Effects of temperature and treated urban wastewater on seed germination and seedling growth in different populations of Moringa oleifera (Lam.)

Abstract

Drought is an environmental concern in North Africa. Hence, countries in this region promote treated wastewater reuse in agricultural irrigation as sustainable practice in reducing the increasing stress on water resources. Here, we evaluated the treated urban wastewater (TUW) impact on seed germination and seedling growth of four Moringa oleifera (MO) populations in different temperature conditions. Seeds were brought from Morneg and Kairouan in Tunisia and from India and Egypt. Germination tests were performed using different TUW concentrations at 25 and 35°C for 9 days under darkness and distilled water for control. Parameters such as germination percentage (GP), mean germination time (MGT), shoot length (SL) and TUW half-maximal effective concentration (EC₅₀) were measured. GP, MGT, and SL varied significantly with incubation temperature and seed source. Only SL did not show any significant variations in all TUW concentrations. Increased temperature had a positive influence on GP and SL; on the contrary, a negative impact on MGT was observed in Kairouan, Egyptian and Indian seeds. EC₅₀ evaluation showed that TUW was less harmful on Indian Moringa seeds. Seeds incubated at 25°C were structured into two groups: the first containing Morneg, Indian and Egyptian seeds; and the second one with Kairouan seeds. At 35°C, Egyptian seeds left the first group and joined the second indicating that their germination didn’t occur rapidly for temperature increase. Considering Tunisian climate conditions, results showed that Moringa oleifera is able to acclimatize to temperatures of this country.