Ultrastructural characteristics of callus cells of Nicotiana tabacum L. var. BELW3 grown in presence of NaCl

摘要

An investigation by electron microscopy has been carried out on Nicotiana tabacum L. var. BELW3 callus cells grown in a medium containing different NaCl concentrations (0.1, 0.2, 0.3 M) for 60 days to study the salt effect at cell level. Control N. tabacum callus exhibited parenchymatous cell types with normal cytoplasm, nucleus, organelles and membranes, together to cells forming meristematic zones by normal mitosis and cytokinesis. The callus cells exposed to the lowest salt dose did not show specific structural changes in comparison to control cells. On the contrary, the callus cells treated with the salt at the highest doses showed alterations of chloroplasts, severe damages at nuclear and cytoplasmic level, until to a complete disorganization of the whole protoplast. Also mitochondria and the membranous system appeared injured. However, in all the salt treated callus cells amylopasts were very abundant. A peculiar phenomenon was the presence in these calli under salt stress of cells contiguous to the damaged or dead cells which appeared normal in their structure. This fact confirmed the possibility to regenerate plants from callus under salt treatment in view to obtain salt tolerant crops.