Comparative Evaluation of Physiological Response and Drought Tolerance between Cunninghamia unica and C. lanceolata Seedlings under Drought Stress

Cunninghamia plays an important role in China's southern forest industry in the face of increasingly arid climate; thus it is urgent to identify and screen drought-tolerant varieties. In this study, 2-year-old seedlings of C. unica and C. lanceolata from four provenances were subjected to water-break tests, and their physiological responses to different drought conditions were observed. The results showed that with the aggravation of drought stress, C. unica had more stable changes in relative water content (RWC), water potential (psi w) and intercellular CO2 concentration (Ci) with more cumulative amounts of proline (PRO) than C. lanceolata, and its H2O2 maintained at a lower level, along with antioxidant enzyme activities decreasing later as compared with C. lanceolata. Moreover, comprehensive evaluation showed that C. unica had a higher drought tolerance than C. lanceolata as a whole, which could have been shaped by maintaining psi w and opening stomata in its relative drought conditions. This work provides a theoretical basis for understanding the drought tolerance of C. unica and C. lanceolate individuals, so as to accelerate selective breeding in Chinese fir.