Causes of cell death following exposure to different fungicides and heat

The lethal effects of several agricultural fungicides, the mutagen ICR-170, and heat have been studied in multinucleated spores from heterokaryotic mycelia ofPhycomyces blakesleeanus. The fungicides captafol, captan, Manzate (maneb), Benlate (benomyl), and ZZ-melprex (dodine) induce exclusively cytoplasmic lethality. The mutagen ICR-170 causes three different kinds of lethal events: mitotic, recessive, and cytoplasmic. Heat exposure of dormant spores results in only cytoplasmic lethal damage. Germination increases heat sensitivity, particularly that of nuclei; while most of the lethality in germinating spores is still cytoplasmic, there is a definite contribution of mitotic lethality, i.e., events blocking the division of the affected nuclei.