chla correlated with cell‐N until exhaustion of the N‐source, when Chla ml−1 of culture declined significantly. The contribution of intracellular amino‐N to cell‐N was less than 3% throughout exponential and stationary phases. The major intracellular amino acids were glutamate (Glu), glutamine (Gln) and alanine; concentrations of tyrosine (on a population basis) increased steadily during N‐deprivation. The intracellular concentrations of other amino acids showed fluctuations corresponding with changes in growth rate (e.g. arginine) or cell‐N (e.g. glycine). The intracellular ratio of Gln/Glu reached a peak of more than 26 within 3 h of inoculation of stationary phase cells into fresh medium, before falling to around 0.6 during exponential growth, and then remained below 0.1 after NH4− exhaustion. Of the extracellular amino acids, concentrations of alanine and serine remained relatively constant throughout, while those of glycine, glutamate and of total dissolved free amino acids increased during exponential and early post‐exponential phases, before levelling off at 1.4μM amino‐N. The behaviour of Nannochloropsis oculata is contrasted with the growth and physiology of Isochrysis galbana
Differences in photosynthetic performance between cyanobacterial and green algal components of lichen photosymbiodemes measured in the field
Authors: GREEN T. G. A. , BUDEL B. , HEBER U. , MEYER A. , ZELLNER H. , LANGE O. L.
Published: April 2006

Photosymbiodemes are lichens which contain a single mycobiont but have cyanobacteria and green algae as primary photobionts in different parts of the thallus. Members of a photosymbiodeme can be found as separate, free‐living lichen species. The photosynthesis of the components of two Pseudocyphellaria photosymbiodemes were studied in the natural forest environment in New Zealand. It was found that the green algal component had a large photosynthetic advantage when thallus water contents were low and the thalli were in equilibrium with atmospheric humidity. The cyanobacterial components were at an advantage when thallus water contents were very high. The environment in which photosymbiodemes are found, forest margins in high humidity areas, seems to provide the correct combination of thallus water contents so that neither component has a major advantage. The photosymbiodemes appear to be models, preserved by the special habitat and showing a possible early stage in the evolution before the definite separation of ecologically specialised green algal and cyanobacterial species.
Sites of entry of water into the symplast of maize roots
Authors: VARNEY G. T. , MCCULLY M. E. , CANNY M. J.
Published: April 2006

Following our publication of a new method of calculating rates of water uptake by roots from measurements of the rate of accumulation on the roots of a marker solute, this paper describes the sites of accumulation of the solute, which indicate the sites where the water entered the symplast. Sulphorhodamine G (SR) was supplied in aeroponic mist culture to large maize plants with fully developed root systems. Root samples were collected after 4 to 8 h of transpiration in the dye‐mist from both axes and branches of the main roots, and from non‐transpiring (detopped) controls, frozen rapidly, freeze‐substituted, and embedded and sectioned by an anhydrous procedure that preserves the SR in place. Whole mounts and sections were examined by bright‐field, polarizing and epifluorescence microscopy. Major accumulations of SR were all at the outer surface of the roots, on Epidermal or root hair cell walls, or, in older roots where the epidermal cells were separating or dead, on the outer wall of the hypodermis. On some branch roots, though not on any main axes, the accumulations of SR were conspicuously aligned in the grooves over anticlinal cell walls of the epidermis. Non‐transpiring plants showed very slight accumulations. Diffusion of SR into the cell wall apoplast was limited by the suberized lamellae and Casparian bands of the hypodermis, except in some branch roots, where SR diffused throughout the cortical cell walls. In parts of roots where the epidermis and hypodermis had been damaged, SR diffused through cell walls of the cortex from the wound site. These patterns of accumulation show that water enters the symplast of roots at the outermost cell membranes of the root, whether they are epidermal or hypodermal cells. Water enters roots with fully developed hypodermises at high rates. The rote of the hypodermal suberization is to limit solute movement in the wall apoplast. A symplastic path for water throughout the cortex, endodermis and living cells of the stele is suggested.
A simple method for locating the start of symplastic water flow (flumes) in leaves
Authors: O'DOWD N. A. , CANNY M. J.
Published: April 2006

The identification of sites in leaves where transpiration water crosses cell membranes and enters the symplast has previously been made using freeze‐substitution to locate concentrations of dye [e.g. sulphorhodamine (SR)] moving with the transpiration stream, and left outside the membranes where the water passes through. These concentrations were called sumps, and the sites of entry to the symplast were called flumes. A simple method of locating sumps, and therefore flumes, is described. Fresh leaves, fed SR solution through their cut petioles for pulse periods of 0.5 h or more, followed or not by a chase of water, were sectioned by hand under paraffin oil, and the sections mounted in the same fluid. Observation of the sections by simple bright‐field microscopy revealed sumps of SR at the same sites, and of the same crystalline nature as found in the freeze‐substituted preparations. The saving in preparation time is of the order of > 100‐fold, at the sacrifice of resolution (5–10 μm compared with 0.2 μm). A limited survey of grass, sedge and dicotyledon leaves by this method confirmed in all essentials the results found by freeze‐substitution, and in addition, revealed flumes at the fusoid cells on the flanks of the veins of bamboo leaves, and at the same position next to the water tissue of Cyperus leaves. The rate of accumulation of crystalline SR in the sumps inside tracheary elements suggests that the concentration of this non‐permeating solute in the xylem sap increased by about 1000‐fold in the finest veins during 1–2 h of transpiration in the dye solution.
Humidity and light affect the growth, development and nitrogenase activity of stem nodules of Sesbania rostrata Brem
Authors: PARSONS RICHARD , SPRENT JANET I. , RAVEN JOHN A.
Published: April 2006

The growth and nitrogenase activity of stem nodules of Sesbania rostrata Brem were strongly influenced by the humidity surrounding the nodule. Nodules developed under high humidity showed the fastest rates of growth and the highest specific nitrogenase activity (determined by acetylene reduction). Development of stem nodules in both the light and dark was similar and showed a similar lowering of growth and activity with decreasing humidity. Stem nodules developed in the dark were pale and unlike the dark green nodules that developed in the light, they did not have chloroplasts in the nodule cortex. Adventitious root development required darkness and relative humidities approaching 100%. In stem nodules that were grown at high humidity and subsequently exposed to lower humidities, there was only a small loss of nitrogenase activity, and high rates of acetylene reduction were maintained for 6 d after treatments were begun. The area of nodule attachment to the stem or root was measured in nodules of many sizes and found to be consistently greater in stem nodules. This may have implications for the comparative water balance of nodules on these two organs.
Specificity of the Rhizobium—legume symbiosis obtained after mutagenesis in pea (Pisum sativum L.)
Authors: SAGAN M. , MESSAGER A. , DUC G.
Published: April 2006

Within a set of 13 induced symbiotic pea (Pisum sativum L.) mutants, two distinct mutated genes sym25 and sym26, selected for ineffective nodulation have been counteracted in their effect by Rhizobium strains 254 and 94 respectively, thereby establishing an N2‐fixing symbiosis. This suggests that mutagenesis can be a helpful tool in creating specificity systems such as those described in centres of origin and diversification of legume species.
Concentrations of indole‐3‐acetic acid in plants of tolerant and susceptible varieties of Chinese cabbage infected with Plasmodiophora brassicae Woron.
Authors: LUDWIG‐MÜLLER JUTTA , BENDEL ULRIKE , THERMANN PETRA , RUPPEL MANFRED , EPSTEIN EPHRAIM , HILGENBERG WILLY
Published: April 2006

A convenient method for infecting Brassica seedlings in liquid medium with the Phytopathogenic fungus Plasmodiophora brassicae was developed. The infection rates of two susceptible and two tolerant Chinese cabbage varieties with wild type P. brassicae were investigated. The content of free indole‐3‐acetic acid (IAA) was determined using combined gas chromatography‐mass spectrometry (GC‐MS) with [13C6]‐IAA as internal standard during the first period of infection with the fungus (5–14 d) and compared with the indole glucosinolate content of two Chinese cabbage varieties (one tolerant, one susceptible) in the same developmental stages, The results showed that the mean of the IAA content in the infected plants was approximately 66.5% higher than that of the non‐infected controls. In both the susceptible and tolerant varieties higher levels of IAA were found in the infected plants 10 d after the beginning of incubation. After 14 d of incubation IAA levels decreased in the susceptible, infected plants and increased in the tolerant, infected plants.
Apoplastic antioxidants as decisive elimination factors within the uptake process of nitrogen dioxide into leaf tissues
Authors: RAMGE P. , BADECK F.‐W. , PLÖCHL M. , KOHLMAIER G. H.
Published: April 2006

Uptake of NO2 via stomata and its elimination in the mesophyll are investigated by use of mathematical models. Systems of differential equations describe simultaneous diffusion and reaction of the chemical species taken into account. The common hypothesis, postulating the disproportionation reaction of NO2 being the predominant path for the transformation of NO2 into the cellular nitrate and nitrite pools, could be false because of its failure to reproduce the measured sorption characteristics. If however the reduction of the pro‐oxidative NO2 by apoplastic ascorbate is taken into account the calculated uptake rates and the effects of changes in immission concentration and vegetational characteristics fit well within corresponding experimental results. The onset of acute injury in case of a fall in apoplastic ascorbate concentration below a critical level is postulated.
Environmental influences on the development of spruce needle cuticles
Authors: CAPE J. N. , PERCY K. E.
Published: April 2006

Seedlings of Norway [Picea abies (L.) Karst.], red (P. rubens Sarg.), black [P. mariana (Mill) B.S.P.] and white [P. glauca (Moench.) Voss] spruce were grown from bud break to bud set outdoors, in the greenhouse, and in controlled environment chambers. The outdoor and greenhouse treatments also included adjacent shaded (50%) seedlings. The effects of growth environment on needle epicuticular wax production and morphology, and on needle wettability were investigated. Red and black spruce exhibited free growth in addition to determinate growth, but only in the greenhouse. Although relative growth rate was significantly lower for seedlings grown outdoors, there were no differences in wax morphology between outdoor‐ and greenhouse‐grown seedlings, Wax deposits on controlled environment seedlings were significantly more crystalline. Wax tubes were crystallized in ‘tufts’. There were significant differences in wax amounts recovered between species and treatments. Wax amounts relative to needle dry weights decreased in the order greenhouse > outdoors > controlled environment. Shaded red and black spruce produced significantly more wax than unshaded. Needles from seedlings grown in controlled environment chambers had the largest needle/droplet contact angles. These data indicate that seedling growth environment affects needle epicuticular wax characteristics and wettability. Studies designed to investigate factors determined by needle surface phystcochemical characteristics should include a consideration of growth environment.
Growth analyses on in vitro, ex vitro and auxin‐rooted hypocotyl cuttings of Pinus contorta Dougl. ex Loud.
Authors: GRÖNROOS ROLAND , FLYGH GUNNAR , KÄHR MONIKA , VON ARNOLD SARA
Published: April 2006

Three different types of rooted hypocotyl cuttings showed relative growth rates close to those recorded as maximal for seedlings of Pinus contorta Dougl. ex Loud. However, slight differences in growth rate were noted depending on how the cuttings had been rooted. (I) Cuttings rooted in vitro initially formed a large wound tissue at the base from which roots subsequently developed. (II) Cuttings rooted ex vitro formed roots without previous formation of a wound tissue at the root‐shoot connection. I and II produced plants with in average two roots per plant and the plants grew at similar relative growth rates (6.86 and 6.88 % per day respectively). (III) Auxin‐rooted cuttings also formed roots (21 per plant) without previous formation of a wound tissue and had a slightly higher growth rate (7.65 % d−1). The growth rate of auxin‐rooted cuttings was not significantly different from the 8.67 % d−1 obtained in seedlings. The conclusions drawn from these experiments were that; (1) rooted cuttings have the capacity to grow almost as fast as seedlings, (2) wound tissue produced prior to rooting or an extended period before the roots develop does not have a negative affect on the growth capacity of the cuttings, (3) the number of roots per cutting did not affect growth rate.
Effects of cadmium on non‐mycorrhizal and mycorrhizal Norway spruce seedlings [Picea abies (L.) Karst.] and its ectomycorrhizal fungus Laccaria laccata (Scop, ex Fr.) Bk. & Br.: Sulphate reduction, thiols and distribution of the heavy metal
Authors: GALLI ULRICH , MEIER MARTIN , BRUNOLD CHRISTIAN
Published: April 2006

The effect of cadmium on assimilatory sulphate reduction and thiol content was studied in non‐mycorrhizal and mycorrhizal Norway spruce seedlings (Picea abies) and its ectomycorrhtzal fungus Laccaria laccata. The distribution of cadmium was also investigated. Isotope dilution experiments indicated that the fungus reduced sulphate via adenosine 3′‐phosphate 5′‐phosphosulphate sulphotransferase, whereas Norway spruce seedlings assimilated sulphate via adenosine 5′‐phosphosulphate sulphotransferase in both roots and needles. In mycorrhizal roots only the plant sulphotransferase activity could be measured. Mycorrhizal and non‐mycorrhizal roots and the mycelium of Laccaria laccata contained increased activities of sulphotransferase and more acid‐soluble thiols when cultivated with cadmium. The increase in acid‐soluble thiols was due to phytochelatins in roots and to glutathione in Laccaria laccata, where neither phytochelatins nor metallothioneins could be detected. Even though the cadmium content of mycorrhizal roots was slightly higher than that of non‐mycorrhizal roots, concentrations of phytochelatin were only half as high as in non‐mycorrhizal roots. Cadmium content of needles of mycorrhizal plants was significantly lower than that of non‐mycorrhizal plants. Most of the cadmium in Laccaria laccata was associated with the cell walls and could be exchanged with Ni2+.
Contrasting effects of elevated CO2 on the root and shoot growth of four native herbs commonly found in chalk grassland
Authors: FERRIS RACHEL , TAYLOR GAIL
Published: April 2006

The aim of this study was to investigate the impact of ambient (345 μl l−1) and elevated (590 μl l−1) CO2on the root and shoot growth of four native chalk grassland herbs: Sanguisorba minor Scop, (salad burnet), Lotus carniculatus L. (birdsfoot trefoil), Anthyllis vulneraria L. (kidney vetch) and Plantago media L. (hoary plantain).

Elevated CO2 had contrasting effects on both shoot and root growth of the four species studied. Both leaf expansion and production were stimulated by elevated CO2 for S. minor, L. corniculatus and P. media, whilst for A. vulneraria, only leaflet shape appeared to be altered by elevated CO2, with the production of broader leaflets, compared with those produced in ambient CO2. After 100 d shoot biomass was enhanced in elevated CO2 for S. minor and L. corniculatus, whilst there was no effect of elevated CO2 on shoot biomass for A. vulneraria or P. media. Contrasting effects of CO2 were also apparent for measurements of specific leaf area (SLA), which increased for L. corniculatus, decreased for A. vulneraria and remained unaltered for S. minor and P. media in elevated compared with ambient CO2.

Elevated CO2 also had contrasting effects on both the growth and morphology of roots. The accumulation of root biomass was stimulated following exposure to elevated CO2 for S. minor and L. corniculatus whilst there was no effect on root biomass for A. vulneraria or P. media. Root length was measured on three occasions during the 100 d and revealed that exposure to elevated CO2 promoted root extension in S. minor, L. corniculatus and P. media, but not in A. vulneraria. Specific root length (SRL, length per unit dry weight) was increased in elevated CO2 for one species, P. media, whilst the root to shoot ratio of all four species remained unchanged by CO2.

These results show that four native herbs differ in their response to CO2, suggesting that the structure of this plant community may be altered in the future.
Plasmolysis: new insights into an old process
Authors: OPARKA KARL J.
Published: April 2006

Early microscopists made detailed observations of the phenomenon of plasmolysis, many of which have passed into the historical record without comment. This review considers the significance of these observations in the light of recent cell‐biological studies which are addressing the complex relationships between the plasma membrane (PM) and the extracellular matrix, as well as the interrelationships of the PM, endomembrane system and cytoskeleton. Emphasis is placed on the relative roles of Hechtian strand formation and PM vesiculation as mechanisms allowing the conservation of PM during a plasmolysis/deplasmolysis cycle. The behaviour of plasmodesmata during plasmolysis is considered in relation to the ability of cells to resume intercellular transport following deplasmolysis. Finally, the behaviour of cells during freeze‐induced ptesmolysis is addressed.

ContentsSummary571I.Introduction572II.The vagaries of plasmolysia573III.The behaviour of the plasma membrane (PM) during plastnolysis575IV.Plasmodesmata582V.Vesiculation of the PM584VI.Effects of plasmolysis on wall growth587VII.Injury arising from plasmolysis588VIII.Concluding remarks589Acknowledgements589References589
Stay‐green genotypes of Phaseolus vulgaris L.: chloroplast proteins and chlorophyll catabolites during foliar senescence
Authors: BACHMANN ANDRÉ , FERNÁNDEZ‐LÓPEZ JOSE , GINSBURG SAMUEL , THOMAS HOWARD , BOUWKAMP JOHN C. , SOLOMOS THEOPHANES , MATILE PHILIPPE
Published: April 2006

Leaf senescence was analyzed in stay‐green mutants of Phaseolus vulgaris. Impaired yellowing in these genotypes was accompanied by abnormal retention of thylakoid membrane proteins including the light‐harvesting chlorophyll‐binding protein of photosystem II, the 33 kDa polypeptide of the oxygen‐evolving complex, cytochrome f and the psaF protein of photosystem I. On the other hand, ribulose bisphosphate carboxylase was somewhat more labile in the mutant than the wild‐type. The stay‐green character was not associated with unusual persistence of chlorophyll biosynthesis enzymes. During senescence, normal leaf tissue accumulated an array of fluorescent (FCC) and non‐fluorescent (NCC) compounds with chromatographic and spectrophotometric properties similar to those of chlorophyll catabolites previously identified in other species. With the exception of one prominent NCC and a trace of one FCC, these constituents were absent from extracts of stay‐green genotypes, strongly supporting the proposal that they are indeed products of chlorophyll breakdown. The kinetics of their accumulation during senescence was consistent with a primary or intermediary role for FCCs in the catabolic pathway whereas NCCs seem to be final products. The complement of FCCs and NCCs in Phaseolus vulgaris was as distinct from that of the previously‐studied species barley and rape as the latter are from each other. Genotypic and interspecific variations in the biochemistry of senescence are discussed in relation to genetic regulation of the process.
Extra‐ and intra‐cellular carbonic anhydrase in relation to culture age in a high‐calcifying strain of Emiliania huxleyi Lohmann
Authors: NIMER N. A. , GUAN Q. , MERRETT M. J.
Published: April 2006

The relationships between extra‐ and intra‐cellular carbonic anhydrase, calcification rate, utilization of dissolved inorganic carbon (DIG) and culture age were investigated in a high‐calcifying strain of Emiliania huxleyi. The detection of carbonic anhydrasc was dependent on culture age; neither the extra‐cellular activity of intact cells nor activity in crude homogenates was detected until the stationary phase. By the stationary phase DIC in the medium was totally depleted and the calcification rate had decreased by 60°0. Extra‐ and intra‐cellular carbonic anhydrase was stimulated by Na+but not Cl ions. The isolation of intact organelles by isopycnic gradient centrifugal ion from exponential and stationary phase cultures of high calcifying cells showed high carbonic anhydrase activity in the chloroplast fraction but carbonic anhydrase was not detected in low‐calcifying cells even after gradient centrifugation. Although 50/IM ethoxyzolamide was an effective inhibitor of carbonic anhydrase activity in vitro, photosynthetic 14CO2 fixation was only inhibited 30%, calcification rate 10%, and the internal inorganic carbon pool unaffected in intact cells. It is proposed that chloroplast carbonic anhydrase maintains the steady state flux of COj, from the chloroplast envelope to Rubisco, much of the CO2 arising by release from HCO3−in the cytosol, required to maintain cytoplasmic pH near neutrality in high‐calcifying cells.
Does ozone stress change the primary or secondary metabolites of birch (Betula pendula Roth.)?
Authors: LAVOLA A. , JULKUNEN‐TIITTO R. , PÄÄKKÖNEN E.
Published: April 2006

In field experiments three clones of two‐year‐old birch (Betula pendula Roth.) were exposed for one growing season to an ozone concentration 1–2 times higher than ambient. At the end of August, leaf and stem material was analyzed for a wide range of primary and secondary metabolites. Although most of these metabolites were not significantly affected by ozone exposure, ozone‐treated leaves contained larger concentrations of total sugars and reduced amounts of the phenolic glucoside, dehydrosalidroside. In the stems, greater amounts of catechin pentoside, hyperoside and papyriferic acid were found. The results indicated considerable inter‐ and intra‐clonal variation in the production of phytochemicals in both leaves and stems.
Reconstitution of the symbiosis of Gunnera manicata Linden: cyanobacterial specificity
Authors: JOHANSSON CHRISTINA , BERGMAN BIRGITTA
Published: April 2006

The ability of various cyanobacteria to establish a symbiosis with Gunnera manicata Linden was examined under sterile conditions. Cyanobacterial strains were classified as infective if they could be found in a well‐defined infected area within the Gunnera gland tissue 40 d after inoculation. Nine out of 17 tested Nostoc strains were able to infect G. manicata. The infecting strains were all symbiotic isolates. These included six out of ten isolates from Gunnera spp., the isolate from the cycad Macrozamia sp., that from the hornwort Anthocerns sp., and that from the lichen Peltigera canina. None of the seven strains belonging to genera other than Nostne was capable of infection, even though the majority of them were also able to form motile hormogonia. Negative staining revealed fimbria‐like structures in both infective and non‐infective strains. In fact, two of the non‐infecting strains had the most abundant fimbria‐like filaments. No conspicuous structural or ultrastructural differences between infecting and non‐infecting strains were detected using light‐ and transmission electron microscopy. We conclude that selection between conceivable microsymbionts is exerted at the recognition and/or entrance stage.
Biology of the ectomycorrhizal genus, Rhizopogon
Authors: MOLINA RANDY , TRAPPE JAMES M.
Published: April 2006

Twenty nine isolates of Rhizopogon from 20 spp. differed markedly in their ability to form ectomycorrhizas with Douglas fir, western hemlock and lodgepole pine in pure‐culture syntheses, Within the four sections of Rhizopogon there were similarities in ectomycorrhizal appearance and range of potential hosts. Intermediate and overlapping ectomycorrhiza! characters were evident in closely related species complexes. Although the host‐specificity of many species, based on field observations of sporocarps, often correlated with their host range in the syntheses, some fungi formed well‐developed ectomycorrhiza on hosts with which they appear not to be associated in the field. The specificity of host associations is suggested as a major contributor to the speciation and diversification of Rhtzopogon in the Pacific Northwest of the USA and Canada.
Plant species that can be linked by VA mycorrhizal fungi
Authors: NEWMAN E. I. , DEVOY C. L. N. , EASEN N. J. , FOWLES K. J.
Published: April 2006

Pairs of plant species were grown in soil in transparent plastic containers, one grass with one dicotyledonous species. All the species are normally VA mycorrhizal. Hyphal links were observed between eight of the species‐pairs. However, in only three of these pairs was internal VA mycorrhizal infection clearly seen in both species. These involved a grass plus a legume, and grasses with the woody climber Hedera helix.
Secondary metabolites in plant defence mechanisms
Authors: BENNETT RICHARD N. , WALLSGROVE ROGER M.
Published: April 2006

Many secondary metabolites found in plants have a role in defence against herbivores, pests and pathogens. In this review, a few examples are described and discussed, and some of the problems in determining the precise role(s) of such metabolites highlighted. The role of secondary metabolites in defence may involve deterrence/anti‐feedant activity, toxicity or acting as precursors to physical defence systems. Many specialist herbivores and pathogens do not merely circumvent the deterrent or toxic effects of secondary metabolites but actually utilize these compounds as either host recognition cues or nutrients (or both). This is true of both cyanogenic glucosides and glucosinolates, which art discussed in detail as examples of defensive compounds. Their biochemistry is compared and contrasted. An enormous variety of secondary metabolites are derived from shikimic acid or aromatic amino acids, many of which have important roles in defence mechanisms. Several classes of secondary products are ‘induced’ by infection, wounding or herbivory, and examples of these are given. Genetic variation in the speed and extent of such induction may account, at least in part, for the difference between resistant and susceptible varieties. Both salicylates and jasmonates have been implicated as signals in such responses and in many other physiological processes, though their prescise roles and interactions in signalling and development are not fully understood.

Contents

Summary
617

I.
Introduction
617

II.
Cyanogenic glucosides
618

III.
Glucosinolates
619

IV.
Non‐protein amino acids
621

V.
Alkaloids
622

VI.
Plant phenoiics
623

VII.
Plant terpenes, sesquiterpenoids and sterols
626

VIII.
Phytoalexins
626

IX.
Salicylic acid and methyl jasnionate
627

X.
Conclusions
628

References
629
Effects of atmospheric ammonia and ammonium sulphate on vesicular–arbuscular mycorrhizal colonization in three heathland species
Authors: HEIJNE B. , DUECK A. , VAN DER EERDEN L. J. , HEIL G. W.
Published: April 2006

Three heathland species. Arnica montana L., Viola canina L. and Nardus stricta L., were exposed to gaseous ammonia and artificial rain containing ammonium sulphate for 11 wk. Plants infected with Glomus fasciculatum (Thaxter Sensu Gerdemann) Gerd & Trappe grew faster than non‐mycorrhizal plants. Ammonia increased the shoot dry weight of both mycorrhizal and non‐mycorrhizal V. Canina and mycorrhizal N. stricta. Only mycorrhizal V. canina and non‐mycorrhizal N. stricta grew faster when supplied with increasing concentrations of ammonium sulphate. The nitrogen tissue concentration, in all three species, was not influenced by vesicular–arbuscular mycorrhiza (VAM), but increased when plants Wete treated with ammonia. Mycorrhizal and non‐mycorrhizal N. stricta and mycorrhizal V. canina had a higher N tissue concentration when supplied with ammonium sulphate. The phosphorus tissue concentration was higher when plants were infected VAM, but tended to be lower in the presence of ammonia or ammonium sulphate. Mycorrhizal plants had higher total amounts of N and P than non‐mycorrhizal plants and plants treated with ammonia had higher total amounts of N than non‐treated plants. VAM colonization increased in all three species when treated with ammonia but was not affected by exposure to ammonium sulphate. Mycorrhiza decreased the sensitivity of N. stricta to drought, while ammonia decreased the sensitivity to drought for all three species. The effects of additional nitrogen in relation to N/P ratios are discussed with respect to the ecological consequences for these heathland species.
Morphological changes and photosynthate allocation in ageingHebeloma crustuliniforme(Bull.) Quel. andLaccaria bicolor(Maire) Orton mycorrhizas ofPinus ponderosaDougl. ex. Laws
Authors: DURALL D. M. , MARSHALL J. D. , JONES MELANJE D. , CRAWFORD R. , TRAPPE J. M.
Published: April 2006

Seedlings ofPinus PonderosaDougl, ex. Laws were grown in root observation containers. They were inoculated with eitherHebeloma crustuliniforme(Bull.) Quel. orLaccaria bicolor(Maire) Orton or left uninoculated (control). Oil a monthly basis starting at the eighth month of a 12‐month growing period, roots (mycorrhizal root tips from inoculated plants, non‐mycorrhizal from control plants) were traced onto acetate sheets. Each root tip was classified as light, ‘intermediate’ or ‘dark’ in colour. Roots initiated between months eight and nine were monitored for the next 90 d. All root tips progressed from light‐brown to dark‐brown to black for all three treatments.Hebeloma crustuliniforme, and to a lesser extentL. bicolor, retarded this progression relative to the control. At the end of 12 months, seedlings were labelled with14CO2to determine the effects of ectomycorrhizal inoculation on carbon supply to roots of the different morphological categories. The amount of14C in ‘light’L. bicolorandH. crustuliniformemycorrhizas was 2.3 and 1.8 times greater, respectively, than that in ‘light’ control root tips. The amount of14C in mycorrhizas of the inoculated treatments and, to a lesser extent, roots of the control seedlings decreased as they progressed from ‘light’ to ‘dark’. It is concluded that pondersa pine seedlings continue to allocate photosynthate to morphologically older roots, perhaps to meet maintenance requirements or to supply carbon for growth and metabolism of extra‐matrical hyphae. Such allocation may enhance root longevity, which would have an important influence on tree, forest and soil carbon budgets.