Application of a polymeric coating can protect coniferous trees from acute pollution injury

Abstract

SO 2 and NO x are main primary pollutants which often occur together in Europe. In three experiments small spruce trees were exposed to SO 2 or to SO 2 + NO 2 in controlled environmental conditions. A polymeric coating (spodnam), based on a natural terpenoid compound was applied to half the trees fumigated in each experiment and the influence of this material on the sensitivity to pollutant injury was observed. Picea abies and Picea rubens (Norway and Red spruce) were more sensitive than Picea sitchensis (Sitka spruce) to acute damage from 8000 ppb SO 2 experienced for 12-h periods during dormancy. A single application of 15% (ν/ν) of the polymeric coating substantially decreased the extent of acute injury in all three species. Dormant P. sitchensis fumigated with 250 ppb SO 2 and SO 2 + NO 2 also showed less pollutant injury at the end of a 2-month fumigation when 5% (ν/ν) spodman had been applied. Exposure of coated and uncoated seedlings of P. sitchensis to 400 ppb SO 2 during growth in 8-h and 16-h photoperiods confirmed the strong protective effect of a 15% (ν/ν) application. After 6 weeks in 16-h photoperiods, the coated plants grown in SO 2 had larger dry weights than uncoated plants in SO 2. Spodnam also caused decreases of dry weight which were greater in the 8-h daylength, indicating that growth rate was important in determining the physiological cost of having an additional coating over the foliage. Further analysis of the effects of the coating on plant growth and of its protective function against air pollutants are required to determine whether application would be beneficial in forest areas were large concentrations of gaseous air pollutants occur. The timing, concentration and degree of coverage achieved during application would influence the impact of this material; and the benefit gained would depend on the severity of pollutant damage and on the way in which spodnam effects other factors which influence growth.