Effects of ozone and drought on fluorescence physiology of seedlings of three afforestation tree species in South China

Objective This study was conducted to demonstrate the fluorescent physiology of ozone resistance and drought physiology mechanism in the seedlings of three native tree species and provide reference for screening stress-resistant tree species in South China.

Method Seedlings of Elaeocarpus apiculatus, Mytilaria laosensis and Castanopsis fissa were treated with ozone fumigation and drought condition, and their chlorophyll fluorescence parameters were determined.

Result and conclusion The results showed that with increasing treatment time, minimal initial fluorescence (F₀) of the three seedling types increased and then decreased, and their PSⅡ maximum photochemical efficiency (F_v/F_m) remained stable; active quantum efficiency of PSⅡY (Ⅱ) treated with ozone stress decreased, followed by an increase and other treatments remained stable; non-photochemical quenching (NPQ) of E. apiculatus seedlings remained stable and other seedling types increased and then decreased. Principal component analyses showed that resistance of the three seedling types to ozone stress and drought stress was C. fissa > E. apiculatus > M. laosensis, whereas their resistance to intercross stress of ozone and drought was E. apiculatus > C. fissa >M. laosensis. In general, the three seedling types have a certain ability to resist ozone or drought by starting an adjustment mechanism of photoprotection under ozone stress or drought stress.