Radiation hormesis in plants.

Many reports discuss plant growth stimulation by exposure of seeds or plants to low doses of ionizing radiation. The reported effects include increased height, weight, growth rate, flowering and yield. The magnitude of the effect(s) is usually small, being about 10% of control values; and the effects often are not reproducible. None has been independently confirmed. The exposure level reported to induce such effects is about an order of magnitude greater than that reported for similar hormetic responses in animals. There is no understanding of the mechanism(s) of such responses or of the cellular and physical factor(s) pertinent to the induction of such effect(s). However, observations that certain low-level exposures result in increased yield (e.g. more branches, flowers and fruits) are consistent with known mechanisms of cellular damage and known responses of plants to a compromise in apical dominance.