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

- Seed germination and recovery of Z. propinquum to different abiotic factors were investigated.
- Seeds were photoblastic, germinated in up to 200 mM NaCl, and preferred moderate thermoperiods.
- Germination responses to isotonic solutions of different salts showed some variations.
- Magnesium salts and mannitol were comparatively less inhibitory than isotonic NaCl.
- Recovery data hints at greater role of osmotic than ionic constraint in germination inhibition.

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 (12 h light/12 h dark and 24 h 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 12 h photoperiod. Seed germination decreased with increases in salinity and only few seeds (<30%) germinated at 200 mM NaCl. However, most un-germinated seeds from high salinity showed recovery of germination when transferred to water. Among chloride (Cl−) salts inhibitory effects at −1.2 MPa 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.