Physiological and Biochemical Characters of Eight Native Tree Seedings in Guangdong Province During Drought Stress and Rewatering Treatment

Native tree species play a crucial role in addressing the challenge of seasonal drought in South China. In this study, one-year-old seedlings of eight native tree species in Guangdong Province were subjected to continuous simulated drought stress and rewatering. In order to identify key drought-resistant traits and best performing tree species, physiological and biochemical responses were assessed through 21 indicators. The results showed the following: (1) All species exhibited responses to drought stress prior to the fourth day, as evidenced by reductions in morphological indicators (crown breadth and ground diameter) and photosynthetic parameters (chlorophyll content, transpiration rate, net photosynthetic rate and stomatal conductance), along with increases in osmotic substances (soluble protein and proline) and antioxidant-related indicators malondialdehyde, peroxidase and superoxide dismutase). (2) The crown breadth, leaf relative water content, chlorophyll content, and ascorbate peroxidase activity were significantly decreased under drought stress. And these indicators were not recovered to pre-stress levels following rewatering. (3) Mantel tests revealed that growth morphological characteristics, particularly plant height, were significantly and positively correlated with most osmotic substances indicators (p < 0.001). Specifically, plant height showed the strongest coupling with these traits, with Mantel’s r ranging from 0.44 to 0.89. In addition, the leaf relative water content, net photosynthetic rate, superoxide dismutase, and malondialdehyde were regarded as the key drought-resistant traits, providing insights into future research on plant improvement, stress-resilience breeding and even drought resistance mechanisms. (4) The eight tree species are ranked from most to least drought-resistant as follows: Zenia insignis, Michelia macclurei, Phoebe zhennan, Phoebe bournei, Erythrophleum fordii, Dalbergia odorifera, Cinnamomum burmanni and Michelia chapensis. This study provides a scientific basis for selecting tree species for afforestation in seasonally arid regions.