Effect of osmotic stress and salinity on germination and mucilage expansion of seeds of Plantago albicans L. (Plantaginaceae): Inter-population variation

Plantago albicans L. (Plantaginaceae) grows in wastelands, slopes, and stony pastures, with dry and sun-exposed soils. Its seeds produce a mucilaginous coat. The main aim of this study was to evaluate intraspecific variation of osmotic and salinity stress response and mucilage production in P. albicans seeds. The relationships between osmotic and salinity stress, germination characteristics, and mucilage expansion were studied in eight populations of P. albicans. Seeds were germinated in distilled water, 20% (w/v) polyethylene glycol 6000 (PEG), or 100 mM NaCl solutions. In most populations, PEG and NaCl reduced final germination. Also, germination was slowed more significantly under osmotic stress than under salinity, while mucilage expansion was more affected by salinity. Therefore, there was an inverse correlation between mucilage expansion and germination under salinity and osmotic stress. Seed populations with similar climatic parameters showed different germination response; however, a correlation was found between mucilage expansion and some climatic parameters. Seeds from drier habitats germinated faster under water stress and produced more mucilage under control and water stress than populations from more humid areas.