【作者】 郑朝元；

【导师】 张福锁； 张俊伶； James D.Bever；

【作者基本信息】 中国农业大学 ， 植物营养学， 2014， 博士

【摘要】 植物-菌根真菌共生体是自然界形成较早、分布最广的一类互利共生体系,共生体双方的碳-磷交易是菌根研究的核心内容,对理解自然界长期进化过程中生物共生体的稳定性具有重要的意义。本研究通过盆栽和分根模拟试验,结合14C、32p和33p三标记方法,在改变光照时长和土壤磷供应强度条件下,分别研究了自交系玉米L224和葱属植物Allium vineale L与不同菌根真菌共生体的菌根效应和碳-磷互作。此外,通过盆栽试验,研究了早期、晚期演替草原植物与外来植物的本地菌根效应。主要结果如下：盆栽试验研究了自交系玉米L224在不同土壤磷供应强度下的菌根效应。接种(Funneliformis mosseae和Rhizophagus irregularis)以及土壤磷供应强度(10,20,30,40,50,100mg kg-1)显著影响了宿主植物生长和磷吸收效应。低磷条件下接种Rhizophagus irregularis和中等磷供应水平条件下接种Funneliformis mosseae菌根生长效应较高。接种和磷供应强度未显著影响特异性转运蛋白ZEAma;Pht1;6的表达。接种和提高磷供应强度显著提高了玉米根系的磷吸收效率,说明自交系玉米L224具有较高的菌根依赖性。采用分根装置室内模拟研究了不同光照时长(遮光4周,6周,8周,不遮光对照)对菌根共生体碳分配和磷吸收的影响。有益菌根真菌Claroideoglomus candidum促进了宿主植物Allium vineale L的生长,且遮光降低了宿主植物的菌根效应。宿主植物优先分配碳供给有益菌根真菌侧,并从该侧吸收了较多的磷。接种非有益菌根真菌Gigaspora margarita并未显著促进宿主植物生长。植物对有益菌根真菌的碳优先分配程度随着光照时长的延长而增加。宿主对Claroideoglomus candidum侧碳优先分配对光照变化反应敏感,碳的分配比率从不遮光时的25%下降到遮光8周的15%。宿主植物对非有益菌根真菌Gigaspora margarita的碳优先分配对光照变化不敏感,所有处理约在11%左右,说明菌根共生体碳优先分配给有益菌根真菌。与非有益菌根真菌相比,有益菌根真菌对光照变化响应较敏感。采用分根装置利用32p,33p和14C三标记方法,模拟研究了不同土壤磷供应强度对菌根共生体碳分配和磷吸收的影响。土壤磷供应强度的增加(1X、2X、3X和4X,1X代表土壤背景磷浓度)降低了宿主植物的菌根效应,有益菌根真菌Claroideoglomus candidum对植物生长的正效应随土壤磷供应强度的增加而下降。根室双侧接种同一菌根真菌时,宿主Allium vineale L表现为优先分配碳给高磷侧,并从该侧吸收较多的磷。宿主植物同样从非有益菌根真菌Gigaspora margarita高磷侧吸收较多的磷。植株分配给Claroideoglomus candidum高磷侧的碳从2012年的1.09上升到2013年的7.05,而Gigaspora margarita高磷侧碳从2012年的2.02下降到1.86。双侧分别接种不同的菌根真菌时,在不同磷供应强度条件下(1X,2X,4X),宿主植物依然优先分配碳给有益菌根真菌,且分配比率随磷供应的强度升高而增加,说明有益菌根共生体植物碳的优先分配受土壤磷供应强度的影响,而非有益菌根真菌高磷侧磷吸收的增加则可能提高了根系吸磷途径的吸磷能力。盆栽模拟研究了3种早期、4种晚期演替草原植物以及6种外来植物的本地菌根生长效应。不同演替背景植物种间的菌根效应存在显著差异。早期演替种菌根生长效应和变异程度均较低；晚期演替植物种对本地菌根真菌的响应最敏感,易于受到外来物种变化影响；接种本地菌根真菌显著促进外来植物种的生长,但菌根生长效应与早期演替植物种的效应相当。在外来植物种中,Allium vineale L.菌根效应为其他外来植物的两倍,且显著高于早期和晚期演替种,菌根生长效应均值和变异系数存在显著相关。说明本地AM菌根真菌一定程度上提高了本地植物种的适应性,影响了外来植物种的本地定殖。更多还原

【Abstract】 In nature, the symbiosis between land plants and arbuscular mycorrhizal fungi is one of the most common, oldest and ecologically important mutualisms in terrestrial ecosystems. The trade-off between carbon and phosphorus is the key component in understanding the stabilization of the mycorrhizal mutualism. In the present study, we used triple isotopic labeling of carbon (14C) and phosphorus (32P and33P) within split root chambers to investigate the trade-off of carbon and phosphorus of host plant Allium vineale L. with varying light inputs and phosphorus supply levels. In addition, pot experiments were used to study the mycorrhizal growth responsiveness among plant species of early succession, late succession and exotic plant species. The main results were as follows:1. Pot experiment was used to study the mycorrhizal responsiveness (MR) of inbred maize (Zea mays L. vs. L224) with different soil P supply levels. The mycorrhizal responsiveness of maize plants was significantly affected by the fungal inoculum (Funneliformis mosseae、 Rhizophagus irregularis) and P supply levels (10,20,30,40,50,100mg kg-1). Maize plants exhibited higher MR at lower P supply when inoculated with R. irregularis, and at intermediate P supply when inoculated with F. mosseae. The expression of the AM-inducible Pi transporter gene ZEAma;Phtl;6was neither significantly affected by soil P supply, nor by fungi species. Root P uptake efficiency (RPUE) of maize was greatly increased by mycorrhizal colonization at all P supply level. In conclusion, the maize inbred line of L224was highly responsive to mycorrhizal inoculation.2. Roots of the host plant of Allium vineale L. were grown in spatially separated root chambers. Half of the roots were inoculated with beneficial fungal species of Claroideoglomus candidum and the other was with non-beneficial AM fungal species of Gigaspora margarita. The above-ground was treated with four different shading treatments (no shading, shading for8,6and4weeks). Carbon allocation and phosphorus uptake by host plants were calculated by measuring the radioactivity of labeled C (14C) in roots and P(32P/33P) in shoots. The biomass of host plant was promoted by the beneficial fungi, and the mycorrhizal growth responsiveness (MGR) declined with prolong of the shading treatments. Whereas the growth of host growth was not significantly affected by either shading or the inoculation of non-beneficial mycorrhizal fungus. Host plants preferentially allocated more carbon toward roots associated with the beneficial AM fungus, and in return the fungus delivered more phosphorus to host plant across all shading treatments. The proportion of preferential carbon allocation declines with the increase of shading duration. The host plant allocated approximate25%of the labelled carbon to roots associated with the beneficial AM fungus under un-shading condition and the value declines to15%under8weeks shading treatment. The proportion of preferential carbon allocation to roots associated with the non-beneficial fungus (Gigaspora margarita) did not different among shading treatments and the value was approximate11%. Our findings demonstrate that host plants preferentially allocated more carbon toward the effective mycorrhizal fungus and the allocation was highly relevant to the above-ground light conditions.3. Using the same split root chambers, the C allocation and P uptake across four different soil P levels (1X,2X,3X and4X,1X was background P level) was investigated in the present experiment. Roots were inoculated with the same or different fungi isolates on both sides. The mycorrhizal growth response (MGR) of Claroideoglomus candidum inoculated plants decreased with the increasing soil P supply levels. Host plants preferentially allocated more carbon toward high P side and in return received more phosphorus regardless of the fungi species when both root sides were inoculated with the same fungus species. The carbon allocation to high P vs low P in Gigaspora margarita inoculated treatment increased from3.27in2012to6.03in2013, and the corresponding ratio in Claroideoglomus candidum inoculated plants increased from1.09in2012to7.05in2013. When roots were inoculated with different fungi isolates on both sides, host plants preferentially allocated more carbon toward Claroideoglomus candidum under P supply levels of1X,2X and4X, and the ratio increased with increasing soil P supply levels. Our results indicate that host plants preferential allocated more carbon toward the effective mycorrhizal fungus and the allocation proportion varied with below-ground soil P supply levels.4. Pot experiments were conducted to investigate the mycorrhizal growth responsiveness (MGR) among plant species of early succession (3species), late succession (4species) and exotic (6species) plants. The MGR was significantly different among plant species of different succession stages. The variation and MGR of early succession plants was smaller compared to late succession and exotic plant species. The late succession plant species were more sensitive to local AM fungi and prone to be influenced by exotic plant species. The biomass of exotic plants was promoted when inoculated with local AM fungi species, and the effect was equivalent to those of early succession plant species. The MGR of Allium vineale L. was almost twice higher than those of other exotic plant species. The average MGR of different plant species was significantly correlated with the coefficient of variation. In conclusion, local AM fungi species improve the adaptability of the native plant species and may affect the invasion of exotic plant species.更多还原