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.

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.

Changes in metal-binding peptides due to acclimation to cadmium transferred between ramets of Salvinia minima.

Different ramets of a clonal plant exploiting a patchily metal-contaminated habitat may be exposed to different levels of toxic metals. This study investigated whether the exposure of older ("parent") ramets to Cd affected the levels of metal-binding peptides and essential elements in younger ("daughter") ramets which were not exposed to ambient Cd. Pre-treatment of parent ramets of Salvinia minima with 50 µg Cd·l-1 increased the levels of thiols and phytochelatins (PCs), decreased Mg and increased Cu, Zn and S in daughter ramets growing in a Cd-free medium. Acclimation of parents to lower Cd levels (10 and 25 µg Cd·l-1) increased thiols and decreased cysteine and glutathione in daughters, but did not increase PCs. Parental acclimation to all Cd concentrations tested reduced PC production in daughter ramets during subsequent Cd exposure. Daughter ramets from parents pre-treated with 25 µg Cd·l-1 were more Cd tolerant than controls. Although the tolerant daughters contained 35% more thiols than controls, fractionation of tissue Cd showed no difference between the control and tolerant ramets in the fraction of Cd bound by thiol compounds. Thus, while the acclimation of parent plants to Cd increased levels of metal-binding peptides and thiols in daughter ramets, the relationship between these compounds and the Cd tolerance of daughters is unclear.

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.

Effects of cadmium on integration and resource allocation in the clonal fern Salvinia molesta.

In clonal plants exposed to pollution, ramets which are physiologically integrated may be less fit than ramets which are independent, if (a) translocation of toxins from contaminated ramets produced toxicity, or (b) toxicity in parent ramets reduced the degree of nutritional support to otherwise non-exposed daughters. These hypotheses were tested in the aquatic fern Salvinia molesta exposed to cadmium. Pre-treatment of parent ramets with cadmium decreased the number and biomass of daughters subsequently produced in a cadmiumfree medium, because of reduced parental support of the first daughter generation. Second generation and later daughters were unaffected. Pre-treatment did not affect the pattern of integration (which, in terms of apical daughters' biomass, was bimodal with increasing colony size), or concentrations of essential elements in new growth. However, a diversion of resources from lateral to apical daughters occurred as a result of pre-treatment, especially in colonies with ≤3 attached parents. Loss/gain analysis showed that the diversion was almost reciprocal in terms of biomass, ramet numbers and phosphorus content. Integration between contaminated and uncontaminated ramets was not disadvantageous to the clone as a whole. However, integration was disadvantageous for Ca, Mg and Zn concentrations in daughters, which declined 15-22%. Because of enhanced apical growth, an indirect benefit of integration may be a more rapid fragmentation and dispersal of daughters from the site of contamination than if the parents were independent.

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.

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.

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.

Effect of H+ ion activity and Ca2+ on the toxicity of metals in the environment.

The role of acidity in determining and restricting plant distribution and performance is discussed. In soils especially, a key effect of H+ ion concentration is on the solubility of potentially toxic heavy metals such as aluminum, managenese, zinc, iron, copper, and nickel. Al has been reported from many studies since the 1920's as the key determining toxic factor in acid soils. Some acid-tolerant species have been shown to be especially tolerant of Al, and mechanisms of tolerance have been suggested. Mn is also a commonly toxic factor at soil pH less than 5.0. Calcium has been shown to alleviate Mn toxicity. Low pH soils are also generally low in Ca, K, Na, and P; all essential major elements for plant growth. In lakes and marine situations acidic waters are uncommon as the waters are buffered. Calcium is again ameliorative of metal toxicities. The pH, redox, and valency state are critical in determining nutrient availability and metal speciation. Recent increases in the H+ ion content of precipitation have caused increased acidities of freshwater lakes in Scandinavia and eastern North America, which have depleted biota, including fish populations.

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.