入侵新疆的外来植物意大利苍耳和刺苍耳的果实于深秋季节成熟后,便开始陆续脱落.脱离母体的果实可能会落置在干燥的地面上,还有可能会掉落在水体中,还有部分果实会保留在枝条上并不脱落直到翌年春天.由于越冬生境的差异会直接影响翌年春天种子的萌发活性,为了评价外来入侵植物意大利苍耳和刺苍耳的入侵能力,预测其潜在分布区,为对其实施有效防控提供科学指导.故模拟了其种子在新疆自然条件下可能遭遇的冬季生境类型,设计了4种实验处理,即低温换水浸泡(模拟了落入流水或大型水体中结冰前的生境)、低温不换水浸泡(模拟了落入小型静水中结冰前的生境)、冰冻(模拟了落入水体中结冰后的生境)和干燥冷冻处理(模拟了掉落在干燥地面或一直停留在植株上的生境类型),并以室温干燥储存为对照.处理90 d后,进行种子萌发实验,结果显示干冻、冰冻及低温换水浸泡处理后意大利苍耳的萌发率与对照组无显著差异,不换水浸泡处理降低了意大利苍耳种子的活力,显著降低了其萌发能力.而干冻处理对刺苍耳种子的萌发没有影响,冷水浸泡(换水浸泡和不换水浸泡)显著降低刺苍耳的萌发率,与对照组相比分别下降了37％、65％.冰冻处理后刺苍耳没有萌发.说明意大利苍耳种子对新疆的各种越冬生境均有较好的耐受性,而刺苍耳种子对低温和水淹环境的耐受性较差.鉴于二者种子萌芽习性的特点,建议在全疆范围内的中生、湿生和季节性水涝生境中对意大利苍耳实施全方位的监控,农田、林下、路边、渠旁、湖泊及水库周围都有可能成为其潜在的入侵地;对刺苍耳的重点监测区域则应当放在低纬度、低海拔的中生和中旱生生境,尤其要切实加强南疆各国际口岸进口货物的检疫工作.%The fruits of the Italy cocklebur (Xanthium italicum Moretti) and stab cocklebur (X.spinosum Linnaeus),two kinds of invasive plants in Xinjiang,begin to fall after it matures in late autumn.Some of the fruits detach from mother plant and drop onto dry ground,some fall in the water,and others remain on the branches and do not detach until the next spring.The habitat to which seeds are exposed to in winter directly affects seed germination in the following year.To assess their invasiveness,predict their potential distribution area,and provide scientific guidance for effective prevention and control of these invaders,four kinds of natural winter habitats in which seeds might be exposed in Xinjiang were simulated (i.e.,cold flowing water,cold dead water,cold dead water followed by freezing,and cold dry soil or cold air).Treatments in which seeds were soaked in frequently changed cold water (5 ℃),soaked in still cold water (5 ℃),frozen in the air less than -20 ℃,and soaked in still water for 24 h then frozen with the water less than-20 ℃ were designed.Seeds kept at dry room temperature served as controls.After 90-day pretreatment,seed germination experiments were conducted.The results showed that:(1) For the Italy cocklebur,the germination percentage of seeds soaked in unchanged cold water was significantly lower than other treatments.Others were not significantly different.(2) For stab cocklebur,seeds that were stored at dry room temperature and frozen in the air had the highest germination percentage (70％),and germination percentage of the seeds soaked in changed and unchanged water was 37％ and 65％ lower than that of the control.The soaked and frozen seeds did not germinate.It was suggested that multiple habitats,including those with moderate moisture,and wet and seasonally flooded habitats throughout Xinjiang should be strictly monitored for Italy cocklebur,including farmland,understory,roadsides,riversides,and around lakes and reservoirs,which might be potential invasion areas.The key monitoring area for stab cocklebur should have moderate moisture and dry habitats at low latitude and low elevation.The quarantine of imported goods in international ports around southern Xinjiang should be strengthened.
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