Factors influencing seed germination of the pastoral plant Retama raetam subsp. bovei (Fabaceae): interactive effects of fruit morphology, salinity, and osmotic stress

Abstract

The aim of this work was to study the morphology of retama seeds and the combined effects of salt and water stress on the seeds germination of four Tunisian populations of Retama raetam. Seeds were harvested from Bouhedma National Park, Meknassi, Oueslatia, and Rtiba. In this study we were interested in evaluating different parameters of germination in presence of the salinity and osmotic stress. The results revealed that this species can withstand salinity up to 15 g/l of salt (the germination percentage of the Rtiba population reached 42%) and it can also tolerate severe drought resulted in significant doses of PEG₆₀₀₀ (germination percentage reached 29% to the water potential of –1.6 MPa of Oueslatia population). The morphological traits of the seeds were measured to find a relationship between the size of the seeds and their germination capacity under salinity and osmotic stress. Results have shown that for the correlation between morphological traits of seeds and the germination percentage, the seed weight is a major factor in promoting germination under stress and confirmed that saline water and sprouting inhibition have impact on the small caliber of seeds.