Photosynthetic Characteristics and Water Use Efficiency of Thuja sutchuenensis Franch. During Water Stress and Recovery

Photosynthetic characteristics and water use efficiency (WUE) were monitored in four year old seedlings of Thuja sutchuenensis Franch.during drought stress and recovery.Results showed that leaf relative water content (LRWC) decreased after soil relative water content (SRWC) fell below 30% under water stress.Net photosynthetic rate(P_n),transpiration rate (T_r), intercellular CO₂ concentration (C_i),light saturation point (LSP)and the maximum photosynthetic rate (P_max) decreased along with available water reduction, while apparent quantum yield (Q),apparent quantum requirement (1/Q),and light compensation point (LCP) remained.The WUE gradually increased as SRWC fell.P_n reached zero due to leaf wilting after 50 days drought stress (SRWC decreased about 95%).After three days of rewatering, P_n recovered to 88.59% of the control levels and WUE reduced to 88.63% that of the control levels.Through the analysis of physical signs above,we concluded that Thuja sutchuenensis Franch.is a drought-avoiding plant.