Sulfur dioxide effects on plants exhibiting Crassulacean Acid Metabolism

The effects of SO(2) on species exhibiting Crassulacean Acid Metabolism (CAM) were determined with short term-high concentration 'acute' greenhouse exposures (0.6 to 3.0 microl liter(-1) (ppm) SO(2) for 2 and 8 h), and long term-low concentration 'chronic' field exposures (0.35 to 0.90 microl liter(-1) SO(2) for 32 to 79 h periodically over 7 to 13 days). In the acute greenhouse exposures, visible injury was observed on Opuntia basilaris Engelm. & Bigel., exposed to 2.0 microl liter(-1) SO(2), but no injury was observed on Ananas comosus (L.) Merr., Bryophyllum blossfeldiana Poelln., Bryophyllum pinnata (Lam.) Pers., or Bryophyllum tubiflora (Harv.) Hamet, exposed to up to 2.8 microl liter(-1) SO(2) for 8 h. Stomatal conductance during the exposures averaged 0.067+/-0.021mol(-2)s(-1) for Opuntia basilaris, 0.029+/-0.008mol(-2)s(-1) for Ananas comosus, and 0.029+/-0.008mol m(-2)s(-1) for Bryophyllum pinnata. Opuntia basilaris was injured early during the day, but not at night; with the injury appearing as a white necrotic banding across just fully expanded pads. Moderately injured pads would regreen beginning 1 to 2 weeks after exposure. In chronic field exposures, no visible injury from SO(2) was observed on Opuntia basilaris, Dudleya arizonica Rose or Agave deserti Engelm. plants, grown either with supplemental irrigation or natural rainfall. In addition, in the field SO(2) had no effect on CO(2) uptake, total sulfur content, transpiration, or tissue acidity in either the light or the dark, or in irrigated vs natural rainfall plots.     

Interactive effects of CO2 and O3 on a ponderosa pine plant/litter/soil mesocosm.

To study individual and combined impacts of two important atmospheric trace gases, CO2 and O3, on C and N cycling in forest ecosystems; a multi-year experiment using a small-scale ponderosa pine (Pinus ponderosa Laws.) seedling/soil/litter system was initiated in April 1998. The experiment was conducted in outdoor, sun-lit chambers where aboveground and belowground ecological processes could be studied in detail. This paper describes the approach and methodology used, and presents preliminary data for the first two growing seasons. CO2 treatments were ambient and elevated (ambient + 280 ppm). O3 treatments were elevated (hourly averages to 159 ppb, cumulative exposure > 60 ppb O3, SUM 06 approximately 10.37 ppm h), and a low control level (nearly all hourly averages <40 ppb. SUM 06 approximately 0.07 ppm h). Significant (P < 0.05) individual and interactive effects occurred with elevated CO2 and elevated O3. Elevated CO2 increased needle-level net photosynthetic rates over both seasons. Following the first season, the highest photosynthetic rates were for trees which had previously received elevated O3 in addition to elevated CO2. Elevated CO2 increased seedling stem diameters, with the greatest increase at low O3. Elevated CO2 decreased current year needle % N in the summer. For 1-year-old needles measured in the fall there was a decrease in % N with elevated CO2 at low O3, but an increase in % N with elevated CO2 at elevated O3. Nitrogen fixation (measured by acetylene reduction) was low in ponderosa pine litter and there were no significant CO2 or O3 effects. Neither elevated CO2 nor elevated O3 affected standing root biomass or root length density. Elevated O3 decreased the % N in coarse-fine (1-2 mm diameter) but not in fine (< 1 mm diameter) roots. Both elevated CO2 and elevated O3 tended to increase the number of fungal colony forming units (CFUs) in the AC soil horizon, and elevated O3 tended to decrease bacterial CFUs in the C soil horizon. Thus, after two growing seasons we showed interactive effects of O3 and CO2 in combination, in addition to responses to CO2 or O3 alone for a ponderosa pine plant/litter/soil system.     

浅析环境监测QC/QA过程的采样环节

对环境监测布点采样中的QC/QA以及由采样引起的误差来源做了简要分析,并对监测采样过程中QC/QA的操作提出了一些设想。     

False-negative prenatal exclusion of Wiskott-Aldrich syndrome by measurement of fetal platelet count and size

The study of the fetal platelet count and size can, according to the literature, be used for the prenatal diagnosis of the Wiskott-Aldrich syndrome (WAS). So far, no affected fetuses have been identified by this method. All pregnancies in which this method had been applied to resulted, as correctly predicted, in the birth of normal children. Here we report on a familial case of WAS where the haematological parameters failed to reveal the affected second child. Hence we assume that the platelet count and size of platelets remain normal in fetuses with WAS to the gestational age of 22 weeks and cannot be used for prenatal diagnosis.     

Injury and physiological responses of Larrea tridentata (DC) Coville exposed in situ to sulphur dioxide

The response of shrubs of Larrea tridentata (DEC) Coville (creosotebush) exposed to sulphur dioxide (SO(2)) was evaluated using in situ plants of the Majove Desert. Larrea was exposed to acute levels of 0.3 to 2.0 microl litre(-1) SO(2) for periods up to 13 days using field chambers or an open-air fumigation system. Plants exposed in the spring exhibited considerable leaf injury (necrosis and defoliation) when exposed to 2.0 microl litre(-1) SO(2), and in the autumn had leaf injury when exposed to >0.4microl litre(-1) SO(2). Injured plants had higher transpiration rates, less negative water pressure potentials, and/or lower photosynthetic rates than control plants. It is likely that Larrea would not be injured by the typically low SO(2) concentrations and dry environmental conditions of the Mojave Desert. However, if injury were to occur, it would be accompanied by changes in plant-water relations and photosynthesis, followed by recovery after the SO(2) stress was removed.     

Responses of field-grown Medicago sativa L. to acidic fog and ambient ozone

The relationship between pollutant-induced leaf drop or reductions in foliar pigment concentrations and yield was determined for field-grown alfalfa (Medicago sativa L. 'Moapa') exposed to simulated fogs of pH 7.24, 2.69 and 1.68 singly, and in combination with ambient ozone (O3) over an 11-week period. Highly acidic fog (pH 1.68) or ambient O3 significantly reduced totalseason dry yield and foliar pigment concentrations, and increased leaf drop. Significant interactive effects between acidic fog and O3 were observed for the leaf parameters, but not for yield. Thus, multiple exposures to acidic fog at current ambient levels of acidity (i.e. pH 2.69) could effect leaf quality in the absence of significant effects on yield. Alternatively, O3-induced effects on leaves may have utility as bioindicators of potential yield losses.     

Effects of low concentrations of herbicides on full-season, field-grown potatoes

Current phytotoxicity plant test protocols for US pesticide registration require testing for effects on seedling emergence and early growth without regard to other important factors, such as plant reproduction. Yield and quality reduction can have significant economic and ecological effects. Therefore, field trials were conducted to determine if potato (Solanum tubersum L.) vegetative growth and tuber yield and quality were affected by herbicides at below recommended field rates. Potatoes were grown in fields at the Oregon State University Horticulture Farm with herbicides applied at below recommended field application rates 14 d after emergence (DAE) or at 28 DAE. Plant height was measured before and 14 d after application. Visual foliar injury was rated 14 d after application, and tuber yield and quality parameters were measured at harvest (120 DAE). Some tubers were grown in the greenhouse the following year to determine if there were carry-over effects. Potato vegetation and tuber yield quality were generally more affected by herbicides applied at 14 DAE than at 28 DAE. Tuber yield and quality parameters were more affected by lower herbicide rates than were plant height or injury. There were significant yield losses caused by low rates of sulfometuron methyl and imazapyr and, to a lesser extent, with glyphosate and cloransulam-methyl. Bromoxynil and MCPA ((4-chloro-2-methylphenoxy)acetic) acid had little effect on the plants. Vegetative responses did not accurately predict yield and quality responses of tubers; therefore, reproductive responses should be considered in phytotoxicity test protocols for pesticide registration in the USA.     

Crop loss assessment for California: modeling losses with different ozone standard scenarios

Crop yield losses were estimated for ambient O3 concentrations and for a series of potential O3 air quality standards for California, including the current statewide 1-h oxidant (O3) standard of 0.10 ppm (196 microg m(-3)), 12-h growing season averages, and other models. A model for statewide losses was developed using hourly O3 data for all sites in the State, county crop productivity data, and available O3 concentration-yield loss equations to determine potential yield losses for each crop in each county in California for 1984. Losses were based on comparison to an estimated background filtered air concentration of 0.025 or 0.027 ppm, for 12 or 7 h, respectively. Potential losses due to ambient air in 1984 were estimated at 19% to 25% for dry beans, cotton, grapes, lemons, onions, and oranges. Losses of 5% to 9% were estimated for alfalfa and sweet corn. Losses of 4% or less were estimated for barley, field corn, lettuce, grain sorghum, rice, corn silage, spinach, strawberries, sugar beets, fresh tomatoes, processing tomatoes, and wheat. Implementation of either a modified rollback to meet the current 1 h California O3 standard (0.10 ppm) or a three-month, 12-h growing season average of 0.045 ppm was necessary to produce large reductions in potential crop losses.     

California Statewide Assessment of the Effects of Ozone on Crop Productivity

Six properties appear desirable for any set of ozone attainment criteria: (1) sufficient stringency to protect public health, (2) simplicity and understandability, (3) sensitivity to real changes in air quality, (4) stability against meteorological fluctuations, (5) use of as much data as possible, and (6) equivalence between the stringency the criteria appear to mandate, and what they actually mandate. We consider how the federal attainment criteria might be improved with respect to Properties 4 through 6 while being equally strong on 1 through 3. Whether the federal standard meets Property 1 has been the subject of debate, but our analysis would apply also to a modified standard. We show that there are subtleties in how improvements might be made. In particular, basing the attainment status on a statistic with low variance may not lead to a more stable criterion, and although it is easy to find a criterion that makes it hard for a district with bad air to reach attainment, or a district with good air to get out of attainment, it is hard to find a criterion that does both. This suggests using different criteria for districts that are out of attainment from districts that are in attainment. Initially the burden of proof would be on the district to prove that its air is of attainment quality. However, once the district has achieved attainment the burden of proof would shift; the district would remain in attainment unless there was strong evidence to the contrary. An evaluation of a set of criteria based on this idea showed improvements over the federal criteria with respect to the last three desirable properties-stability, use of data, and equivalent stringency-with some sacrifice in simplicity and sensitivity.     

Photochemical oxidant pollution and vegetation: effects of mixtures of gases, fog and particles

Photochemical 'smog' contains mixtures of gases (e.g. ozone, nitrogen dioxide), and dry particles (e.g. nitrates). Intermittent fog in the same geographical area can be acidic with high concentrations of nitric acid. Results from recent field studies in the Los Angeles Basin have emphasized the relative toxicity of these components of photochemical air pollution. Studies have focused on gaseous+fog or gaseous+dry particulate effects on conifers, gaseous+fog effects on crops, and the effects of trace pollutants produced during generation of ozone on crops. Data from these studies indicate that direct alterations in growth and physiological responses were observed only with gaseous pollutants (primarily ozone), or repeated applications of highly acidic fogs (pH < 2.7). Direct particle dry deposition effects are unclear. Few interactions have been found between gaseous pollutants and acidic fog. Charcoal-filtered open-top chambers are highly effective in removing pollutants in the following order: fog (100%) > peroxyacetyl nitrate > ozone > nitrogen dioxide > sulfur dioxide > nitrate ion > ammonium ion > sulfate ion. However, nitric oxide concentrations are higher in charcoal-filtered chambers than in ambient air. The studies point out the importance of considering other components of photochemical pollution in addition to ozone, especially when investigating subtle, long-term effects on vegetation.