甘肃马先蒿不同寄生密度对紫花针茅内生真菌共生体生理特性的影响

Effects of Pedicularis kansuensis parasitism on physiological characteristics of grass-Epichloë symbiont under different hemiparasite density

摘要:

[目的] 根寄生植物持续掠夺禾草体内营养物质成为禾草生长过程中的生物逆境，禾草内生真菌提高冷季型禾草对生物和非生物逆境耐受能力。然而，有关禾草内生真菌对根寄生逆境下禾草生理过程调控作用的研究鲜有报道。[方法] 开展温室盆栽试验，以带菌（E+）和不带菌（E-）紫花针茅为研究对象，研究甘肃马先蒿不同寄生密度对紫花针茅抗氧化酶活性、渗透调节物质和根系活力影响的动态变化规律。[结果] 甘肃马先蒿寄生显著增加紫花针茅抗氧化酶活性、丙二醛和脯氨酸含量，而根系活力却快速降低；高密度寄生紫花针茅植株生理特性指标显著高于低密度寄生或自然生长植株；同时，E+紫花针茅抗氧化酶活性、脯氨酸含量和根系活力显著高于E-植株，而E-植株丙二醛含量显著高于E+植株。[结论] 禾草内生真菌通过增强抗氧化酶活性、调节细胞膜透性和增强根系生长能力的途径提高紫花针茅对根寄生逆境的耐受能力，利用植物替代方法带菌紫花针茅可以作为一种生物防治手段用于防控根寄生杂草。

关键词:根寄生植物;生物逆境;密度;内生真菌;抗氧化酶;根系活力

Abstract:

[Objective] Root hemiparasites should be taken into account as another biotic stress of grasses as they take directly water and nutrients from their hosts through haustoria. Cool-seasonal grasses have established mutualistic symbioses with Epichloë endophytes:the grass-Epichloë symbionts perform better than endophyte-free plants in biotic or abiotic stresses. However, few studies have considered the benefits of Epichloë endophyte on the physiological characteristics of host grasses under parasitic stress.[Methods] We performed a manipulated pot experiment with endophyte-infected (E+) and endophyte-free (E-) Stipa purpurea. Host grasses were planted with different densities of the hemiparasitic plant Pedicularis kansuensis. The antioxidant enzymes, osmotic materials and root vitality of S. purpurea were determined during different parasitising periods.[Results] The presence of P. kansuensis increased the malondialdehyde (MDA) and proline content and activities of antioxidant enzymes but decreased the root vitality of S. purpurea, and the physiological parameters of S. purpurea parasitised by high hemiparasite density were higher than low hemiparasite density. Meanwhile, activities of antioxidant enzymes, proline content and root vitality of E+ S. purpurea were significantly higher than in E-counterparts; in contrast, the MDA content of E+ plants was lower than E-counterparts.[Conclusion] Our results suggest that Epichloë endophyte can improve S. purpurea tolerance to parasitic stress by increasing activities of antioxidant enzymes, adjusting cell membrane permeability and strengthening the root vitality of host plants. Consequently, endophyte-infected S. purpurea may be a potential candidate as a biological method for effective and sustainable management of the hemiparasite weed-P. kansuensis.

Key words:root hemiparasite;biotic stress;density;Epichloë;antioxidants;root vitality