Abstract: During the imbibition of barley (Hordeum vulgate L. ) seeds, the effect of salt stress on the ultrastructure of radicle cells was investigated. At 12 h after barley seeds in distilled water, the cytoplasmic membrane of radicle cells was apparent, the plastid membranes were continuous, and the mitochondria had bilayer membranes and internal cristae. However, at 12 h after seeds in 2 % NaCl solution, the cytoplasmic membranes in the radicle cells were unclear, the plastid membranes were not continuous, and mitochondria bad no bilayer membranes and cristae. The membrane system in the radicle cells developed very well at 72 h after seeds in distilled water. At 72 h after the seeds in 2% NaCl solution, the radicle cells became round in shape and the inter-cellular spaces enlarged. Many small vacuoles appeared in the cytoplasm. The plastids greatly increased in size and contained many osmiophilic droplets and few lamellae. The bilayer membrane and cristae of mitochondria were still not distinguished. The cytoplasmic membrane seemed still not to be recognizable and in some regions the plasmclysis occurred. These results showed that the salt stress resulted in the difficulty of the membrane system restoration and organelie reconstruction in the radicle cells. It is possible that the ion toxicity may affect the inhibition of the membrane system restoration.

Key words: Hordeum vulgate, Imbibition, Salt stress, Ion toxicity, Membrane System