Analysis of the symbiotic mechanism between vesicular-arbuscular mycorrhizal fungi and plants

本研究的结果如下：1)从百海草根提取物的25%甲醇洗脱液中分离鉴定了一些新的促泡状丛枝菌根（VAM）真菌生长的物质。一个是2,3 -二羟基均衡素。其余为非黄酮类化合物，对菌丝生长有很大的促进作用。2)根系分泌物对土壤的施用促进了三叶草根系VAM的发育，减轻了土壤铝毒性对树木生长的抑制作用。3)为了改进VAM真菌的无菌培养技术，我们研究了光对VAM真菌生长的影响，而波长在450 nm左右（蓝色）的光对VAM真菌生长有抑制作用。通过使用led和新的VAM生长刺激剂，我们进行了进一步的实验。4)为了阐明VAM共生机制，我们选用了一些非VAM植物，如芸苔科和藜科植物。结果表明，VAM共生与乙烯的生物合成有关。5)在芸苔科约140种拟南芥植物中，我们只发现了一种高度定殖的植物。利用该植物，我们正在分析与VAM共生有关的基因。6)利用高分辨率CCD相机观察到，在种植三叶橙树或番木瓜树的土壤中间作百喜草、谷子和鼠尾羊茅时，VAM菌丝网络很容易建立。而与非vam植物间作的土壤菌丝较少，裸地菌丝很少。菌丝网络的建立主要由根系分泌物的数量和质量决定。结果表明，利用有利于VAM真菌繁殖的禾草进行草皮培养，将有助于构建一种低投入、高产、环保的新型果树种植体系。

The results of our study are as follows :1) Some of the new growth stimulants for vesicular-arbuscular mycorrhizai (VAM) fungi in the 25 % methyl alcohol eluates of bahiagrass root extracts fractionated by flash chromatography were isolated and identified. One is 2, 3-dihydroxy eupalitin. The others are non-flavonoid compounds, and have a great stimulatory effect on hyphal growth.2) Application of root exudates to the soil stimulated VAM development of trifliate orange roots, and decreased tree growth inhibition by soil Al toxicity.3) In order to improve our axenic cultural techniques for VAM fungi, we investigated the effect of light on the growth of VAM fungi growth, while the wavelength around 450 nm (blue) inhibited it. By using the LEDs and new VAM growth stimulants, we tried further experiments.4) In order to clarify the mechanism of VAM symbiosis, we used some non-VAM plants such as Brassicaceae and Chenopodiaceae plants. The results indicated that the VAM symbiosis was related to the biosynthesis of ethylene.5) We discovered only one very highly colonized plant out of about 140 species of Arabidopsis plants in the Brassicaceae family. By using this plant, we are analyzing the genes related to VAM symbiosis.6) By using a high resolution CCD camera, we observed that the network by VAM hyphae was easily established when bahiagrass, millet and rat-tail fescue (Vulpia myuros) were intercropped in the soils planted trifoliate orange trees of papaya trees. However, there were a few hyphae in the soil intercropped with non-VAM plants, and very few hyphae in bare ground. The hyphal network establishment was mainly caused by the quantity and quality of grass root exudates. The results suggest that the introduction of sod culture using the grasses that help the propagation of VAM fungi will contribute to constructing a new fruit growing system with the lower input and sustained fruit productivity with environmental conservation in mind.