外源钙离子对南方菟丝子寄生入侵植物喜旱莲子草效果的影响

Effect of exogenous calcium ions on the parasitic effects of Cuscuta australis on the invasive plant Alternanthera philoxeroides

外源钙离子可以有效地缓解植物在胁迫下受到的毒害,提高植物组织或细胞抗胁迫的能力。以喜旱莲子草为研究对象,采用完全随机区组的实验设计,研究不同钙离子浓度与南方菟丝子寄生对喜旱莲子草茎生物量的影响,探讨外源钙离子是否可以减少南方菟丝子对喜旱莲子草的损伤。研究表明南方菟丝子寄生对喜旱莲子草的根、茎和叶的生物量具有显著影响,且南方菟丝子寄生与外源钙离子对喜旱莲子草茎和叶的生长具有显著的交互作用。不同浓度的钙离子与南方菟丝子寄生对喜旱莲子草茎生物量存在拮抗的交互作用;而仅8 mmol/L Ca2+与南方菟丝子寄生对喜旱莲子草叶生物量存在拮抗的交互作用。不同浓度钙离子均可以缓减南方菟丝子对喜旱莲子草茎的有害效应,仅8 mmol/L Ca2+可以缓减南方菟丝子对喜旱莲子草根和叶的有害效应。2—6 mmol/L的外源钙离子对南方菟丝子寄生下的喜旱莲子草的丙二醛(MDA)含量无显著影响,但可以显著地降低过氧化物酶(POD)活性,表明低浓度的外源钙离子的添加可以缓减南方菟丝子对喜旱莲子草的寄生胁迫,并体现在生理指标上。

The invasive plant Alternanthera philoxeroides （Amaranthaceae）, which is native to South America, has spread widely throughout China. The native holoparasite Cuscuta australis （Convolvulaceae） parasitizes A. philoxeroides in the field and can significantly inhibit the growth of this invasive plant. Therefore, C. australis might be a potential biological control agent to control existing populations and/or prevent further spread of A. philoxeroides. Exogenous calcium ions can effectively alleviate the deleterious effects of stress on plants, and improve their stress resistance. Previous studies have shown that there can be an antagonistic interaction between parasitism and exogenous calcium ions. Specifically, supplying exogenous Ca2＋ ions increased the collenchyma and cortex thickness of A. philoxeroides stems, thus improving its resistance to parasitic plants. However, no empirical studies have been conducted to verify the hypothesis that exogenous calcium ions can reduce the damage caused by parasitic plants to their hosts. In this study we conducted a greenhouse experiment to test the relationship between exogenous calcium ions and C. australis, in terms of its effect on the growth of A. philoxeroides. C.australis had significantly negative effects on the root, stem, and leaf biomass of A. philoxeroides. There were significant interactive effects between C. australis and exogenous calcium ions on the stem and leaf biomass of A. philoxeroides. There was a significant interactive effect between exogenous calcium ions at all tested concentrations （2-8 mmol/L） and C. australis on the stem biomass of A. philoxeroides, while this interactive effect was significant only between 8 mmol/L Ca2＋ and C. australis for leaf biomass of A. philoxeroides. Exogenous calcium ions at all tested concentrations significantly decreased the deleterious effects of parasitic C. australis on the stem biomass of A. philoxeroides, while only 8 mmol/L Ca2＋ significantly decreased the deleterious effects of C. australis on the root biomass and leaf biomass of A. philoxeroides. These results confirmed that there is an antagonistic interaction between exogenous Ca2＋ and parasitism of C. australis. That is, exogenous Ca2＋ could alleviate the deleterious effects of parasitic C. australis on its host, A. philoxeroides. When supplied at concentrations of 2 to 6 mmol/L, Ca2＋ did not significantly affect the malondialdehyde content in the leaves of A.philoxeroides parasitized by C. australis, but peroxidase activity was significantly decreased. These findings suggest that changes in cellular biochemistry are associated with the ability of Ca2＋ to alleviate the deleterious effects of C. australis on A.philoxeroides.