Physiological and Photosynthetic Characteristics with Ecological Restoration Application of Nerium indicum Under Salt Stress

Marine salinity affects mainly the roots, stems and leaves of coastal plants through groundwater intrusion, splashing and salt spray. Two-year-old Nerium indicum L. seedlings with good growth were used to carry out the salt tolerance experiments in their roots and leaves by setting multiple concentration gradients of control 0%, 0.3%, 0.6%, 1.0%, 2.0% and 3.0%. Normal watering for 4 weeks was followed by 13 weeks of salt stress treatment. The net photosynthetic rate (Pn), transpiration rate (Tr), stomatal conductance (Gs) and water use efficiency (WUE) were measured at the end of salt stress and after normal irrigation. At the same time, physical and chemical indices, such as the cell membrane permeability and water saturation deficit (WSD) of leaves, were measured. The results showed that both soil salt stress and foliar salt stress affected the morphology and growth of Nerium indicum. When the soil salt stress was ≥1.0%, the growth status of Nerium indicum decreased irreversibly to less than 2, while under