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This paper describes the effects of the fungicides Benlate, Aliette and Ridomil on plant growth and on mycorrhizal development in onion plants. An attempt was made to distinguish effects on plants from those on the fungus by making comparisons between mycorrhizal plants in the absence of added phosphorus and non-mycorrhizal equivalent size plants. Vital staining techniques were used to analyse the effects of the fungicides on the living fungus both within the root and in the soil. Benlate had no effect on shoot dry weight or root length of onion plants whereas a reduction in plant growth was observed following the application of Aliette or Ridomil, in comparison to control plants. Benlate had negative effects on the num,bers of living internal hyphe, arbuscules, fungal plant interface and living external hyphae in the soil. Aliette had no effect on the number of living intercellular hyphae and arbuscules. However, it markedly reduced the root length and the length of infected root per plant. There length of external hyphae per gram of soil was reduced following the application of aliette, though not as severely as with Benlate. Ridomil had more complex effects on vesicular-arbuscular mycorrhizal symbiosis; treated plants showed a reduction in plant growth and also reduction in all fungal parameters, namely the number of living intercellular hyphae, arbuscules and fungal-plant interface, the length of infested root and the development of external hyphae in the soil. [ABSTRACT FROM AUTHOR]

In many parts of the world soils are detrimental to plant growth owing to elevated levels of metal ions, caused either by natural processes or by the result of man's activities. Many plants have evolved ecotypes or varieties that are able to grow more-or-less normally on these soils. This paper reviews our knowledge of the genetics of this phenomenon. The nature of tolerance and the problems of its measurement are discussed. Tolerance is frequently measured by an index produced by comparing growth in a contaminated environment with growth in a control environment. It is argued that this measurement is inappropriate for many genetical studies, and that it is frequently more useful to use growth at a single critical level of metal as a measure of tolerance. Polygenic inheritance provides a null hypothesis that has to be tested in a genetical analysis. Examples of major genes for tolerance to aluminium, arsenic, boron, cadmium, copper and manganese are discussed. Even where major genes have been demonstrated, it is probable that other minor genes, 'modifiers', are present as well. Because of the nature of tolerance as a character, dominance and epistasis are likely to vary with the level of metal at which an analysis is performed. Tolerance is generally found to be dominant at some levels of the metal. Studies which have mapped tolerance genes, particularly to aluminium and salt, are discussed. The specificity of tolerance is a matter of some confusion. Some studies indicate that tolerances evolve independently to different metals, but others have suggested that tolerance to one metal may often confer a degree of tolerance to some other metals. Very little is known about the molecular genetics of tolerance, and the mechanisms of tolerance to most metals. The possible role of phytochelatins and metallothionein-like proteins in metal tolerance is discussed. [ABSTRACT FROM AUTHOR]

Fructopolysaccharide (asparagosin, fructan) was prepared from an extract of asparagus roots by chromatography on carbon-Celite, paper and Toyopearl HW-40S (gel permeation). The asparagus fructopolysaccharide was a mixture of saccharides ranging from DP (degree of polymerization) 12 to 22 approximately. It yielded fructose and glucose by hydrolyzing with acid or yeast β-fructofuranosidase. The ratio of fructose to glucose in the enzyme hydrolysate was 13:1 by HPLC analysis. Structural determinations were made by 13C-NMR spectroscopy. Strong signals corresponding to carbon-1 (C-1), C-2, C-3, C-4, C-6 and C-5 of fructose residues in the fructopolysaccharide were observed at &deta;61.08-61.77, 103.64-104.26, 77.42-78.08, 74.43-75.09, 62.71-63.00 and 81.74 respectively. These chemical shifts were similar to those of inulin. Moreover, weaker signals were also detected at &deta;92.85, 71.80, 73.13, 69.79 and 72.23 due to C-1, C-2, C-3, C-4 and C-5 of the glucose residue. The chemical shifts are almost identical to those of glucose carbons in raffinose, neokestose, 6G(1-β-D-fructofuranosyl)2sucrose and 1F,6G-di-β-D-fructofuranosyl sucrose. These findings were confirmed by analysis of methanolysate from permethylated fructopolysaccharide by using gas-liquid chromatography. The fructopolysaccharide from asparagus roots was composed of saccharides possessing approximately 11-21 fructose residues linked by β-2,1 bonds and a non-terminal glucose residue bound with fructose residues at positions C-1 and C-6. [ABSTRACT FROM AUTHOR]

Rape (Brassica napus L.) plants are efficient users of rock phosphates. This has been ascribed to the excretion of malic and citric acids from the roots during phosphorus deficiency, resulting in a decrease of the pH in the rhizosphere and a consequent solubilization of the rock phosphate. In this paper the biosynthesis and excretion of organic acids were investigated, partly by comparing physiological reactions to P deficiency of rape with those of an inefficient user of rock phosphate from the same family, hedge mustard (Sisymbrium officinale Scop.). In the leaves of both species, both citrate levels and phosphoenolypyruvate carboxylase were nearly doubled in P-deficient plants, and the citrate/sugar ratio in the phloem exudate into EDTA solution was doubled as well. After exposure of the shoots of rape plants to 14CO2 in the light, the specific activities of citrate in the root and in the nutrient solution were ten times higher than those of malate, and also much higher than the respective activities of citrate in P-sufficient controls. It is suggested that citrate produced in the leaf is exported to the roots, where it is accumulated in the excretion region. Malic acid which is prevailing in the exudate is probably newly synthesized within the excreting root segment. When no phosphate is supplied, this excretion zone is located 1-2 cm behind the root tips. However, when rock phosphate is applied locally this zone shifts along the root to that part which is in direct contact with the rock phosphate particles. No accumulation and excretion of organic acids could be observed with the roots of P-deficient Sisymbrium. [ABSTRACT FROM AUTHOR]

This paper re-examines the question of the susceptibility of plant roots to infection by vesicular-arbuscular mycorrhizal fungi, particularly near the root apex. The cumulative distributions of the observed distance between the root apex and the most apical mycorrhizal entry points are compared with expected distributions based on (i) a random distribution of successful encounters between hypha and root and (ii) an uninfectible apical region (of length Z0). Data for both Allium porrum L. (leek) and Trifolium subterraneum L. (clover) are well fitted by the expected distributions and in the majority of cases (17/31) the best fit is obtained with zero Z0, with 8 additional cases being best fitted by values of Z0 of 1 mm or less, Even where the best fits are obtained with values of Z0 greater than zero, the distribution using Z0 = 0 is still within the confidence limits for the data. These findings indicate that in neither species is there clear evidence for a subapical region that is immune to infection. The fact that there are short uninfected lengths immediately behind the apex is interpreted as representing a delay between an encounter and a detectable infection. Other consistent deviations of the data from the theoretical distributions are discussed. Fitting the distributions yields values for the frequency of infection (A). These are compared for the two host plants at different propagule densities. The values for leek are much lower than for clover. In both species there are increases in A with increases in propagule density which are consistent with earlier findings. [ABSTRACT FROM AUTHOR]

This paper reports a comparison of the effects of the same ozone exposure given at different stages of growth on a population major L., which is as sensitive to ozone as Bel-W3 tobacco. Plants were grown from seed for eight weeks in controlled environment chambers and exposed to 70 μl O3 l-1 7 h d-1 for the whole period or for 2-wk episodes during weeks 1+2, 3+4, 5+6 or 7+8. Controls had charcoal filtered air. Effects on leaf, flower, seed and dry matter production, and on relative growth rate of shot and root are given. At whatever time the ozone was given it altered relative growth rate, dry matter partitioning and seed output. The experiment supports the view that assessment of the sensitivity of a herbaceous species can be indicated by a short-term exposure of young plants, even though the nature of the response may change with development. Comparison of the effect of ozone on dry matter partitioning at different stages of growth suggested that at each stage in development, ozone relatively strengthened the currently dominant sink, therefore reducing allocation to subsidiary sinks. As a plant develops, the relative strengths of sources and sinks change so the effects of an ozone episode on allocation will depend upon the timing. It is concluded that the commonly held view that ozone tends to reduce root growth more than shoot may be an over-simplification. For native plants growing in the field, the timing of episodes in relation to development may be crucial to understanding ozone impact. On the ecosystem level we need knowledge of response and source - sink relationships at times of the year when episodes occur. [ABSTRACT FROM AUTHOR]

This paper reports the nodulation status of 172 legume species from different ecosystems within the Amazon region of Brazil. The nodulation ability of 98 species and eight genera was observed for the first time. Occurrence of nodulation is discussed in the context of the taxonomy of the family and the different ecosystems. The frequency of nodulation among tribes and genera was found to be higher in flooded (varzea and igapo) than in non-flooded sites (terra firme), moreover, more plants had nodulated in nursery beds consisting of soil from flooded areas. The symbiosis may therefore be favored in flooded areas. [ABSTRACT FROM AUTHOR]

Ectomycorrihizas were synthesized between Picea abies (L.) Karst, and Hebeloma crustuliniforme (Bull. ex St Amans) Quél, in growth pouches containing activated charcoal filter paper. Immediately emanating hyphae from inoculated plugs contacted root hairs and root surfaces, hyphal morphology was altered. They became short-celled with few clamp connections, highly branched, and lacked cell wall ornamentation. Then, hyphae on root surfaces formed an inner synenchymatous mantle and loose hyphae formed an outer prosenchymatous mantle. Simultaneously, root cap cells bacame invaded by fungal hyphae and their remnants were incorporated into the inner mantle. Further root elongation took place but root hair production was suppressed. Thirdly, a Hartig net began to form in basal portions of developing ectomycorrhizas and the fungal mangle became denser and thicker. Fourthly, growth of the root was reduced and the hyphae of the Hartig net penetrated between cortical cell moving toward the apex. Fifthly, metacutis occasionally surrounded the meristem. At this stage the formation of the ectomycorrhiza can be considered to be complete and the rootlet itself is temporarily in a dormant state. [ABSTRACT FROM AUTHOR]

Pea plants (Pisum sativum 1,. cv. Melbourne Market), each with a single developing pod, were pulse-fed [4- 14C]aspartate through the cut stem at stages from 11 to 32 d after full blossom. The distribution of radioactivity in soluble metabolites of the hull, seedcoats, embryo sac liquid and embryo was determined by 2-dimensional paper chromatography and radioautography after feeding intervals of 6 h, 24 h or 48 h. At the earliest stage, radioactivity was recovered mainly in sucrose, serine, homoserine and threonine in the hull. At the 15-16 d stage, threonine became the major derived amino compound secreted into the embryo sac, and sucrose became the predominant derivative recovered from both hull and seed tissues. Stem-fed aspartate can therefore be transferred to stem phloem, and sucrose synthesized from aspartate in stems and leaves ran be transferred to phloem in both organs. [ABSTRACT FROM AUTHOR]

Ozone concentrations in many parts of Europe exceed the proposed UN-ECE Critical Levels for the protection of ecosystems but there is so little known about the effects on native, herbaceous species, that it is presently impossible to judge what effect, if any, these concentrations are having on this group of plants. This paper reports the results of an initial screening of 32 taxa that was used to select a small number of species for further work. All were exposed to 70 nI I-1 O2 given for 7 h d-1 for two weeks and the response measured in terms of mean relative growth rate (&Rbar;), the allometric root/shoot coefficient (K), arid changes in induced chlorophyll fluorescence (FR). Only six species showed visible symptoms but 14 showed a significant reduction &Rbar;. There was no relationship between the extent of visible symptoms and growth reduction, confirming that visible symptoms are often of little value in determining growth sensitivity to O3 stress. There were marked differences within genera and within species; a population of Plantago major collected in Athens showed no effects, while a Derbyshire population, with a 24% , reduction in R, was the most sensitive of taxa tested, including Bel-W3 tobacco which has been specifically bred for O3 sensitivity. There was a significant regression of &Rbar;% change on the &Rbar; of controls (&Rbar;% = 12.4- 10.4 × R, P = 0.0007, r = -0.56), implying that > 30%. of the variation in response between taxa was related to the inherent &Rbar;; faster growing taxa tending to show a greater reduction in &Rbar; on exposure to O3. It is tentatively suggested that this may be related to differences in stomatal conductance. [ABSTRACT FROM AUTHOR]

This paper reports the conditions for the assay of sucrose-sucrose fructosyltransferase (SST); fructan-fructan fructosyltransferase (FFT), invertase and fructan hydrolase (FH) in extracts of leaves of Lolium rigidum Gaudin. Invertase had a temperature optimum between 30 and 35 °C and a pH optimum between 4.5 and 5.0 whereas the enzymes of fructan metabolism had temperature optima at 25 °C and pH optima at about 5.5. Analysis of the products of enzyme assays showed that crude SST activity produced mainly 1-kestose from 100 mM sucrose and when incubated with 500 mM sucrose, neokestose and possibly 6-kestose were also formed in low concentrations. FFT produced two tetrasaccharides and neokestose after incubation with 100 mM 1-kestose and FH produced fructose exclusively after incubation with high-molecular-weight fructan extracted from Lolium rigidum and Helianthus tuberosus L. and with a commercial preparation of bacterial levan. Enzyme activities were also measured during a phase of fructan accumulation. FH activity declined by 50% but SST and FFT activities increased about 2.5-fold during this period. The data supported the proposed synthetic pathway of fructan accumulation from sucrose via 1-kestose into high-molecular-weight fructan and indicated that fructan synthesis may occur at low substrate concentrations. Extracts from leaves which had not accumulated fructans contained measurable activities of SST and FFT. [ABSTRACT FROM AUTHOR]

In this paper, we have reviewed how the hydraulic design of trees influences the movement of water from roots to leaves. The hydraulic architecture of trees can limit their water relations, gas exchange throughout the crown of trees, the distribution of trees over different habitats and, perhaps, even the maximum height that a particular species can achieve. Parameters of particular importance include: (1) the vulnerability of stems to drought-induced cavitation events because cavitation reduces the hydraulic conductance of stems, (2) the leaf specific conductivity of stems because it determines the pressure gradients and most negative water potentials needed to sustain evaporation from leaves, (3) the water storage capacity of tissues because this might determine the ability of trees to survive long drought periods. All of these parameters are determined by the structure and function of anatomical components of trees. Some of the ecological and physiological trade-offs of specific structures are discussed. [ABSTRACT FROM AUTHOR]

The paper describes monthly biomass, seasonal and annual net primary productivity and monthly and seasonal nutrient content of four submerged macrophytes in a lentic wetland situated in the campus of Banaras Hindu University. The seasonal variation of six nutrients (NO3--N, PO4--P, K, Ca, Mg, Na) in water is described and their mean concentrations used in multiple regression equations to examine the relationship between nutrients in water, plant biomass and nutrient accumulation in plant body. Hydrilla verticillata (L.f.) Royle, Potamogeton crispus L., P. pectinatus L. and Aponogeton natans (L.) Engle and Krause are the constituent species. Plants show rapid growth in post-monsoon and pre-winter months. All the four species showed biomass accumulation in the rainy season. The highest rate of production in the submerged zone was 0.73 g m-2 d-1 and the minimum was 0.29 g m-2 d-1. Maximum annual production of any species was 69 g m-2 in P. pectinatus. In all the four species the nutrient concentration decreased in the following order : calcium > nitrogen > potassium > magnesium > sodium > phosphorus. Seasonal variation of nutrient content was dependent on the period of germination, growth and development of the species. Nitrogen, phosphorus and potassium were higher in the season of growth of particular species and calcium was higher when plants matured. There was no definite trend for sodium, though magnesium varied with species. Uptake and accumulation of nutrients in submerged plants largely depend upon nutrient concentration of water, except nitrogen which was also dependent on biomas change. Sources of nutrient for plants are both sediment and water. Translocation of potassium from the overlying water to the mud by Hydrilla plants is possible as there is reduction in potassium concentration of water around Hydrilla. [ABSTRACT FROM AUTHOR]

Recent data obtained in this laboratory have shown that a number of triazole fungicides induce in leaves of barley and Elodea densa an early release of solutes and an inhibition of H+ extrusion. This paper deals with the early effects of two triazoles, penconazole and flusilazol, on intracellular pH and plasmamembrane permeability in Elodea densa leaves. Different effects were found at low (0.1-0.15 mM) or at high (0.3-0.5 mM) triazole concentrations. At the low concentrations the triazoles induced a marked intracellular acidification (corresponding to an acidification of both the cytosol and the vacuole) as evaluated by the weak acid and weak base distribution method. For higher triazole concentrations (0.3-0.5 mM) the intracellular pH became very close to that of the external medium (pH 5.5), and cytosolic and vacuolar pH measurements became unreliable. Triazoles at concentrations higher than 0.1-0.15 mM induced an early and very marked increase in net efflux of K+ and Cl-. At these 'toxic' concentrations the sorbitol-permeable space (apparent free space) was increased from about 20% to more than 90%. These results suggest that triazoles at low 'sub-toxic' concentrations inhibit some mechanism involved in the regulation of intracellular pH (possibly the plasmalemma proton pump), whilst at higher concentrations they induce a non-specific increase in passive permeability of the plasmamembrane. [ABSTRACT FROM AUTHOR]

In 1988, open-top chambers (OTCs) based on the Raleigh (USA) design were used to investigate the effect of ambient pollutants on field-sown Vicia faba cv. Ticol. This paper reports an aspect of this study in which the effect of the chamber itself on crop growth and development was investigated. Non-filtered chamber (NF OTC) microclimates were typically 0.8 °C warmer, with 20% less radiation and reduced wind speeds compared with open-field sub-plots (AA treatments). These differences are sufficient to induce alterations in the growth and development of V. faba. Plant development progressed more quickly inside the chambers in response to the faster accumulation of thermal time. Chamber-grown V. faba were up to 20 cm taller and had fewer branches (0.7 compared with 1.2 per plant) than plants grown in the AA treatments. Larger leaf areas developed on the NF plants, and there were fewer stomata per unit leaf area in this treatment (34 compared with 42 mm-2, P = 0.01). Enclosure within an OTC did not alter the number of flowers per plant or the number of flowers which formed pods. However, at harvest, chamber-grown plants had a 13% higher yield than the plants grown in open-field plots. These differences in growth are described in relation to the microclimate differences between AA and NF treatments. [ABSTRACT FROM AUTHOR]

This paper relates the 13;C/12C ratio of C3 plant material relative to that of source. CO2 to the N source for growth, the organic N content of the plant, and the extent of organic acid synthesis. The 13C/12C ratio is quantified as Δ, defined as (δ13C substrate-δ13C product)/(1 +δ13C product), where δ13C values of substrate or product (i.e. the samples) are defined as [(13C/12C)sample]/[(13C/12C)standard]-1. The computation is performed by relating differences in plant composition as a function of N nutrition and acid synthesis to the fraction of plant C which is acquired via Rubisco and via other carboxylases. The fractional contribution of the different carboxylases to C gain is then related, using the known isotopic fractionations exhibited by these carboxylases, in a model to predict the final Δ of the plant (relative to atmospheric CO2). Application of this approach to a `typical' C3 land plant yields predictions of the decrease of Δ relative to a hypothetical case in which all C is fixed via Rubisco. The predicted decreases range from 0.24%o for NH4+ assimilation (which always occurs in the roots) to 2.80%o for NO3- assimilation in shoots with the organic acid salt which results from acid-base balance, plus any additional organic acid salts plus free acids for a plant with a basal C: N molar ratio in organic material of 15. Intermediate values are predicted for symbiotic growth with N2, or where NO3- assimilation in root or shoot is accompanied by some acid-base regulation via OH- loss to the root medium. Comparison with published data on the difference in Δ of Ricinus communis cultured with NH4+ or NO3− shows that the measured influence of nitrogen source is in the right direction (NO3− grown plants with a smaller Δ, i.e. a larger deviation from the value predicted for the absence of non‐Rubisco carboxylations) to be explained by the observed difference in composition and hence fractional C contribution by the various carboxylases. However, the effect of N source on Δ is greater than that predicted by the model, i.e. a 2.1 % decrease as opposed to a 0.10 % decrease. It is likely that the major cause of the difference in δ13C of the plants grown on the two N sources is a change in the ratio of transport and biochemical conductances of leaf photosynthesis. Such a change is quantitatively consistent with the lower water use efficiency of NH4+ ‐grown plants. The predicted, and observed, changes in Δ as a function of N source are of the same magnitude as those found for C3 terrestrial species grown at different temperatures or photon flux densities, or in environments yielding different water use efficiencies by changing root water supply relative to shoot evaporation potential. Variations in N source should be added to the factors which might alter δ of plants growing in the field. [ABSTRACT FROM AUTHOR]

Iron is involved in many photosynthetic, respiratory and nitrogen assimilation reactions of plants as Fe bound tightly to polypeptides catalysing redox reactions. Manganese is involved as tightly bound Mn in photoreaction II of photosynthesis and in certain superoxide dismutases, while loosely bound Mn2+ is the unique activator of some enzymes, and is an alternative to Mg2+ in activating many enzymes. This paper uses data on the quantitative role of Fe and Mn in catalysts to predict the efficiency with which Fe and Mn are used in C assimilation [mol C assimilated (mol catalytic metal in enzyme)-1 s-1] and the metal cost of C assimilation [mol catalytic metal in enzyme (mol C assimilated)-1 s-1] in photolithotrophic growth in relation to genetic and environmental variables. The genetic variables were the relative content of thylakoid proteins in major taxa (cyanobacteria and red algae, chlorophytes and chromophytes) and smaller-scale taxonomic differences (various subtypes of C4 metabolism, and C3 metabolism, in terrestrial vascular plants). The environmental variables were the range of photon flux densities in which photolithotrophic growth of O2 evolvers can occur, and the inorganic C supply conditions controlling the repression/de-repression of the inorganic C concentrating mechanism in cyanobacteria and microalgae. The results of the computations yield the following conclusions. The largest predicted difference in Fe and Mn costs of photolithotrophic growth is related to changes in the photon flux density for growth. The predicted Fe cost increased 50-fold, and the Mn cost increased 80-fold, at the lowest extreme of photon flux density compared to the highest found naturally. [ABSTRACT FROM AUTHOR]

Nonlinear models were fitted to selected data sets, obtained from published papers, in which inoculum of a fungal plant pathogen or microbial antagonist of a pathogen increased and then decreased with time. Conventional models that have been widely used in botanical epidemiology, such as the logistic, monomolecular and Weibull functions, could not be fitted to these non-monotonic curves. Two models, the over-damped in which Y = A + B exp(α1 t)+C exp(α2 t), and the critically damped in which Y= A+(B+Ct) exp (-λt), were fitted: Y is a measure of the pathogen or antagonist, t is time, A is an asymptote, B and C are locational parameters and α1.2 and λ are rate parameters. These models are standard solutions of a second order differential equation. They have a single cycle, involving a rise and subsequent decline in the population density of the micro-organism which ultimately tends to an asymptotic equilibrium. The over-damped model was successful only in fitting large datasets and was used to describe the population dynamics of bacterial colonization of live- and heat-killed conidia of Cochilobolus sativus (Ito & Kurib.). Drechs. ex Dastur as well as the population dynamics of Laetisaria arvalis Burdsall in untreated and in pasteurized soil with and without subsequent reinfestation with Pythium ultimum Trow. The critical damping model was used to describe pre-emergence damping-off of Rhizoctonia solani Kühn in successive crops of radish, the population dynamics of P. ultimum and low-temperature Pythium spp. in untreated soil and pasteurized soil with L. arvalis, the population dynamics of Trichoderma viride (Maub.) Ashby in soil and, lastly, the colonization of organic fragments by P. ultimum with and without antagonism from P. nunn Lifshitz, Stanghellini & Baker. The selected model was first fitted to the empirical progress curve for each treatment. Subsequently one or more common parameters were constrained to fit all treatments while the remaining parameters were fitted separately. None of the treatments affected the rate parameters but treatments did affect the asymptote and locational parameters. The shapes of the models are discussed in relation to initial amounts of inoculum, the initial rate of increase of inoculum and the time to achieve maximum levels of disease or microbial biomass. The over-damping model is shown to represent the solution of a set of simple linked differential equations for two interacting populations. The derivation of these elementary models is discussed in relation to the study of biological control of plant pathogens. [ABSTRACT FROM AUTHOR]

Mechanistic hypotheses to explain mycorrhizal enhancement of root hydraulic conductivity (Lp) suggest that phosphorus (P) nutrition, plant growth substances and/or altered morphology may be responsible. Such ideas are based on work with VA (vesicular-arbuscular) mycorrhizas. Since VA mycorrhizas and ectomycorrhizas differ in many respects, they may alter host plant water uptake via different mechanisms. This paper examines Lp in various ectomycorrhizal associations while considering factors which are important to the VA mycorrhizal effect on Lp. Douglas fir Pseudotsuga menziesii (Mirb.) Franco] seedlings inoculated with the ectomycorrhizal fungi Laccaria bicolor (Maire) Orton and Hebeloma crustuliniforme (Bull. ex St. Amans) Quel. and non-inoculated seedlings infected naturally with Thelephora were grown under three low levels of P fertilization (1, 10 and 100 μM P). Seedling morphology, tissue P levels, Lp and plant growth substance levels in xylem sap were measured after nine months growth. Increased tissue P and decreased root/shoot ratio correlated with increased Lp in each of the mycorrhizal treatments. When adjusted for the effect of these two factors, Lp of Laccaria and Hebeloma seedlings was still lower than the Thelephora seedlings. In a subsequent experiment, the Lp of seedlings with Hebeloma and Rhizopogon vinicolor Smith mycorrhizas was compared to the Lp of non-mycorrhizal seedlings (grown at 100 mM P) and no differences were found among treatments. The lack of an ectomycorrhizal effect on Lp, is quite different from the enhancement of host Lp, by VA mycorrhizas. Zeatin ribsoside concentrations of Thelephora- and Hebeloma-infected seedlings were similar, yet higher than with Laccaria. There was no relationship between plant growth substances and Lp in ectomycorrhizal Douglas fir, despite lower zeatin riboside concentration for Laccaria-incoculated plants. [ABSTRACT FROM AUTHOR]

Two isolates of the ectomycorrhizal fungus Pisolithus tinctorius (Pers.) Coker and Couch were inoculated on to roots of Eucalyptus urophylla S. T. Blake in vitro and a comparison made of the rate of ectomycorrhizal development. Both isolates initiated ectomycorrhizal roots hut the rime of onset of root colonization and the rate of formation varied with the isolate An isolate cultured from a sporocarp collected from under eucalypts in Australia rapidly colonized roots of E. urophylla and initiated mycorrhizas after 2 d incubation, whereas an isolate obtained from sporocarps collected from under pines in the United States developed ectomycorrhizas only after 7 d incubation. Dual inoculation of E. urophylla seedlings using a paper-sandwich technique again showed the rapid colonization of roots by the eucalypt isolate even when roots were inoculated 7 d previously with the pine isolate. These in vitro observations support field observations that there are variable degrees of plant species - fungal isolate compatibility, implying specificity, and this is an important factor influencing successful ectomycorrhiza formation and development. [ABSTRACT FROM AUTHOR]

A 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. [ABSTRACT FROM AUTHOR]

This paper examines the qualitative and quantitative chemical composition of phenols occurring in the cell wall of vesicular-arbuscular (VA) mycorrhizal and non-mycorrhizal roots of Allium porrum L., and Ginkgo biloba L., their localization at the cellular level, and the phenylalanine ammonia lyase (PAL) activity of these tissues. Constitutive phenols occurred in both species of plants, and did not change when the symbiont fully colonized the roots. Cell wall bound-phenols were more abundant in A. porrum than in G. biloba, and PAL activity was higher too. Tyrosol, 2-(4-hydroxyphenyl ethanol), was identified as the most abundant component in A. porrum, where it occurred with vanillic, syringic and ferulic acids. In G. biloba, p-coumaric, protocathecuic vanillic and ferulic acids were found. Cell-wall bound phenols (revealed by UV fluorescence and by transmission electron microscopy) were localized in the epidermal and hypodermal cells, but did not usually occur in the cortical cells, where the fungus developed arbuscules. We show that cell wall bound-phenols are consecutive compounds in leek arid in ginkgo, and that the VA mycorrhizal fungus does activate metabolic pathways leading to the synthesis of new phenols as antimicrobial substances, at least in the host cell walls. [ABSTRACT FROM AUTHOR]

summary: This paper is the first to report cadmium tolerance in a dicotyledonous species, Silene vulgaris (Moench.) Garcke. The response to cadmium of five populations originating from one uncontaminated and various heavy‐metal contaminated sites was examined under standardized conditions for three weeks. The tolerance index (TI), based on the mean relative growth rate (R), was determined. Populations originating from cadmium‐contaminated sites showed a distinct tolerance to cadmium. A population from a site enriched only with copper also exhibited a marked co‐tolerance to cadmium. A clear difference in biomass production between the sensitive and tolerant populations was attained at 1 μM cadmium. An optimum biomass production in tolerant populations at a metal concentration higher than in the control, as demonstrated for zinc and copper, could not be established for cadmium. The pattern of cadmium uptake and translocation differed between tolerant and sensitive populations. All tolerant populations accumulated cadmium in the roots and showed some degree of restricted transport to the shoots. The effect of cadmium on the elemental distribution in roots and shoots was population‐independent for some elements (copper, zinc, potassium) and population‐specific for others (phosphorus, magnesium and sodium). The phenomenon of co‐tolerance to cadmium is discussed in relation to possible tolerance mechanisms, especially with regard to metal‐binding compounds (metallothioneins, phytochelatins). [ABSTRACT FROM AUTHOR]

This paper is the first to report cadmium tolerance in a dicotyledonous species, Silene vulgaris (Moench.) Garcke. The response to cadmium of five populations originating from one uncontaminated and various heavy-metal contaminated sites was examined under standardized conditions for three weeks. The tolerance index (T1), based on the mean relative growth rate (R), was determined. Populations originating from cadmium-contaminated site showed a distinct tolerance to cadmium. .A population from a site enriched only With copper also exhibited a marked co-tolerance to cadmium A clear difference in biomass production between the sensitive and tolerant populations was attained at I μM cadmium. An optimum biomass production in tolerant populations at a metal concentration higher than in the control, as demonstrated for zinc and copper, could not be established for cadmium. The pattern of cadmium uptake and translocation differed between tolerant and sensitive populations. All tolerant populations accumulated cadmium in the roots and showed some degree of restricted transport to the shoots. The effect of cadmium on the elemental distribution in roots and shoots was population-independent for some elements (copper, zinc, potassium) and population-specific for others (phosphorus, magnesium and sodium). The phenomenon of co-tolerance to cadmium is discussed in relation to possible tolerance mechanisms, especially with regard to metal-binding compounds (metallothioneins. phytochelatins). [ABSTRACT FROM AUTHOR]

This paper is concerned with the value of the ecological information provided by response functions. Two questions are considered. The first deals with the spatial reproducibility of response functions depending on the tree population and the location of the meteorological station that yielded the climatic data. The second concerns the temporal stability of the response function. The climate ring- width relationships are calculated for six populations of Pinus silvestris (L.). Twelve meteorological stations are involved in this calculation, over the period 1890-1980, divided in five sequences of 50 years . Analogies and differences between response functions are investigated using multi-dimensional analysis (principal component analysis and cluster analysis). Spatial analysis reveals that the climate ring-width relationship mainly depends on the population habit. The temporal analysis shows that instability is linked with the evolution of the habitat, more especially with the expansion of the forest cover. [ABSTRACT FROM AUTHOR]

This paper gives a detailed outline of Swiss vegetation history during the last 18 000 years. For each pollen zone, a map is given showing vegetation development from the late Würmian to the present. A concise historical review of the Swiss pollen analytical research during the last 60 years is presented is followed by some discussion of the central European glacial refugia. Based on a selection of over 100 pollen-analytical]y investigated sites, the development of Swiss vegetation since the late Würmian can be presented as follows: 1. Oldest Dryas. After the Würm maximum the ice network melted back quickly to small mountain glaciers. At some localities, several types of an Artemisia-Chenopodiaceae-Juniperus-Ephedra-Helianthemum-Poaceae steppe/tundra have been recorded, representing an apparent uniformity over the whole Swiss area. 2. Bölling Interstadial. This first, late Würmian, warm phase is characterized by the occurrence of Betula, Hippopha&euml, Juniperus, Ephedra and Salix. 3. Older Dryas. Little evidence for this period has yet been found in Switzerland. 4. Alleröd Interstadial. This marked warm phase led to a typical late Würmian reforestation, with both Betula and Pinus up to about 1200-1600 m above sea level. 5. Younger Dryas. In the whole alpine area there is good evidence for this last, late Würmian climate deterioration, which led to renewed glacier activity and to an alpine timber-line depression of 200 300 m. 6. Preboreal. For the central Alps and the Prealps a wide occurrence of Pinus sylvestris/mugo, P. cembra, Larix and Betula has been recorded, whereas in southern Switzerland the first mixed oak forest developed. 7. Boreal. Corylus and mixed oak forest spread in some cases rapidly over a wide area, chiefly in the Prealps, the Plateau, the Jura and in southern Switzerland. In the high mountains Pinus sylvestris/mugo, P. cembra and Larix still dominated.8. Older Atlantic. In both the Plateau and the Prealps, Corylus and mixed oak forest dominated, whereas in the continental Alps Pinus slvestoris/mugo, P. cembra and Betula grew with some elements of mixed oak forest. In the Grisons the immigration of Picea from east to west has been identified; in the eastern Prealps abies spread. 9. Younger Atlantic. This period is characterized in' a first maximum of' the timber-line extension to an altitude of about 2300 m. The spread of Fagus from west to east is seen on both the montane and subalpine belt, first Abies and later Picea dominated. Picea immigration to the west continued. 10. Subboreal. Until 3000 yr B.P. forest achieved its optimum development with a distribution tip to 2000 in above sea level. In both the Plateau and the Jura the major spread of Fagus took place in this period. Piece;now reached southwestern jura and even the Lake Geneva region. 11 .Subatlantic, This period is characterized by man's influence on the vegetation .According to the evidence of both pollen anal sis and archaeology, the first anthropogenic influences on Swiss vegetation took place between 6000 and 4500 yr B.P. In the anthropogenic timber-line belt secondary forests of Betula, Allunus and Pinus formed. On the southern alpine border, the Romans introduced Castanea, whereas on the Plateau Picea, Abies and Pinus have been planted. [ABSTRACT FROM AUTHOR]