Physiological response of banana seedling to exogenous ALA under drought stress.

【Objective】The objective of this study was to investigate the effects of exogenous 5-aminolevulinic acid (ALA) on banana seedling growth and physiological characteristics under drought stress so that theoretical references could be provided for appropriately using ALA to improve drought resistance of banana seedlings. 【Method】Several growth indicators of brazil banana seedlings treated by ALA under drought stress (10% PEG-6000) were measured. Some physiological indicators of the functional leaves like relative water content,MDA and soluble protein content,relative conductivity,and the activities of SOD and POD were also determined. 【Result】The growth of banana seedlings under 10% PEG-6000 stress was inhibited, but after the treatment of different concentrations of ALA,all the growth indicators increased. Especially every index of the seedlings treated by 10 mg/L ALA had the maximum value,in which the leaf area,overground-FW,underground-FW and root/shoot ascended by 11.59%, 19.53%, 6.73% and 13.63%,respectively,compared with the control. Each treatment of ALA could improve the contents of soluble protein and proline of the seedlings, slow down the falling trend of RWC, reduce the content of MDA and membrane permeability in leaves, and markedly enhance the activities of SOD and POD. Additionally, 10 mg/L ALA treatment led to the strongest enzyme activity. 【Conclusion】These results showed that ALA treatment with the appropriate concentration (10 mg/L) could significantly promote the growth of the seedlings under drought stress, and effectively alleviate the damage of drought stress on banana seedlings by means of adjusting the content of osmotic adjustment substances and preserving enzyme activity.