Phaius delavayi is a long-lived, polycarpic, pseudobulbous clonal orchid species and is endemic to China. Generally, the flower phenology, flower life span, and pollination success are important features for plant species evolution and conservation. Those features in Phaius delavayi were studied detailed in 2005-2007 in Huanglong Valley, Sichuan.
The results showed that the plants have 3 or 4 leaves, and the largest leaf were 16.9-17.5 cm long, 4.8 -4.9 cm wide. The inflorescence is sparsely 1-7-flowered (with mean 3), exceeding height of leaves, 18.4-19.5 cm. Flowers widely opening, with 1.9-2.2 cm long, 1.1 cm wide labellum, and 1.0-1.2 cm long spur. Length of the leaf and floral traits were not significant different, as well as flower phenology during three years. Fruits were 20.78 mm long, 8.10 mm wide, and 00424 g weight. The inflorescence growth began in mid May and last about 50 days, continued until early July. Flowering began in mid June and last about 6-7 weeks, continued until late July/early August, with 80%-90% flowers flowered in a peak time (last about 10 days) in early July.
Life span of inflorescences showed considerable variation among years, which were 23, 21, and 29 days for 2005, 2006, and 2007, respectively. The flower life span was closely correlated with pollination, that with successful pollination was 15-19 days, significantly shorter than that of flowers without pollination (17-22 days). Fruit maturity was in mid-latter September, and the leaves were yellow and withered. The results of pollinia viability and stigma receptivity experiments showed that the flowers are self-compatible, but the reproductive success is strictly dependent on visitation by pollinia vectors (Bombus hypnorum and B. lepidus), and there is no autogamy and apogamy in this speices.
The stigma has receptivity at the first day of flowering, and can last about 15 days, and lost receptivity completely 20 days after flowering. The fruit set was higher 1-10 days after flowering than that 15 days after flowering. The pollinia has also viability at the first day of flowering, and can last about 15 days, lost viability completely 20 days after flowering, but there was no differences in pollinia viability during one to 15 days. The lost of stigma receptivity was sharper than that of pollinia viability. The pollinia viability and stigma receptivity can last even to the flower withered.
Reproductive success showed considerable variation among years and was decline with year. The pollinia removal and nature fruit set were 18%-51% and 10%-36%, respectively, and spraying of pesticides in Huanglong Valley may play a role for the declination of pollination success.