Adolfsson Lisa, Solymosi Katalin, Andersson Mats X, Keresztes Áron, Uddling Johan, Schoefs Benoît, Spetea Cornelia
Department of Biological and Environmental Sciences, University of Gothenburg, Box 461, 405 30 Gothenburg, Sweden.
Department of Plant Anatomy, Eötvös Loránd University, H-1117 Budapest, Hungary.
PLoS One. 2015 Jan 23;10(1):e0115314. doi: 10.1371/journal.pone.0115314. eCollection 2015.
Arbuscular mycorrhizal (AM) fungi play a prominent role in plant nutrition by supplying mineral nutrients, particularly inorganic phosphate (Pi), and also constitute an important carbon sink. AM stimulates plant growth and development, but the underlying mechanisms are not well understood. In this study, Medicago truncatula plants were grown with Rhizophagus irregularis BEG141 inoculum (AM), mock inoculum (control) or with P(i) fertilization. We hypothesized that AM stimulates plant growth through either modifications of leaf anatomy or photosynthetic activity per leaf area. We investigated whether these effects are shared with P(i) fertilization, and also assessed the relationship between levels of AM colonization and these effects. We found that increased P(i) supply by either mycorrhization or fertilization led to improved shoot growth associated with increased nitrogen uptake and carbon assimilation. Both mycorrhized and P(i)-fertilized plants had more and longer branches with larger and thicker leaves than the control plants, resulting in an increased photosynthetically active area. AM-specific effects were earlier appearance of the first growth axes and increased number of chloroplasts per cell section, since they were not induced by P(i) fertilization. Photosynthetic activity per leaf area remained the same regardless of type of treatment. In conclusion, the increase in growth of mycorrhized and P(i)-fertilized Medicago truncatula plants is linked to an increase in the surface for sunlight capture, hence increasing their photosynthetic production, rather than to an increase in the photosynthetic activity per leaf area.
丛枝菌根（AM）真菌通过提供矿质营养，特别是无机磷酸盐（Pi），在植物营养中发挥着重要作用，并且还构成了一个重要的碳汇。AM能刺激植物生长发育，但其潜在机制尚不清楚。在本研究中，用不规则球囊霉BEG141接种物（AM）、模拟接种物（对照）或Pi施肥来培养蒺藜苜蓿植株。我们假设AM通过改变叶片解剖结构或单位叶面积的光合活性来刺激植物生长。我们研究了这些效应是否与Pi施肥相同，还评估了AM定殖水平与这些效应之间的关系。我们发现，通过菌根共生或施肥增加Pi供应会导致地上部生长改善，这与氮吸收和碳同化增加有关。与对照植株相比，菌根化植株和Pi施肥植株都有更多、更长的枝条，叶片更大、更厚，从而导致光合有效面积增加。AM的特异性效应是第一生长轴更早出现以及每个细胞切片中的叶绿体数量增加，因为这些效应不是由Pi施肥诱导的。无论处理类型如何，单位叶面积的光合活性保持不变。总之，菌根化和Pi施肥的蒺藜苜蓿植株生长增加与捕获阳光的表面积增加有关，从而增加了它们的光合产量，而不是单位叶面积光合活性的增加。
