DOI: 10.5061/dryad.00000009p
title: UV treatment of the digestive fluid of Nepenthes hemsleyana pitcher plants affects their digestive process, possibly via reducing microbial inquilines

description: Interactions with microbes are ubiquitous, and many of them are essential
 for the survival and success of plants. In Nepenthes pitcher plants, they
 occur as part of a diverse community of organisms, so-called inquilines,
 that live inside the digestive fluid of the pitcher traps. However,
 evidence is ambiguous regarding the role of microbial inquilines: they may
 complement the plants’ prey digestion, fix atmospheric N, act as
 competitors that reduce plant-available nutrients, or affect the plants in
 other ways unrelated to the breakdown of prey. In a field experiment on
 Borneo, we investigated the effect of a UV-disinfection of the digestive
 fluid on prey digestion of N. hemsleyana that captures and
 digests insects as well as bat faeces in its pitchers. We show that in the
 short term photosynthetic performance of plants with UV-treated digestive
 fluids decreases compared to untreated plants, likely due to lower
 abundances of microbial inquilines. However, at the end of two months,
 responses of pitcher plants with UV-treated and untreated digestive fluids
 tend to equalise. Nutrient source, whether from insects or bat faeces,
 does not influence prey digestion. We expect our findings to be a starting
 point for unveiling the ecological role of microbial inquilines in pitcher
 plants and how they interact with other inquiline groups of higher trophic
 levels. Ultimately, this will also help to improve understanding of the
 functioning and evolution of convergent interactions in other carnivorous
 plants.
description: # The ecological role of microbial inquilines in the digestive process of
 Nepenthes hemsleyana pitcher plants
 [https://doi.org/10.5061/dryad.00000009p](https://doi.org/10.5061/dryad.00000009p) Julien L. Bota, 2025-05-28 In a field experiment on Borneo, we investigated the effect of UV-sterilisation of the digestive fluid in the pitchers on prey digestion in *N. hemsleyana.* We selected 24 *N. hemsleyana* plants and supplied two pitchers per plant with either arthropods or bat faeces as prey items. To assess the role of microbial communities in digestion, half of the plants in each feeding treatment were randomly assigned to a UV-sterilisation group, which likely reduced microbial abundance in the digestive fluid. ## Description of the data and file structure We applied four treatments: * Arthropods: 5 mg arthropods - Arthropods + UV: 5 mg arthropods + UV sterilisation of digestive fluid for 48 s - Faeces: 6 mg bat faeces * Faeces + UV: 6 mg bat faeces + UV sterilisation of digestive fluid for 48 s For a detailed method description, please refer to the original publication: https://doi.org/10.1007/s00442-025-05749-6 Not available values are noted as **NA** in the data files. ### Chlorophyll a fluorescence We measured chlorophyll a fluorescence of the youngest fully developed leaf on days 0, 28 and 56 with a portable photosynthesis yield analyser (MINI-PAM II, Heinz Walz GmbH, Effeltrich, Germany). For exact settings and methods, refer to the original publication. **Files:** 1. **chl_fluoresc_fvfm.csv**: Fv/Fm measurements 2. **chl_fluoresc_induction_curve.csv**: measurements of induction curve programme 3. **chl_fluoresc_light_curve.csv**: measurements of light curve programme **Variables:** * **date** - **record_time** - **type** - **treatment.id** - **prey:** fed prey type (Arthropods/Faeces) - **uv:** sterilisation of fluid (sterile), no sterilisation (nonsterile) - **set:** set-id (replicates were assigned to sets that were blocked in time) - **plant.id** - **species** - **day:** measuring days 0, 28, 56 - **programme:** programme of measuring device - **time:** measuring timepoint in s after start of programme - **F_:** The F corresponds to the momentary fluorescence level (Ft) of an illuminated sample measured shortly before application of a Saturation Pulse - **Fm_:** Maximum fluorescence level of the illuminated sample FM’ - **PAR:** Quantum flux density of photosynthetically active radiation (PAR) impinging on the sample - **YII:** effective photochemical quantum yields of PS II - **ETR:** Relative electron transfer rates - **Fo_:** Minimum fluorescence level of illuminated sample F0’ - **ETRFac:** Sample absorptance (= 1 – transmittance) - **qP and qL:** Coefficients of photochemical fluorescence quenching - **qN and NPQ:** Parameters of non-photochemical quenching - **YNO:** non-regulated losses of excitation energy, including heat dissipation and fluorescence emission - **YNPQ:** regulated energy losses of excitation energy by heat dissipation involving ∆pH- and zeaxanthin-dependent mechanisms - **Fo:** Minimum fluorescence level - **Fm:** Maximum fluorescence level - **FvFm:** Maximum photochemical quantum yield of PS II, FV/FM ### Elemental analyses We marked the youngest fully unfurled leaf of each pitcher plant and harvested it at the end of the experimental period to determine total concentrations of carbon, nitrogen and sulphur with a CNS-Analyzer (Vario EL, Fa. Foss Heraeus, Hanau, Germany) using air-dried and milled plant material (DIN ISO 10694: 1996-08). **File:** foliar_nutrient_content.csv **Variables:** * **ID:** treatment-ID * **sample_number** * **Ca, K, Mg, P, Zn, N, C, S:** in mg/g * **Fe:** µg/g * **N.P:** N:P ratio * **N.K:** N:K ratio * **K.P:** K:P ratio * **plant.id** * **prey:** fed prey type (Arthropods/Faeces) * **uv:** sterilisation of fluid (sterile), no sterilisation (nonsterile) * **set:** set-id (replicates were assigned to sets that were blocked in time) * **species** ### **Measurement of plant growth** We counted the number of newly developed pitchers (&gt; 0.5 cm in length), the number of newly developed leaves, the cumulative leaf surface area of all fully developed new leaves and the specific leaf area of the youngest fully developed leaf at the end of the experiment. **File:** youngest_leaf.csv **Variables:** * **treatment.id**  * **plant.id** * **prey:** fed prey type (Arthropods/Faeces) * **uv:** sterilisation of fluid (sterile), no sterilisation (nonsterile) * **set:** set-id (replicates were assigned to sets that were blocked in time) * **species** * **area_mm2:** leaf area in mm^2 * **area_cm2:** leaf area in mm^2 * **dry_weight_g:** leaf dry weight in g * **comment** **File:** plantgowth.csv **Variables** * **treatment.id** * **plant.id** - **prey:** fed prey type (Arthropods/Faeces) - **uv:** sterilisation of fluid (sterile), no sterilisation (nonsterile) - **set:** set-id (replicates were assigned to sets that were blocked in time) * **species** * **L-1_mm2; L-2_mm2; L-3_mm2; L-4_mm2:** leaf area of newly produced leaves (1-4), measured at the end of the sampling period in mm2. L-1 is always the oldest leaf. * **leaves:** number of newly produced leaves over the sampling period * **pitchers:** number of newly produced leaves over the sampling period * **comment** ### **R Scripts** Find all R scripts used to analyse the data here. The zip folder contains three folders: * Foliar nutrient content * PAM-Measurements * Plant growth There you can find the scripts used for data preparation, statistical analysis, and plotting as R-Markdown (.Rmd) and as an HTML file (.html). If required by the main script, an additional R script containing parameters for plotting is added to the folder. ### Supplement **File:** supplement.pdf * Supplemental data referenced in the published paper. ### S1-2\_Enzyme\_activity Data and statistical analysis of the additional experiment that was performed to measure the impact of the UV-treatment on plant enzyme activity (Supplement 1.2). **File:** Azocassein_Nepenthes_hemsleyana-2022-02-09.csv **Variables** * **Species** * **Treatment:** applied feeding treatment * **Replicate:** replicate number * **A:** sample absorption at 440 nm **File:** Enzyme_activity-azocassein_assay.Rmd and Enzyme_activity-azocassein_assay.html * Script used for data analysis, provided as an R-Markdown file and HTML **File:** graphic parameters.R * R script containing parameters for plotting