Influence of Water Stress on Seed Germination Characteristics in Invasive Diplotaxis harra (Forssk.) Boiss (Brassicaceae) in Arid zone of Tunisia

Abstract

Diplotaxis harra (Forssk.) Boiss (Brassicaceae) has a wide ecological and geographical amplitudes in Tunisia and grows under a variety of environmental conditions. A laboratory experiment was performed to evaluate the effect of water potential on seed germination and recovery responses after transfer to distilled water. The germination responses of seeds at 15°C in complete darkness were determined over a wide range of PEG-6000 solutions of different osmotic potentials: 0 to –1 MPa. Greatest germination was obtained in distilled water (71%), and increases in osmolality of solutions progressively inhibited seed germination, less than 10% of the seeds germinated at –0.8 MPa. No germination was observed for the treatment of –1 MPa. The rate of germination decreased as osmotic potential decreased. When seeds were transferred to distilled water after 20 days of water stress, the recovery of germination increased with an increase in pretransfer PEG-6000 treatments. Seeds subjected to high osmotic potential had higher recovery percentages.