Floral Syndrome And Delayed Autonomous Selfing Of Hyoscyamus Niger

Floral behavior has a critical role in plant pollination and mating system. The stamen elongation is a kind of common floral behavior. It is generally considered to play an important role in ensuring reproduction by self-pollination. In this paper, floral syndrome and breeding system of Hyoscyamus niger were studied in the field, and the relationship between the stamen elongation and breeding system was analyzed. The main results as follows:H. niger displays large and showy flowers, incompletely protogynous, and showed approach herkogamy. All of these floral syndromes were assumed to favor outcrossing; The flower does not produce nectar, pollen quantity was187263.20±15082.26, pollen ovule ratio was314.09±24.2, pollen is the main reward to pollinators; The single flower can last4.11±0.10d, stigma receptivity and pollen viability based on seed number were continued to corolla wilting; Pollination control treatments showed that the species has a mixed-mating system with the ability to self-pollinate autonomously, geitonogamy and xenogamy depended on pollinator visitors; The emasculated flowers produce fewer seeds than not emasculated flowers, indicating that in this species self-pollination can provide reproductive assurance. With the floral longevity, five anthers gradually elongated, the mean distance between the stigma and anthers decreased, and full contacted at the late floral stage; During flower opening, pollinating insects visit flowers which early floral stage, almost no access to that late floral stage, caused the loss of outcrossing opportunities at the late floral stage; Controlled experiments showed that the late floral stage has the largest contribution to self-seed, indicating that the autonomous selfing mainly occur at the late floral stage. Autonomous selfing occurs at the end of anthesis which overlap with the time of stigma and anthers contacting and outcrossing oppourtunities losing; During the continuance of flowering, the female and male features have continued to corolla wilting, so the stigma and anthers contacting can caused the self pollination in H. niger. Loss of outcrossing oppourtunities and contact of anthers and stigma during floral development resulted delayed selfing in this species.H. niger not only select the flower structure that adapt to outcrossing (herkogamy, incompletely protogynous), but also promoting self-pollination through stamen movement (stamen elongation). This delayed selfing insured reproduction of H. niger in the absence of pollinators.