Correlation between Ozone Resistance and Relative Chlorophyll Fluorescence or Relative Stomatal Conductance of Bedding Plants

Abstract

Eight species of bedding plants were exposed to 400 ppb ozone (O3) for 4 h. On the basis of the resulting foliar injury, Madagascar periwinkle (Catharanthus roseus) and impatiens (Impatiens walleriana) were the most resistant to O3, and wax begonia (Begonia xsemperflorens-cultorum) was the most sensitive to O3. Clorophyll fluorescence (Fv/Fm) and stomatal conductance were measured before and after the O3 fumigation. There was a significant regression between, the degree of foliage injury by O3 and relative chlorophyll fluorescence (RCF, ratio of post-fumigation Fv/Fm: pre-fumigation Fv/Fm) or relative stomatal conductance (RSC, ratio of post-fumigation stomatal conductance: pre-fumigation stomatal conductance) (r=-0.84, P＜0.001 and r=0.64, P＜0.05 respectively). That is, species of tested bedding plants that had stronger O3 resistance generally had higher RCF and lower RSC values. It is suggested that RCF and RSC measurements could serve as indicators to screen plants for O3 resistance.