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Pak. J. Bot., 48(4):1335-1343, 2016.

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COMPARISON OF SEED GERMINATION AND RECOVERY RESPONSES OF

A SALT MARSH HALOPHYTE HALOPEPLIS PERFOLIATA TO

OSMOTIC AND IONIC TREATMENTS

SARWAT GHULAM RASOOL¹, ABDUL HAMEED¹, M. ZAHEER AHMED¹,

M. AJMAL KHAN^{1, 2} AND BILQUEES GUL^1*

¹Institute of Sustainable Halophyte Utilization, University of Karachi, Karachi-75270, Pakistan

²Current address: Qatar Shell Professorial Chair for Sustainable Development and Professor

Department of International Affairs, College of Arts and Sciences, Qatar University, PO Box 2713, Doha, Qatar

^*Corresponding author e-mail: bilqueesgul@uok.edu.pk; Tel.: +9221-7700930; fax: +9221-34820258

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 (Ψ_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 (Ψ_S -2.5 MPa). Generally, chloride salts with lowest Ψ_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.

Key words: Dormancy, Halophyte, Salinity, Seed germination, Ionic toxicity, Osmotic potential.