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, rese archers conducting hand-pollinations should attempt to control the fre shness or viability of pollen used. We surveyed hand-pollination exper iments published in seven major journals from 1980 until mid- 1994, co llecting data on the purpose of the experiment, the degree of care tak en 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 w as mentioned more frequently for some types of experiments than for ot hers. Experiments attempting to compare performance of different donor s are especially susceptible to error when donor pollen is not treated equally or otherwise controlled for viability. We discuss strengths a nd weaknesses of tests to measure pollen viability, and experimental p rotocols to reduce differences in pollen condition across donors.