Querejeta José I, Allen Michael F, Alguacil María M, Roldán Antonio
Departamento de Conservación de Suelos y Aguas, Centro de Edafología y Biología Aplicada del Segura-Consejo Superior de Investigaciones Científicas (CEBAS-CSIC), PO Box 4195, Campus Universitario de Espinardo 30100 Murcia, Spain.
Center for Conservation Biology, The University of California, Riverside, CA 92521, USA.
Funct Plant Biol. 2007 Aug;34(8):683-691. doi: 10.1071/FP07061.
We hypothesised that improved plant water status and enhanced transpiration are key mechanisms involved in plant growth stimulation by native arbuscular mycorrhizal fungi (AMF) in semiarid calcareous soils. Seedlings of the dryland shrubs Pistacia lentiscus L. and Retama sphaerocarpa L. were pre-inoculated with a mixture of eight native Glomus spp. fungi, or left un-inoculated, before transplanting into a degraded site in south-eastern Spain. Pre-inoculated Pistacia and Retama shrubs grew faster after transplanting, despite spontaneous colonisation of control plants by local AMF. Pre-inoculation enhanced shoot water content and shoot δN in both shrub species. Increased potassium uptake and improved water relations were key mechanisms behind growth stimulation by native AMF in Pistacia. Shoot δO (a proxy measure of stomatal conductance) was significantly less negative in AMF-inoculated than in control Pistacia seedlings, indicating enhanced cumulative transpiration in the former. In contrast, shoot δO was unaffected by AMF inoculation in Retama, a leafless leguminous shrub with photosynthetic stems. Growth stimulation by native AMF in Retama was attributed to increased phosphorus uptake, enhanced atmospheric nitrogen fixation and a largely nutrient-mediated improvement of plant water status. Shoot δC was not significantly influenced by AMF inoculation in either shrub species, thus suggesting roughly parallel upshifts in photosynthetic and transpiration rates which did not affect plant water use efficiency.
我们推测，改善植物水分状况和增强蒸腾作用是半干旱石灰性土壤中本地丛枝菌根真菌（AMF）促进植物生长的关键机制。在将地中海白松和圆叶骆驼刺这两种旱地灌木的幼苗移植到西班牙东南部一个退化地点之前，先用八种本地球囊霉属真菌的混合物对其进行预接种，或不进行接种。尽管对照植株会被当地AMF自然定殖，但预接种的地中海白松和圆叶骆驼刺灌木在移植后生长得更快。预接种提高了两种灌木的嫩枝含水量和嫩枝δN值。增加钾的吸收和改善水分关系是本地AMF促进地中海白松生长的关键机制。接种AMF的地中海白松幼苗的嫩枝δO（气孔导度的替代指标）负值明显小于对照，表明前者的累积蒸腾作用增强。相比之下，接种AMF对无叶豆科灌木圆叶骆驼刺的嫩枝δO没有影响。本地AMF对圆叶骆驼刺生长的促进作用归因于磷吸收增加、大气固氮增强以及植物水分状况在很大程度上由养分介导的改善。接种AMF对两种灌木的嫩枝δC均无显著影响，因此表明光合速率和蒸腾速率大致平行上升，这并未影响植物水分利用效率。
