An Evaluation of Methods Used to Determine Injury to Plant Leaves by Air Pollutants

Abstract

1. An evaluation was made of three methods of analyzing the damage of plant leaves after exposure to ozone or ozonated hexene gas. A visual estimate was made of the amount of leaf surface damaged. The same plants were used for measurements of the change in fresh weight and of chlorophyll content. The latter two measurements were chosen because injury results in desiccation of parts of the leaf and a loss of pigmentation. Also these would be a measure of the actual amount of functional leaf material which was damaged. 2. It was found that losses in fresh weight were nearly proportional to losses of chlorophyll in injured leaves. The visual-rating system appeared to be sensitive in the lower range of injury but rather insensitive at the upper end of the range. The visual-damage index appears to be logarithmic with respect to both chlorophyll and fresh-weight changes. It was concluded that a measurement of the change in either fresh weight or chlorophyll content would give a better estimate of impairment of ...