It is currently unclear whether the mechanism of endophytic fungi improving the alkali tolerance of Hordeum bogdanii affects secondary metabolites. Unveiling this knowledge is crucial for understanding the tolerance mechanism of H. bogdanii to alkaline stress. The aim of this study was to investigate how endophytic fungi affect secondary metabolites of H. bogdanii under alkaline stress at different concentrations. Endophyte-infected (E +) and endophyte-free (E−) individuals of H. bogdanii were used as materials in this study. The method of indoor vermiculite aseptic planting was adopted. After mixed alkali stress treatment, the roots, stems, and leaves of the plants were collected to measure the indicators related to secondary metabolites. The results showed that endophytic fungi improved the alkali resistance of H. bogdanii by improving the related indicators of secondary metabolites. endophytic fungi significantly increased the contents of phosphorus, polyphenols, and alkaloids, and the activities of polyphenol oxidase and acid phosphatase, and significantly reduced flavonoid content. The content of polyphenols and alkaloids in stems, polyphenol oxidase activity in stems and leaves, and acid phosphatase activity in leaves were significantly affected. The findings of this study may aid in amplifying the alkali resistance mechanism of endophytic fungi to H. bogdanii as well as provide insights into improving the alkali resistance of other plants.

Background: Saline soils severely affect plant growth. Associations between endophytes and plants are known to significantly alter plant metabolism. This study reports the effects of a fungal endophyte species (Botryosphaeria ramosa ssp.) on osmoregulation, antioxidant enzymes, and the regulation of endogenous plant hormones in Casuarina equisetifolia under NaCl stress. C. equisetifolia plants, with and without B. ramosa ssp. colonization, were subjected to different levels of NaCl stress (0%, 5%, 10%, and 15%) for different amounts of time (0 d, 20 d, 40 d, and 60 d). Results: Antioxidant enzymes, phytohormones, and nutritive elements in the leaves and roots were determined. The results showed that colonization of the roots by B. ramosa ssp. improved the growth rate and dry weight of salt-stressed plants. Moreover, B. ramosa ssp. colonization increased the activities of superoxide dismutase, catalase, and peroxide but decreased the hydrogen peroxide content in the branches of C. equisetifolia under salt stress. Meanwhile, compared with non-colonized plants, endophyte colonization reduced the abscisic acid and proline contents but increased the contents of auxin, zeatin, and gibberellins. Importantly, the nutrient elements in the roots and branches of colonized plants were significantly different from those in the roots and branches of non-colonized plants under saline conditions. Conclusions: The results of this study showed that B. ramosa ssp. colonization can enhance the salt tolerance of C. equisetifolia. by improving the antioxidant enzyme content, regulating the phytohormones, and adjusting proline accumulation under NaCl stress.

Purpose: The aim of this study was to investigate how endophytic fungi affect secondary metabolites of H. bogdanii under alkaline stress at different concentrations. It is currently unclear whether the mechanism via which endophytic fungi improve the alkali tolerance of Hordeum bogdanii affects secondary metabolites. Unveiling this knowledge is crucial for understanding the tolerance mechanism of H. bogdanii to alkaline stress. Methods: Endophyte-infected (E+) and endophyte-free (E-) individuals of H. bogdanii were used as materials in this study. Vermiculite was used for plant cultivation and was carried out in the laboratory. After mixed alkali stress treatment, the roots, stems, and leaves of the plants were collected to measure the indicators related to secondary metabolites. Results: The results showed that endophytic fungi significantly increased the contents of phosphorus, polyphenols, and alkaloids, and the activities of polyphenol oxidase and acid phosphatase, and significantly reduced flavonoid content. The content of polyphenols and alkaloids in stems, polyphenol oxidase activity in stems and leaves, and acid phosphatase activity in leaves were significantly affected. In general, endophytic fungi improved the alkali resistance of H. bogdanii by improving the related indicators of secondary metabolites. Conclusions: The findings of this study may aid in amplifying the alkali resistance mechanism of endophytic fungi to H. bogdanii as well as provide insights into improving the alkali resistance of other plants.