Effects of chilling on the root cell ultrastructure of two soybean cultivars

Two soybean [Glycine max (L.) Merr.] cultivars: Aldana (more resistant) and Essor (less resistant to low temperature) were subjected to chilling at 5A degrees C for 24 h, and then the ultrastructure of the root meristem cells was investigated. The ultrastructure of control root cells of the tested cultivars differed in the number of condensed mitochondria, plastids with phytoferritin, deformed vacuoles, as well as multivesicular bodies (MB) in cytoplasm and vacuoles. Chilling induced concentric endoplasmic reticulum (ER) arrangement in both soybean cultivars, while the circular Golgi apparatus (GA) occurred only in cv. Essor and MB in the cytoplasm of cv. Aldana cells. Additionally, in cv. Aldana chilling increased the number of condensed mitochondria, MB in vacuoles and multilamellar structures (MS) in cytoplasm whereas in cv. Essor it enlarged the population of plastids with phytoferritin and the number of MB in cytoplasm. After chilling treatment the population of deformed vacuoles with phenolic compounds in the form of electron dense granules increased but the number of multilamellar structures (MS) in the vacuoles of both cultivars decreased. The ultrastructural changes induced by the chilling stress were not lethal but rather adaptive, especially in more resistant cv. Aldana.