Drought Alleviated the Negative Effects of Elevated O3 on Lonicera maackii in Urban Area

Abstract

Open top chambers were used to study the changes in photosynthesis, physiology and stomata characteristics in 1-year-old Lonicera maackii seedlings exposed to drought (DT, 30%–35% soil saturated water content) or/and elevated ozone (EO, 80 ppb). The results showed that DT or/and EO significantly decreased net photosynthetic rate (Pn), stomatal conductance (gs), maximum photochemical efficiency (Fv/Fm), but increased the activity of superoxide dismutase (SOD), and malondialdehyde content (p < 0.05). Compared with EO alone, the combination of EO and DT caused higher values in Pn, Fv/Fm, SOD activity (p < 0.05), and smaller stomata size and lower visible injury rate. DT alleviated the adverse impact of EO on the shrub by increasing enzyme activity and decreasing stomatal size, particularly stomatal width. The study provided increasing evidence that moderate drought might exert a beneficial effect on the tested plants to adapt to the future climate change, particularly in high ozone regions.