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 (Prunus persica L. Batsch) seedlings under NaCl stress were investigated to ameliorate the effects of 5-aminolevulinic acid (ALA). Growth and physiological parameters of NaCl stressed peach seedlings treated with exogenous ALA were investigated; these parameters included shoot and root dry mass, leaf area, plant height, stem diameter, intercellular CO2 concentration (Ci), stomatal conductance (Gs), net photosynthetic rate (Pn), transpiration rate (Tr), membrane permeability, and root vitality. The contents of chlorophyll, proline, soluble sugars, soluble proteins, malondialdehyde (MDA), as well as the activities of antioxidant enzymes were evaluated. Results showed that the physiological characteristics of peach seedlings under NaCl stress (100mM) were inhibited. Peach seedlings treated with 100mM NaCl and 200mg/l ALA for every growth parameters recovered. Moreover, peach seedlings treated with 200mg/l ALA exhibited improved effectively physiological characteristics. Treatment with exogenous ALA increased stem diameter, plant height, leaf area, shoot and root dry mass, net photosynthetic rate (Pn), transpiration rate (Tr), intercellular CO2 concentration (Ci), stomatal conductance (Gs), and root vitality. The treatment also increased the contents of chlorophylls, 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 NaCl stress injury of peach seedlings by increasing photochemical efficiency, osmotic content, and antioxidant enzyme activity.