Effects of drought stress on chlorophyll fluorescence parameters of two fast-growing tree species

Objective A comparison of drought resistance was made between two fast-growing species in South China, Eucalyptus urophylla×E. grandis (EE for abbr.) and bamboo willow (BW for abbr.).

Method Effective quantum yield of PSⅡ photochemistry(Yield), apparent electron transport rate(ETR), the photochemical quenching (qP), the non-photochemical quenching (qN), minimal fluorescence(F₀), maximal fluorescence(F_m), potential photochemical efficiency of PSⅡ(F_v/F_m) in EE and BW were tested by OS5P pulse modulated chlorophyll fluorometer under drought stress.

Result and conclusion Yield, ETR, qP, F_m and F_v/F_m all declined during the drought. At day 24 after treatment, ETR declined by 48.02% and 25.12% EE and BW, respectively. qN and F₀ in the 2 species increased. qN in BW rose by 217.59%, which was significantly higher than that in EE (146.40%, P < 0.05). The relative increment in F₀ in BW (49.11%) was smaller than that in EE (92.03%) at the end of the drought treatment. Correlation analyses were made concerning chlorophyll fluorescence characteristics and soil water content. In both species, ETR showed a significant positive correlation with soil water content (P < 0.01). F₀ in EE showed a significant negative correlation with soil water content (P < 0.01). F_m and F_v/F_m of BB and soil water content showed a significant positive correlation (P < 0.01). These results indicate that correlations existe among chlorophyll fluorescence characteristics in two species under drought. BW has greater drought resistance than EE as revealed by chlorophyll fluorescence characteristics.