Leaf Litter Microbes Significantly Reduce Seedling Survival of the Invasive Plant Ageratina adenophora

Core Concepts

Leaf litter microbes have more adverse effects on seed germination and seedling survival of the invasive plant Ageratina adenophora compared to soil microbes, especially during the early growth stage.

Abstract

The study investigated the distinct effects of phyllosphere (leaf litter) and rhizosphere (soil) microbes on the early life stages of the invasive plant Ageratina adenophora. The key findings are:

Leaf litter harbored more potential pathogens and thus had more adverse effects on seed germination and seedling survival than soil inoculation. Nonsterile leaf litter inoculation at the early growth stage (G0) caused extremely high seedling mortality (96.7%).

Microbial inoculation at different growth stages altered the microbial community and functions in seedlings, and earlier inoculation had a more adverse effect on seedling survival and growth. Younger seedlings were more susceptible to pathogen infection than older seedlings.

The nutrient level did not affect microbe-mediated seedling growth and the relative abundance of microbial community and functions involved in seedling growth.

Several fungal genera, such as Allophoma and Alternaria, isolated from dead seedlings exhibited significant phylogenetic signals and caused high seedling mortality.

Leaf litter microbes played an essential role in regulating A. adenophora population density by killing conspecific seedlings, which may help maintain A. adenophora monocultures at established sites.

Stats

Nonsterile leaf litter inoculation at G0 caused 96.7% seedling mortality.
Sterile leaf litter inoculation at G0 caused 19.7% seedling mortality.
Leaf litter harbored a greater abundance of plant pathogens (68.20%) than soil (33.93%).
Allophoma and Alternaria strains isolated from dead seedlings caused 54-100% seedling mortality.

Quotes

"Leaf litter possibly produces allelochemicals that adversely impact A. adenophora seed germination time and seedling survival."
"Younger seedlings were more susceptible to pathogen infection than older seedlings."
"Leaf litter microbes played an essential role in regulating A. adenophora population density by killing conspecific seedlings, which may help maintain A. adenophora monocultures at established sites."

Key Insights Distilled From

Distinct effects of phyllosphere and rhizosphere microbes on invader Ageratina adenophora during its early life stages

by Zeng,Z.-y., ... at www.biorxiv.org 01-09-2024

https://www.biorxiv.org/content/10.1101/2024.01.09.574925v2

Deeper Inquiries

How do the allelopathic effects of leaf litter interact with its microbial effects to influence seed germination and seedling survival of A. adenophora?

The allelopathic effects of leaf litter, which involve the release of allelochemicals that can inhibit the germination and growth of other plants, interact with its microbial effects to influence seed germination and seedling survival of A. adenophora. Leaf litter harbors a diverse microbial community, including potential pathogens, which can have adverse effects on seed germination and seedling survival. The presence of these pathogens in leaf litter can lead to longer germination times, lower germination rates, and higher seedling mortality rates compared to soil inoculation. The combination of allelopathic compounds and pathogenic microbes in leaf litter creates a challenging environment for seedlings, affecting their establishment and survival.

How do the mechanisms underlying the distinct effects of the same microbial genera on seedling survival versus growth of A. adenophora?

The distinct effects of the same microbial genera on seedling survival versus growth of A. adenophora can be attributed to several factors. Firstly, the timing of microbial inoculation plays a crucial role in determining the impact on seedling survival and growth. Young seedlings are more susceptible to pathogen infection due to fewer defense resources, leading to higher mortality rates when inoculated with certain microbial genera at early growth stages. Additionally, the specific species or strains within a microbial genus may have varying effects on seedling survival and growth. For example, some strains may promote growth, while others may be pathogenic and cause seedling mortality. Furthermore, the interaction between seed-borne endophytes and external microbial sources can influence the overall effect on seedling survival and growth. Seedlings inoculated with leaf litter microbes may experience different interactions with seed-borne endophytes compared to those inoculated with soil microbes, leading to varying outcomes in terms of seedling survival and growth.

Could the self-limiting effect of leaf litter microbes on A. adenophora seedling establishment be a common strategy for other invasive plant species to maintain their monocultures?

The self-limiting effect of leaf litter microbes on A. adenophora seedling establishment could potentially be a common strategy for other invasive plant species to maintain their monocultures. Leaf litter harboring diverse microbial communities, including potential pathogens, can create a hostile environment for seedlings, leading to higher seedling mortality rates. This self-limiting effect may help prevent high-density seedling establishment, reducing intraspecific competition and promoting the maintenance of monocultures. Other invasive plant species may also utilize similar mechanisms involving leaf litter microbes to regulate seedling density and establish monocultures. Understanding the role of leaf litter microbes in regulating seedling establishment could provide valuable insights for the management and control of invasive plant species in various ecosystems.