LEAF DIFFUSION RESISTANCE RESPONSES OF 3 PETUNIA CULTIVARS TO OZONE AND-OR SULFUR-DIOXIDE

The response of stomata to O3 and/or SO2 in two humidity regimes was evaluated in terms of leaf diffusion resistance (LDR) of petunia (Petunia hybrida Vilm.) plants of three cultivars of differing O3 sensitivity. At about 50% relative humidity, exposure to O3 or O3 and SO2 resulted in rapid increases in LDR with the fastest response in the mixture. There were only slight increases in LDR with O3 or O3 and SO2 exposure at about 90% relative humidity and there were only slight effects of SO2 alone on LDR at either 50% or 90% relative humidity. The LDR of the sensitive cultivar ’White Cascade’ increased most rapidly in O3 alone and the least sensitive ’Capri’ most rapidly in the O3 and SO2 mixture but the maximum LDR reached with continued exposure was similar for all cultivars. © 1979 Air & Waste Management Association.