Plant Volatiles Inhibit Pollen Germination of Apple and Other Species

were collected from field-grown trees ‘at full bloom. With the exception of the rose petals, all tissues were tested either intact or macerated by light grinding in a mortar and pestle. In addition, to determine if ethylene released upon maceration had an effect, intact tomato leaves were dipped in 1000 ppm 2-chloroethyl phosphonic acid (ethephon) before bioassay. After 2 h, microphotographs ( × 40) of the pollen were taken. Four fields from each agar block were photographed. Total and germinated pollen grains were counted from the photographs, recording only single grains on the agar surface. Grains were classified as germinated when the pollen tube length exceeded the diameter of the grain. Percent germination values were derived for each treatment and tested by analysis of variance. After determining that data transformation was not necessary, treatments means were compared by Dunnett’s test.