Effect of temperature, pretreatments, gibberellin (GA3), salt and drought stress on germination of Thymus satureioides coss of Morocco

Abstract

Thymus satureioides Cosson is an endemic medicinal and aromatic plant species of both Morocco and Algeria, holds significant cultural and economic importance. It is used in traditional medicine to treat various diseases and also as a culinary spice herb. T. satureioides has become a key export for Morocco. However, increasing market demand and the effects of climate change have led to a decline in its wild populations, raising concerns about the scarcity of this valuable natural resource. To address these challenges, a comprehensive understanding of the environmental requirements for the germination of T. satureioides is essential for planning and prioritizing conservation efforts in its native habitats. In this context, the aim of this study was to assess the combined effects of various pretreatments and temperature and of salinity, drought stress, and gibberellin on the germination parameters of T. satureioides. Seeds were collected from a wild plant population in the Anti-Atlas Mountains. The tests included five pretreatments (mechanical scarification, sulfuric acid (95%), dry heat, boiling water and hydrogen peroxide) in conjunction with five temperature conditions (10, 15, 20, 25 and 30 °C). Additionally, six concentrations of sodium chloride (0, 25, 50, 100, 150 and a 200 mM), six water potential levels of polyethylene glycol (PEG-6000) (0, −0.07, −0.14, −0.22, −0.32 and - 0.53 MPa) and six concentrations of gibberellin (0, 50, 100, 500, 1000 and 2000 ppm) were tested. Results showed that seeds can germinate without any treatment. However, seeds treated with dry heat followed by incubation at 20 °C improved all the germination parameters. In addition, germination parameters progressively decreased and delayed with increasing levels of both salt and water stress. Without stress, the germination percentage was 100%, with increasing salt stress to 200 mM germination was completely inhibited. Although, seeds showed a low germination percentage (5,67%) at the highest osmotic potential (−0.53 MPa).