ASSESSMENT OF POLLEN VIABILITY IN HAND-POLLINATION EXPERIMENTS - A REVIEW

Pollen viability is known to decline, sometimes rapidly, with age and exposure to environmental stresses. Because of the potential impact of nongenetic factors on the ability of pollen to fertilize ovules, researchers conducting hand-pollinations should attempt to control the freshness or viability of pollen used. We surveyed hand-pollination experiments published in seven major journals from 1980 until mid- 1994, collecting data on the purpose of the experiment, the degree of care taken to ensure pollen viability, and the degree of care taken to ensure stigmatic receptivity. Fewer than one-third of the papers reported any consideration of pollen freshness or viability, whereas over one-half made some mention of stigmatic receptivity. Pollen freshness or age was mentioned more frequently for some types of experiments than for others. Experiments attempting to compare performance of different donors are especially susceptible to error when donor pollen is not treated equally or otherwise controlled for viability. We discuss strengths and weaknesses of tests to measure pollen viability, and experimental protocols to reduce differences in pollen condition across donors.