Pollination characteristics of the ephemeroid plant Eremurus anisopterus

This study was conducted to examine the pol-lination characteristics of Eremurus anisopterus,an ephe-meroid plant in the Gurbantunggut Desert in Xinjiang,China.An integrative approach combining field studies with lab analysis was adopted.Pollen traps were used to measure air-borne pollen loads and artificial isolation experiments were applied to test the potentiality of cross-pollination or apomixes.Results show that the duration of the flowering of Eremurus anisopterus varied from late April to mid-May.Anthesis of a single flower often lasted for 1 d.However,if the daily maximum air temperature was under 20℃,the anthesis of a single flower could be prolonged up to 2 d.The pollen dispersion period of the single flower could last for 4 to 5 h,from 10:30 to 15:00 local time,with the duration of pollen dispersion for a single anther lasting approximately 40 min.The heterotypical maturation of the stigma could significantly prolong the pollen dispersion period of the single flower suggesting an adaptation to the habitat of E.anisopterus in the desert where the pollinators were not reliable.The timing of the blossoms of the ephemeroid plant show close correlations with the wind velocity and the habit and characteristics of the pollinators in the desert.Plant pollens may be spread to over 70 m by wind with approximately 60%of the pollens falling within 20 m away from the plant.Insects,especially bees,hover flies,flesh flies,mason bees and Halictus sp.were very important pollinators.Bees and hover flies usually landed on the yellowish green spot on the tepal and then entered the flower along the purple vein on the pink tepals.The yellowish green spot might be a mimetic structure of nectar that could attract insects to visit.This was also an adaptation of the plant to the sandy desert environment.A higher visiting frequency was reached between 10:30 and 13:30.The pollen-ovule ratio(P/O)of E.anisopterus(6164)suggested that the species was from cross-pollination according to Cruden’s criterion.However,the arti-ficial isolation experiment shows that E.anisopterus is self-compatible which might act as a compensation mechanism for the inadequate opportunities for breeding in the desert environment.Since there was no seed set in the bagged emasculated flowers,apomixes did not occur.In conclusion,E.anisopterus might adapt to the unreliable pollinator habits by self-pollination and by lengthening the pollen dispersion period of a single flower.