Effects of acidic gases and mists on the reproductive capability of three fern species

The effects of exposure to 40 nl litre(-1) SO2 + 40 nl litre(-1) NO2 on the reproductive biology of Polypodium interjectum (Shivas), Dryopteris affinis (Lowe) Fraser-Jenkins and Phyllitis scolopendrium (L.) Newman were investigated after 14 weeks exposure in a closed chamber fumigation system. The numbers of sori per pinna were reduced in response to SO2 and NO2 for D. affinis but were unaffected for the other species. Numbers of sporangia in sori and spore viability were reduced in P. interjectum and P. scolopendrium but not in D. affinis in response to the SO2 and NO2 treatment. Spore size was not affected by the pollution treatment. A separate experiment tested viabilities of spores collected from the three species in response to daily spraying with simulated mists at pHs of 2.5, 3.5, 4.5 and 5.6. For all three species, there was little or no spore germination in the pH 2.5 treatment and significantly reduced germination in response to the pH 3.5 as compared to the pH 4.5 and pH 5.6 treatments.     

Growth responses of three legume species exposed to simulated acid rain

Seedlings of Vicia faba L., Phaseolus multiflorus L. and Pisum sativum L. were raised during exposure to simulated acid rainfall treatments of pHs 5.6, 4.5, 3.5 and 2.5 at a rate of 30 mm per week. All three species were found to be adversely affected by the more acid pH 3.5 and pH 2.5 treatments after 7-8 weeks of exposure. There were total plant dry weight reductions of 40% for V. faba, 31% for P. sativum and 28% for P. multiflorus exposed to the pH 2.5 treatment, as compared to those grown in the control (pH 5.6 treatment). In addition, V. faba was found to be sensitive to the pH 4.5 treatment with an 18% reduction in total plant weights (compared to plants grown in the pH 5.6 treatment). In P. multiflorus, reduction in the dry weights of shoots in response to increasing acidity of rain was not accompanied by reduction in root weights, indicating an interference in the partitioning of assimilates. It is concluded that these three species, and V. faba in particular, may be growing below their potential in much of the UK.     

Genotypic differences in effects of cadmium exposure on plant growth and contents of cadmium and elements in 14 cultivars of bai cai

Fourteen cultivars of bai cai (Brassica campestris L. ssp. chinensis var. communis) were grown in the nutrient solutions containing 0-0.5 microg mL(-1) of cadmium (Cd) to investigate genotypic differences in the effects of Cd exposure on the plant growth and uptake and distribution of Cd in bai cai plants. The Cd exposure significantly reduced the dry and fresh weights of roots and shoots, the dry weight ratio of shoot/root (S/R), total biomass, and chlorophyll content (SPAD value). Cd concentrations in bai cai ranged from 13.3 to 74.9 microg g(-1) DW in shoots and from 163.1 to 574.7 microg g(-1) DW in roots under Cd exposure, respectively. The considerable genotypic differences of Cd concentrations and accumulations in both shoots and roots were observed among 14 bai cai cultivars. Moreover, Cd mainly accumulated in the roots. Cd also caused the changes of uptake and distribution of nutrients in bai cai and under the influence of cadmium, the concentration of potassium (K) decreased in shoot and increased in root. However, the concentrations of magnesium (Mg), phosphorus (P), manganese (Mn), boron (B), and iron (Fe) increased in shoots and decreased in roots. In addition, Cd exposure resulted in an increase in calcium (Ca), sulphur (S), and zinc (Zn) concentrations in both shoots and roots but had no significant effects on the whole uptake of the examined mineral nutrients except for S.     

Effects of salinity and ozone,individually and in combination,on the growth and ion contents of two chickpea (Cicer arietinum L.) varieties

The aim of this study was to determine the effects of ozone and salinity, singly and in combination, on the growth and ion contents of two chickpea (Cicer arietinum L.) varieties. Chickpea plants were grown in non-saline and saline conditions, with and without a repeated exposure to ozone. Salinity at a concentration of 30 mM NaCl caused a substantial reduction in plant height, number of leaves and the dry weights of the leaves, stems and roots. Biomass allocation to the leaves increased, predominantly at the expense of the roots. Ozone at a concentration of 85 nmol mol(-1) for 6 h per day for 25 days reduced plant height and dry weights but had no effect on leaf number. The results show substantial effects of salinity and ozone on chickpea growth and ion concentrations. When ozonated plants are grown in the presence of salinity, further reductions in growth occur.     

Responses of greening bean seedling leaves to nitrogen dioxide and nutrient nitrate supply

Phaseolus vulgaris cv. Kinghorn Wax seedlings grown in darkness at 25 degrees C for 7 days with half strength Hoagland's nutrient solution containing no nitrogen, were transferred to lit continuous stirred tank reactors (CSTRs) in atmospheres containing 0 or 0.3 ppm NO(2) and irrigated with a nutrient solution containing 0 or 5 mm nitrate as sole nitrogen source and allowed to grow for a period of up to 5 days in a 14 h photoperiod. Exposure to NO(2) increased total Kjeldahl nitrogen in the leaves. Further, the exposure to NO(2) increased chlorophyll content from day 3 onwards and inhibited the leaf dry weight substantially on days 4 and 5. The primary leaves of the seedlings exposed to 0.3 ppm NO(2) and supplied with nitrate accumulated some nitrite after 5 days of exposure. Some of the seedlings were returned from CSTRs to growth chambers and allowed to grow for a further period of 5 days in a 14 h photoperiod without NO(2). The growth which developed after the NO(2) exposure growth period, as measured by fresh and dry weights of the leaves, was significantly less in NO(2)-exposed plants than in nitrate-grown plants. The experiments demonstrate that the leaves of greening seedlings are able to assimilate NO(2) and that a reduction in leaf dry weight by prolonged NO(2) exposure in the presence of nutrient nitrate can be associated with nitrite accumulation, and that NO(2) has a carry-over effect beyond the duration of NO(2) exposure. It is apparent that NO(2) induces some durable biochemical or cytological aberration in the presence of nutrient nitrate, which adversely affects subsequent leaf growth.     

The sensitivity of early 20th century cultivars of wheat to air pollution

The effects of a mixture of SO(2) and NO(2) at a concentration of 0.08 to 0.10 ppm (in microg m(-3): 164-205 for NO(2); 229-286 for SO(2)) were tested for four weeks on two old varieties of winter wheat, Little Joss and Holdfast, introduced in 1908 and 1938, respectively, grown in simulated autumn conditions. After two weeks, root dry weights of both varieties were significantly decreased but, although there was some leaf necrosis, shoot dry weights were unaltered. After a further two weeks, the dry weights of the shoots as well as the roots were significantly decreased. These effects, amounting to a combined 40% decrease in total dry weight, were greater than those in identical experiments carried out with the present day variety Avalon, in which the decrease was 20%. The results suggest that the modern cultivar Avalon is more tolerant of SO(2) and NO(2) than Little Joss and Holdfast, which were grown many years ago.     

Tomato response to concurrent and sequential NO2 and O3 exposures

In the ambient environment, concentrations of air pollutants vary on a diurnal cycle, resulting in various patterns of concurrent and sequential exposures of plants. The response of tomato plants to sequential and concurrent NO2 and O3 exposures was determined using pollutant levels equal to the maximum acceptable levels recommended by the National Ambient Air Quality Objectives of Environment Canada for a 1 h average. The concurrent treatment, 1 h of NO2 + O3, was compared to 1 h of NO20, O3 or control in plants at the 4 to 6 or the 9 to 11 leaf stage. At the 4 to 6 leaf stage, leaf and stem fresh weights were significantly reduced by the NO2 + O3 treatment relative to control, whereas these growth parameters were not reduced relative to control by the single pollutants indicating a coalitive response. Leaf area was significantly smaller as a result of the NO2 + O3 treatment relative to the NO2 treatment. A main effect of O3 was observed on leaf dry weight. The sequential treatments were: NO2 followed by O3 (NO2-O3); O3 followed by NO2 (O3-NO2); NO2 at night followed by O3 during the daytime (NO2(N)-O3(D)). Each gas exposure was 1 h; only plants at the 4 to 6 leaf stage were treated. Only the O3-NO2 treatment significantly reduced leaf area, leaf fresh weight and stem fresh and dry weights relative to control plants. Inconsistencies among treatments occurring at different time periods of the day suggest that time period of exposure should reflect ambient time periods. The coalitive action, and the sequential treatment response, of these pollutants indicated that criteria based on single pollutants may not be adequate to establish air quality objectives when these pollutants occur together.     

Effects of air filtration at small SO2 and NO2 concentrations on the yield of barley

Two cultivars of Igri and Gerbel winter barley Horteum vulgare L. were grown in open-top chambers in filtered and unfiltered air at a site with approximately 10 nl litre(-1) SO2 and 12 nl litre(-1) NO2 (seasonal mean). The experiment ran for three consecutive seasons 1982-1983, 1983-1984, 1984-1985, and significant effects of filtration were observed for each crop. In years 1982-1983 and 1984-1985, the crops in unfiltered air yielded larger grain dry matter, 9% in 1982-1983, and 8% in 1984-1985. For both crops, the differences were statistically significant at the 5% level. Differences were also observed for the remaining above-ground dry matter, and these were consistent in direction in each year but statistically significant only in 1984-1985. In both growing seasons (1982-1983 and 1984-1985), there were no major pest infestations and no long-term water stress or photochemical ozone episodes. In the remaining experiment (1983-1984) similar air concentrations of SO2 and NO2 produced effects of the opposite sign to those observed in 1982-1983 and 1984-1985. Significant reductions in grain yield (13%) were obtained in unfiltered air. The only major environmental difference for the 1983-1984 crop was a notable dry period in May and June 1984 with marked water stress in the crop, requiring irrigation. These results suggest that the relationship between yield and pollutant concentration may be confounded by additional stresses, many of which are a common component of the growing season for major crops.     

Yield responses of different crop species to long-term fumigation with sulphur dioxide in open-top chambers

Potted plants of commercial cultivars of rape (Brassica napus L., cv. 'callypso'), summer barley (Hordeum vulgare L., cvs. 'arena' and 'hockey') and bush beans (Phaseolus vulgaris L., cvs. 'rintintin' and 'rosisty') were continuously exposed in open-top chambers to sulphur dioxide (SO(2)) for the whole growing season in order to assess effects of this pollutant on growth and various yield parameters. Treatments consisted of charcoal-filtered air (CF) and CF supplemented with four levels of SO(2), resulting in mean exposure concentrations (microg m(-3)) of approximately 8, 50, 90, 140 and 190. With the exception of the 1000 seeds weight, which was slightly reduced, dry matter production and yield parameters of rape remained unaffected by all SO(2) concentrations or were even stimulated. Compared to CF vegetative growth of both bean cultivars was reduced by 10-26% at all SO(2) levels; however, with significant effects only for cv. 'rintintin'. While all SO(2) additions reduced significantly the yield (dry weight of pods) of the bean cultivar 'rosisty' between 17% and 32%, cv. 'rintintin' showed a significant reduction of up to 42% only at the two highest pollutant concentrations. Dry matter production of the barley cultivars was mainly impaired at SO(2) concentrations > 100 microg m(-3) with a reduction of 30-52%. While nearly all yield parameters of cv. 'hockey' reacted similar to the dry matter production, the yield of cv. 'arena' was reduced already at the low SO(2) levels. At a treatment concentration of 90 microg SO(2) m(-3) a significant yield loss of 30% was recorded. A reduction of the 1000 grains weight mainly contributed to these yield losses observed for both barley cultivars. From these results, it may be assumed that SO(2) concentrations within the range 50-90 microg m(-3) are potentially phytotoxic to some crop species.     

Nitrilotriacetate- and citric acid-assisted phytoextraction of cadmium by Indian mustard (Brassica juncea (L.) Czernj, Brassicaceae)

In a pot experiment the effects of nitrilotriacetate (NTA) and citric acid applications on Cd extractibility from soil as well as on its uptake and accumulation by Indian mustard (Brassica juncea) were investigated. Plants were grown in a sandy soil with added CdS at four levels ranging from 50 to 200 mg Cd kg(-1) soil. After 30 days of growth, pots were amended with NTA or citric acid at 10 and 20 mmol kg(-1). Control pots were not treated with chelates. Harvest of plants was performed immediately before and one week after chelate addition. Soil water-, NH(4)NO(3)- and EDTA-extractable Cd fractions increased constantly with both increasing soil metal application and chelate concentration. Shoot dry weights did not suffer significant reductions with increasing Cd addition to the soil except for both NTA treatments in which at 200 mg Cd kg(-1) a 30% decrease in dry matter was observed. Generally, following NTA and citric acid amendments, Cd concentration in shoots increased with soil Cd level. However, due to Cd toxicity, at the highest metal application rate both NTA treatments lowered Cd concentration in the above-ground parts. Compared to the control, at 10 mmol kg(-1) citric acid did not change Cd concentration in shoots, whereas NTA-treated plants showed an about 2-fold increase. The addition of chelates at 20 mmol kg(-1) further enhanced Cd concentration in shoots up to 718 and 560 microg g(-1) dry weight in the NTA and citrate treatments, respectively.     

Copper uptake and translocation in a submerged aquatic plant Hydrilla verticillata (L.f.) Royle

A comprehensive understanding of the uptake, tolerance and transport of heavy metals in the wetland system through aquatic plants will be essential for the development of phytoremediation technologies. Copper accumulation and translocation of a submersed macrophyte Hydrilla verticillata (L.f.) Royle were investigated. Plant shoots showed a significant accumulation of Cu with a maximum of 30830 mg Cu kg?1 dry weight after exposed to 4000 μg L?1 Cu for 4d. Both roots and shoots can directly take up Cu from solution and Cu mainly accumulated in cell wall fractions. Moreover, H. verticillata predominantly accumulated Cu through shoots from the aqueous solutions because of the higher weights and bioaccumulation factors of shoots than those of roots. Acropetal translocation of Cu in the plant is higher than the basipetal translocation, which implies that upward translocation of Cu is mainly via the xylem and downward translocation is mainly through the phloem. These findings contribute to the application of submerged aquatic plants to copper removal from moderately contaminated waters.     

The impact of SO2 and SO2 + ascorbic acid treatments on growth and partitioning of dry matter in Trigonella foenum-graecum L

To study the impact of SO(2) and SO(2) + ascorbic acid on growth and partitioning of dry matter in Trigonella foenum-graecum L., two-week-old plants were exposed to SO(2) for 2 h daily over a 42 day period. One of the exposed sets was treated with ascorbic acid. Plants were grown in a wire house and unexposed plants were used as controls for comparison. The parameters measured, such as dry weights of leaf, stem and root per plant, were found to be lower in the exposed sets than in the controls. The reductions were greater in dry weights of stem and root as compared with weights of leaves, indicating that the partitioning of the dry matter was altered. Greater amounts of soluble sugars and starch in the leaves of exposed plants, compared with the stem, also revealed that translocation was hampered. Reductions were greater in fruiting than in flowering, suggesting that fruit abortion was high. Although ascorbic acid treatment could mitigate the effect of SO(2), the differences were not found to be statistically significant. Significant changes were seen in fruit yield, suggesting that the effect of ascorbic acid is cumulative. The impact of SO(2) and SO(2) + ascorbic acid on partitioning of dry matter to different 'sinks' is discussed.     

Effects of chronic ozone exposure on growth, root respiration and nutrient uptake of rice plants

To clarify the response of growth and root functions to low concentrations of ozone (O(3)), rice plants (Oryza sativa L.) were exposed to O(3) at 0.0 (control), 0.05 and 0.10 ppm for 8 weeks from vegetative to early heading stages. Exposure to 0.05 ppm O(3) tended to slightly stimulate the dry weight of whole plants up to 5 weeks and then slightly decrease the dry weight of whole plants. However, these effects were statistically significant only at 6 weeks. Exposure to 0.10 ppm O(3) reduced the dry weight of whole plants by 50% at 5 and 6 weeks, and thereafter the reduction of the dry weight of whole plants was gradually alleviated. Those changes in dry weight can be accounted for by a decrease or increase in the relative growth rate (RGR). The changes in the RGR caused by 0.05 and 0.10 ppm O(3) could be mainly attributed to the effect of O(3) on the net assimilation rate. Root/shoot ratio was lowered by both 0.05 and 0.10 ppm O(3) throughout the exposure period. The root/shoot ratio which had severely decreased at 0.10 ppm O(3) in the first half period of exposure (1-4 weeks) became close to the control in the latter part of exposure (5-8 weeks). Time-course changes in NH(4)-N root uptake rate were similar to those in the root/shoot ratio especially for 0.10 ppm O(3). On the other hand, root respiration increased from the middle to later periods. Since it is to be supposed that plants grown under stressed conditions change the ratio of plant organ weight to achieve balance between the proportion of shoots to roots in the plant and their activity for maintaining plant growth, these changes in root/shoot ratio and nitrogen uptake rate under long-term exposure can be considered to be an adaptive response to maintain rice growth under O(3) stress.     

The relationship between foliar injury, nitrogen metabolism, and growth parameters in ozonated soybeans

A single 12 h ozone exposure peaking at 0.20 ppm proved phytotoxic to greenhouse-grown 'Cutler 71' soybeans at each growth stage tested from V5 to R6. Visible injury occurred within 40 h on the unifoliodate leaves and middle-aged and older trifoliolates while the younger leaves were free from toxicity symptoms. In some instances visible injury was accompanied by a decrease in chlorophyll and an increase in leaf diffusive resistance. Although nitrogen fixation was not significantly altered except at early pod formation (R3), and nitrate reductase activity was significantly reduced only if the ozone exposure occurred at the time of maximal enzyme activity (V5), nitrogen content of the leaves was reduced by ozone treatment. Shoot dry weight was not affected 40 h after ozone treatment, but root dry weight was significantly reduced. Plants grown with supplemental NO(3)(-) were more sensitive to ozone than those dependent on fixed nitrogen. At plant maturity, there was no evidence of an ozone effect on shoot, root, or seed dry weight, NO(3)(-) -grown plants showed a significant increase in growth and yield over N(2)(-) plants; but no ozone effect was observed, despite the increased foliar sensitivity. Multiple ozone exposures at growth stages V3, R1 and R3 exacerbated the effects noted with a single episode and also reduced nitrogenase activity (reflected in specific and total nodule activity) and shoot and root dry weight. At plant maturity, there was again no evidence of a significant effect of multiple ozone treatment on shoot dry weight or seed yield although root weight remained low. The results would tend to support the hypothesis that older leaves of soybean do not make a significant contribution to seed yield. Although they may be injured by ozone during the reproductive phases of growth, seed yield may not be affected if the younger O(3)-tolerant leaves remain functional.     

An open-top chamber study with filtered and non-filtered air to evaluate the effects of air pollutants on crops

Four non-filtered and four charcoal-filtered open-top chambers were employed to determine the effects of ambient levels of gaseous air pollutants at Braunschweig, FRG, on growth and yield of potted plants of winter and spring barley. During the exposure period (November 1985-August 1986) monthly mean values of gaseous air pollutants (microg m(-3)) ranged between 34 and 127 for SO(2), 34 and 52 for NO(2) and 12 and 33 for O(3) in winter (November-March), and 16 to 26 for SO(2), 20 to 33 for NO(2) and 42 to 53 for O(3) in spring-summer (April-August). Monthly 2% percentile values for these gases reached (microg m (-3)) 561 for SO(2), 140 for NO(2) and 170 for O(3). The filtering efficiencies of the charcoal filters used averaged 60% for SO(2), 50% for NO(2) and 70% for O(3). All plants of winter barley from the unchambered plot were killed by severe frost periods in winter, 1986. Little frost damage occurred on plants grown in the chambers. Air filtration resulted in higher numbers of plants of winter barley per pot, i.e. a higher number of individuals per area, and a higher dry weight of whole plants and ears compared to the non-filtered atmosphere. In the experiments with spring barley, fresh and dry weight of whole plants were lower and dry weight of leaves were higher in the filtered open-top chambers. These effects could not be observed at all harvests which were carried out during the growing season. Grain yield and sulphur content of the leaves of both barley cultivars were not affected by the air filtration. Production of biomass of spring barley grown in ambient air was higher than of that grown in open-top chambers.     

Phytoextraction of metals from a multiply contaminated soil by Indian mustard

The effects of nitrilotriacetate (NTA) and citric acid applications on metal extractability from a multiply metal-contaminated soil, as well as on their uptake and accumulation by Indian mustard (Brassica juncea) were investigated. Desorption of metals from the soil increased with chelate concentration, NTA being more effective than citric acid in solubilising the metals. Plants were grown in a sandy soil collected from a contaminated field site and polluted by Cd, Cr, Cu, Pb and Zn. After 43 days of plant growth, pots were amended with NTA or citric acid at 5 mmol kg-1 soil. Control pots were not treated with any chelate. Harvest of plants was performed 1 week after chelate addition. Soil water-, NH4NO3- and DTPA-extractable Cd, Cu, Pb and Zn fractions were enhanced only in the presence of NTA. In comparison to unamended plants, Indian mustard shoot dry weights suffered significant reductions following NTA application. NTA treatment increased shoot metal concentrations by a factor of 2-3, whereas citric acid did not induce any difference compared to the control. Chromium was detected in the above-ground tissues only after NTA amendment. Due to differences in dry matter yield, a significant enhancement of metal uptake was observed in NTA-treated plants for Cu and Zn.     

Genotypic Differences in Effects of Cadmium Exposure on Plant Growth and Contents of Cadmium and Elements in 14 Cultivars of Bai Cai

Abstract

Fourteen cultivars of bai cai (Brassica campestris L. ssp. chinensis var. communis) were grown in the nutrient solutions containing 0–0.5 μg mL^?1 of cadmium (Cd) to investigate genotypic differences in the effects of Cd exposure on the plant growth and uptake and distribution of Cd in bai cai plants. The Cd exposure significantly reduced the dry and fresh weights of roots and shoots, the dry weight ratio of shoot/root (S/R), total biomass, and chlorophyll content (SPAD value). Cd concentrations in bai cai ranged from 13.3 to 74.9 μg g^?1 DW in shoots and from 163.1 to 574.7 μg g^?1 DW in roots under Cd exposure, respectively. The considerable genotypic differences of Cd concentrations and accumulations in both shoots and roots were observed among 14 bai cai cultivars. Moreover, Cd mainly accumulated in the roots. Cd also caused the changes of uptake and distribution of nutrients in bai cai and under the influence of cadmium, the concentration of potassium (K) decreased in shoot and increased in root. However, the concentrations of magnesium (Mg), phosphorus (P), manganese (Mn), boron (B), and iron (Fe) increased in shoots and decreased in roots. In addition, Cd exposure resulted in an increase in calcium (Ca), sulphur (S), and zinc (Zn) concentrations in both shoots and roots but had no significant effects on the whole uptake of the examined mineral nutrients except for S.     

Effects of nitrogen dioxide on biochemical and physiological characteristics of soybean

One month old soybean (Glycine max (L.) Merrill) cv. 'Williams' plants were exposed to nitrogen dioxide (NO2 at 0.1, 0.2, 0.3, and 0.5 microl liter(-1) and carbon filtered air (control), 7 h per day for five days, under controlled environment. Data were collected on net photosynthetic rate (PN), stomatal resistance (SR), and dark respiration rate (DR), immediately following the fifth day of exposure and 24 h after termination of exposure. Chlorophyll a (Ch a), chlorophyll b (Ch b), total chlorophyll (tot Ch) and foliar nitrogen (N) were measured before and after exposures. Growth characteristics--relative growth rate (RGR), net assimilation rate (NAR), leaf area ratio (LAR), and root shoot ratio (RSR) -- were computed for treated plants using standard growth equations. Increases of 18% and 23% in PN were observed immediately following exposure to 0.2 microl liter(-1) NO2 and after 24 h recovery period, respectively. With 0.5 microl liter(-1) NO2 treatment, reductions in PN of 23% and 50% were observed, immediately after exposure and following 24 h recovery, respectively. DR rates with 0.2 l liter(-1) treatment were higher than the control. Chlorophyll a and tot Ch showed significant reduction with 0.5 microl liter(-1) NO2 treatment. The percent reduction in Ch a and tot Ch with 0.5 microl liter(-1) NO2 were 45% and 47%, respectively. Increases in foliar nitrogen content after 0.2 and 0.3 microl liter(-1) NO2 treatments were 46% and 69%, respectively. Nitrogen dioxide at 0.5 microl liter(-1) reduced RGR and NAR by 47% and 51%, respectively. Leaf area ratio was 42% higher in 0.5 microl liter(-)1 NO2 treated plants, compared with the control; this increase was insufficient to compensate for the decrease in NAR resulting in a net decline in RGR. Nitrogen dioxide up to 0.2 microl liter(-1) increased PN and foliar-N content of soybean. With 0.5 microl liter(-1) NO2, significant decreases were observed in PN, leaf chlorophyll, foliar-N, NAR and RGR. Nitrogen dioxide up to 0.2 microl liter(-)1 has a favorable influence on overall growth characteristics of soybean; however, inhibitory effects were seen with NO2 treatment at 0.5 microl liter(-1).     

Single and interactive effects of low levels of O3, SO2 and NO2 on the growth and yield of spring rape

During three consecutive seasons (1987-1989), the effects of low-levels of O3, SO2 and NO2 singly and in all possible combinations (NO2 in 1988 and 1989 only) on growth and yield of potted plants of spring rape (Brassica napus L. var. napus, 'callypso') were investigated by means of factorial fumigation experiments in open-top chambers. Plants were exposed from the early vegetative stage of development until seed harvest, to charcoal-filtered air (CF; control) and CF which was supplemented for 8-h per day (8.00-16.00) with O3, for 16-h per day with NO2 (16.00-8.00) and continuously with SO2. Including the controls, the 24-h daily mean concentrations [microg m(-3)] ranged between 6-44 (O3), 9-88 (SO2) and 10-43 (NO2). The corresponding daily mean concentrations during the time of fumigation were 10-121 and 11-60 microg m(-3) for O3 and NO2, respectively. Single effects of O3 on growth and yield parameters were mostly negative and the magnitude of this effect was dependent on the season. O3 reduced plant dry weight by 11.3-18.6% and yield of seeds by 11.4-26.9%. While medium levels of SO2 stimulated the weight of pods up to 33%, higher concentrations (88 microg m(-3)) caused a decline of yield of 12.3%. From the significant interactive effects which were observed, it could be established that SO2 and NO2 alone mostly acted positively, but that their interaction with each other and especially with O3 was antagonistic, as some of the detrimental effects of O3 were mitigated by these pollutants. An important antagonistic effect between SO2 and O3 or NO2 was observed on yield. While 56 microg m(-3) SO2 increased yield by 9.9% compared to the control treatment, it aggravated the yield loss caused by O3 from -16.18% to -21.4%, and it reduced the yield stimulation caused by NO2 from +11.8% to +4.2%. Leaf area was the only parameter which was negatively affected by all pollutants, their joint action being synergistic.     

Relative sensitivity of greenhouse pot plants to long-term exposures of NO- and NO2-containing air

Thirty-five cultivars of pot plants of 20 families were exposed for 50-64 days in a greenhouse facility to either 1 microl litre(-1) NO with 0.5 microl litre(-1) NO2, or 1 microl litre(-1) NO2 with 0.1 microl litre(-1) NO for 15 h each day, with air which was free from these gases as the reference. A sensitivity ranking of the pot plants was compiled, with the highest priority on visible injuries, followed by growth reductions, primarily as a response to the NO-dominated exposures, simulating the NOx-polluted environment in direct-fired, CO2-enriched greenhouses. This treatment reduced the leaf dry weight more than the number and area of the leaves. Twenty-two cultivars were significantly injured, while two (Hibicus sp, Epipremnum pinnatum, green) were significantly improved. The NOx-sensitivity of pot plants was highest in cultivars with variegated, small or narrow leaves, and in the Moraceae family. Nine cultivars (Ficus elastica 'Robusta', F. benjamina, F. pumila 'Sonny', Dieffenbachia maculata 'Camilla', F. elastica 'Tineke', Epipremnum pinnatum 'Marble Queen', Begonia elatior 'Nelson', Cyclamen persica, Poinsettia 'Mini') were specifically sensitive to the NO-containing exposure; six were specifically sensitive to the NO2-containing exposure (F. elastica 'Robusta', Asparagus den. 'Sprengeri', Hedera helix 'Shamrock', Aspledium nidus, Aster novo-belgii, Hypoestes phyl. 'Betina'); and 12 (Soleirolia soleirolii, Asparagus den. 'Sprengeri', H. helix 'Ester', Codiaeum 'Pictum', Rosa 'Minimo Red', F. benjamina 'Starlight', Saintpaulia ionantha 'light blue', F. pumila, Rhododendron simsii, H. helix 'Shamrock', Hibiscus sp., E. pinnatum) were equally sensitive to mixtures dominated by either gas, as measured by at least one response parameter.