Thymus broussonetii and Thymus maroccanus are under intensive utilization because of their wide ranging medicinal potential. In an effort to improve and promote the cultivation of this over-exploited medicinal herb, the effects of temperature and water potential on the germination of their seeds were investigated. Six water potentials (0, -0.07, -0.14, -0.22, -0.32 and -0.53 MPa) and three incubated temperature (15, 20 and 25°C) were tested. The result showed that seeds of T. maroccanus and T. broussonetii germinated rapidly and reached highest germination percentage in distilled water under no stressful condition of germination at all temperature tested. Decrease in osmotic potential progressively inhibited seed germination of the two thyme species. Germination was severely decreased at -0.53 MPa indicating that the two thyme species resistance limits to the water stress is between -0.32 and -0.53 MPa. The cumulative effect of water potential and temperature on the final germination depends on the species. For T. broussonetii, no significant effect of the interaction between water potential and temperature was observed. The temperature between 15 and 20°C seem to be favorable for the germination of the two thyme species. Regarding to the water stress, T. broussonetii appears to be more tolerant than T. maroccanus.
Key words: Thymus maroccanus, Thymus broussonetii, water potential, temperature, seed germination, Morocco.
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