Plants living at the edge of their range boundary tend to suffer an overall decline in their fitness, including growth and reproduction. However, the reproductive performance of plants in ...artificially expanded habitats is rarely investigated, although this type of study would provide a better understanding of range limitations and improved conservation of ex situ plants. In the current study, we transplanted a narrowly dispersed species of Gentiana officinalis H. Smith (Gentianaceae) from its natural area of distribution to two different elevations and natural elevation to comprehensively study its pollination biology, including flowering phenology and duration, floral display, reproductive allocation, pollinator activity, and seed production. The findings indicated that the starting point and endpoint of the flowering phenology of G. officinalis were earlier at the low elevation, but the peak flowering periods did not differ significantly between any of the experimental plots. When transplanted, the flowering duration, especially the female phase, was reduced; the floral display, including spray numbers, flower numbers, and flower size (length and width), decreased, especially at high elevations. Moreover, the pollen numbers and pollen-ovule ratio were decreased at both high and low elevations, although the ovule numbers showed no change, and aboveground reproductive allocation was decreased. Furthermore, pollinator richness and activity were significantly decreased, and the seed-set ratio decreased under both natural conditions and with supplemental pollination. Finally, more severe pollen limitation was found in transplanted individuals. These results indicated an overall decrease in reproductive fitness in plants living outside their original area of distribution when the geographical range of G. officinalis was expanded.
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).
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.
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.
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.
In this work, we report a repeatable floral closure rhythm, that is, open in the morning but close in early afternoon, first in an alpine species belonging to Gentianaceae. By monitoring the petal movement under treatments of changed environmental factors, detecting the microenvironment changing inside and outside flowers, and measuring the seed production, we found that endogenous rhythm regulates floral closure, but which was also strongly influenced by high/low temperature. The floral closure at noon provides a stable microenvironment inside the flower from possible damage of both high and low temperature. Interestingly, high temperature could promote a rapid floral closure, which is a new finding because low temperature, rather than the high temperature, is assumed as the key limiting environmental factor. Besides, we found that floral closure at noon could assure the seed production. We conclude that floral closure at noon of Gentianopsis paludosa might be an effective adaptive strategy to against unfavourable environmental conditions. This is the first report of this petal movement rhythm of Gentianaceae as we know.
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.
In this study, we used 16S and ITS amplicon sequencing to compare endophyte diversity among different tissue types and ages of
. Endophyte diversity and abundance was also analyzed in relation to the abundance of four secondary metabolites (Gentiopicroside, Loganic acid, Swertiamarine and Sweroside).
The diversity and richness of
endophyte differed as a function of tissue types and ages. Four metabolites of
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
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.
During the evolution of angiosperm flowers, some floral traits may undergo certain changes in order to participate in screening. The stamens and pistils of Delphinium caeruleum are covered by two ...“door-like” staminodes, the evolutionary function of which, however, is quite unknown. In this study, we investigated whether D. caeruleum staminodes acted as visitor filters by assessing the respective strengths of staminodes and visitor insects (six bee species). We measured the operative strength required to open the staminodes and the strength that insects were capable of exerting using a biological tension sensor. Furthermore, we compared the strength required to open staminodes at different phases of the flowering period (male and female phases) and the strength of different visitors (visitors and non-visitors of D. caeruleum). The results showed that the strength needed to open staminodes in the male phase was significantly higher than that in the female phase. There was no significant difference between the strength exerted by visitors and required by staminodes of D. caeruleum in the male phase, but the visitor strength was significantly higher than that required to open staminodes in the female phase flowers. The strength of non-visitors was significantly lower than that required to open staminodes in the male phase. Furthermore, there was a significant positive association between the strength and the body weight of the bees. These results highlighted the observation that only strong visitors could press the two staminodes to access the sex organs and achieve successful pollination. Furthermore, these results revealed the function of pollinator screening by the staminodes of D. caeruleum. The biomechanical approach to the study of flowers allowed us to address relevant ecological and evolutionary questions of the plant–pollinator interaction and explore the functional modules within the flower structure in other plant species.
The intervention of nectar robbers in plant pollination systems will cause some pollinators to modify their foraging behavior to act as secondary robbers, consequently adopting a mixed foraging ...strategy. The influence of nectar robbing on pollinator behavior may be affected by spatio-temporal difference of robbing intensity, and consequently, may have different effects on the pollination of host plants. However, whether and how the nectar robbing might influence pollinators under different robbing intensity still needs further investigation. In this study,
Symphytum officinale
was used to detect the effect of nectar robbers on pollinators under different robbing intensity as well as their effects on plant reproductive success. Six robbing levels and three bumblebees with mixed foraging behaviors were used to evaluate the effect of different robbing intensity on pollinator behavior, visitation rate, flower longevity and pollen deposition. Our results indicated that the robbing rate increased gradually with the proportion of robbed flowers, but which did not affect the frequency of legitimate visits. The increase of robbing rate promoted the corolla abscission, and then enhanced the self-pollen deposition, but which had no significant effect on cross-pollen deposition. These results indicate that the overall fitness of
S. officinale
was improved by combined self and cross-pollination modes when visited by both pollinators and nectar robbers simultaneously. Although nectar robbing is not uncommon, its consequences for pollination in the interaction web have not been well studied. Our results emphasize the significance of indirect impacts in mediating the adaptive outcomes of species interactions.
•The changes of plant reproductive traits are strongly correlated with pollinators.•Changes of environmental conditions lead to the adjustment of plant resource allocation.•There is a trade-off ...between sexual reproduction and asexual reproduction.
That trade-offs result from the allocation of limited resources is a central concept of life history evolution. Many plants combine sexual reproduction with asexual reproduction, and the relationships between different reproductive modes reflect more general plant reproduction and resource allocation strategies, but how trade-offs between these reproductive modes affect fitness when plants face environmental changes, especially caused by changed growing seasons, is poorly understood. A long florescence (from late April to early November) and combined with sexual and asexual reproduction species, Trifolium repens, was selected in this study. We divided the flowering time of T. repens into three flowering phases, early (May to July), middle (July to September) and late (September to November), and compared the changes of environmental factors, pollinators, plant reproductive traits, resource allocation strategies and fitness of two reproductive modes at different phases, aiming to test how clonal plants change reproduction strategy to respond the environmental changes. Our results showed that the pollinator visitation activity was highest in early flowering phase and decreased as the season progressed. The seasonal fluctuations of environment condition and pollinators lead to significant differences in floral traits: the inflorescence size increased significantly in middle flowering phase (the flower length, flower numbers and inflorescence diameter were increased), and did not differ significantly between early and late flowering; the flower duration prolonged significantly in late flowering phase, but there was no significant difference between early and late flowering phase; inflorescence number and seed yield decreased along with the seasonal changing, i.e. bear the most at early, and the least inflorescences at late flowering phases. On the contrary, quantitative characteristics of stolon were increased as the season progressed. Correspondingly, a significant increase of resource allocated to sexual reproduction and decrease to asexual reproduction as the season progressed. These results indicate that the environmental factors in different flowering phases and corresponding variation in pollinators lead to different phenotypes, ultimately resulting in the divergence of plant reproductive traits. T. repens can adjust investment in the two reproductive modes with respect to the cost required for each new plant under different environment, and predicted to regulate overall fitness.
During the evolution of angiosperm flowers, some floral traits may undergo certain changes in order to participate in screening. The stamens and pistils of Delphinium caeruleum are covered by two ...“door-like” staminodes, the evolutionary function of which, however, is quite unknown. In this study, we investigated whether D. caeruleum staminodes acted as visitor filters by assessing the respective strengths of staminodes and visitor insects (six bee species). We measured the operative strength required to open the staminodes and the strength that insects were capable of exerting using a biological tension sensor. Furthermore, we compared the strength required to open staminodes at different phases of the flowering period (male and female phases) and the strength of different visitors (visitors and non-visitors of D. caeruleum). The results showed that the strength needed to open staminodes in the male phase was significantly higher than that in the female phase. There was no significant difference between the strength exerted by visitors and required by staminodes of D. caeruleum in the male phase, but the visitor strength was significantly higher than that required to open staminodes in the female phase flowers. The strength of non-visitors was significantly lower than that required to open staminodes in the male phase. Furthermore, there was a significant positive association between the strength and the body weight of the bees. These results highlighted the observation that only strong visitors could press the two staminodes to access the sex organs and achieve successful pollination. Furthermore, these results revealed the function of pollinator screening by the staminodes of D. caeruleum. The biomechanical approach to the study of flowers allowed us to address relevant ecological and evolutionary questions of the plant–pollinator interaction and explore the functional modules within the flower structure in other plant species.
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