Morphophysiological adjustments and Antioxidant defense in main tree species of southern China to simulated acid deposition

A b s t r a c t. Acid deposition has become a significant issue due to increased pollution and forest degradation.To examine the response of acid deposition in Fuzhou, a city in Fujian Province, we investigated the physiology, morphology, osmotic adaptation, photosynthetic characteristics, and antioxidant defense of Pinus massoniana, Cunninghamia lanceolata, Liquidambar formosana, Schima superba, and Phoebe zhennan.Seedlings were subjected to pH levels of 2.5, 3.5, 4.5, and 5.5 in a greenhouse experiment.Plant height, diameter, and biomass increased in the control group (6.5); however, pH 4.5 and 5.5 resulted in tall and thin seedlings.Height and diameter decreased under increased acid deposition specifically at pH 2.5 and 3.5.Biochemical parameters and chlorophyll contents were reduced under low pH levels.The activities of catalase, peroxidase, superoxide dismutase, malonaldehyde, and proline increased initially under low pH, but decreased later due to high acidity, whereas soluble sugar and protein contents were inhibited under higher acidity levels (pH 2.5 and 3.5).The findings showed that the seedlings responded differently but more sensitively to acid deposition below pH 4.5.The exposure to less acidic deposition had a slight effect on the development of these tree seedlings.This trial aids in detecting bioindicators and resilient species to acid deposition existing in forests and urban areas.K e y w o r d s: acid rain, photosynthesis, antioxidant enzyme, gas exchange, osmotic adjustment 2-) (Cape, 1993).Fuzhou, the capital of Fujian Province, is substantially affected by acid deposition, with higher severity observed in spring and winter compared