Nectar peroxide: Assessing variation among plant species, microbial tolerance and effects on microbial community assembly

Nectar contains antimicrobial constituents including hydrogen peroxide, yet it is unclear how widespread nectar hydrogen peroxide might be among plant species or how effective against common nectar microbes. Here, we surveyed 45 flowering plant species across 23 families and reviewed the literature to assess the field-realistic range of nectar hydrogen peroxide (Aim 1). We experimentally explored whether plant defense hormones increase nectar hydrogen peroxide (Aim 2). Further, we tested the hypotheses that variation in microbial tolerance to peroxide is predicted by microbe isolation environment (Aim 3); increasing hydrogen peroxide in flowers alters microbial abundance and community assembly (Aim 4), and that microbial community context affects microbial tolerance to peroxide (Aim 5). Peroxide in sampled plants ranged from undetectable to ~3000 µM, with 50% of species containing less than 100 µM. Plant defensive hormones did not affect hydrogen peroxide in floral nectar, but..., Aim 1: Assessing natural levels of hydrogen peroxide in floral nectar
We sampled the floral nectar of 45 flowering plant species (Plantae: Angiospermae) (in addition to four cultivars of Epilobium canum) growing on the campus of University of California, Davis (38.540 °N, 121.756 °W, USA: California: Yolo County) and in the Sierra Nevada Mountain Range (Incline Lake, USA: Nevada: Washoe County) between March-July 2023 & 2024. We selected plant species that were in flower in spring/summer (2023 & 2024), produced nectar in volumes high enough to be extracted using glass microcapillary tubes (VWR International, Drummond Scientific Company, 50 μL) and have been previously studied with interest in microbial community inoculation ] (J. Cecala et al., 2024). Nectar was always extracted, protected from UV light under aluminum foil, kept at room temperature and processed with 3 hours of flower collection to reduce potential peroxide degradation.
To determine the concentration of nectar p..., , # Nectar Peroxide measurements and experiments

[https://doi.org/10.5061/dryad.wwpzgmsvr](https://doi.org/10.5061/dryad.wwpzgmsvr)

## Description of the data and file structure

Data are structured in tables containing metadata and measured variables for nectar and artificial nectar solutions, microbial growth in nectar and artificial nectar solutions, and measurements of hydrogen peroxide in solutions. Files are structured around the aims described in the accompanying manuscript.

Aim 1: Comparing nectar peroxide values among plant species

Phylogeny_Nectar_Peroxide_Signal.xlsx

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This experiment compared measured nectar peroxide values among plant species using a phylogenetic context.  
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Aim 2: Assessing effects of plant hormones on nectar traits

MeSA_JA_Nectar_Peroxide-CLEAN.xlsx

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This experiment assessed nectar traits of plants treated with plant hormones methyl salicylate (MeSA) or methyl jasmonate (MeJA).  
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Aim 3: variation in microbial tolerance to peroxide is pr...,