Chelator production by Deschampsia cespitosa (L.) Beauv. in adaptive Ni/Cu hyper-tolerance derived from fields in the Sudbury region and lab assessment

Plants possess a complex network of mechanisms to utilize and, if necessary, detoxify metals. Plants utilize constitutive basal tolerance mechanisms to maintain appropriate internal metal levels under normal conditions. However, adaptive hyper-tolerance mechanisms are used in order to tolerate excess metal exposure. The production of metal binding chelators could be one way to convey these tolerances. Chelator production of field and greenhouse-derived materials was investigated to determine any multi-metal hyper-tolerances in different populations of the grass Deschampsia cespitosa (L.) Beauv. Plant tissue was collected from metal-contaminated mine sites, and from specimens grown in metal exposure hydroponic experiments. The chelator metabolites from these samples were simultaneously analyzed using HPLC-tandem mass spectrometry. In the hydroponic grown grass, histidine was produced at high concentrations solely in the hyper-tolerant populations during metal exposure. In all of the populations, the responses of chelators were metal-specific, where levels of nicotianamine were at high concentrations during Ni exposure, and levels of phytochelatins were high during Cu exposure. Moreover, a similar pattern of chelator production was seen in the root specimens collected from mine sites contaminated with Ni and (or) Cu. Histidine was the strongest Ni chelator involved in adaptive hyper-tolerance, while constitutive basal tolerance to Ni and Cu was observed via the responses of nicotianamine and phytochelatin, respectively.

Chelator profiling in Deschampsia cespitosa (L.) Beauv. Reveals a Ni reaction, which is distinct from the ABA and cytokinin associated response to Cd

Plant hormones, including abscisic acid (ABA) and cytokinins (CKs), fluctuate as a result of excess metal exposure. Changes in hormonal concentration regulate plant growth and may also signal activation of metal chelators. The grass Deschampsia cespitosa was dosed with either Ni or Cd or pulsed with exogenous ABA. The roots were analyzed for ABA and CKs and for multiple potential metal chelators including: amino acids, nicotianamine (NA), and phytochelatins (PCs). They were quantified after 3 h and after 7 days, using LC-ESI MS/MS. The Ni treatment caused no measurable change in ABA or CK concentration; however, an increase in NA was documented. The Cd treatment resulted in a short-term ABA increase followed by a reduction in CKs and an increase in PC concentration. An exogenous ABA pulse in non-metal challenged plants induced changes in CKs and PCs that followed those of Cd treatment. Ni and Cd stress resulted in distinctly different detoxification responses. Since the reaction of CKs and putative metal chelators to Cd stress can be mimicked by an exogenous ABA pulse, it is suggested that ABA acts as a stress signal, resulting in reduced growth by way of decreased CK concentration and reduced metal toxicity through increased PC production.

Responses of secondary chemicals in sugar maple (Acer saccharum) seedlings to UV-B, springtime warming and nitrogen additions

Anticipated effects of climate change involve complex interactions in the field. To assess the effects of springtime warming, ambient ultraviolet-B radiation (UV-B) and nitrogen fertilization on the foliar chemistry and herbivore activity of native sugar maple (Acer saccharum Marsh.) seedlings, we carried out a field experiment for 2 years at two sugar maple forests growing on soils of contrasting acidity. At the Oliver site, soils are derived from a strongly calcareous till, whereas the naturally acidic soils and base-poor soils of the Haliburton site are derived from the largely granitic Precambrian Shield. At both sites, removal of ambient UV-B led to increases in chlorogenic acid and some flavonoids and reduced herbivore activity. At Haliburton, ammonium nitrate fertilization led to further increases in foliar manganese (Mn), whereas at Oliver there were no such changes. Nitrogen additions led to decreases in the concentrations of some flavonoids at both sites, but seedlings at Oliver had significantly higher concentrations of flavonoids and chlorogenic acid than seedlings at Haliburton. We suggest that this could be associated with increased mobilization of Mn due to increased soil acidity, which interferes with the role of calcium (Ca) in the phenolic biosynthetic pathway. It appears that the composition of the forest soil governs the response of seedlings when they are exposed to abiotic stressors.

Foliar phenolics in sugar maple (Acer saccharum) as a potential indicator of tropospheric ozone pollution

Tropospheric O3 has been implicated in the declining health of forest ecosystems in Europe and North America and has been shown to have negative consequences on human health. We have measured tropospheric ozone (O3) in the lower canopy through the use of passive monitors located in five woodlots along a 150 km urban-rural transect, originating in the large urban complex of Toronto, Canada. We also sampled foliage from 10 mature sugar maple trees in each woodlot and measured the concentration of a number of phenolic compounds and macronutrients. O3 concentrations were highest in the two rural woodlots, located approximately 150 km downwind of Toronto, when compared to the woodlots found within the Greater Toronto Area. Foliar concentrations of three flavonoids, avicularin, isoquercitrin, and quercitrin, were significantly greater and nitrogen concentrations significantly lower at these same rural woodlots, suggesting some physiological disruption is occurring in those sites where exposure to tropospheric O3 is greater. We suggest that foliar phenolics of sugar maple may be a biochemical indicator of tropospheric ozone exposure.

Butterfly assemblages along a human disturbance gradient in Ontario, Canada

This study relates patterns of butterfly abundance and species richness to position along an urban disturbance gradient in southeastern Ontario, Canada. Observed assemblages along the gradient (N = 15) included butterflies from the Papilionidae, Pieridae, Lycaenidae, Nymphalidae, and Hesperiidae families. Of the total 26 observed species, 15 were noticeably absent from the disturbed sites. Butterfly assemblages had equal or higher number of individuals and species richness at moderately disturbed sites compared with the least disturbed sites. In relation to distribution patterns along the gradient, 28% of butterfly species were classified as disturbance adaptable and 58% as disturbance avoiders. These classifications were correlated with host-plant use and voltinism. Canonical correspondence analysis of local-scale data strongly associated disturbance avoiders with a specific environmental variable (e.g., Everes comyntas (Godart, 1824) with grasslands), whereas disturbance-adaptable species were weakly associated with any variable. One-time disturbances (i.e., mowing) during the survey resulted in pronounced changes in butterfly abundance and species composition at two sites, reducing species richness and total abundance by up to 80%. Species were patchily distributed along the gradient, suggesting that they respond differentially to disturbance in the landscape.

The quantification and distribution of pollution Pb at a woodland in rural south central Ontario, Canada

Lead concentrations and Pb isotope ratios were measured in the forest floor, mineral soil and vegetation at a white pine and a sugar maple stand in a woodland in south central Ontario. Lead concentrations decreased and 206Pb/207Pb ratios increased with mineral soil depth reflecting the mixing of pollution and natural Pb sources. Lead concentrations and 206Pb/207Pb ratios at 20-30 cm depth were approximately 6-7 mg/kg and 1.31-1.32, respectively. Assuming an integrated 206Pb/207Pb ratio in deposition over time of 1.18, estimated from lichen measurements and published data for the region, approximately 65% of Pb in the surface (0-1 cm) mineral soil is from anthropogenic sources. Approximately 90% of pollution Pb is found in the 0-10 cm soil layer (Ah) and less than 3% of the pollution Pb is present in the forest biomass and mull-type forest floor combined. Despite low Pb concentrations in vegetation (<2.5 mg/kg), we estimate that between 65 and 100% of the Pb in vegetation and approximately 75% of the Pb in the forest floor is from pollution sources. In total, the pollution Pb burdens at the pine and maple stands are estimated to be 860 and 750 mg/m2, respectively.

Uptake of 207Pb and 111Cd through bark of mature sugar maple, white ash and white pine: a field experiment

A field study was undertaken to determine whether 207Pb and 111Cd, applied to the exterior bark of sugar maple (Acer saccharum Marsh.), white ash (Fraxinus americana L.) and white pine (Pinus strobus L.), could enter xylem tissue. Stable isotope tracers (3 microg Pb ml(-1); 2 microg Cd ml(-1)) were applied separately to bark in simulated rainfall, acidified to pH 4.5, in multiple doses over a 4 month (July-October) period. Tree cores were extracted from the region of application in the following March, and Pb and Cd isotopes were measured in bark and the outer tree rings using inductively coupled plasma mass spectrometry. The majority of the applied stable isotope tracer recovered (over 94%) was present in bark tissue, although a small amount of each metal tracer entered the outer (1-3) tree rings in all trees. Despite high concentrations of excess 207Pb in bark (up to 50 microg g(-1)), the maximum concentration of excess 207Pb measured in tree rings was only around 50 ng g(-1), which represents less than 30% of the background Pb concentration in wood at the study site. High excess 111Cd concentrations in bark (up to 35 microg g(-1)) also resulted in small increases in 111Cd in wood (up to 50 ng g(-1)), but due to lower background Cd concentrations in wood, such increases more than doubled the amount of Cd in wood compared with background levels. However, at sites where such high bark Cd concentrations are found, uptake from Cd-contaminated soil would probably be much greater than found at our study site. It appears that Cd and Pb applied to bark can enter woody tissue, but that this route of uptake is likely to be a minor contributor to the metal burden in wood.

Historical changes in lead concentrations in tree-rings of sycamore, oak and Scots pine in north-west England

Lead concentrations in tree rings of sycamore (Acer pseudoplatanus L.), oak (Quercus robur L.) and Scots pine (Pinus sylvestris L.) sampled at a parkland in north-west England were measured in wood formed since the mid-1800s. Concentrations of Pb in Scots pine and oak peaked in wood formed between 1900 and 1940, most likely because of Pb accumulation in heartwood, indicating that oak and Scots pine are unsuitable for monitoring temporal changes in Pb deposition at the study site. In contrast, Pb concentrations in sycamore, a species that has similar heartwood and sapwood chemistry, were relatively constant in wood formed between the mid-1800s and 1950. Lead concentrations decreased steadily in sycamore tree rings formed after the 1950s, and decreased more abruptly in wood formed after 1985. This sharp decrease in wood Pb cannot be due to decreases in soil Pb concentration. Stable Pb isotope analysis was used to further investigate Pb patterns in sycamore wood. Excess 206Pb/207Pb ratios in tree-rings of sycamore were relatively constant, approximately 1.17, in wood formed prior to the 1930s, but decreased steadily thereafter reaching a minimum value of approximately 1.16 in wood formed between 1975 and 1985 after which time 206Pb/207Pb ratios increased. This pattern is consistent with changes in Pb isotope ratios measured in peat, sediment and aerosol samples in the UK. However, the magnitude of the decrease in 206Pb/207Pb (largely due to gasoline Pb) is considerably lower than in other studies and our estimates indicate that less than 20% of the total Pb in sycamore wood measured since the mid-1800s is derived from gasoline emissions. A more likely explanation for the pattern of Pb observed in sycamore tree rings is that soil Pb accumulates within rings of the diffuse porous wood over a number of years. Such uptake patterns would result in lower Pb concentrations in the outer (more recently formed) tree rings, which coincide with recent reductions in Pb deposition in the UK. Overall, this study indicates that tree ring chemistry is unsuitable for monitoring historical changes in Pb deposition at the study site.

Analysis of tree rings using inductively coupled plasma mass spectrometry to record fluctuations in a metal pollution episode

Analysis of Acer pseudoplatanus L. (sycamore) tree rings using ICP-MS was used to assess the impact of metal deposition on trees growing in the vicinity of a metal refinery at Prescot, north-west England compared to a reference site at Croxteth 6 km distant receiving minimal deposition. No difference in tree growth between sites was recorded. Large reductions in Cu and Cd deposition since the late 1970s was accompanied by a steep decline in Cd concentrations in the outer rings in trees close to the refinery. A similar reduction in Cu concentrations was less apparent due to a tendency for Cu to increase in the outer rings. Zinc and Ni were higher in xylem at Prescot compared to Croxteth. There was no trend in Zn concentrations at either site although Ni concentrations increased in trees close to the refinery after 1982. Manganese concentrations in xylem were much higher at Prescot; Mn levels declined until the late 1970s and then increased slightly in later years interspersed by large concentration peaks within individual years during the 1980s. There was little change in Mn concentrations in trees at Croxteth during this period. Calcium, Mg and Sr concentrations remained steady or declined slightly in rings formed since 1965 in trees at Croxteth. Concentrations of Ca, Mg and Sr were higher in rings formed prior to the mid 1970s in trees at Prescot, but declined steadily after this period, although peaks in concentrations of each element were recorded in individual years during the 1980s. Phosphorous concentrations in rings increased towards the cambium at Croxteth, although P levels decreased in rings formed after 1982 at Prescot. No difference in K concentrations between sites was recorded. Lead concentrations in xylem at both sites declined steadily in rings formed after 1970, although concentrations were higher at the reference site. Analysis of individual sycamore tree rings appears to record short-term changes in pollution episodes, with little lateral movement of elements occurring. It is suggested that changes in element concentrations in trees close to the refinery are a result of reduced metal deposition combined with increased soil acidity due to reduced buffering capacity of metal ions in rainfall.

Occurrence of heavy metal tolerance and co-tolerance in Deschampsia cespitosa (L.) Beauv. from European and Canadian populations

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.

Nickel and zinc tolerance and co-tolerance in populations of Deschampsia cespitosa (L.) Beauv. subject to artificial selection

The occurrence of co-tolerance to four heavy metals was investigated among seedlings selected from three different non-tolerant Canadian and German Deschampsia cespitosa (L.) Beauv. populations. Plants selected following screening of seedlings in solution containing Ni or Zn ions, subsequently showed enhanced tolerance to Ni and Zn, respectively. 'Nickel screened' seedlings exhibited no increased tolerance to Zn.'Zinc screened' seedlings, in contrast, had somewhat elevated tolerance to Ni in two of the three populations tested (Elm and Cypress Lake). Thus, co-tolerance may be a population-specific rather than a species-specific response. Individual Elm plants screened for Ni response did not have elevated Zn tolerance, whereas'Zn screened' seedlings did show elevated Ni tolerance. This confirms the result from the population tolerance tests. We conclude that co-tolerance is not a reciprocal process. While the selection for one metal may confer elevated tolerance to a second, selection for the second may not confer tolerance to the first.

The effects of aluminum and calcium on the growth and nutrition of selected ectomycorrhizal fungi of jack pine

The influence of Al and Ca on the growth, in axenic culture, of three ectomycorrhizal fungi associated with jack pine (Pinus banksiana Lamb.) was examined. Isolates of Hebeloma crustuliniforme (St. Amans) Quél., Rhizopogon rubescens (Tul.) Tulasne, and Suillus tomentosus (Kauff.) Singer, Snell & Dick were obtained from basidiocarps collected in jack pine stands of different ages. Basidiocarps and the soil surrounding them were analyzed for Al and Ca, as well as other elements. Each fungal species was grown for 4 weeks in nutrient solutions containing 37, 185, 370, or 740 μM Al combined in a factorial design with 25, 125, 250, or 500 μM Ca and maintained at pH 3.8. Growth of all three fungal species was reduced at 370 μM Al. Significant interaction was found between fungal species and Al treatment for all six elements measured in mycelial tissue. Stepwise increments in external Al concentration resulted in reduced mycelial concentrations of Ca, Mg, and K, and increased mycelial concentrations of Al, P, and Fe in H. crustuliniforme. High external Al levels resulted in reduced mycelial concentrations of all elements measured except Al and P in R. rubescens. In contrast, for S. tomentosus the same external Al levels increased the mycelial concentrations of all elements except Ca. The response of the three ectomycorrhizal fungi to Ca also differed. Growth of H. crustuliniforme was stimulated by stepwise increments in external Ca concentrations from 25 to 500 μM. Increments in calcium had no effect on the growth of R. rubescens. High external levels of Ca acted synergistically with high external Al concentrations to reduce growth by S. tomentosus. Unlike the other two species, the response of S. tomentosus to Al and Ca could not have been predicted from the soil and basidiocarp analyses. Alterations in Ca to Al ratios of soils may influence the succession of ectomycorrhizal fungi on conifer root systems. Key words: ectomycorrhizae, jack pine, aluminum, calcium, basidiocarps.

Arsenic, cobalt and nickel tolerances in two populations of Silene vulgaris (Moench) Garcke from Ontario, Canada

A population of Silene vulgaris (Moench) Garcke collected from mine tailings near the town of Cobalt, Ontario was compared in its metal tolerance with a population collected at an uncontaminated site (Baymouth, Ontario). Seedlings of the Cobalt population were tolerant to elevated levels of arsenic, cobalt and nickel, both compared with the Baymouth population and with other literature reports for this species. However, the tolerance indices in the Cobalt plants for these toxic elements did not correlate well with their concentration in water extractions in the mine soils. Indices of arsenic tolerance, based on the inhibition of root growth in 12 d experiments, showed a similar response to that in a 28 d experiment for both populations. The latter however, appeared to be a more accurate indicator of As tolerance in S. vulgaris, because the longer-term tolerance indices had lower standard deviations and higher probabilities for tolerance than the short-term tolerance indices. Reduced uptake of As occurred in the roots of tolerant individuals compared with non-tolerant individuals at a low As treatment. At a higher arsenic exposure, however, arsenic entered the roots of tolerant individuals. A partial exclusion or reduced translocation of arsenic to the shoots then appeared to operate in the shoots of tolerant individuals, i.e. arsenic levels were higher in shoots of non-tolerant plants. At the highest arsenic exposure, where the individuals from the Cobalt population were no longer tolerant, this exclusion pattern broke down. From a preliminary selection experiment, some arsenic tolerant individuals occurred in the Baymouth population. This suggests that under circumstances of arsenic contamination this population also has the potential to develop a tolerance to high arsenic exposure.

The use of lichen growth abnormalities as an early warning indicator of forest dieback

Combinations of pollutants including acidic fog and ozone occur at high levels at a number of sites in eastern North America and Europe. Mountainous regions such as the Laurentians (Quebec), Appalachians (N.Y.) and the Green Mountains (Vermont) are especially vulnerable, with both conifers and hardwoods being affected. Ongoing measurements of atmospheric chemistry (e.g. The Chemistry of High Elevation Fog-CHEF project of the Canadian Atmospheric Environment Service) reveal that extreme cloudwater events of less than pH 3.0 and ozone episodes in excess of 100 ppb are common occurrences. The purpose of this study was to gather information about the response of epiphytic lichens to deteriorating air quality at selected locations for which atmospheric chemical data are readily available. A multidisciplinary approach is being used to analyse the lichens.Morphological and cellular aberrations previously documented by the authors to occur in terricolous lichens exposed to simulated acidic rain events will be evaluated for their usefulness are early warning indicators of forest decline. In addition, tissue chemistry of species such as Hypogymnia physodes will be correlated with parameters such as altitude and decline index and compared with published elemental values for lichens from similarly polluted sites in Europe and Scandinavia.

Crystal occurrence and wax disruption on leaf surfaces of cabbage treated with simulated acid rain

Epicuticular waxes on leaves of Brassica oleracea L. (cabbage) were studied using scanning electron microscopy after a single treatment with simulated rain of pH 5.6, 3.0 or 2.5 which was either sprayed on to plants in an exposure chamber or applied as droplets with a micropipette. Treatments with acidified rain caused serious structural degradation of the wax crystals. The alteration of crystalline wax structures was similar for leaves treated with nitric acid solutions, but less severe, than for leaves treated with sulphuric acid solutions. With both H₂ SO₄ , and HNO_a -derived rain solutions numerous gypsum (CaSO₄ ) crystals were found in and near lesions on the leaves treated with rain of pH 3.0 and 2.5. The crystals probably resulted from damage of cuticular membranes by acidic rain which significantly altered their permeability to ions in the area of lesions. Crystalline leaf waxes may be an important target for acidic pollutants, and the physiological consequences of their degradation are discussed.

A comparison of the effects on Canadian boreal forest lichens of nitric and sulphuric acids as sources of rain acidity

The effects of different levels of nitrate and sulphate in acidic precipitation on the growth of the lichens Cladina rangiferina (L.) Wigg. and C. stellaris (Opiz.) Brodo were compared. Permanent Held plots in a Canadian boreal forest ecosystem received two years of spraying with artificial rains of pH 4.2 (ambient), 3.5 or 2.8, each containing one of four molar ratios of sulphate to nitrate, i.e. sulphuric acid alone, nitric acid alone: 2:1 or 1:2. A substantial fertilization effect was observed when C. rangiferina was watered with rain of pH 2.8, derived from nitric acid alone. Compared with before-treatment values, gains in mean dry weight (+ 62%) and mean podetial height (+14%) were obtained for this species, in addition to elevated levels of N in air-dried tissues. Post-treatment values for the mean dry weight of C. rangiferina were significantly reduced for those podetia sprayed with rain of low pH, derived from sulphuric acid alone. Although podetia of C. stellaris were stimulated by rains of pH 4.2, based on a higher concentration of nitric acid, there was no N fertilization following the most acidic sprays. Data from this study support the view that the N content of acidic rain can cause a short-term growth stimulation for those species able to absorb nitrate from solution. However, beneficial effects on growth of prolonged fertilization via acid rain inputs are unlikely.

Contrasting responses of lichens and Vaccinium angustifolium to long-term acidification of a boreal forest ecosystem

Over a 5-year period, we investigated the effects of simulated acidic precipitation on boreal forest understory species. Percent cover, net photosynthetic rate, and growth of three species of subarctic lichens were evaluated. Throughout the growing season, Cladina stellaris, Cladina rangiferina, and Cladina mitis, along with the associated vascular perennial, Vaccinium angustifolium, received twice-monthly sprays of artificial rain adjusted to pH 5.6, 4.0, 3.5, 3.0, or 2.5 using a 2:1 ratio of sulfuric to nitric acids. Changes in percent cover of the flora in permanent plots were measured annually during treatment years and then for a 6th year to monitor postspray recovery. Following 5 years of spraying, combined cover values for the three lichen species had decreased by up to 27% in plots sprayed with rain of less than pH 4.0, while percent cover of V. angustifolium had increased by 55 %. Although losses in net photosynthesis of 65% occurred for lichens receiving rains of pH 2.5, differences were not significant and data were highly variable. However, increasing acidity of the sprays significantly suppressed mean podetial height and dry weight of C. stellaris and C. mitis. The effect on these lichens of shading by the potential competitor V. angustifolium was investigated in a companion study, and it was concluded that the growth suppression of C. stellaris was most likely related to rainfall acidity and not to light attenuation. Cladina mitis was more sensitive to low light levels. Although adversely affected by rain of pH 2.5, C. rangiferina showed stimulation of a number of growth parameters in plots sprayed with rain of pH 3.0. It was concluded that responses of boreal understory species are variable and complex, and that several species (i.e., C. rangiferina and V. angustifolium) are tolerant of rainfall of less than pH 3.5.

Chemical changes in simulated raindrops following contact with leaves of four boreal forest species

Simulated raindrops of pH 5.6 or 3.2 were sprayed on four boreal forest plant species in situ, and raindrops were subsequently collected from their leaves for chemical analysis. The purpose was to understand better the changes involved in foliar neutralisation of acidic raindrops. The species used were Cornus canadensis, Aralia nudicaulis, Maianthemum canadense, and Acer spicatum. Samples were analysed for Ca2+, Mg2+, Na+, K+, [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text], Cl−, and F−, as well as pH. Changes in leaf raindrop ion concentrations were greater when sprayed with the pH 3.2 than with the pH 5.6 rain. Both increases and decreases in ion concentration were found, indicating leaching and (or) dissolution of particulates on the leaf or retention by the canopy, respectively. Rapid changes in ion concentrations suggest surface deposits play an important role in leaf raindrop neutralisation. Increases in [Ca2+] and [Mg2+] in raindrops with greater neutralisation are evidence that cation exchange may also be occurring (r2 = 0.170 and 0.321, respectively, at pH 3.2; p < 0.01). There were significant negative correlations between changes in [H+] and changes in[Formula: see text], [Formula: see text], and [Formula: see text] (r2 = 0.562, 0.525, and 0.297, respectively, at pH 3.2;p < 0.01). Most of the other ions measured also showed significant correlations with changes in [H+], but generally the correlation could account for only a small percentage of the observed results (low r2). Dry deposition was also measured.

Extreme metal and acid tolerance ofEuglena mutabilis and an associated yeast from Smoking Hills, Northwest Territories, and their apparent mutualism

In isolates ofEuglena mutabilis and an associated yeast from strongly acidic tundra ponds (pH 1.8-2.0) at the Smoking Hills, North West Territories (N.W.T.), and in isolates from acidic ponds in the Yukon, a remarkable degree of tolerance to a number of toxic elements and to very low pH has been found. Growth was used as a measure of tolerance. The tolerances to both low pH and to elevated metal concentrations were markedly enhanced when both organisms were present together. This mutualism occurred even betweenE. mutabilis from one field location and a yeast from another. In every field collection we made ofEuglena, the yeast was also found. The tolerances to metals are 10-100 times higher than the highest reported previously for algae, and include tolerance to some metals not elevated in the ponds from which isolations were made. Reciprocal combinations of algal-yeast partners suggest a generalized benefit of association and an increased benefit for co-selected pairs from a specific site. This algal-yeast association may be a major factor in allowing colonization of these extreme acid habitats, paralleling the cyanobacteria-bacterial associations of extremely alkaline waters.

The effect of infection by Lactarius rufus or Scleroderma flavidum on the uptake of 63Ni by paper birch

Nickel tolerance of birch seedlings is increased by infection with one ectomycorrhizal fungus, Scleroderma flavidum, but not by another, Lactarius rufus. The possibility that this difference is related to differences in uptake and (or) translocation of Ni was investigated using 63Ni. Mycorrhizal and nonmycorrhizal seedlings were grown either with or without Ni for 22 weeks before the presentation of 63Ni to roots. Both control and pretreated seedlings were exposed to 63Ni, in 85 μM Ni, for periods of 2 min to 48 h. After Ni uptake, the roots were desorbed with 50 mM Ca at 5 °C for 30 min. Total nonexchangeable 63Ni uptake into roots was unaffected by inoculation treatment, either in the presence or absence of dinitrophenol, a general metabolic inhibitor. However, the amount of Ca-exchangeable Ni was significantly affected by infection, and was lowest in S. flavidum infected seedlings. Additionally, infection influenced the effect of dinitrophenol on Ni uptake into shoots. Application of dinitrophenol increased Ni uptake into the shoots of L. rufus infected and uninfected plants, but this increase did not occur in S. flavidum infected plants. All shoots absorbed similar amounts of Ni in the absence of dinitrophenol. Thus, the S. flavidum birch mycorrhizae do not require metabolic energy to reduce Ni translocation from roots to shoots, while the other seedlings do. This may contribute to the increased Ni tolerance of this mycorrhizal association.

The response of the feather moss, Pleurozium schreberi, to 5 years of simulated acid precipitation in the Canadian boreal forest

Permanent plots dominated by the feather moss, Pleurozium schreberi (Brid.) Mitt., were established at a Canadian boreal forest site to study the effects of simulated acid precipitation on percent cover, growth, and photosynthesis of vegetation. For a 5-year period, beginning in 1981, plots of P. schreberi received twice-monthly sprayings of simulated rain, adjusted to pH 5.6, 4.0, 3.5, 3.0, or 2.5 with a 2:1 molar mixture of sulfuric and nitric acids. Unsprayed plots were also monitored. Almost complete elimination of the moss had occurred in the plots sprayed with pH 2.5 by the end of the 2nd year of treatment, and substantial decreases in cover were also recorded at pH 3.0 and 3.5 over the 5 years. Significant reductions of up to 75% in total and living frond height and dry weight were recorded at pH 3.5 and lower. Lateral branches produced in acid-treated plots also were stunted and few in number. This decline in growth and percent cover of P. schreberi may have resulted from the decreased net photosynthetic rates measured in the field and would be accelerated by increased rates of evapotranspiration in the altered moss microhabitat.

The effects of nickel and copper on the axenic growth of ectomycorrhizal fungi

Isolates of several ectomycorrhizal fungi, some from a Cu- and Ni-contaminated smelter site near Sudbury, Ont., and some from an uncontaminated site, were grown on solid media containing 25 or 100 mg nickel/L, or 25 or 100 mg copper/L. The influence of the metals on lag time prior to the commencement of growth, on the maximum increase in colony diameter, and on the final colony dry weight was determined. Isolates from the metal-contaminated site did not outperform those from the uncontaminated site on any of the metal-amended media. In a second experiment, isolates of Laccaria proximo, Lactarius hibbardae, Lactarius rufus, and Scleroderma flavidum were grown in liquid media containing 2 or 5 mg Ni/L or 4 mg Cu/L. These fungi have previously been shown to vary in their effect on the metal tolerance of Betula papyrifera, at these concentrations. The axenic growth of the fungi in the presence of Ni showed no relationship to their effect on the birch seedlings. In general, the fungi that were least tolerant to Cu in liquid culture, Lactarius rufus and Laccaria proximo, were the same ones that proved most detrimental to the birch grown in the presence of Cu. These results indicate that axenic screening tests will not necessarily select fungi that will increase host metal tolerance.

The influence of benthic tundra pond vegetation and prey behavior on Zooplankton predation by the flatworm Mesostoma lingua

Experiments were conducted at the Smoking Hills and Tuktoyaktuk, N.W.T., to determine if Mesostoma lingua, a common pond inhabitant, preys selectively on co-occurring Zooplankton, and whether predation rates are affected by the presence of pond vegetation. Experiments were conducted in 250-mL containers at the sites. Mesostoma fed heavily on Daphnia pulex and Chironomus riparius, but not on Branchinecta paludosa or Diaptomus arcticus. The presence of alternative prey led to significant reductions in Daphnia predation rates, while the presence of the pond plants Cladophora insignis and Drepanocladus aduncus, which provide shelter and cover, significantly increased predation rates. The advantage of the moss and algal habitat was largely to the predator.

Effect of low pH on sodium regulation in two species of Daphnia

The effect of low pH on sodium-22 influx and outflux of Daphnia magna and Daphnia middendorffiana was assessed. Experiments were conducted in both hard and soft water with experimental pHs ranging from 3.5 to 8.0. In hard water, at and below pH 4.0, there was a net loss of sodium from both species. The rate of sodium loss (outflux) increased significantly, while the rate of uptake (influx) remained constant at pH 4.0 compared with the reference pH 8.0. Only at extremely low pH (pH 3.5) was sodium influx inhibited in hard water. In soft water, D. magna responded quite differently. Sodium influx was inhibited by 23% at pH 5.0 and by 69% at pH 4.5 compared with the control (pH 6.5). Sodium outflux was stimulated to 125% of the control at pH 4.5. The net loss of sodium in soft water was due to both an increase in sodium outflux and a decrease in sodium influx, while in hard water the effect was primarily on sodium outflux. Daphnia magna and D. middendorffiana have problems with sodium regulation below pH 5.5 in soft water and below pH 4.5 in hard water, which indicates that they are considerably more sensitive to low pH in soft water than in hard water.

Adaptation of plants to atmospheric pollutants

Man-made air pollutants are a recent phenomenon in the evolutionary experience of plants and animals although natural air pollutants from volcanic eruptions, forest fires and dust storms have accompanied evolution for geological eras. Plants have responded to increasing concentrations of such pollutants as sulphur dioxide, fluorides, photochemical oxidants and acid rain at the community, species, population and individual levels. The lichens and bryophytes have shown particularly dramatic changes in urban and industrial areas. Many species have had their distribution severely limited. Tolerances to sulphur dioxide have evolved in populations of a number of grasses and herbs, and some sulphur dioxide-tolerant lichens have invaded inner city areas. Sensitivity to pollutants is partly a function of substrate chemistry. Synergistic interactions occur between various pollutants and also between pollutants and pathogens. A good deal of genetic variation occurs within crops, and this allows for selection of pollution-tolerant varieties. The nature of specific adaptations is not generally well known although, for sulphur dioxide, recent studies in poplar and spinach strongly suggest that increased production of the enzyme superoxide dismutase may be a key factor. In other adaptations, morphological and anatomical features play a part.

RELATIONSHIP OF HYDROCARBON SOLUBILITY TO TOXICITY IN ALGAE AND CELLULAR MEMBRANE EFFECTS

Recent studies have demonstrated that under carefully controlled conditions there is a highly significant correlation between the solubilities of a wide range of hydrocarbons and their toxicity to unicellular green algae. 38 different hydrocarbons have been studied, including alkanes, aromatics, polynuclear aromatics, and chlorinated hydrocarbons. Toxicity has been determined in terms of the effects of hydrocarbons in solution on photosynthesis using 14 C-uptake as a measure. For each hydrocarbon, it was found that the molar concentration required to cause a 50 percent reduction in photosynthesis could be predicted from a knowledge of its solubility alone. A regression coefficient of 0.97 was obtained on a log plot. Chlorinated hydrocarbons behaved exactly as did other hydrocarbons. The effect of adding or subtracting methyl groups influenced toxicity through the effect on solubility. The linear toxicity/solubility response suggests a common mechanism of hydrocarbon action. Since hydrocarbons are lipophilic, it was hypothesized that the cellular membranes may be the site of cellular disruption. This has been tested by determining the amount of potassium and manganese leakage from algal cells, using neutron activation analysis, when exposed for a given time to equi-molar concentrations of selected hydrocarbons. Loss of relabeled organic material has also been determined in previously tagged cells when exposed to these hydrocarbons. The predictions seem to be very strongly borne out. Implications for the prediction of effects of oil spills on a variety of aquatic organisms are present. The less soluble hydrocarbons are the most toxic on a per mole basis. Partition coefficients appear to provide a key to the common effects.

Phylogenetic implications of comparative primate growth rates

Growth data from a number of species of Old and New World primates have been analyzed by calculating instantaneous relative growth rates. Species discussed are the New World species Saimiri sciureus and Saguinus nigricollis, and the Old World species Pan troglodytes and Macaca mulatta. The analysis of the perinatal growth data indicated that differences in relative growth rates are present during early periods of growth. More specifically, it was found that the closer taxonomically a species is to man the greater the deceleration of growth during the first postnatal year. It is suggested that this may be a general primate trend.

Lead contamination around secondary smelters: estimation of dispersal and accumulation by humans

A high rate of lead fallout around two secondary lead smelters originated mainly from episodal large-particulate emissions from low-level fugitive sources rather than from stack fumes. The lead content of dustfall, and consequently of soil, vegetation, and outdoor dust, decreased exponentially with distance from the two smelters. Between 13 and 30 percent of the children living in the contaminated areas had absorbed excessive amounts of lead (more than 40 micrograms per 100 milliliters of blood and more than 100 micrograms per gram of hair) as compared with less than 1 percent in a control group. A relationship between blood and hair was established which indicated that the absorption was fairly constant for most children examined. It seemned that the ingestion of contaminated dirt and dusts rather than "paint pica" was the major route of lead intake. Metabolic changes were found in most of 21 children selected from those with excessive lead absorption; 10 to 15 percent of this group showed subtle neurological dysfunctions and minor psychomotor abnormalities.

Squirrel monkey reproduction: the "fatted" male phenomenon and seasonal spermatogenesis

Records of reproduction in a Miami colony of squirrel monkeys living in a seminatural state and of monkeys in the field indicate that the male undergoes an annual testis cycle. The spermatogenic phase is associated with the seasonal acquisition of a secondary sexual characteristic which we have termed the "fatted" condition. Body weights, measurements of subcutaneous fat, and testicular histology studied over a 12-month period further establish this cycle. Climatological analyses suggest that this cycle is associated with the precipitation cycles of the respective environments.