INFLUENCE OF WATER AND SALT STRESS ON SEED GERMINATION IN RETAMA RAETAM FROM TUNISIA

Autores UPV
Año
CONGRESO INFLUENCE OF WATER AND SALT STRESS ON SEED GERMINATION IN RETAMA RAETAM FROM TUNISIA

Abstract

Introduction. Seed germination is one of the main factors determining plant survival in adverse habitats, and soil humidity and salinity are the most important environmental conditions affecting this critical phase of the plant life cycle. Aims. The effects of water and salt stress on seed germination were analysed in the medicinal plant Retama raetam (Forssk.) Webb (Fabaceae), a frequent xerophytic shrub, from two regions of Southern Tunisia. Materials and Methods. Retama raetam seeds were collected from a saharian (Dhaher) and a semi-arid (Djefara) climate regions in Tunisia. Seeds were germinated on Petri dishes in different isosmotic PEG and NaCl solutions, with the following water potentials: 0, -0.3, -0.7, -1.0, -1.2 and -1.4 MPa. Germination was carried out in a germination chamber at 15°C in darkness for 20 days, and the final percentages and rates of germination were calculated. Results. The highest germination percentages were registered in distilled water, in both treatments and for seeds from the two regions. Germination was reduced with increasing salinity and water stress. In both, PEG and NaCl treatments, below -0,7 and -1 MPa a higher reduction of germination percentage and velocity was observed in those seeds collected from Djefara. Under the highest levels of stress tested, germination of seeds from this provenance was severely limited, whereas seeds from Dhaher still germinated in high percentages and with a relatively high germination rate. Conclusion. Although salt and water stress affected the seeds collected in the two regions, those from Dhaher (the driest), showed more tolerance to both stresses than those from Djefara. The different physiological traits evidenced here, in addition to other morphological differences, support the proposal to split Retama raetam from Tunisia in two subspecies (Le Floch¿h et al., 2010). References 1. Le Floch¿h E., Boulos L. and Vela E. (2010). Catalogue synonymic commenté de la Flore de Tunisie. Minister de l¿environnement et du développement durable, République Tunisienne.