Impacts of Decaying Aromatic Plants on the Soil Microbial Community and on Tomato Seedling Growth and Metabolism: Suppression or Stimulation?

Aggeliki Ainalidou,Despoina Vokou,Katerina Karamanoli,Urania Menkissoglu-Spiroudi,Foteini Bouzoukla

doi:10.3390/plants10091848

Aggeliki Ainalidou, Despoina Vokou + Show 3 more

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https://doi.org/10.3390/plants10091848

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Abstract

This study provides insight into changes in the features of tomato seedlings growing in soils enriched with spearmint, peppermint, or rosemary leaves and into changes in the microbial communities of these soils used as seedbeds; an organic amendment was also applied as a positive control. While the soil microbial community flourished in the presence of all three aromatic plants, tomato growth was inhibited or stimulated depending on the plant that was used. More specifically, phospholipid fatty acid (PLFA) analysis showed an increase in the total microbial biomass and in the biomass of all the groups examined, except for actinobacteria, and changes in the microbial community structure, with Gram-negative bacteria and fungi being favoured in the mint treatments, in which the microbial biomass was maximized. Seedlings from the rosemary treatment were entirely inhibited; they were at the open-cotyledon stage throughout the experiment. Seedlings from the mint treatments were the heaviest, longest, and had the highest chlorophyll content and photosynthetic yield. Metabolomic analysis showed metabolism enhancement associated with both growth and priming in seedlings from the mint treatments and disruption of metabolic pathways in those from the rosemary treatment. There is a great potential for applying these aromatic plants as soil amendments and as either biostimulants of plant growth or as herbicides.

Highlights

Demand for agricultural products has been continuously expanding in response to the rapidly growing human population and a constantly changing environment
To investigate the impact of aromatic plants incorporated in the soil on microbial biomass and to further explore the induced structural and functional changes in the microbial communities, the treated soils were subjected to phospholipid fatty acid (PLFA) analysis
Our results highlighted the strong negative impact that rosemary had on tomato seedling growth, which was evident from the beginning to the end of the experimental period, and, in contrast, the positive impact of soil enrichments with spearmint or peppermint, which was detected with agronomic and photosynthetic measurements

Summary

Introduction

Demand for agricultural products has been continuously expanding in response to the rapidly growing human population and a constantly changing environment. To satisfy this demand, several strategies have been developed, including the extensive use of agrochemicals. While contributing to higher agricultural production, agrochemicals are associated with serious environmental impacts such as pollution, toxicity, low soil fertility, high disease incidence, reduced product quality or low efficacy, and heavy dependence on energy inputs [1], contributing to the current climate change. Aromatic plants are candidate sources for such products. Because of their multifaceted biological activity and the important roles that they play in plant–plant and plant–microbe interactions [2,3,4], essential oils produced

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