Effect of salinity on germination and seedling growth of two Atriplex species (Chenopodiaceae)

Salinity is one of the environmental factors that has a critical influence on the germination of halophyte seeds and plant establishment. Salinity affects imbibition, germination and root elongation. However, the way in which NaCl exerts its influence on these vital processes, whether it is through an osmotic effect or a specific ion toxicity, is still not resolved. Dimorphic seeds of the halophytes Atriplex prostrata and A. patula were treated with various iso-osmotic solutions of NaCl and polyethylene glycol (PEG). For each treatment, imbibition, germination rate, percent germination, germination recovery and nuclear area of root tip cells were compared. Higher concentrations of NaCl (-1.0 MPa) were more inhibitory to imbibition, germination and seedling root elongation than iso-osmotic PEG solutions. All seeds recovered from a pre-treatment with -2.0 MPa NaCl; and PEG solutions, except large seeds of A. prostrata which failed to germinate following transfer from -2.0 MPa NaCl. NaCl caused a greater increase in nuclear volume than iso-osmotic PEG solutions. These data suggest that the influence of NaCl is a combination of an osmotic effect and a specific ion effect. (C) 1998 Annals of Botany Company.