Responses of Chlorophyll Content and Fluorescence to Water Stress in Vitex Negundo var. Heterophylla: Take Hilly area of Taihang Mountain in Henan for Example

In this study, we investigated the response of chlorophyll content and characteristics of chlorophyll fluorescence to water stress in 1-year-old Vitex negundo var. Heterophylla. The results showed that there was no significant difference between the chlorophyll parameters under the mild water stress condition and those under normal water condition. With the increases of the water stress intensity, the primary fluorescence (F₀) and nonphotochemical quenching coefficient (NPQ) were increased gradually, while chlorophyll content (CHL%), variable fluorescence (F_v), the maximal photochemical efficiency of PSII (F_v/F_m), potential activity of PSII (F_v /F₀) and photochemical quenching coefficient (qP) were decreased significantly. We concluded that F₀, F_v, F_v/F_m, F_v/F₀, qP and NPQ had good sensitivity to water stress and can be used as indicators to identify drought-resistant Vitex negundo var. heterophylla.