Abstract
Although pollen viability promises to be a very sensitive indicator of environmental mutagenesis, its utility in this regard is confounded by the fact that it is influenced also by nonmutagenic environmental stress. However, with appropriately homozygous material, we may discriminate between mutagenic and nonmutagenic influences on pollen viability. Pollen inviability resulting from mutagenesis will exhibit a strong tendency to segregate, whereas stress induced inviability will not. When pollen grains are shed individually, evidence for genetic segregation is often lost, but with pollen in tetrads, this evidence, a specific indicator of environmentally induced mutation, is preserved. A further advantage of pollen in tetrads is that, again because evidence for genetic segregation is preserved, tetrads allow us to distinguish between pre- and postpachytene mutations. This capability eliminates the problem of mutant sectors whereby a single mutational event may give rise to a large number of mutant cells. Methods of examining pollen tetrads are discussed.