丛枝菌根网络对不同喀斯特适生植物生长及氮摄取的影响

Effects of common mycorrhizal networks on nitrogen acquisition and growth traits of different plants in karst areas

丛枝菌根真菌(arbuscular mycorrhizal fungi,AMF)能够通过菌丝体在不同的植物个体间形成公用菌根网(Common mycorrhizal networks,CMN)。针对喀斯特生境中不同植物个体间通过CMN调控营养分配和生物性状的问题,本研究选择了喀斯特生境3种不同的适生植物作为研究对象,模拟自然环境构建微生态系。试验设置同位素供体室和受体室,供体隔室种植香樟并进行同位素^(15)N标记,受体隔室种植不同生长型植物香樟、构树和鬼针草;利用20μm(M^+)和0.45μm尼龙网(M^-)对受体隔室进行处理,同位素^(15)N标记供体植物香樟根系,测定受体植物幼苗叶片δ^(15)N值、植株氮摄取量、生物量以及生长性状指标。试验结果表明:(1)M^+处理的3种受体植物叶片δ^(15)N值分别显著高于M^-处理;同时M^+处理显著提高了香樟幼苗地上、地下部分及植株总氮摄取量,构树和鬼针草的氮摄取量在不同处理间差异未达到显著水平。(2)M^+处理显著提高了香樟地上、地下和总生物量,但对构树没有显著影响;M^+处理下香樟幼苗株高、地径及叶面积和鬼针草幼苗株高、地径分别显著高于M^-处理,但构树在M^+和M^-处理间没有显著差异。(3)M^+处理的香樟幼苗根系平均直径、根长,根表面积和根体积分别显著高于M^-处理,但M^+处理的构树幼苗则显著降低。研究表明,微生态系中丛枝菌根网CMN非平衡性地影响了不同植物个体的氮摄取及植物生长性状,CMN更有利于提高与供体植株为同一物种的受体香樟叶片δ^(15)N、植株N摄取量以及促进其生物量积累和苗木根系生长。

Common mycorrhizal networks （CMN） are formed by the mycelium of arbuscular mycorrhizal fungi （AMF） via connection with roots of different plant individuals. The present study was conducted in a simulated microcosm to explore how CMN regulate nutrient allocation and growth of three different plant species （Cinnamomum camphora, Broussonetia papyrifera, and Bidens pilosa） in karst areas. The microcosm included one donor compartment and six receiver compartments. The donor compartment was planted with C. camphora, and its seedlings were inoculated with Glomus etunicatum and labeled with isotope 15N. Three receiver compartments were treated with 20 μm nylon mesh（M＋ treatment）, and the other three receiver compartments were treated with 0.45 μm nylon mesh （M- treatment）. All the receiver compartments were planted with C. camphora, Br. papyrifera, and Bi. Pilosa,and were not inoculated with AMF. From this research, we evaluated the effect of CMN on the growth of plants and measured the δ15N value of leaves, nitrogen acquisition, biomass, and growth traits in the two treatments. The results were as follows：（1） The leaf δ15N value of the three plants in the M＋ treatment were significantly higher than those in the M- treatment. The belowground and aboveground nitrogen acquisition, and total nitrogen of C. camphora in the M＋ treatment were significantly higher than those in the M- treatment, while the M＋ treatment did not affect the nitrogen acquisition of Br. papyrifera and Bi. pilosa. （2） The belowground, aboveground, and total biomass of C. camphora in the M＋ treatment were significantly higher than those in the M- treatment, while there was no significant difference in the biomass of Br. papyrifera between different treatments. The height, ground diameter, and leaf area of C. camphora,and the height and ground diameter of Bi. pilosa in the M＋ treatment were significantly higher than those in the M- treatment, while there was no significant difference in Br. papyrifera between the M＋ and M-treatments. （3） The root average diameter, root length, root surface area, and root volume of C. camphora in the M＋ treatment were significantly higher than those in the M- treatment, while these measurements in Br. papyrifera were significantly lower in the M＋ treatment. Our results suggest that CMN unequally affected the growth traits and nitrogen acquisition of different plant individuals in the microcosm, and CMN are more beneficial for improving leaf δ15N values, nitrogen acquisition, and biomass of C. camphora, and promoting root growth, than in the other two species.