DETECTION OF INJURY TO PLANTS CAUSED BY EXPOSURE TO GASEOUS AIR POLLUTANTS

THE HARMFUL EFFECTS ON THE ECONOMY OF FORESTRY AND AGRICULTURE, AS WELL AS THE DETERIORATION OF THE RECREATIONAL ENVIRONMENT, WHICH ARE CAUSED BY GASEOUS AIR POLLUTANTS, ARE WELL RECOGNIZED. ONE SERIOUS PROBLEM AFFLICTING THE STUDY OF POLLUTANT INDUCED INJURY TO PLANTS IS THE GREAT DIFFICULTY OF DETECTING THE INJURY EARLY. TECHNOLOGICAL DEVELOPMENTS OVER THE LAST FEW YEARS, HOWEVER,PRESENT THE OPPORTUNITY TO EVALUATE TWO NEW TECHNIQUES FOR THEIR ACCURACY AND USEFULNESS IN DETECTING INJURY CAUSED BY THE EXPOSURE OF PLANTS TO GASEOUS AIR POLLUTANTS. THE TWO NEW TECHNIQUES WHICH WE PROPOSE TO EVALUATE ARE BASED ON: (1) THE DETERMINATION OF THE RELATIVE VARIABLE IN VIVO CHLOROPHYLL FLUORESCENCE LEVEL, AND (2) THE DETERMINATION OFTHE COMPOSITION OF STABLE CARBON ISOTOPES ( 13C-VALUES OF LEAF TISSUE. PLANTS OF TEN SPECIES WILL BE ESTABLISHED IN POTS IN A GREENHOUSE. THE PLANT SPECIES FALL INTO THREE GROUPS WHERE EACH GROUP, FOR ITS OWN REASONS, IS OF INTERESTIN POLLUTED AREAS. THE PLANTS WILL BE TRANSFERRED IN THE ACTIVE STAGE TO FOUR OPEN TOP FIELD CHAMBERS. AFTER ONE WEEK OF ACCLIMATION IN THE FIELD CHAMBERS, FUMIGATIONS WILL START WITH A MIXTURE OF SO2 ANDO2 AT THREE DIFFERENT LEVELS IN THREE OF THE OPEN TOP FIELD CHAMBERS. THE REMAINING CHAMBER WILL BE USED AS A CONTROL WHERE THE PLANTS ARE EXPOSED TO FILTERED AIR ONLY. THE FUMIGATIONS WILL TAKE PLACE EVERY SECOND DAY FOR FIVE MIDDAY HOURS DURING A PERIOD OF THREE WEEKS. EVERY TWO DAYS (BETWEEN FUMIGATIONS)FLUORESCENCE INDUCTION CURVES WILL BE RECORDED FOR ALL PLANTS AND THE RELATIVE VARIABLE FLUORESCENCE (FV/FTOT, VARIABLE FLUORESCENCE RELATED TO TOTAL FLUORESCENCE) WILL BECALCULATED. THE PLANTS WILL, FURTHER, BE RATED VISUALLY DURING THE EXPERIMENT FOR THE LEAF AREA FRACTION SHOWING CHLOROSIS AND NECROSIS. LEAF SAMPLES WILL BE COLLECTED BEFORE AND AGAIN AFTER THE END OF THE FUMIGATION PHASE AND THE 13C-VALUES DETERMINED. THE CHLOROPHYLL CONCENTRATION AND THE CHLOROPHYLL A/B RATIO WILL ALSO BE DETERMINED BEFOREAND AFTER THE EXPOSURE TO AIR POLLUTANTS.