Lipid Peroxidation, Antioxidant Enzyme Activities, and Osmotic Adjustment in Platycladus orientalis and Amorpha fruticosa Differ during Drought and Rewatering

Platycladus orientalis and Amorpha fruticosa are important pioneer species in arid and semi-arid regions, playing a crucial role in ecological restoration in water-limited areas. The purpose of this research was to examine how different watering and rewatering schedules influence the antioxidant enzyme activities and biochemical responses of P. orientalis and A. fruticosa. Five different water regimes (100%, 88%, 70%, 52%, and 40% of soil relative water content) were applied to seedlings for 15, 30, 45, and 60 days, after which they were rewatered. The levels of malondialdehyde (MDA), antioxidant enzyme activities (superoxide dismutase, peroxidase, and catalase), and osmotic solutes (soluble sugar and proline) were assessed in the leaves of P. orientalis and A. fruticosa. Measurements were taken at various growth stages, namely the initial, fast, and late stages, both during the drought period and after 2, 24, 48, and 72 h of rewatering. The results revealed that the malondialdehyde content in the leaves of P. orientalis and A. fruticosa increased with the level of stress. The activities of antioxidant enzymes and the levels of osmotic solutes in the leaves of P. orientalis and A. fruticosa exhibited varying enhancements as the water stress intensified. During the recovery phase, the antioxidant enzymes and soluble sugar content returned to the control level 72 h after rewatering at different growth stages. However, the proline content remained slightly elevated compared to the control plants. Overall, these findings suggest that the two plant species displayed minor differences in their responses to drought stress and rewatering in terms of antioxidant enzymes and other biochemical responses. This indicates their remarkable adaptability to severe drought conditions and their potential for rapid recovery after rewatering. These observations are highly significant for irrigation management strategies when establishing plantations in arid and semi-arid regions.