The root microbiome:Community assembly and its contributions to plant fitness

The root microbiome refers to the community of microbes living in association with a plant's roots,and includes mutualists,pathogens,and commensals.Here we focus on recent advances in the study of root commensal community which is the major research object of microbiomerelated researches.With the rapid development of new technologies,plant-commensal interactions can be explored with unprecedented breadth and depth.Both the soil environment and the host plant drive commensal community assembly.The bulk soil is the seed bank of potential commensals,and plants use root exudates and immune responses to build healthy microbial communities from the available microbes.The plant microbiome extends the functional system of plants by participating in a variety of processes,including nutrient absorption,growth promotion,and resistance to biotic and abiotic stresses.Plants and their microbiomes have evolved adaptation strategies over time.However,there is still a huge gap in our understanding of the regulatory mechanisms of plant-commensal interactions.In this review,we summarize recent research on the assembly of root microbial communities and the effects of these communities on plant growth and development,and look at the prospects for promoting sustainable agricultural development through the study of the root microbiome.

Cattle change plant reproductive phenology,promoting community changes in a post-fire Nothofagus forest in northern Patagonia,Argentina

Aims Variations in rates and length of flowering and fruiting not only affect the reproduction of a given plant species but also the behavior and reproduction of associated taxa.Flowering and fruiting variations may be influenced by herbivory,especially by large mammals.The aim of this study was to determine the effects of cattle browsing on the reproductive phenology of understory species in a subalpine post-fire Nothofagus forest in Patagonia.Methods The effects of herbivory on plant reproductive phenology were studied in a set of experimental exclosures(fenced plots)installed since 2001 in a post-fire N.pumilio forest,located in Nahuel Huapi National Park(NHNP),Argentina.We monitored the beginning and duration of each reproductive phenological stage:floral bud,open flower,immature fruit and mature fruit.We also counted the number of flowers,fruits,seeds and viable seeds of the dominant plants to assess whether browsing modifies temporal patterns of the flowering and fruiting periods.Important Findings Cattle reduced the total number of species flowering and fruiting and changed the reproductive phenology of some species.We found that palatable species seem to be negatively affected by browsing in terms of reduced fitness due to changes in flowering and fruiting periods.In contrast,cattle benefitted the reproduction of non-palatable species and could promote the invasion of shade-intolerant exotic forbs such as Cirsium vulgare.The effects of livestock reported in this study are important to understanding how browsing could alter native species establishment and possibly alter successional trajectories during recolonization after fire.

In nomen omen:the effect of flower distance on female reproductive success of the lax-flowered orchid Anacamptis laxiflora(Orchidaceae)

Aims In multiflowered species,the architecture of inflorescences is of primary importance in shaping plant attractiveness.The aim of this study was to disentangle the role of inflorescence traits in plant female reproductive success and pollination patterns along the inflorescence in the lax-flowered orchid Anacamptis laxiflora,a terrestrial species exploiting a deceptive pollination strategy.We also evaluated whether the relationship between inflorescence traits and female reproductive success was modified by the height of surrounding vegetation and/or by population density.Methods We delimited experimental plots in a natural population of A.laxiflora.We tallied the individuals within each plot and categorized low-density plots and high-density plots;then,in part of the plots we manually removed surrounding grass thus producing an equal number of plots with high grass and low grass.Within these plots,we recorded inflorescence traits and female reproductive success(i.e.the number of fruit and their position along the inflorescence).We analyzed these data using generalized linear mixed-effects models(GLMMs)and calculated selection gradients.Important Findings We found that all the investigated inflorescence traits influenced female reproductive success.In particular,our GLMMs showed that'average flower distance'was the best predictor for shaping reproductive success patterns.We detected significant positive selection on the investigated inflorescence traits,but these selective trends were strictly linked to both the height of the surrounding vegetation and the population density,suggesting a significant influence of local environmental context in shaping selective patterns.Female reproductive success was not linked to the position of flowers along the inflorescence,suggesting that pollinators visit flowers randomly along the inflorescence without a detectable preference for a specific part.This study highlights the importance of inflorescence traits in shaping female reproductive success of multiflowered deceptive orchids,and confirms a primary role for the environmental context in modifying pollinator-mediated selection patterns.