Serendipita indica improve seed germination and seedling growth of Lolium multiflorum Lam. through amelioration of osmotic adjustment, nutrient accumulation and Na<sup>+</sup>/K<sup>+</sup> homoeostasis under salinity conditio

A pot experiment was carried out to determine the effect of Serendipita indica on the salt response of Lolium multiflorum Lam. Although the salinity decreased the root colonisation of S. indica by 28.34%, successful colonisation of S. indica increased the seed germination rate, fresh weight, leaf relative water content and chlorophyll content by 28.09, 59.01, 38.78 and 28.80%, respectively, compared with uncolonised seedlings. Under salinity, leaf malondialdehyde content, leaf relative electrical conductivity, as well as Na+ content and Na+/K+ ratio in leaves and roots of S. indica-colonised seedlings were decreased by 33.99, 33.31, 63.40% and 47.42, 85.66 and 55.88%, respectively, compared with uncolonised seedlings. Meanwhile, compared with uncolonised seedlings under salinity, the contents of proline in leaves, N, P and K+ in leaves and roots of the S. indica-colonised seedlings were increased by 47.47, 45.69 and 30.05%, and 41.77, 19.51, 19.18 and 155.00%, respectively. These results indicate that S. indica colonisation confers salt tolerance in L. multiflorum seedlings by enhancing osmotic adjustment via actively accumulating proline and K+, increasing the uptake of nutrients such as N and P, and improving Na+/K+ homoeostasis. The study would provide a new idea for the combined application of salt-tolerant plants and symbiotic microorganisms in the ecological restoration of saline-alkali lands.