The Pollination Biology Of Four Species Of Impatiens L.

The comparative pollination biology of four species of Impatiens L.distributed in China is studied firstly.Results are as follows:1.There are some remarkable differences in vegetative and floral morphology of the four species.Male phase lasts for longer time than female phase.The pollen viability of both I. chinensis flowers and I.macrovexilla var.yaoshanensis flowers maintain high level,and decrease slowly before androecium abscission.Both species secret more nectar on the second day of anthesis than the first day.The nectar of the four species contains over 30%sugar.There is a high P/O in each study species,and suggest that they have outcrossing reproductive systems.The tests of reproductive systems of I. chinensis and I.macrovexilla var.yaoshanensis indicate that both species are self-compatible but have not autonomous self-pollination and apogamy.There is obvious outcrossing adavantage in I.chinensis.No significant difference is observed in fruit set and seed set between self-pollination flowers and cross-pollination ones in I.macrovexilla var. yaoshanensis.These results show that both species have mixed mating system,the flowers require multiple pollinators to ensure pollination success.2.In total of 29 species of insects from 7 families visit the flowers of plants studied.Pollinators of I.chinensis and I.macrovexilla var.yaoshanensis are comprised of several different taxon such as bees,butterflies and hawkmoths. However,the insect species in I.monticola and I.hunanensis are less than that in the other two plants.I.monticola and I.hunanensis are not visited by Lepidoptera individuals but fertilized mainly by medium long-tongued bees.Most pollinators appear in study populations during 10:00-12:00 and 14:00-16:00,and visit flowers actively.The insect species and the number of individuals are variable in two different years. The observations to species,number,behaviour and frequency of pollinator indicate that the pollinators may apply selection pressure on floral traits,so they are very important in molding floral morphology.3.The results of experimantal removal of floral structures show that lateral united sepal is significant in pollination success;the effect of dorsal petal removal or lower sepal removal is correlated with the size and depth of the floral structure.The results also suggest that dorsal petal and lower sepal play important roles in attracting pollinators and ensuring effective pollination.4.We investigated the influence of nectar robbing on pollination via the method of nectar spur removal.Results show that the removal of spur didn't affect pollination success evidently.We conclude that robbers may regulate pollination process as "messengers" or "dispatchers",and the action may force pollinators to transfer pollen to longer distance, promote cross-pollination rate,increase female fitness,so robbeingmay be an antagonistic principle against inbreeding depression.