外源钙离子与南方菟丝子寄生对喜旱莲子草茎形态结构的影响

Antagonistic interactive effects of exogenous calcium ions and parasitic Cuscuta australis on the morphology and structure of Alternanthera philoxeroides stems

外源钙离子对植物响应外界环境胁迫具有重要作用。寄生植物对入侵植物具有显著的抑制作用。以入侵植物喜旱莲子草为研究对象,采用完全随机区组的实验设计分析不同钙离子浓度与南方菟丝子寄生对喜旱莲子草茎形态结构的影响,探讨外源钙离子在寄主植物响应寄生植物胁迫中的作用。研究结果表明南方菟丝子寄生可以显著改变喜旱莲子草茎的形态结构,如显著降低喜旱莲子草茎的总长、分枝数、分节数、茎直径和髓腔直径,显著增加茎的厚角厚度与皮层厚度。外源钙离子对喜旱莲子草茎总长、分枝数、分节数、茎直径、髓腔直径和维管束直径没有显著影响,但可增加喜旱莲子草茎的维管束数目,降低茎的节间长、厚角厚度与皮层厚度。外源钙离子与南方菟丝子寄生相互作用可以显著增加喜旱莲子草茎的厚角厚度与皮层厚度,表明南方菟丝子寄生与高浓度的钙离子对喜旱莲子草茎的厚角厚度和皮层厚度具有显著的拮抗的交互作用。这种交互作用可以提高寄主植物的防御能力,减少寄生植物对寄主植物的损伤。

Exogenous calcium ions play an important role in the response of plants to environmental stresses,and parasitic plants cause significant damage to the growth of invasive plants.However,there has been no empirical study on the interactive effect of exogenous calcium ions and parasitic plants on the growth of invasive plants.Alternanthera philoxeroides(Amaranthaceae),native to South America,is a globally noxious invasive weed that has expanded into China and is now widespread throughout the country.Cusucta australis(Convolvulaceae),a native holoparasitic plant,is found to parasitize A.philoxeroides in the field.Here,we conducted a greenhouse experiment to test the interactive effect of parasitic C.australis and exogenous calcium ions on the morphology and structure of invasive Alternanthera philoxeroides stems,with the aim of elucidating the role played by calcium ions during the response of invasive plants to native parasitic plants.Parasitic C.australis significantly decreased the total length,branch number,internode number,diameter and pulp cavity diameter of A.philoxeroides stems,but significantly increased the collenchyma and cortex thickness of A.philoxeroides stems.The addition of exogenous calcium ions had no significant effect on the total length,branch number,internode number,diameter,pulp cavity diameter and vascular bundles diameter of A.philoxeroides stems,but increased the number of vascular bundles,and decreased the internode length,collenchyma thickness and cortex thickness of A.philoxeroides stems.The interaction between parasitism and exogenous calcium ions was found to have an effect on the collenchyma and cortex thickness of A.philoxeroides stems,with the result of increased thickness in both parts.This indicated an antagonistic interactive effect between parasitism and exogenous calcium ions on the collenchyma and cortex thickness of A.philoxeroides stems.This antagonistic interactive effect suggests that exogenous calcium ions could significantly improve the defense of host plants to parasitic plants and reduce the damage caused by parasitic plants on their hosts.