Effects of Ozone and Drought on Biomass Allocation of Four Seedlings in South China

Seedlings of Michelia macclurei, Cinnamomum camphora, Rhodoleia championii and Mytilaria laosensis were placed in open-top chambers (OTC) with three ozonic treatments including E20 (20 ppb), E40 (nature air, 40 ppb) and E160 (160 ppb) and two water treatments. Root biomass, stem biomass and leaf biomass total biomass and root/shoot ratio of four seedling types were evaluated. The results showed that there were no significant differences in impacts of ozone stress and drought stress on root, stem, leaf, and total biomass of M. macclurei among different treatments. The biomass of M. laosensis decreased with increasing ozone concentration, whereas biomass of C. camphora and R. championii changed irregularly. Most of the biomass of four kind seedlings under ozone and drought intercross stresses was lower than those under ozone stress. The root/shoot ratios of four seedling species were all low. The ratios under high concentration ozone (160 ppb) were lower than the control treatment. And the ratios of different treatments under drought were lower than those were not under drought when they were under the same concentration of ozone.