土著菌根真菌和混生植物对羊草生长和磷营养的影响

植物种间相互作用直接影响植物生长、根系可塑性及养分吸收,而与植物共生的丛枝菌根真菌可以改变植物个体和种间养分资源的分配,具有协调种间竞争的潜力.以我国北方草甸草原建群种羊草(Leymus chinensis)和混生植物紫花苜蓿(Medicago sativa)及独行菜(Lepidium spetalum)为供试植物,通过模拟盆栽试验,研究了土著菌根真菌和混生植物对羊草生长、根系形态及磷营养的影响.试验结果表明,土著菌根真菌能够与羊草及紫花苜蓿形成良好共生,而独行菜根内基本未形成菌根共生结构.土著菌根真菌显著降低了羊草及独行菜的生物量,但促进了紫花苜蓿的生长；混种紫花苜蓿显著促进了羊草的生长,而混种独行菜则显著抑制了羊草的生长.土著菌根真菌对羊草根系形态的影响表现出与植株生物量类似的趋势,但不同混生植物对羊草根系生长均无显著影响.土著菌根真菌和混生植物对羊草植株磷含量均无显著影响.与混生植物相比,羊草具有较高的比根长和磷吸收能力,这也解释了其负向菌根依赖性.研究证实了菌根真菌和植物种间相互作用均是影响草原优势植物生长和根系发育的重要因素,深入研究其交互作用对于科学管理草地生态系统,维持植物群落的稳定性和生态系统生产力具有重要意义.

Effects of indigenous AM fungi and neighboring plants on the growth and phosphorus nutrition of Leymus chinensis

Plant interactions may directly affect plant growth, root plasticity and nutrient uptake, while arbuscular mycorrhizal (AM) symbioses can redistribute resources among plants at both individual and community levels, and consequently mediate plant interactions and influence plant community structure. In the present study, a pot experiment was carried out to investigate the influences of indigenous mycorrhizal fungi and neighboring plants, Medicago sativa and Lepidium spetalum, on the growth and phosphorus nutrition of Leymus chinensis, a dominant grass species on the meadow steppe in North China. At experimental harvest, plant growth, root morphology and phosphorus uptake of both plant species were recorded. The results indicated that the indigenous mycorrhizal fungi formed symbiosis with L. chinensis and M. sativa, but not with non-host plant, L. spetalum, while in the non-mycorrhizal treatment where mycorrhizal fungi were eliminated by radiation sterilization, the mycorrhizal colonization rates were generally lower than 2%. The indigenous mycorrhizal fungi significantly suppressed the growth of L. chinensis and L. spetalum, but promoted growth of M. sativa. Neighboring plant M. sativa promoted, but L. spetalum suppressed the growth of L. chinensis. Analysis of variance showed that mycorrhizal fungi and neighboring plants exhibited significant interactions on mycorrhizal colonization. The effects of mycorrhizal fungi on the root length and root surface area were similar with that on plant biomass, but plant combinations showed no significant effects. As for plant phosphorus concentration, both mycorrhizal fungi and plant combinations showed no significant effects. Compared to the neighboring plants, L. chinensis had higher relative root length and P uptake efficiency, which can well explain its negative responses to mycorrhizal fungi. The study demonstrated that mycorrhizal fungi and plant interactions are important factors influencing plant growth and root proliferation. Further studies are still necessary for a better understanding of the importance of mycorrhizal fungi in maintaining plant community stability and productivity, and also for sustainable management of the grasslands.