Abstract:

Objective: This study aims to investigate the growth and physiological responses of Fraxinus mandshurica inoculated with arbuscular mycorrhizal fungi （AMF） to drought environment, so as to provide theoretical basis for the application of AMF in drought environment, and technical support for the seedling cultivation and production of F. mandshurica in drought environment. Method: F. mandshurica seedlings were used as test plants, and inoculated with AMF of Glomusetunicatum and Glomus mosseae.Three methods of inoculation were set up, namely, single inoculation of G. etunicatum (Ge), single inoculation of G. mosseae (Gm) and mixed inoculation (Mix: Ge+Gm). The non-inoculated seedlings served as the control group (CK). In the greenhouse, potted plants were subjected to different water regimes to simulate natural drought, including light drought (LD) (water control for 5 days), moderate drought (MD) (water control for 10 days) and severe drought (SD) (water control for 15 days), which were compared with normal water (NW) supply in the whole process, to study the response of F. mandshurica seedlings inoculated with AMF in mycorrhizal infection rate, growth, osmotic regulation and antioxidant system under different water conditions. Result: 1）Under drought stress, inoculation was able to promote seedling growth and improve seedling quality. Mixed inoculation was more helpful to improving seedling growth than single inoculation. Mix treatment had a higher mycorrhizal infection rate. Correlation analysis showed that mycorrhizal infection rate was significantly positively correlated with seedling height increment, ground diameter increment, biomass increment, root length, root surface area, average root diameter, soluble protein（Sp）and proline content（Pro）, peroxidase（POD）and superoxide dismutase（SOD）activity (P<0.05), and significantly negatively correlated with malondialdehyde（MDA）content (P<0.05). 2）Under light drought, the increase of seedling height in Mix treatment was 230.30% of CK; Sp content of Mix treatment was 1.1, 1.3 and 1.5 times of that of Ge, Gm and CK, respectively, and Pro content was 25.12%, 34.03% and 68.30% higher than that of Ge, Gm and CK, respectively. Under drought stress, the MDA content in inoculated seedlings was significantly lower than that in non-inoculated seedling（P<0.05）. The activities of POD , SOD and catalase（CAT）were significantly higher than those of non-inoculated seedlings（P<0.05）. Conclusion: Under drought stress, inoculation promotes the growth of seedlings, enhances the osmotic regulation and antioxidant system regulation of seedlings. Compared with single inoculation, mixed inoculation seedlings have stronger drought resistance.

Key words: Fraxinus mandshurica, arbuscular mycorrhizal fungi, drought stress, growth response, physiological characteristics