CELLULAR LOCALIZATION OF COPPER AND ITS TOXICITY ON ROOT TIPS OF HORDEUM VULGARE

Copper (Cu) localization and cell damage in Hordeum vulgare root tips under Cu stress by means of electron microscopy with energy dispersive X-ray spectrum analysis (EDXA), propidium iodide (PI), Carbol Fuchsin and silver staining and indirect immunofluorescent microscopy were investigated. The results indicated that the mitotic index (MI) in the root tips decreased significantly by increasing the concentration of Cu. Cu accumulated in the meristem and disturbed cell division, inducing C-mitosis, anaphase bridges (two types) and chromosome stickiness, which resulted in the inhibition of root growth. Cu had toxic effects on nucleoli in root tip cells. It could induce some particles containing argyrophilic proteins scattered in the nuclei and extruded from nucleoli into cytoplasm. Using indirect immunofluorescent microscopy, we found that the two nucleolar proteins, nucleolin and fibrillarin, were translocated from nucleolus to nucleoplasm and cytoplasm. Data from EDXA showed that the mature, elongation and meristem zones in the root tips could absorb Cu ions. The Cu level in meristem zone in the root tips was higher, suggesting that it could be considered as a primary target of Cu toxicity. There was a clear correlation between Cu content and cell damage in root tips of H. vulgare. The degree of cell damage increased with prolonged period of treatment.