Jean-Pierre Garrec

Biomonitoring of traffic-related nitrogen oxides in the Maurienne valley (Savoie, France), using purple moor grass growth parameters and leaf 15N/14N ratio

Effects of traffic-related nitrogenous emissions on purple moor grass (Molinia caerulea (L.) Moench) transplants, used here as a new biomonitoring species, were assessed along 500 m long transects orthogonal to roads located in two open areas in the Maurienne valley (French Alps). Leaves were sampled during summer 2004 and 2005 for total N-content and (15)N-abundance determination while nitrogen oxides (NO and NO(2)) concentrations were determined using passive diffusion samplers. A significant and negative correlation was observed between plant total N-content, and (15)N-abundance and the logarithm of the distance to the road axis. The strongest decreases in plant N parameters were observed between 15 and 100 m from road axis. They were equivalent to background levels at a distance of about 800 m from the roads. In addition, motor vehicle pollution significantly affected vegetation at road edge, as was established from the relationship between leaf (15)N-abundance, total N-content and road traffic densities.

Pigment Concentrations and Ratios of Aleppo Pine Seedlings Exposed to Ozone

Two-year-old Aleppo pine (Pinus halepensis Mill.) seedlings were exposed to ambient air+50 ppb O3 in open-top chambers (24 hours/day, 7 days/week) during May-October 1997 and to ambient air+70 ppb O3 from May 1998 onwards. One growing season fumigation with ozone did not affect the pigment concentrations of the current-year (c) needles, nor were there any differences in photosynthesis or stomatal conductance. In May 1998, however, a marked carry-over effect was seen in the chlorophyll a and b and total carotenoid concentrations of the O3-fumigated one-year-old (c+l) needles. The chlorophyll a and b and total carotenoid concentrations of newly flushed needles of the O3-fumigated seedlings also seemed to be slightly decreased, as was their net photosynthesis when compared to the values of the filtered-air control needles. The chlorotic mottle and the changes in chloroplast pigments and photosynthesis of the c and/or c+l needles of the NFA+O3 seedlings in May 1998 indicate that frequent episodes of ozone concentrations of ≥ 100 ppb, especially when they also occur during the evening and night hours, as in some areas in southern Europe, may result in visible needle damage on Aleppo pine.

Cuticular Characteristics in the Detection of Plant Stress Due to Air Pollution — New Problems in the Use of these Cuticular Characteristics

The foliar surface, and particularly the cuticle, is the first zone of impact of air pollutants on leaves. At the level of the cuticle, it is mainly studies on the modifications of the physico-chemical properties of the waxes that allow us to detect and estimate plant stress. However, during recent years, with modifications in the nature and level of air pollution (decrease of primary pollutants: SO2, HF; increase of secondary pollutants: O3, acid deposits; increase of nitrogen deposits; increase of organic micropollutants; appearence of global environmental problems: CO2, climatic change), the physiological impact on plants and in particular on the cuticle is different. For this reason, new problems have appeared and use of cuticular characteristics in the detection of plant stress due to air pollutants has recently evolved. Some examples are given, but much remains to be done to understand the effects on the cuticle of these new modifications of the atmospheric environment of plants.