Tobacco plants detect a decrease of environmental genotoxicity in Toulouse (France).

Tobacco plants, heterozygous for two independent loci involved in the chlorophyll parenchyma differentiation, allow the genotoxic effects of the atmosphere of the industrial estate South of Toulouse to be estimated. Somatic spots of green cellular colonies on yellow-green background, were counted to calculate the cellular rates of reversion. Two experiments were carried out in 1981, and in 1997. A general decrease of genotoxic effects was observed. These observations were interpreted as being due to a general decrease of the air pollution evaluated by the development of the concentrations of three toxic gases before and after the implementation of cleanup devices. The results obtained demonstrate the efficiency of this bio-indicator, which is easy to use and capable of integrating, in situ, genotoxic variations throughout the duration of plants' growth.

Evaluation of the genotoxic and teratogenic potential of a municipal sludge and sludge-amended soil using the amphibian Xenopus laevis and the tobacco: Nicotiana tabacum L. var. xanthi Dulieu.

The toxic, genotoxic and teratogenic potential of a municipal sewage sludge was assessed using the micronucleus assay on the larvae of the amphibian Xenopus laevis and with the tobacco somatic mutation test using the yellow-green xanthi Dulieu mutant a(1)(+)/a(1) a(2)(+)/a(2). The teratogenic potential was assessed by means of the Frog Embryo Teratogenesis Assay-Xenopus (FETAX). Various doses of the pasty sludge added to a crop soil were tested using the three bioassays. The test systems were performed either directly with sludge or sludge-amended soil samples (plant model) or with aqueous extracts (aquatic animal model). Using the tobacco model, we found no mutagenic impact of the soil amended with the sludge, perhaps because the clay-like nature of the soil, with its high adsorption capacity, may have prevented the contaminants from reaching the target. All leachates of amended soils produced a significant size reduction in Xenopus embryos. Depending on the soil/sludge ratio, some leachates were found to be genotoxic but were never teratogenic. This battery of in vivo test systems enabled us to estimate the global long-term effects under agricultural conditions with various genetic endpoints on ecologically relevant organisms characteristic of the aquatic and terrestrial compartments.

Bioindicator reliability: the example of Bel W3 tobacco (Nicotiana tabacum L.).

The use of the Bel W3 tobacco variety revealed the existence of an intrapopulation variation of sensitivity to the ozone effect leading to the isolation of two categories of plants: sensitive and resistant. The use of sensitive plants revealed the existence of a biological ozone efficiency threshold at a level close to 34.5 ppb. Under the threshold, the biological effects observed were weak or very weak. They can be attributed to the occurrence of secondary phenomena (chemical, physiological, pathological, etc.), inducing or inhibiting necrosis, which become perceptible here.