外来入侵植物意大利苍耳的传粉生态学特性

从开花物候、花粉活力、柱头可受性、传粉媒介、花粉散布距离、雄性、雌性功能以及繁育系统等方面系统地研究了意大利苍耳的传粉生态学特性,旨在为揭示该物种成功入侵的机理提供科学依据。研究结果显示:意大利苍耳种群的花期较长,雌花花期可达40d,雄花花期可达30d。其雄性和雌性功能都很强,意大利苍耳单株雄花序和花粉量分别高达3847个/株和37903037粒/株,单株雌花序和单株胚珠数高达3847个/株和7694枚/株,种群平均结实率高达80.59%,即平均每株个体能形成6200枚成熟的果实。花粉活力的日变化呈单峰型曲线,早晨和傍晚的花粉活力最低,14:00时的活力高达99%。雌蕊柱头一经伸出总苞即具有可受性,可受期长达7d,开花后的3—4d柱头的可受性最强。意大利苍耳为风媒传粉植物,在4.5km/h的微风条件下,其花粉的散布距离可达45m,大量的花粉集中分布在距花粉源0—20m的范围内,这对于往往高密度连片分布的意大利苍耳种群来说无疑是一种高效的传粉策略。意大利苍耳的交配系统灵活多样,盛花期自然结实率达到100%,套袋试验结果表明该植物自交亲和,自株自然授粉的结实率高达93%。表明较长的花期、大量的雌雄花序及花粉数量、较高的花粉活力、较长的柱头可授期、较远的花粉风媒散布距离、混合交配系统、以及较高的结实率是意大利苍耳繁殖成功的重要保障,也是其成功入侵的重要原因。

Study on pollination biology of the invasive plant Xanthium italicum Moretti

This paper systematically studied pollination ecological characteristics of Xanthium italicum Moretti, an invasive plant in Xinjiang, China, with respect to flowering phenology, pollen vitality, stigma receptivity, pollinators, pollen dispersal distance, maternal and paternal function, and mating system, aiming at providing scientific proof of the mechanism of the successful invasion of the species. The results showed that the flowering period of this alien plant is long-40 days for female flowers and 30 days for male flowers. Its maternal and paternal functions are strong. The number of male inflorescence and that of pollen were as high as 3847 and 37903037 per plant, respectively, while the numbers of female inflorescence and ovules were as high as 3847 and 7694 per plant, respectively. The average seed setting rate was 80.59%, which means that 6200 mature fruits per plant could be borne. The variation pattern of daily pollen vitality showed a single-peak curve:in the morning and evening, the pollen vitality was the lowest, and the activity was up to 99% at 14:00. Pistil stigma had 7-day receptivity once out of involucre, and 3-4 days after flowering, stigma receptivity was at its strongest level. Xanthium italicum Moretti was a wind-pollinated plant. Under the breeze condition of wind speed as low as 4.5km/h, its pollen spread distance could reach as far as 45m, and a large number of pollen distributed in the range of 0-20m from pollen source, which is an efficient pollination strategy for this highly continuously distributed species. This exotic plant has a flexible mating system and the natural seed setting rate at the full bloom stage reached 100%. The results of the bagging test showed that it was self-compatible, and the seed setting rate of natural self pollination was as high as 93%. The seed setting rate of different strains by artificial pollination was also as high as 83%. Therefore, long flowering period, massive male and female inflorescence and pollen grains, high pollen vitality, long stage of stigma receptivity, far anemophilous pollen spread distance, flexible mating system, and high seed setting rate were important factors for the successful reproduction of X. italicum Moretti and the main reasons for its successful invasion.