Augé Robert M, Moore Jennifer L, Cho Keunho, Stutz Jean C, Sylvia David M, al-Agely Abid K, Saxton Arnold M
Department of Plant Sciences, 2431 Center Drive, University of Tennessee, Knoxville, TN 37996-4561, USA.
J Plant Physiol. 2003 Oct;160(10):1147-56. doi: 10.1078/0176-1617-01154.
Mycorrhizal symbiosis can modify plant response to drying soil, but little is known about the relative contribution of soil vs. root hyphal colonization to drought resistance of mycorrhizal plants. Foliar dehydration tolerance, characterized as leaf and soil water potential at the end of a lethal drying episode, was measured in bean plants (Phaseolus vulgaris) colonized by Glomus intraradices or by a mix of arbuscular mycorrhizal fungi collected from a semi-arid grassland. Path analysis modeling was used to evaluate how colonization rates and other variables affected these lethal values. Of several plant and soil characteristics tested, variation in dehydration tolerance was best explained by soil hyphal density. Soil hyphal colonization had larger direct and total effects on both lethal leaf water potential and soil water potential than did root hyphal colonization, root density, soil aggregation, soil glomalin concentration, leaf phosphorus concentration or leaf osmotic potential. Plants colonized by the semi-arid mix of mycorrhizal fungi had lower lethal leaf water potential and soil water potential than plants colonized by G. intraradices. Our findings support the assertion that external, soil hyphae may play an important role in mycorrhizal influence on the water relations of host plants.
菌根共生能够改变植物对土壤干旱的响应，但是对于土壤与根系菌丝定殖对菌根植物抗旱性的相对贡献，人们了解甚少。通过测定致死性干燥处理结束时的叶片和土壤水势来表征的叶片脱水耐受性，在被根内球囊霉或从半干旱草原采集的丛枝菌根真菌混合物定殖的菜豆（Phaseolus vulgaris）植株中进行了测定。采用通径分析模型来评估定殖率和其他变量如何影响这些致死值。在所测试的多个植物和土壤特性中，脱水耐受性的变化最好由土壤菌丝密度来解释。相比于根系菌丝定殖、根密度、土壤团聚性、土壤球囊霉素浓度、叶片磷浓度或叶片渗透势，土壤菌丝定殖对致死叶片水势和土壤水势具有更大的直接效应和总效应。被半干旱菌根真菌混合物定殖的植株比被根内球囊霉定殖的植株具有更低的致死叶片水势和土壤水势。我们的研究结果支持以下观点，即外部的土壤菌丝可能在菌根对寄主植物水分关系的影响中发挥重要作用。
