Contrasting Effects of Plant-Soil Feedbacks on Growth and Morphology of Two Clonal Plants

AimSoil abiotic and biotic conditions are often spatially variable, challenging plants with a heterogeneous environment consisting of favorable and unfavorable patches of soil. Many stoloniferous clonal plants can escape from unfavorable patches by elongating stolon internodes, but aggregate in favorable ones through shortening stolon internodes. However, whether these plants can use their stolons to respond to plant-soil feedbacks (PSFs) is largely unknown. MethodsIn the conditioning phase, we grew either Hydrocotyle vulgaris or Glechoma longituba clonal plants separately in mesocosms to condition bulk soil. In the feedback phase, we grew connected mother and daughter ramets of each species in soil inoculated with the unsterilized or sterilized soil conditioned by conspecifics. We grew the plants for 12 weeks and measured the growth of the mother and daughter ramets separately. ResultsThe daughter ramets of H. vulgaris produced more biomass but shorter stolon internodes when grown in soil with sterilized inocula than with unsterilized inocula. However, no difference was found between the daughter ramets of G. longituba grown in soil with unsterilized and sterilized inocula. For both species, no significant difference was found between the mother ramet or between the daughter ramets when the mother ramet was grown in soil with sterilized and unsterilized inocula. ConclusionsThe daughter ramets rather than the mother ramet of H. vulgaris experienced negative biotic PSFs. However, PSF had no effects on the daughter or mother ramet of G. longituba. Moreover, physiological integration or plasticity in stolon internode lengths cannot help H. vulgaris alleviate the negative PSFs.

Ultraviolet B Radiation Triggers DNA Methylation Change and Affects Foraging Behavior of the Clonal Plant Glechoma longituba

Clonal plants in heterogeneous environments can benefit from their habitat selection behavior, which enables them to utilize patchily distributed resources efficiently. It has been shown that such behavior can be strongly influenced by their memories on past environmental interactions. Epigenetic variation such as DNA methylation was proposed to be one of the mechanisms involved in the memory. Here, we explored whether the experience with Ultraviolet B (UV-B) radiation triggers epigenetic memory and affects clonal plants’ foraging behavior in an UV-B heterogeneous environment. Parental ramets of Glechoma longituba were exposed to UV-B radiation for 15 days or not (controls), and their offspring ramets were allowed to choose light environment enriched with UV-B or not (the species is monopodial and can only choose one environment). Sizes and epigenetic profiles (based on methylation-sensitive amplification polymorphism analysis) of parental and offspring plants from different environments were also analyzed. Parental ramets that have been exposed to UV-B radiation were smaller than ramets from control environment and produced less and smaller offspring ramets. Offspring ramets were placed more often into the control light environment (88.46% ramets) than to the UV-B light environment (11.54% ramets) when parental ramets were exposed to UV-B radiation, which is a manifestation of “escape strategy.” Offspring of control parental ramets show similar preference to the two light environments. Parental ramets exposed to UV-B had lower levels of overall DNA methylation and had different epigenetic profiles than control parental ramets. The methylation of UV-B-stressed parental ramets was maintained among their offspring ramets, although the epigenetic differentiation was reduced after several asexual generations. The parental experience with the UV-B radiation strongly influenced foraging behavior. The memory on the previous environmental interaction enables clonal plants to better interact with a heterogeneous environment and the memory is at least partly based on heritable epigenetic variation.

Effects of Soil Microbiomes and Enzymatic Activities on Glechoma longituba

Soil microbes and enzymes play important roles in plant growth and metabolism. However, for Glechoma longituba (Nakai) Kupr., an important crop with edible and medicinal uses in China, their effects are not well elucidated. To explore their impacts on plant morphology and bioactive compounds, the plant samples and rhizosphere soil of five different G. longituba populations were collected and investigated in this study. After high-throughput sequencing combined with data analyses, high microbial diversity and richness in the rhizosphere soil of each G. longituba population were observed, and the variations on bacterial and fungal community compositions among these soil samples were also proved. The activities of urease, neutral phosphatase, sucrase, protease, and polyphenol oxidase were significantly different among the rhizosphere soils from different G. longituba populations. Among the major microbial communities and soil enzymes we studied, the genera of Tomentella, Sebacina, Fusarium, Nitrospira, and the activity of soil sucrase were remarkably correlative with both the morphological indices and the contents of bioactive compounds of G. longituba by redundancy analysis. These findings would help guide the scientific plantation of G. longituba to promote its medicinal quality.