Fluoride- and drought-induced structural alterations of mesophyll and guard cells in cotyledons of jack pine (Pinus banksiana)

Abstract

Fluoride- and drought-induced injuries to mesophyll and guard cells were studied in jack pine (Pinus banksiana Lamb.) cotyledons, using light and electron microscopy techniques. Most early structural alterations were similar in cells of fluoride- and water-stressed seedlings. Both treatments resulted in an appearance of lipid material in the cytoplasm during early stages of injury, suggesting damage to the cell membranes. Treatment with sodium fluoride also resulted in deposition of starch in chloroplasts. Guard cells were more resistant to both stresses than mesophyll cells. Both metabolic injury and collapse of neighbouring cells may be responsible for the opening of stomata in wilting, fluoride-treated seedlings.