Measurement of Ozone Injury by Determination of Leaf Chlorophyll Concentration

A simple, rapid procedure is described for evaluating ozone injury to leaves of Phaseolus vulgaris L. cv. Pinto. Leaf chlorophyll is extracted with ethanol and analyzed spectrophotometrically; the concentration is expressed on the basis of leaf dry weight.The per cent chlorophyll reduction of ozone-injured leaves was highly correlated with the per cent visible necrosis and chlorosis (r = 0.96). The variability in injury estimates with chlorophyll analysis was slightly less than with visual evaluation. An evaluation of chlorophyll a and b concentrations separately showed that the chlorophyll a/b ratio decreased with increasing amounts of injury. Chlorophyll determinations made for leaves harvested at intervals after an ozone treatment indicated that maximum chlorophyll reduction had occurred by 4 days.This procedure for measuring ozone injury should be useful in eliminating the human bias associated with visible estimates of injury.