Comparison of seed germination and recovery responses of a salt marsh Halophyte halopeplis perfoliata to osmotic and ionic treatments

Abstract

Salinity affects seed germination of halophytes by inducing ionic toxicity, osmotic constraint or both. Information about the effects of salinity on seed germination of a large number of halophytes exists, but generally little is known about the basis of salinity-induced germination inhibition. In order to partition salinity effects, we studied seed germination and recovery responses of a coastal salt marsh halophyte Halopeplis perfoliata to different isotonic treatments (?S: -0.5, -1.0, - 1.5, -2.0 and -2.5, MPa) of various salts and polythylene glycol (PEG) under two light regimes (12-h light photoperiod and 24-h complete darkness). Highest seed germination was observed in distilled water under 12-h light photoperiod and reduction in osmotic potential of the solution decreased seed germination. However, some seeds of H. perfoliata could germinate in as low as -2.5 MPa (~600 mM NaCl), which is equivalent to seawater salinity. Sea-salt treatment was more inhibitory than isotonic NaCl at the lowest osmotic potential (?S -2.5 MPa). Generally, chloride salts with lowest ?S inhibited germination more than the isotonic sulfate salts. Comparable germination responses of the seeds in NaCl and isotonic PEG treatments as well as high recovery of germination in un-germinated seeds after alleviation of NaCl salinity indicated prevalence of osmotic constraint. These results thus indicate that the seeds of H. perfoliata could tolerate high levels of a wide variety of salts found in soil. 2016, Pakistan Botanical Society. All rights reserved.