Foliar injury, growth, and SOD activity of Pinus densiflora exposed to ozone

Abstract

This study was conducted to compare ozone sensitivity among half-sib families of Japanese red pine (Pinus densiflora S. et. Z). Ninety families were exposed in walk-in type chambers to charcoal-filtered air and 100ppb ozone for eight hours daily over a period of five consecutive months. We surveyed the foliar injury, relative diameter at root collar (DRC) growth, and relative dry weight after fumigation. We selected five tolerant families and five sensitive families. After one year, the selected ten families were exposed to 100ppb ozone for 90 days. Every 30 days after ozone fumigation, the DRC, superoxide dismutase (SOD) activity, and malondialdehyde (MDA) content were measured. In the earlier stage of ozone fumigation, the tolerant group showed a relative DRC growth rate three times higher than that of the sensitive group. As well, during the entire fumigation period, the growth rate of the tolerant group was superior to that of the sensitive group. Relative SOD activity in the sensitive group was increased 30 days after fumigation, and in accordance with the fumigation period extended it was decreased. MDA content in the ozone treatment manifested at higher levels than in the control group, and the MDA content of the tolerant group manifested at higher levels than that found in the sensitive group. The tolerant group has more antioxidative activity than the sensitive group; therefore the tolerant group can restrain lipid peroxidation and other adverse effects on physiological activity. Ozone-induced growth reduction may thus be decreased in the tolerant group.