CN--induced degradation of nuclei in cells of pea leaves

Degradation of nuclei in epidermal and guard cells of pea leaves was induce d by NaCN. Guard cells were considerably more resistant to CN- than epiderm al cells. CN--induced nucleus degradation in guard cells was accelerated by illumination. The effect of illumination was negligible in epidermal cells that, unlike guard cells, do not contain chloroplasts. These data may indi cate a role of chloroplasts in CN--induced cell death. CN--induced nucleus degradation in epidermal cells was retarded by antioxidants (butylated hydr oxytoluene and vitamin E). The effect of CN- in guard cells was largely rem oved by vitamin E. Salicylic acid, an inhibitor of catalase and ascorbate p eroxidase, induced 100% degradation of nuclei in epidermal cells but did no t significantly affect nuclei in guard cells. CN--induced inhibition of cat alase and peroxidase is assumed to lead to generation and accumulation of r eactive oxygen species inducing apoptosis. Like mitochondria, which play an important role in animal cell apoptosis, chloroplasts may take part in apo ptosis in plant cells.