Ecological role of bracteoles in seed dispersal and germination of the North African halophyte Atriplex mollis under contrasting environments

The patterns of germination responses of Atriplex mollis seeds reveal species-specific tolerances and represents the adaptive strategies of species to stressful environments. To the best of our knowledge, this is the first report about germination patterns of A. mollis providing basic information for its conservation and reintroduction into degraded lands. Herein, two seed lots, with and without bracteoles, were tested for germination (i.e. salinity and drought). The highest germination percentage was under non-saline conditions, and with increasing NaCl-salinity, seed germination is inhibited. Bracteoles did not affect germination at low salinity levels, but significant inhibition becomes evident at -0.75 MPa. Moreover, PEG-induced osmotic stress had an adverse effect on germination of seeds with or without bracteoles at -0.75 MPa (ca. 20% and 10%, respectively). Bracteoles have a significant decreased effect on germination during recovery; they showed more detrimental effects following NaCl than PEG incubation. Importantly, the flotation of dispersal units with bracteoles was less than 60% under in freshwater and reached 100% at 27 g NaCl L-1. It is concluded that bracteoles play a dual role by inhibiting germination under high salinity levels and enhancing it under less negative osmotic potential.