CAN FERTILIZATION OF SOIL SELECT LESS MUTUALISTIC MYCORRHIZAE
CAN FERTILIZATION OF SOIL SELECT LESS MUTUALISTIC MYCORRHIZAE
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DOI：
10.2307/1942106
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发表时间：
1993-11-01
影响因子：
5
通讯作者：
JOHNSON, NC
中科院分区：
文献类型：
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作者：
JOHNSON, NC
以前已经注意到，营养胁迫的植物通常在根分泌物中释放更多的可溶性碳水化合物，因此比营养充足的植物支持更多的菌根。如果使VAM真菌在碳水化合物含量较低的根中成功的相同特征也减少了真菌为寄主植物提供的益处，则施肥可能会选择较差的共生菌（VAM）真菌菌株。这个两阶段的研究实验验证了一个假设，即施肥低营养土壤选择的VAM真菌是劣等共生菌。第一阶段研究了化肥对长期田间地块VAM真菌群落物种组成的影响。第二阶段测量了来自施肥和未施肥地块的VAM真菌组合对温室中生长的大蓝茎草的影响。田间结果表明，8年施肥改变了VAM真菌群落的种类组成。巨芽孢菌、玛格丽芽孢菌、褐孢菌和隐匿球囊菌的相对丰度随施肥而降低，而根内球囊菌的相对丰度则升高。温室试验结果表明，与未施肥土壤中VAM真菌定殖的大蓝茎相比，施肥土壤中VAM真菌定殖的大蓝茎在1个月后体积较小，在3个月时花序数量较少。大蓝茎根部的真菌结构表明，来自施肥土壤的VAM真菌对宿主的净碳成本高于来自未施肥土壤的VAM真菌。来自肥沃土壤的VAM真菌产生较少的菌丝和丛枝（从而为其宿主提供较少的土壤无机养分），并产生与来自未施肥土壤的真菌一样多的囊泡（从而在同一水平上提供自己的储存结构）。这些结果支持了受精选择VAM真菌这一劣等共生菌的假设。
It has been noted previously that nutrient-stressed plants generally release more soluble carbohydrate in root exudates and consequently support more mycorrhizae than plants supplied with ample nutrients. Fertilization may select strains of vesicular-arbuscular mycorrhizal (VAM) fungi that are inferior mutualists if the same characteristics that make a VAM fungus successful in roots with a lowered carbohydrate content also reduce the benefits that the fungus provides a host plant. This two-phase study experimentally tests the hypothesis that fertilizing low-nutrient soil selects VAM fungi that are inferior mutualists. The first phase examines the effects of chemical fertilizers on the species composition of VAM fungal communities in long-term field plots. The second phase measures the effects of VAM fungal assemblages from fertilized and unfertilized plots on big bluestem grass grown in a greenhouse. The field results indicate that 8 yr of fertilization altered the species composition of VAM fungal communities. Relative abundance of Gi-gaspora gigantea, Gigaspora margarita, Scutellispora calospora, and Glomus occultum decreased while Glomus intraradix increased in response to fertilization. Results from the greenhouse experiment show that big bluestem colonized with VAM fungi from fertilized soil were smaller after 1 mo and produced fewer inflorescences at 3 mo than big bluestem colonized with VAM fungi from unfertilized soil. Fungal structures within big bluestem roots suggest that VAM fungi from fertilized soil exerted a higher net carbon cost on their host than VAM fungi from unfertilized soil. VAM fungi from fertilized soil produced fewer hyphae and arbuscules (and consequently provided their host with less inorganic nutrients from the soil) and produced as many vesicles (and thus provisioned their own storage structures at the same level) as fungi from unfertilized soil. These results support the hypothesis that fertilization selects VAM fungi that are inferior mutualists.