Plants of Ricinus communis L. in the city of Porto Alegre, in southern Brazil, were exposed to urban traffic exhaust emissions for 5 months and compared with controls kept at a site essentially free of direct motor vehicle emissions. No symptomatic visible injuries were observed, but significant differences could be measured in growth, enzymatic activities of total peroxidase and nitrate reductase, chlorophyll content, leaf buffering capacity, and N contents in leaves. Additionally, these data were compared with results from fumigation experiments under controlled conditions. The study showed that some physiological parameters in R. communis L. plants could be used as an appropriate bioindicator system for urban traffic contamination, and therefore it is recommended that dose-response relationships should be developed.

Monitoring of urban traffic emissions using some physiological indicators in Ricinus communis L. plants.

This review presents the status of knowledge about gasoline exhaust pollution and its impact biochemical and physiological characteristics of plants. Parameters on such as leaf conductance, membrane permeability, ascorbic acid, chlorophyll and relative water content have been used as indicators to assess the impact of gasoline exhaust pollution on plant health. Tolerant plants such as Mangifera indica Linn. are reported showing an insignificant decrease in the percentage of chlorophyll content (3.6%) and a significant increase in the percentage of ascorbic acid (84.6%) and sensitive plants such as Cassia fistula are reported showing a significant decrease in the percentage of chlorophyll (66.4%) as well as ascorbic acid (32.9%). In the case of ornamental plants, Dracaena deremensis has been reported to show an insignificant decrease in the chlorophyll content but a significant increase in the ascorbic acid, pH and relative water content, which were found to be in tolerant category, while Dianthus ...

The impact of gasoline emission on plants – a review

The influence of the main fuel oxygenate methyl tert-butyl ether (MTBE) and its key metabolite, tert-butyl alcohol (TBA), on the growth of a plant seedling was studied separately and in combination. The test plants were mung bean (Phaseolus radiatus), cucumber (Cucumis sativus), wheat (Triticum aestivum), sorghum (Sorghum bicolor), kale (Brassica alboglabra), Chinese cabbage (Brassica campestris), and sweet corn (Zea mays). The growth of all the plants was adversely affected by TBA and MTBE. The 5-d median effective concentration (EC50) for the plants exposed to MTBE and TBA were in the range of 680 to 1,000 mg MTBE/kg soil (dry wt) and 1,200 to 3,500 mg TBA/kg soil (dry wt), respectively. The relative order of the sensitivity rankings is almost the same for MTBE and TBA. Methyl tert-butyl ether is more toxic than TBA to most of the test species. Based on the EC50 values, MTBE is approximately 1.5 to 3 times more potent than TBA. The sum of the toxic unit (TU) at 50% inhibition of the mixture (EC50mix) was calculated from the dose (TU-based)-response relationships using the trimmed Spearman-Karber method. The combined effect of MTBE + TBA on the plant growth was less than additive because the EC50mix values were greater than I TU. This phenomenon may be due to the competition of MTBE and TBA in terms of their intake by plants. The combined effects of MTBE and TBA should be taken into account to assess their risk in gasoline-contaminated sites.

Decreased toxicity to terrestrial plants associated with a mixture of methyl tert‐butyl ether and its metabolite tert‐butyl alcohol

Plants of Ricinus communis L. were fumigated with different dilutions of exhaust gases from gasoline or ethanol from sugar cane commonly used in Brazil. Alcohol proved less toxic than gasoline in terms of visual injuries produced by acute toxic concentrations. Exhaust gases first attacked leaf palisade parenchyma resulting in necrotic spots with reduced chlorophyll content and led to a decrease in peroxidase and nitrate reductase activities. Non-lesion-producing exhaust gas concentrations from both fuel types stimulated peroxidase and nitrate reductase activities, but reduced soluble protein content in the leaves. Levels of nitrate and nitrite were higher after fumigation and chlorophyll content not altered. It was concluded that from an environmental standpoint, alcohol fuel from sugar cane is a reasonable alternative energy source to fossil gasoline. Additional index terms: chlorophyll, fossil fuel, fumigation experiments, nitrate reductase, nitrogen metabolism, peroxidase, soluble protein, sugar cane.

Hans Kammerbauer

Papers

Plant response to motor exhaust emissions from gasoline and alcohol.