Partitioning Water Potential and Specific Salt Effects on Seed Germination of Kochia scoparia

Abstract

Salinity is one of the environmental factors that have a critical influence on the germination of halophyte seeds and plant establishment. Salinity affects imbibitions, germination and root elongation. However, the way in which NaCl exerts its influence on these vital processes (seed germination), whether it is through an osmotic effect or specific ion toxicity, is still not resolved. Seeds of the halophyte Kochia scoparia were treated with various iso-osmotic solutions of NaCl and polyethylene glycol 6000 (PEG) over the water potential range of 0 to -1.9 MPa. After 10d of treatment, the ungerminated seeds were transferred to distilled water for 3 d. The germination results revealed that both NaCl and PEG inhibited germination and seedling growth, but the effects of NaCl compared to PEG were less on final germination. The seeds of kochia differ in their response to salinity and failure of seeds to recover from high salinity when transferred to deionized water, revealed the toxicity of NaCl. In contrast, the increase in germination and during the recovery period after exposure of PEG suggested that PEG was not toxic. It was concluded that at low levels of salinity the main effect of NaCl was to reduce the rate of germination due to the reduce water potential and at a higher salinity NaCl had a toxic effect since many seeds failed to germinate even salinity stress was removed.