外生菌根可以有效促进林木水分吸收,提高林木抗旱能力,维持森林生态系统稳定性。沙地樟子松是一种典型的外生菌根依赖型树种,为比较分析沙地樟子松菌根化幼苗抗旱能力,以点柄乳牛肝菌（Suillus granulatus）（Sg）、口蘑属真菌（Tricholoma sp.）（Ts）和褐环乳牛肝菌（Suillus luteus）（Sl）3种重要外生菌根真菌侵染后的菌根化幼苗为研究对象,通过室内控制试验设置土壤饱和含水率80%（水分充足）、40%（湿润）、20%（水分适宜）、10%（轻度干旱）和5%（重度干旱）5个水分处理梯度,测定干旱胁迫下沙地樟子松幼苗的生理特征参数。结果表明：（1） Sl处理组主要通过提高抗氧化酶活性减轻自由氧对细胞的伤害,进而抵御干旱胁迫。在轻度干旱时,超氧化物歧化酶和过氧化物酶活性达到最大值425.16 U·g^-1和202.73 U·g^-1。（2） Sg处理组既可以提高抗氧化酶活性抵御干旱胁迫,又通过积累脯氨酸调节细胞渗透压减缓干旱胁迫的影响。在轻度干旱时,超氧化物歧化酶活性和可溶性糖含量达到最大值397.01 U·g^-1和199.50 μg·mL ^-1。（3） Ts处理组主要通过提高最大光化学效率抵御干旱胁迫。在水分正常和轻度干旱胁迫时,叶片最大光化学效率显著高于对照组（P<0.05）。发生干旱胁迫时,菌根化幼苗能够通过提高抗氧化酶活性、调节渗透物质含量和提高叶片光化学效率等方式保障沙地樟子松正常生理活动,抵御干旱胁迫,但不同外生菌根真菌提高沙地樟子松耐旱性的途径存在差异。研究结果可为深入理解外生菌根生态功能和沙地樟子松菌根化造林技术研发提供理论依据。

Ectomycorrhiza plays an effective role in the water absorption and drought resistance of host plants and contributes to the stability maintenance of the forest ecosystem. Pinus sylvestris var. mongolica is one of the typical tree species for windbreak shelterbelts in northern China, which depends on ectomycorrhiza during its life process. In this study, seedlings infected by three important ectomycorrhizal fungi, namely, Suillus granulatus (Sg), Tricholoma sp. (Ts), and Suillus luteus (Sl), were tested to compare the drought resistance of mycorrhizal seedlings. A controlled experiment was conducted under the following drought stress gradients: 80% (sufficient water supply), 40% (moist water supply), 20% (suitable water supply), 10% (mild drought), and 5% (severe drought) of saturated soil moisture content. The physiological parameters of P. sylvestris var. mongolica seedlings were measured accordingly. Results indicated that (1) the Sl treatment efficiently alleviated the damage of reactive oxygen by increasing antioxidant enzyme activities to resist drought stress. Under mild drought, superoxide dismutase (SOD) and peroxidase activities reached the maximum values of 425.16 U·g^-1 and 202.73 U·g^-1, respectively. (2) Sg treatment not only increased the antioxidant enzyme activities to resist drought stress but also relieved this impact by accumulating proline to regulate penetration. Under mild drought, the maximum SOD and soluble sugar levels were 397.01 U·g^-1 and 199.50 μg·mL^-1, respectively. (3) The Ts treatment largely increased the maximum photosynthetic efficiency. Under normal moisture content and mild drought stress, the maximum photosynthetic efficiency was significantly higher than that of the referenced group (P<0.05). To resist drought stress, ectomycorrhiza maintained the regular physiological activities of P. sylvestris var. mongolica seedlings by improving antioxidant enzyme activities, regulating osmotic substance contents, and increasing the photochemical efficiency. However, the approaches of ectomycorrhiza were different in the drought resistance improvement of P. sylvestris var. mongolica seedlings. This study provided the physiological evidence of ecological functions of ectotrophic mycorrhiza and contributed to investigations on afforestation technology by using mycorrhizal seedlings.