不同水分处理下双接种丛枝菌根真菌和根瘤菌对疏叶骆驼刺生长及氮素转移的影响

以疏叶骆驼刺为研究对象，设定3个水分梯度正常水分（土壤相对含水量（70±5）%）、干旱胁迫（土壤相对含水量（20±5）%）和复水处理（干旱胁迫60天后恢复至正常水分）与四组接种处理（单接种丛枝菌根真菌（AMF）、单接种根瘤菌、双接种AMF+根瘤菌和不接种），分析不同水分条件下双接种丛枝菌根真菌和根瘤菌对疏叶骆驼刺的生长以及供、受体疏叶骆驼刺之间氮素转移的影响。结果表明，正常水分处理时，双接种疏叶骆驼刺的AMF侵染率、地上生物量、地下生物量、总生物量以及氮含量均要高于单接种处理；根瘤数量、最大荧光（Fm）、初始荧光（Fo）、最大光化学效率（Fv/Fm）与单接种处理之间无差异；在遭遇干旱胁迫时，双接种疏叶骆驼刺的AMF侵染率、总生物量、Fv/Fm均小于单接种处理；地上生物量、地下生物量、根瘤数、Fm、Fo以及氮含量与单接种之间无差异。复水后，双接种疏叶骆驼刺的地上生物量、地下生物量、总生物量、根瘤数均优于单接种；AMF侵染率、氮含量低于单接种；Fm、Fo、Fv/Fm均与单接种之间无差异。在氮素转移方面，正常水分时，双接种与单接种的氮素转移率无差异，在遭遇干旱胁迫时，双接种疏叶骆驼刺的氮素转移率显著降低，即使复水后，仍得不到恢复。可见，与单接种AMF或单接种根瘤菌相比，双接种AMF和根瘤菌在正常水分时更具有优势，干旱胁迫会导致AMF和根瘤菌协同促生优势的减弱，复水后双接种疏叶骆驼刺能及早的对水分变化做出响应，对其生长具有一定的补偿作用，但仍不能抵消干旱胁迫所带来的损伤。丛枝菌根网络促进氮素转移一定程度上提高了疏叶骆驼刺幼苗耐旱性，但是在干旱条件下双接种疏叶骆驼刺的氮素转移率要低于单接种AMF，复水后仍得不到恢复。

Effects of double inoculation with arbuscular mycorrhizal fungi and rhizobia under different water treatments on growth and nitrogen transfer of Alhagi sparsifolia

In this study, three water gradients and four inoculation treatments were established to analyze the effects of a double inoculation of arbuscular mycorrhizal fungi (AMF) and rhizobia on the growth of Alhagi sparsifolia and nitrogen between the donor and recipient plants. The water gradient included normal water (soil relative water content (70±5)%), drought stress (soil relative water content (20±5)%) and rewatered treatment (return to the water content after 60 days of drought stress). The plants were inoculated singly with AMF or rhizobia. In addition, other plants were inoculated with both organisms (double AMF+rhizobia inoculation), and there was a control of no inoculation. The infection rate of AMF, the aboveground, belowground total biomass and the nitrogen content of double inoculation treatment was higher than that of the single inoculation when there was a normal amount of water. The nodule number, Fm, Fo and Fv/Fm did not differ from those of the single inoculation treatment. However, the AMF infection rate, total biomass and Fv/Fm rate of the double inoculation treatment were all lower than those of single inoculation under drought stress. There was no difference in the aboveground and belowground biomass, nodule number, Fm, Fo and nitrogen content compared with the single inoculation under drought stress. After rehydration, the aboveground, belowground and total biomass and the number of nodules on A. sparsifolia that had been treated with both AMF and rhizobia were higher than those inoculated singly. The rates of infection and nitrogen content rate of AMF after rehydration were lower than those that followed a single inoculation. The values of Fm, Fo, Fv/Fm did not differ from those of the single inoculation. An analysis of the amount of nitrogen transfer indicated that there was no difference between double and single inoculation under normal water conditions. However, the growth of A. sparsifolia that had been double inoculated decreased significantly under drought stress and could not be restored even after rehydration. It was apparent that the double inoculation of AMF and rhizobia compared with their single inoculation provides more benefits when the water content is normal and that drought stress will weaken the ability of AMF and rhizobia to synergistically enhance plant growth. After rehydration, A.sparsifolia that had been treated with both species quickly responded to changes in the water content. This ability can somewhat compensate for the effects of drought stress. However, it still cannot offset the damage. Arbuscular mycorrhizal network promoted nitrogen transfer and increased drought tolerance of A. sparsifoliaseedlings to a certain extent. However, the nitrogen transfer rate of double inoculation was lower than that of the single inoculation of AMF under drought conditions, which could not be reversed after rehydration.