Seed germination ecology of a medicinal halophyte Zygophyllum propinquum: responses to abiotic factors

Abstract

Information about the seed biology of the medicinally important halophyte Zygophyllum propinquum is limited. We therefore studied seed germination and recovery responses to different abiotic factors. Seed germination and recovery responses to different thermoperiods (10/20, 15/25, 20/30 and 25/35°C), photoperiods (12h light/12h dark and 24h dark), salts (chloride and sulphate salts of Na, K, Ca and Mg), and mannitol were studied. Seeds were non-dormant and germinated maximally (≈95%) in distilled water. Relatively high seed germination was observed under moderate (15/25 and 20/30°C) temperature regimes and in 12h photoperiod. Seed germination decreased with increases in salinity and only few seeds (<30%) germinated at 200mM NaCl. However, most un-germinated seeds from high salinity showed recovery of germination when transferred to water. Among chloride (Cl−) salts inhibitory effects at −1.2MPa under light were in following order of magnitude: KCl>CaCl2> NaCl=MgCl2, while for sulphate (SO4−−) salts inhibitory effects were in following order: K2SO4>MgSO4>Na2SO4. Germination inhibition under various osmotic treatments of mannitol was generally lesser than the iso-osmotic NaCl treatments. These results indicate that seeds Z. propinquum were moderately salt tolerant and preferred to germinate under moderate temperatures and in the presence of light. Recovery data following different salt treatments hints at greater role of osmotic constraint than the specific ion effects.