Germination responses of Ballota hirsuta seeds under conditions of temperature, salinity and water stress

Temperature, salinity and water deficit can be major environmental constraints which reduce distribution of indigenous plants in the Mediterranean region. Laboratory experiments were carried out to assess the effect of temperature, sodium chloride (NaCl) and polyethylene glycol 6000 (PEG) on germination of Ballota hirsuta seeds. The germination responses of seeds were determined over a wide range of temperature (5 to 35°C), salinity (0 to 136 mM NaCl) and water stress (0 to −1 MPa PEG). Germination percentage was optimum at 20°C (78%), and showed a decline at lower (5°C, 25%) or higher (30°C, 18%) temperature values and total inhibition of germination at 35°C. Under salinity and water stress conditions, there was a significant deterioration in most germination parameters such as lower final germination percentage, increased mean germination times and lower germination rates.