外来入侵植物美洲商陆的繁殖生物学特性及其与入侵性的关系

Traits of reproductive biology associated with invasiveness in alien invasive plant Phytolacca americana

美洲商陆（聊tolacca ameHcana）是一种我国广泛分布的商陆科入侵植物。通过实验观察和人工控制套袋等方法，对其开花动态、花部综合特征、繁育系统和种子萌发率等与繁殖相关的特性进行了研究，探讨了这些繁殖特性与入侵性的关系。结果表明，美洲商陆每年6—8月开花，单花序的花期为6～7d，单花的花期为2～4d。其花直径、雄蕊长、花柱长、柱头直径分别为（6．43±0．15）、（2．83±0．10）、（O．92±0．06）和（1．02±0．08）mln。套袋实验表明，美洲商陆自交亲和，自交结实率较高，为（93．33±1．92）％，而其同样存在异交结实现象，开花前去雄，不套袋，自然条件下其结实率为（42．22±2．22）％，其P／O值为372．37±31．24，杂交指数为3。综合套袋实验、P／O值及杂交指数，表明其繁育系统为兼性自交，有时需要传粉者。主要访花昆虫为蜜蜂科（Apidae）、胡蜂科（Vespidae）、麻蝇科（Sarcophagidae）和食蚜蝇科（Syrphidae）昆虫。种子千粒质量为6．43g，室内萌发率相对较低，但出苗整齐，寿命长。交配机制灵活、结实量大、种子寿命长、具有克隆繁殖等特性增强了美洲商陆的入侵性，是其入侵成功的重要因素。

Phytolacca americana is one of the widespread invasive weeds in Phytolaccaceae in China. The reproductive traits of this species such as phenology of flowering, floral syndrome, breeding system and seed germination characteristics were studied by experimental observation and bagging treatment to assess the association of these reproductive traits with invasiveness. P americana flowered during June to August every year in Ji＇an city. The lifespan of a single capitulum was approximately 6 to 7 days, 2 to 4 days for a single flower. The diameter, stamen length, style length and stigma diameter were （6.43 ± 0.15）, （2.83 ± 0.10）, （0.92 ± 0.06） and （1.02 ± 0.08） mm respectively. Bagged flowers without emasculation showed high maturing rate （93.33±1.92）% which means a high self-compatibility, but it also exhibited a certain cross-compatibility with a maturing rate of （42.22±2.22）% in the emasculation treatment, its P/O ratio was 372.37 ± 31.24, and out-crossing index was 3, which suggests that the breeding system of P. americana is facultative selfing, and sometimes needs pollinators. The main floral visitors were insects of Apidae, Vespidae, Sarcophagidae, Syrphidae. The thousand seed weight was 6.43 g, the seed emerged relatively lowly, but orderly and with a long life activity. Our experimental findings suggested that the reproductive traits such as the versatile mating system of self- and cross-pollination, high seed production, long seed life span and strong asexual capacity might contribute to the invasive capability of P. americana.