Background The influence of external environmental factors on secondary metabolites of medicinal plants has always been studied. However, little is known about the relationships between endophytes and host metabolites, especially the relationship differences between different plant species. Thus, we used high-throughput sequencing methods to compare endophyte diversity from roots of two closely related species, Gentiana officinalis and G. siphonantha, from the same production area, and analyze the association with four secondary metabolites (Gentiopicroside, Loganic acid, Swertiamarine and Sweroside). Results The fungal and bacteria communities’ richness and diversity of G. siphonantha was higher than G. officinalis. Ascomycota and Proteobacteria were dominant fungal and bacterial phylum of the two closely related species. At the genus level, Tetracladium and Cadophora were dominant fungal genus in G. officinalis and G. siphonantha samples, respectively. While Pseudomonas was dominant bacterial genus in two closely related species, with relative abundances were 8.29 and 8.05%, respectively. Spearman analysis showed that the content of loganic acid was significantly positively correlated with endophytic fungi, the content of gentiopicroside, swertiamarine and sweroside were significantly positively correlated with endophytic bacteria in the two related species. PICRUSt and FUNGuild predictive analysis indicated that metabolism and saprotroph was primary function of endophytic bacteria and fungi in the two related species. Conclusion Our results will expand the knowledge on relationships of plant-microbe interactions and offer pivotal information to reveal the role of endophytes in the production of Gentiana plant and its important secondary metabolite.

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Repeatable floral closure with diurnal rhythms, that is, flower opening in the morning and closing in the evening, was widely reported. However, the rhythm of flower opening in the morning but closing in the midday received much less attention.Gentianopsis paludosa, Gentianaceae, has an obvious petal movement rhythm opening in the morning and closing at noon at northeast of the Qinghai-Tibetan Plateau.In this study, we examined the effects of temperature (T), relative humidity (RH), and illumination intensity (II) on G. paludosa's flower closure. Furthermore, we monitored the environmental changes inside and outside of the flowers, aiming to test the effect of floral closure on the stability of microenvironment inside the flower. Finally, we artificially interrupted temporal petal closure and investigated its effects on reproductive fitness. The results showed that high/low temperature contributed more to the flower closure than low RH, while illumination intensity had no significant effect on it. The medium temperature, relative humidity and illumination intensity (environmental conditions at 10:00) did not delay flower closure when flowers at pre-closing period or stimulate reopen when flowers full closed. Floral closure provided a stable temperature condition and a higher RH condition inside the flower. Meanwhile, compulsive opening and delayed closure of flowers decreased the seed-set ratio while no effect was found when flowers were forced to close. We conclude that endogenous rhythm regulates floral closure. The rhythm of petal movement providing a stable microenvironment for G. paludosa, increasing the seed production and saving energy from flower opening maintenance, which might be an adaptive strategy to against unfavorable environmental conditions.

Background The difference of metabolites in medicinal plants has always been concerned to be influenced by external environmental factors. However, the relationship between endophytes and host metabolites remains unclear. Methods In this study, we used 16S and ITS amplicon sequencing to compare endophyte diversity among different tissue types and ages of Gentiana officinalis. Endophyte diversity and abundance was also analyzed in relation to the abundance of four secondary metabolites (Gentiopicroside, Loganic acid, Swertiamarine and Sweroside). Results The diversity and richness of G. officinalis endophyte differed as a function of tissue types and ages. Four metabolites of G. officinalis were significantly correlated with the abundance of dominant endophyte genera. The predictive function analysis showed that metabolism was main function of endophytic bacteria in different tissue and year root samples, while saprotroph was dominant trophic modes of endophytic fungi in the different year root samples. The dominant trophic modes of endophytic fungi was saprotroph and pathotroph, and relative abundances differed in the different tissue samples. The results of this study will help to elucidate the plant-microbial interactions and provide key information on the role of endophytes in the production of G.officinalis and its important metabolites.

Nectar robbers, which affect plant fitness (directly or indirectly) in different degrees and in different ways, potentially constitute a significant part of mutualistic relationships. While the negative effects of nectar robbing on plant reproductive success have been widely reported, the positive effects remain unknown. The target of our study was to evaluate the effects of nectar robbers on the reproductive success of Symphytum officinale (Boraginaceae). We observed the behavior, species and times of visitors in the field, and we assessed the effect of nectar robbers on corolla abscission rate and time. To test the fitness of corolla abscission, we detected the changes in stigma receptivity, pollen viability, pollen amount and appendage opening size along with the time of flower blossom. The flowering dynamics and floral structure were observed to reveal the mechanism of self-pollination. Finally, pollen deposition seed set rate and fruit set rate were determined to estimate the effect of nectar robbers on reproduction success. We observed 14 species of visitors and 2539 visits in 50 h of observation; 91.7% of them were nectar robbers. The pressure and nectar removal of nectar robbers significantly promoted corolla abscission during a period when pollen grains are viable and the stigma is receptive. In addition, corolla abscission significantly increased the pollen deposition and seed setting rate. Our results demonstrate that nectar robbing contributes to enhancing seed production and positively and indirectly impacts the reproductive success of S. officinale. This mechanism involved the movement of anthers and indirect participation by nectar robbers, which was rarely investigated. Considering the multiple consequences of nectar robbing, understanding the impact of nectar robbers on plant reproduction is essential to comprehend the evolutionary importance of relationships between plants and their visitors.