Seed set of Ginkgo biloba L. as related to pollination and its optimum pollination time

Abstract

Ovule set and growth were investigated on ginkgo as related to open- and hand-pollination as well as the critical pollination period. 1. The ginkgo pollen placed on an agar medium under 25 °C took 3 days to germinate. Over 73% of the pollen stored for less than 7 days after anthesis at room temperature germinated but pollen stored much longer at room temperature did not. 2. All ovules which were covered with paper bags during anthesis to be free from pollen contamination abscised for 41 days after leafing. 3. When non-viable, heat-treated pollen were used for hand-pollination, the ovules began to drop 28 days after leafing; the percentage ovule set decreased from 19 to 47 days after leafing. Thereafter, for 82 days after leafing, fewer ovules dropped; the final seed set was 7%. These female reproductive organs set parthenocarpically because no embryo formed. The seeds and nuts resulting from hand-pollination were larger than those obtained from open-pollination. 4. Of seeds that set by hand-pollination 16 and 19 days after leafing, 59% and 94%, respectively, remained at harvest and their sizes were significantly larger than those obtained from open-pollination. None of the ovules pollinated 23 days after leafing persisted until harvest.