Universidade de Lisboa, Faculdade de Ciências, Centro de Biologia Aplicada, Campo Grande C2. Piso 4, 1749-016 Lisbon, Portugal.
Mycorrhiza. 2011 Jan;21(1):35-51. doi: 10.1007/s00572-010-0309-3.
With regard to mycorrhiza, conflicting theories try to explain how the balance between fungal demand for carbohydrates and the plant’s needs for nutrients varies, resulting in conflicting predictions. In order to evaluate current concepts, we investigated some metabolic parameters, which are indicative for plant carbon allocation in response to mycorrhization at limited and optimal N supply. Pinus pinaster seedlings were inoculated with living or dead (control) cultures of Pisolithus tinctorius, supplied with ammonium at 4 (limiting) or 7% d−1 (non-limiting) N relative addition rate (RARN), and followed development for 29 days. Mycorrhizal colonization of roots was quantified by the determination of ergosterol. A series of enzymes (sucrose and trehalose metabolism, anaplerosis) and metabolites (soluble carbohydrate, including trehalose; fructose 2,6 bisphosphate, free amino acids) relevant in the C/N exchange between symbionts, and in the carbon allocation and sink strength within the plant were assayed for 2-day-intervals for up to 14 days, and at 5-day-intervals for the rest of the experiment. The first 10 days reflected the establishment of mycorrhizal interaction, and the carbon allocation to the root was higher in M plants independent of N supply. Following this period, carbon allocation became N-related, higher at low, and lower at high N supply. The belowground C investment of M plants was dependent on N availability, but not on N gain. Finally, increased belowground C allocation was accompanied by a shift from plant to fungal metabolism.
关于菌根，相互矛盾的理论试图解释真菌对碳水化合物的需求与植物对营养物质的需求之间的平衡如何变化，从而产生相互矛盾的预测。为了评估当前的概念，我们研究了一些代谢参数，这些参数表明在有限和最佳氮供应下，植物对碳的分配对菌根的响应。用活的或死的（对照）聚囊盘菌（Pisolithus tinctorius）培养物接种欧洲赤松（Pinus pinaster）幼苗，以 4（限制）或 7% d-1（非限制）的铵相对添加率（RARN）供应氮，并在 29 天内进行后续发育。通过测定麦角固醇来量化根的菌根定殖。在共生体之间的 C/N 交换以及植物体内的碳分配和汇强度方面，测定了一系列相关的酶（蔗糖和海藻糖代谢、氨甲酰磷酸合成）和代谢物（可溶性碳水化合物，包括海藻糖；果糖 2,6-二磷酸、游离氨基酸），每隔 2 天测定一次，最多 14 天，其余时间每隔 5 天测定一次。前 10 天反映了菌根相互作用的建立，并且在氮供应不变的情况下，M 植物的根碳分配更高。在此期间之后，碳分配与氮有关，在低氮和高氮供应下更高和更低。M 植物的地下 C 投资取决于氮的可用性，但与氮的获得无关。最后，增加地下 C 分配伴随着从植物到真菌代谢的转变。
