不同氮水平下瘤突苍耳、苍耳及其杂交种形态、光合及生长特征比较

入侵种与本地种杂交可能会改变其入侵性。为探讨入侵种与本地种杂交是否能促进植物入侵, 我们通过盆栽实验比较了高、中和低3种氮水平下入侵植物瘤突苍耳(Xanthium strumarium)、本地近缘种苍耳(X. sibiricum)及两者杂交种(X. strumarium♀ × X. sibiricum♂)的形态、光合及生长特征的差异。结果表明, 杂交种的总生物量在中氮和高氮水平下显著低于瘤突苍耳而高于苍耳。然而, 杂交种的茎粗在低氮水平下显著高于两个亲本, 叶绿素总含量和蒸腾速率在高氮水平下显著高于瘤突苍耳, 相对生长速率在低氮和高氮水平下显著高于两个亲本。此外, 在3种氮水平下瘤突苍耳的株高均显著小于苍耳, 而杂交种的株高在中氮和高氮水平下均与苍耳无显著差异。这些特性有可能提高了杂交种对资源的捕获和利用能力, 使其不仅能适应贫瘠的养分环境, 还能在有利条件下扩大自身优势。杂交带来较高的生长速率可能与瘤突苍耳的入侵性相关。

Comparison of morphology,photosynthesis, and growth among Xanthium strumarium,X. sibiricum and their hybrid under different nitrogen levels

Hybridization of invasive plants with native plants may alter their invasiveness. To investigate whether hybridization can promote plant invasions, we carried out a pot experiment to compare morphology, photosynthesis, and growth of the invasive plant Xanthium strumarium, the native plant X. sibiricum and their hybrid (X. strumarium♀ × X. sibiricum♂) under three nitrogen (N) levels, i.e. low, medium and high. Total biomass of the hybrid was smaller than that of X. strumarium but larger than that of X. sibiricum at the medium and high N levels. However, stem diameter of the hybrid was significantly higher than its parents at the low N level, its total chlorophyll content and transpiration rate were significantly higher than X. strumarium at the high N level, and its relative growth rate was higher than its parents at the low and high N levels. Moreover, plant height of X. strumarium was significantly lower than that of X. sibiricum at all three N levels, but plant height of the hybrid was not significantly different from that of X. sibiricum at the medium and high N levels. These characteristics may improve the hybrid’s ability to capture and use resources, which can not only help the hybrid adapt to a poor nutrient environment, but can also help to improve its advantages under favorable conditions. The higher growth rate of the hybrid may be associated with the invasiveness of X. strumarium.