RESPONSES OF AGROSTIS-CAPILLARIS TO GASEOUS-POLLUTANTS AND WET NITROGEN DEPOSITION

Agrostis capillaris L. plants were exposed to combinations of gaseous pollutants and wet nitrogen mist in Solardome glasshouses. Gaseous pol lution treatments were (a) charcoal-filtered air (control), (b) 10 ppb SO2 + 10 ppb NO2, (c) 20 ppb SO2 + 20 ppb NO2, (d) 40 ppb SO2 + 40 pp b NO2. Within each Solardome, four plant blocks were allocated differe nt wet deposition treatments which provided a North Wales maritime rai n with the equivalent of 0, 20, 40 or 60 kg N per hectare per year wit hout changes in hydrogen ion concentration. Progressive senescence of leaves in the gaseous pollution treatments correlated well with leaf d ry weight data, showing increasing injury with time. Growth analysis w as performed after 11, 13 and 15 weeks exposure to pollutants. Gaseous pollution treatments resulted in substantial reductions in leaf areas and dry weights of A. capillaris in both the 20 ppb SO2 + 20 ppb NO2 and the 40 ppb SO2 + 40 ppb NO2 treatments compared with the plants ex posed to charcoal filtered air and the 10 ppb SO2 + 10 ppb NO2 treatme nt. Adverse effects of the gaseous pollution treatments were greater o n shoots than roots. Additions of wet nitrogen caused reductions in th e numbers of tillers and leaf areas of A. capillaris is compared with plants with zero nitrogen application. There were no effects of wet ni trogen treatments on total plant dry weights but all nitrogen addition s above zero application resulted in a reduction in root dry weights a t the final harvest which was reflected in a decrease in root/shoot ra tio in the 60 N treatment. (C) 1997 Elsevier Science B.V.