Abstract: Pollen of orchid plants aggregates into blocks and pollinates in nature in an all-or-none manner. The effects of different pollen load on the development and seed setting of Gastrodia elata were explored. During the flowering period, the whole pollinarium was used as a control group, the pollinarium were divided into 1/2, 1/4, 1/8, 1/16 under the dissecting microscope. The fruit, seed size and weight were measured at 16 days after pollination. The results showed that different pollen load affected fruit size, weight and total seed weight of a single fruit; when the pollen load was 1/4 and below, the length, width and weight of the fruit (fresh and dry weight) were reduced significantly; the dry weight of seeds was about 0.006 g with whole pollinarium and 1/2 pollinarium pollen load, while the dry weights were about 0.003 g and 0.0016 g with 1/4 and 1/8 pollinarium, respectively; different pollen load had no effect on the seed length and the size of the embryo, the length of the seed was about 0.55 cm, and the length and width of the embryo were 0.15 cm and 0.10 cm, respectively; when the pollen load was 1/4 pollinarium and below, the seed width increased significantly, from 0.13 cm to 0.16 cm. The experiment showed that reducing pollen load affected fruit size, weight and seed width, but had little effect on the length of seeds and the size of embryos. It was speculated that the ratio of the number of pollen to the number of ovules of Gastrodia was close to 2∶1.

Key words: Gastrodia elata, pollinarium, pollen load, fruit, seed setting, embryo