2.3. Activity of isolated compounds on the seed germination of Lactuca sativa and on the growth of Lemna minor plants

Metabolites of endophytic fungi can protect the host plants against various classes of pests (like pathogenic fungi, parasitic nematodes, herbivorous insects, etc.) thus, indirectly promoting plant growth (Li and Strobel, 2001; Schwarz et al., 2004; Schardl et al., 2007). Some volatile organic compounds were also confirmed as enhancers of plant development, affecting directly the plants (Berthelot et al., 2016). However, several endophytic metabolites have been shown to be phytotoxic, inhibiting growth of the plants (Choi et al., 2004) and their seedlings (Rivero-Cruz et al., 2003; García-M´endez et al., 2016; Wang et al., 2020).

To test the effects of our isolated metabolites on plants, two standardized assays, i.e., the Lactuca sativa seed germination- and the Lemna minor growth test, both having international recommendations, were performed (Priac et al., 2017; Vanhoutte et al., 2017). Neither the seed germination nor the reproduction and leaf development were affected by the metabolites of F. fulophazii, suggesting their no direct effects on plants (Supplementary Figs. S9 and S10).