Growth response of Moringa oleifera (Lam) to water stress and to arid bioclimatic conditions

A major challenge in agroforestry is the selection of the plant species involved in the systems. This issue is drawing more attention lately due to the changing climate conditions and Moringa oleifera represents a promising species to meet these climatic challenges. The adaptation potential and tolerance of Moringa to water stress was tested in this study. It included a controlled (hydroponic cultivation) and a field experiment in an arid area bordering the Bouhedma National Park (Governorate of Sidi Bouzid) in Tunisia. Water stress was induced by the use of polyethylene glycol (PEG-6000) to create different water potential levels (ψh) and included 0 (control), −0.5, −1 and −1.5 MPa. The growth of the stem and main root, relative growth rate (RGRₕ), and leaf area (LA) of Moringa seedlings subjected to 20 day of water stress was compared to the control. Additionally, Moringa seedlings were grown in the field for 16 months and their growth parameters were evaluated at the end of the experiment. Based on the results, the Moringa seedlings displayed a positive tolerance to water stress. Significant variations were found, such as growth delays in length, reaching up to 30% for the stems and 64% for the roots for ψh = −1.5 MPa. This water potential resulted in a 75% reduction of Relative Growth Rate (RGRₕ) per day for the water stress experiment (hydroponics), as a reaction of the plant to overcome the stress. Additionally, it had the highest negative effect on stem length and leaf area. As for the plants grown in the field, their main stem height increased by 43.13% and their number of branches by 45.34% per year. An overall (RGRₕ) of 0.44 per year was noted accompanied by a total phytomass of 0.46 and tree volume of 23.67 g cm⁻³. Based on the above it can be concluded that Moringa represent a promising species as an ecological solution for use in agroforestry systems, able to minimize the negative effects of drought and to rehabilitate and enhance the soil of arid zones.