入侵种瘤突苍耳细根解剖结构的可塑性与入侵性间的关系

Relationship between plasticity and invasiveness in the anatomical structure of the fine roots of the invasive species Xanthium strumarium

细根是植物吸收地下水分与养分的重要器官,影响植物生长。细根可通过调整自身的形态或解剖结构支持不同环境条件下的植物生长。入侵植物多为群落内的优势种,其根系解剖结构及资源获取能力是否比本地物种的更强?本研究以外来入侵植物瘤突苍耳和本地同属种苍耳为研究对象,设置4种水分-氮梯度模拟异质环境,利用石蜡切片法比较盆栽两种苍耳的细根直径、皮层厚度、中柱直径和气腔面积等的差异。结果表明:瘤突苍耳细根皮层的气腔结构比苍耳的发达。高资源下,瘤突苍耳的细根直径增长程度小于苍耳。氮含量充足时,高水中瘤突苍耳的皮层厚度、内皮层厚度和导管直径均显著小于苍耳;水分充足时,高氮中瘤突苍耳的总导管面积显著小于苍耳。相比低资源环境处理,高资源下瘤突苍耳的皮层厚度是显著升高的。上述结果表明,气腔与皮层结构的可塑性是影响瘤突苍耳细根解剖结构的驱动因子,且瘤突苍耳根部解剖结构可塑性对异质性环境的响应变化与苍耳比相对稳定。瘤突苍耳自身结构可塑性能在多种环境下获得生长优势。因此,本研究认为相比苍耳,瘤突苍耳细根具有相对进化的解剖结构及塑形变化体系,构成一种高地下资源吸收和低成本消耗的高效入侵策略。

Fine roots affect plant growth because they are an important organ for the absorption of groundwater and nitrogen.Plant growth can be supported by adjustments in the morphology and anatomy of fine roots under different environmental conditions.The great majority of invasive plants are dominant species in the community.The aim of this study was to explore whether the root anatomical structure of an invasive plant allows it to acquire more resources compared with a native species.Therefore,we compared the effects of different water and nitrogen treatments on anatomical structure between the invasive species,Xanthium strumarium,and a native species,Xanthium sibiricum.Paraffin sections were used to study various functional traits such as root diameter,cortical thickness,stele diameter,and the aerenchyma area of fine roots formed in different growth environments.The results showed that the aerenchyma area was wider in X.strumarium than in X.sibiricum.Under high-resource conditions,the root diameter of X.strumarium was smaller than that of X.sibiricum.Under sufficient nitrogen conditions,the cortex was thinner and the endodermis and xylem were smaller in X.strumarium than in X.sibiricum under excess water conditions,but under sufficient water conditions,the total xylem area was smaller in X.strumarium than in X.sibiricum.The above results indicate that the plasticity of the aerenchyma and cortical structures is a major factor affecting the anatomical structure of X.strumarium,and the plasticity of the anatomical structure of the root is relatively stable in response to a heterogeneous environment.The anatomical structural plasticity of X.strumarium confers growth advantages in various environments.Compared with X.sibiricum,X.strumarium has fine roots with more highly evolved anatomical structure and plasticity.This is an important factor in its efficient invasion strategy of high underground resource use with a low consumption cost.