【作者】 姚青；

【导师】 李晓林；

【作者基本信息】 中国农业大学 ， 植物营养， 2000， 博士

【摘要】 利用盆栽土培试验、三室隔网根箱装置,以玉米（Zea mays L.）、小麦（Triticum eastivum L.）、三叶草（Trifolium repens L.）、大豆（Glycine max L.）为供试植物,Glomus mosseae、Glomus versiforme为供试菌种,研究了植物对丛枝菌根的依赖性差异、影响植物菌根依赖性的机制。 试验表明:小麦的根毛密度显著地大于玉米,致使小麦的菌根依赖性低于玉米;接种措施能显著地提高玉米根系的磷吸收效率,增加含磷量、吸磷总量和叶绿素含量,而对小麦的影响不明显;菌根对玉米植株吸磷总量的贡献大于对小麦的贡献;玉米和小麦对Glomus mosseae的依赖性高于对Glomus versiforme的依赖性。 高磷水平下大豆的菌根依赖性高于三叶草;接种措施能显著地促进大豆和三叶草的磷吸收效率,提高其含磷量、吸磷总量、叶绿素含量和光合速率;菌根对大豆吸磷量的贡献大于对三叶草的贡献。 以不同磷效率基因型小麦进一步研究了磷效率与菌根依赖性的关系。试验结果表明小麦在低磷条件下对菌根的依赖性很低,而在高磷条件下生长受到菌根侵染的抑制;磷高效小麦基因型的韧皮部蔗糖运输速率和根冠比低于磷低效小麦基因型;菌根能显著地提高小麦的磷效率和根系对磷的吸收效率,从增加幅度来看,磷高效基因型的小于磷低效基因型;相关分析显示,小麦的菌根依赖性与磷效率、根系的磷吸收效率显著负相关;磷高效基因型向根系运输的碳水化合物较少,导致根系的菌根真菌外生菌丝总长度显著地低于磷低效基因型;外生菌丝的吸磷量对磷高效基因型的贡献低于对磷低效基因型的贡献。 综合以上试验结果可以认为,根系的磷吸收效率是植物菌根依赖性的主要影响因子,菌根能提高根系的磷吸收效率,不同植物向根系供应碳水化合物数量不同,引起菌丝的吸磷量差异和根系的磷吸收效率差异,这是菌根依赖性差异的根源;植物在低磷水平下的菌根依赖性高于在高磷水平下的菌根依赖性。 以三叶草为供试植物,Glomus versiforme为供试菌种,采用NaH₂³²PO₄间接标记和原子反应堆中子辐照的直接标记法,对磷酸二钙、磷酸八钙、磷酸十钙、磷酸铁和磷酸铝5种磷酸盐进行³²P标记,结合土壤溶液原位提取技术,研究菌根真菌外生菌丝对5种磷酸盐的活化能力。 试验表明:外生菌丝能活化磷酸二钙、磷酸八钙、磷酸铁和磷酸铝,而几乎不能活化磷酸十钙;三叶草从各种磷酸盐中吸收磷的多少顺序是磷酸二钙>磷酸八钙、磷酸铝>磷酸铁。试验结果进一步证明,菌丝际的土壤pH有所降低（0.2-0.4个单位）;磷酸二钙和磷酸八钙处理的苗丝际土壤溶液中磷浓度显著地高于其他处理。可以认为;菌更多还原

【Abstract】 In pot culture and three-compartment rhizobox cultivation, variation between mycorrhizal dependency of plants and the responsible mechanisms were investigated, with maize (Zea mays L.), wheat (Triticum eastivum L.), clover (Trifolium repens L.) and soybean (Glycine max L.) as host plants, Glomus mosseae and Glomus versiforme as arbuscular mycorrhizal fungal species.Results showed that root hair density was higher for wheat plant than for maize plant, resulting in a higher mycorrhizal dependency for maize than for wheat. Inoculation of AM fungi significantly enhanced P uptake rate by root, increased P content, total P uptake and chlorophyll content for maize plants, without significant impact on wheat plants. Contribution rate of AM to total P uptake was higher for maize plant than for wheat plant. Plant growth of maize and wheat responded greater to Glomus mosseae than to Glomus versiforme.At high P application, mycorrhizal dependency of soybean was higher than that of clover. With inoculation of AM fungi, P uptake rate by root was significantly promoted, P content, total P uptake, chlorophyll content and photosynthetic rate were increased for soybean and clover plants. Higher contribution of AM to total P uptake for soybean thanfor clover was observed.Relationship between P efficiency and mycorrhizal dependency was further investigated, with different P efficient wheat genotypes as host plants. Results indicated that plant growth of wheat responded little to AM at low P application, while it was inhibited at high P application. Compared to low P efficient genotype, high P efficient genotype was lower in phloem sugar translocation rate and R/S ratio. AM significantly promoted P efficiency and P uptake rate by root, with lower increase in high P efficient genotype than in low P efficient genotype. Correlation analysis demonstrated that there was a significantly negative relationship between mycorrhizal dependency and P efficiency, P uptake rate by root. Low amount of carbohydrate was translocated to root system in high P efficient genotype, leading to shorter external hyphae length associated with its root system than low P efficient genotype root system. Lower contribution rate ofhyphae to plant P uptake was found in high P efficient genotype than in low P efficient genotype, of root, which is the original reason responsible for different mycorrhizal dependency.According to these results above, it is concluded that P uptake rate by root is the fundamental factor underlying plant mycorrhizal dependency, AM may increase P uptake rate by root. Amount of carbohydrate translocated to root is much different between plants, resulting in different P uptake by hyphae and P uptake rate by root. Plantmycorrhizal dependency is lower at high P application than at low P application.By methods of indirectly labelling with NaH232PO4 and directly labelling in atomic pile, Ca2-P, Cag-P, Calo-P, Fe-P and Al-P were isotopically labelled. Combining with technology of soil solution extracting in situ, the ability to mobilize phosphates by AM fungi was estimated, with clover as host plant and Glomus versiforme as fungal species.Results demonstrated that external hyphae mobilized CarP, Ca8-P, Fe-P and Al-P, while mobilized almost no Calo-P. P uptake from phosphates by mycorrhizal clover was in the order of Ca2-P > Ca8-P, Al-P > Fe-P. Result further showed that soil pH in hyphosphere was decreased, ranging from 0.2 to 0.4 units. P concentration in hyphosphere was significantly higher with application of Ca2-P and Cag-P than with other phosphates or control. It is concluded that AM fungi and plants mobilize the same kinds of scarcely-soluble phosphates, soil pH decrease is one of the mobilizing mechanisms. The difference between P-supplying potential of phosphates relates to their nature.更多还原