Jones Melanie D, Durall D M, Tinker P B
Natural Environment Research Council, Plant Mycorrhizal Unit, Department of Plant Sciences, Parks Road, Oxford, OX1 3PF, UK.
Natural Environment Research Council, Terrestrial and Freshwater Science Directorate, Polaris House, North Star Avenue, Swindon, SN2 1EU, UK.
New Phytol. 1990 Jun;115(2):259-267. doi: 10.1111/j.1469-8137.1990.tb00451.x.
There is much circumstantial evidence for a role of increased P uptake in the growth response of plants to ectomycorrhizas. Full response curves with and without mycorrhizal infection along a P gradient in soil are, however, required to test this hypothesis fully. In this experiment, rooted cuttings of Salix viminalis L. cv. Bowles Hybrid were grown in a 1:2 mixture by volume of gamma-irradiated soil and sterile sand, with bicarbonate-extractable P concentrations of 4, 6, 10, 21, 60 or 90 mg P kg . The cuttings were inoculated by mixing peat/vermiculite spawn of Laccaria proxima (Boud.) Pat., or Thelephora terrestris (Ehrh.) Fr., or autoclaved spawn 1: 5 by volume with the soil: sand mixture. The plants showed a positive growth response to mycorrhizal infection by either fungus at the two lower P levels, and to L. proxima only at 10 mg P kg . At 21 mg kg and above, infection was reduced and neither mycorrhizal inoculation nor further P additions caused significant growth increases. These results imply that the growth responses to ectomycorrhizas in this experiment were solely due to increases in P uptake. Cuttings infected with L. proxima tended to be larger than those infected by T. terrestris. Estimates of percent mycorrhizal infection did not differ between the fungi at the lower P levels. However, overall production of extramatrical hyphae per gram of soil was highest in soil inoculated with L. proxima. At 10 mg P kg the length of L. proxima hyphae per unit length of mycorrhizal root, P uptake per unit root weight, and total P content in plants infected with L. proxima were significantly higher than for T. terrestris. This study confirms that increased P uptake can be an important component of growth stimulation by ectomycorrhizas. It also presents the first quantification of extramatrical ectomycorrhizal hyphae in soil and suggests a role for them in the growth response.
有许多间接证据表明，植物对ectomycorrhizas（外生菌根）的生长反应中，磷吸收增加起到了作用。然而，要全面验证这一假设，需要在土壤磷梯度条件下绘制有无菌根感染的完整响应曲线。在本实验中，垂柳（Salix viminalis L. cv. Bowles Hybrid）的带根插条种植于γ射线辐照土壤和无菌沙按体积比1:2混合的介质中，碳酸氢盐可提取磷浓度分别为4、6、10、21、60或90毫克磷/千克。插条通过将近似红绒盖牛肝菌（Laccaria proxima (Boud.) Pat.）或土生梭孢多孔菌（Thelephora terrestris (Ehrh.) Fr.）的泥炭/蛭石菌种，或经高压灭菌的菌种按体积比1:5与土壤 - 沙混合物混合进行接种。在两个较低磷水平下，两种真菌的菌根感染均使植物呈现出积极的生长反应，而在磷含量为10毫克/千克时，仅近似红绒盖牛肝菌有此效果。在21毫克/千克及以上时，感染减少，菌根接种和进一步添加磷均未导致显著的生长增加。这些结果表明，本实验中植物对外生菌根的生长反应完全归因于磷吸收的增加。感染近似红绒盖牛肝菌的插条往往比感染土生梭孢多孔菌的插条更大。在较低磷水平下，两种真菌的菌根感染率估计值没有差异。然而，每克土壤中外生菌丝体的总产量在接种近似红绒盖牛肝菌的土壤中最高。在磷含量为10毫克/千克时，感染近似红绒盖牛肝菌的植物中，单位菌根根长的近似红绒盖牛肝菌菌丝长度、单位根重的磷吸收量以及植物总磷含量均显著高于感染土生梭孢多孔菌的植物。本研究证实，磷吸收增加可能是外生菌根促进生长的一个重要因素。它还首次对土壤中外生菌根菌丝体进行了量化，并表明它们在生长反应中发挥了作用。
