水分胁迫和杀真菌剂对黄顶菊生长和抗旱性的影响

利用盆栽试验研究水分胁迫下AM真菌对黄顶菊生长和抗旱性的影响,揭示黄顶菊入侵过程中的微生物学机制.以苯菌灵为杀真菌剂,在土壤相对含水量为120％、80％、40％和20％条件下,分别设灭菌和不灭菌两种处理.结果表明,水分胁迫显著降低了黄顶菊株高、干重和主根长,而对AM真菌侵染率无显著影响.施用苯菌灵显著降低了菌根侵染率、叶片保水力、保护酶活性、可溶性糖和可溶性蛋白含量,提高了MDA含量.不灭菌处理下黄顶菊植株对土壤有效N和有效P的利用率较高,且植株全N、P含量显著高于灭菌处理,菌根贡献率随土壤相对含水量降低而逐渐提高,重度胁迫分别是渍水条件下的1.84和1.88倍.土壤水分状况和AM真菌的交互作用对黄顶菊生物量和生理指标影响显著.AM真菌共生能够促进黄顶菊根系对土壤水分和矿质营养吸收,改善植物代谢活动,提高抗旱性.实验结果为黄顶菊合理防控措施的制定提供了依据,同时作为丛枝菌根的基础性研究也具有重要的意义.

Effects of water stress and fungicide on the growth and drought resistance of Flaveria bidentis

Flaveria bidentis,an exotic plant with strong invasiveness, spreads at most regions of Tianjin, Hebei, Henan and Shandong Province, China, and many evidences prove that it has high potential to expand to other provinces. According to recent studies, F. bidentis is a typical species with arbuscular mycorrhizal (AM) symbiosis and AM symbiosis can alter host plant-water relationships under both well-watered and drought stress conditions by providing water for their hosts thus enhancing the tolerance of the host plants to water deficit. F. bidentis can dominate in a wide range of habitats, such as agricultural land, orchards, lawns, roadsides, watersides and waste ground, and can rapidly form dense nearly monospecific stands within several years. However, it is not clear whether its high invasive potential is due to this plant-fungal symbiosis, especially under drought stress. The present study is to verify the effect of AM fungi on the growth and drought resistance of F.bidentis in its invaded process, and to understand the mechanism involved. Four water conditions were designed in this pot experiment: waterlogging(soil relative water content 120%), normal irrigation(80%), moderate stress (60%) and severe stress(40%), and at each water treatment, both sterilization and no sterilization was contained through adding fungicide benomyl to control AM fungi.Each treatment was repeated three times. The results showed that water stress significantly inhibited the growth of F.bidentis such as plant height, main root length and biomass regardless of fungicide treatment, but infection rate was not affected by water tress. Under different water regimes, fungicide significantly decreased mycorrhizal infection rate and water preservation in leaves. Activity of protective enzymes and total N, P content, soluble sugar, soluble protein significantly decreased with fungicide treatment, while leaf malondialdehyde (MDA) content was significantly increased. The utilization rate of available N and P were higher at no sterilization treatment and total N, P content of F.bidentis plant were significantly enhanced. Simultaneously, the degrees of host plant benefits from AM fungi were affected by environment conditions. The contribution rate of mycorrhizal to host plant related to the extent of water stress, being 1.84 and 1.88 times higher at severe stress than those at waterlogging condition respectively. It is concluded that mycohrrizal associations may significantly related to the invasion history of F.bidentis in newly reclaimed habitats. Mycohrrizal associations could improve the ability of F.bidentis to withdraw the adverse conditions. AM fungi increased soil water and mineral nutrient uptake and improved plant physiological metabolic activities, thus promoting drought resistance and growth of F.bidentis. The results provided the basis for the invasion mechanism and making effective management measures of F.bidentis, meanwhile, it is also a basic research of great significance on AM fungi.