Promotive effects of 5-Aminolevulinic acid on growth, photosynthetic gas exchange, chlorophyll, and antioxidative enzymes under salinity stress in Prunnus persica (L.) Batseh Seedling

The physiological characteristics of peach seedlings (Prunnus persica L. Batseh) under salt stress were investigated to ameliorate the effects of 5-aminolevulinic acid (ALA). Physiological indices of salt-stressed peach seedlings treated with exogenous ALA were investigated; these indices included stem diameter, plant height, leaf area, aboveground and underground weights, net photosynthetic rate (Pn), transpiration rate (Tr), intercellular CO2 concentration (Ci), stomatal conductance (Gs), root vitality, and membrane permeability. The contents of chlorophyll, malondialdehyde (MDA), soluble sugars, soluble proteins, and proline as well as the activities of antioxidant enzymes were evaluated. Results showed that the physiological characteristics of peach seedlings under NaCl stress (100 mM) were inhibited. Peach seedlings treated with100 mM NaCl and 200mg/l ALA for every germination index recovered. Moreover, peach seedlings treated with 200mg/l ALA exhibited enhanced physiological characteristics. Treatment with exogenous ALA increased stem diameter, plant height, leaf area, aboveground and underground weights, net photosynthetic rate (Pn), transpiration rate (Tr), intercellular CO2 concentration (Ci), stomatal conductance (Gs), and root vitality. The treatment also increased the contents of chlorophyll, soluble sugars, soluble proteins, and proline but decreased membrane permeability and MDA content. Furthermore, treatment with ALA significantly enhanced the activities of superoxide dismutase, peroxidase, and catalase. These findings indicate that exogenous ALA treatment could improve the growth and relieve the salt stress injury of peach seedlings by increasing photochemical efficiency, osmotic content, and antioxidant enzyme activity.