Intraspecific variation in stomatal architecture, gas exchange, and drought response of a dominant prairie grass sourced from broad climatic gradients
Data files
Nov 04, 2025 version files 165.17 KB
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Drought_Experiment_ANCOVA_JMP.txt
3.43 KB
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Drought_Experiment_Gas_Exchange_JMP.txt
3.60 KB
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Drought_Experiment_Greenhouse_Conditions.xlsx
33.47 KB
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Drought_Experiment_Network_R_Code.txt
2.13 KB
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Drought_Experiment_PCA_JMP.txt
1.52 KB
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Drought_Experiment.xlsx
29.36 KB
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Main_Experiment_Greenhouse_Conditions.xlsx
36.75 KB
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Main_Experiment_Network_R_Code.txt
2.18 KB
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Main_Experiment_PCA_JMP.txt
1.36 KB
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Main_Experiment_Stomata_Climate_JMP.txt
2.85 KB
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Main_Experiment_Stomata_Gas_Exchange_JMP.txt
5.58 KB
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Main_Experiment.xlsx
32.36 KB
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README.md
10.57 KB
Abstract
Premise: Understanding how plant populations adapt to water limitation through stomatal traits is key to predicting drought responses. The dominant C~4 ~grass Andropogon gerardi, distributed across sharp climate gradients in North America, offers an excellent focal species to study stomatal architecture (size and density). Using a common garden, we tested how stomatal architecture relates to home climate, how stomatal architecture influences gas exchange, and how experimental drought affects these responses in a greenhouse. We hypothesized that aridity drives stomatal architecture, and experimental drought reduces stomatal size but increases density to maintain photosynthesis.
Methods: In our first experiment, we measured stomatal architecture and gas exchange in 25 populations sourced across temperature (4–21°C) and precipitation (350–1400 mm yr⁻¹) gradients under well-watered conditions. A second experiment focused on eight populations (472–1356 mm yr⁻¹), subjected to drought (~15% soil moisture) or well-watered (30% control) to assess plasticity. Stomatal traits were measured with epidermal peels and light microscopy, gas exchange with a LI-COR 6400, and network analyses were used to characterize adaptive strategies.
Results: Arid populations exhibited smaller, denser stomata compared to wet populations and networks demonstrated a trade-off between stomatal size and density. Under experimental drought, stomatal size decreased while density increased, with dry populations showing fewer changes than wet populations. Key traits in the network were stomatal size and water-use efficiency.
Conclusions: This study reveals that A. gerardi demonstrates adaptive changes in stomatal architecture. Our findings emphasize the interplay between adaptation and climate, providing important insights into how plants may respond to increased droughts.
Dataset DOI: 10.5061/dryad.pg4f4qs3k
The dataset was collected to investigate the relationships between stomatal architecture, gas exchange, and climate in Andropogon gerardi populations under both natural and experimental conditions in a greenhouse. In the main experiment, populations were sampled across a range of climatic gradients to quantify variation in stomatal traits (size and density) and physiological traits (photosynthetic rate, transpiration, stomatal conductance, water-use efficiency, and internal CO₂). In the drought experiment, plants from multiple populations were subjected to control and drought treatments to assess how water limitation influences stomatal traits and gas exchange. Measurements were taken at the population level, and mean values per population were calculated for all traits. The experimental design allowed for the analysis of climate effects, treatment effects, and trait coordination, including the evaluation of trait networks under both well-watered and drought conditions.
1. Overview
This dataset investigates the relationships among stomatal architecture, gas exchange, and climate in Andropogon gerardii populations sampled across broad climatic gradients. Data were collected under both natural field conditions(Main Experiment) and controlled drought treatments (Drought Experiment) in a greenhouse setting.
The dataset enables evaluation of how variation in stomatal traits and physiological performance corresponds to climate and drought responses, as well as the coordination of traits within and across environmental contexts.
2. Description of Data and File Structure
2.1 Main Experiment
File: Main_Experiment.xlsx
This file contains population-level measurements of stomatal and gas exchange traits collected from natural field populations spanning a climatic gradient.
Variables:
- Population (Site): Unique identifier for each population sampled in the field.
- Block: Experimental or measurement block used for replication within the site.
- Mean abaxial diameter (µm): Average stomatal pore length on the abaxial (lower) leaf surface, measured in micrometers.
- Mean abaxial density (stomata mm⁻²): Mean number of stomata per square millimeter on the abaxial leaf surface.
- Mean adaxial diameter (µm): Average stomatal pore length on the adaxial (upper) leaf surface.
- Mean adaxial density (stomata mm⁻²): Mean number of stomata per square millimeter on the adaxial leaf surface.
- Abaxial stomatal diameter/density: Individual-level measurements of stomatal size and density on the abaxial surface, averaged by population.
- Adaxial stomatal diameter/density: Individual-level measurements on the adaxial surface, averaged by population.
- Photosynthetic rate (µmol CO₂ m⁻² s⁻¹): Rate of CO₂ assimilation measured under standardized light and CO₂ conditions.
- Transpiration rate (mmol H₂O m⁻² s⁻¹): Rate of water vapor loss from leaves.
- Stomatal conductance (mol H₂O m⁻² s⁻¹): Leaf conductance to water vapor, indicating the extent of stomatal opening.
- Intrinsic water-use efficiency (iWUE; µmol CO₂ mol⁻¹ H₂O): Ratio of photosynthetic rate to stomatal conductance.
- Internal CO₂ (µmol mol⁻¹): Intercellular CO₂ concentration within the leaf, derived from gas exchange.
- Mean annual temperature (°C): Long-term mean air temperature at the source population’s location.
- Mean annual precipitation (mm yr⁻¹): Total annual precipitation at the population’s source site.
- Growing season precipitation (mm): Total precipitation during the primary growing season.
- Aridity index (unitless): Ratio of mean annual precipitation to potential evapotranspiration; higher values indicate wetter climates.
- Growing season aridity index (unitless): Same ratio calculated specifically for the growing season.
- Growing season length (days): Number of days suitable for plant growth (based on temperature thresholds).
- Evaporative index (unitless): Ratio of actual to potential evapotranspiration, representing water availability.
- Growing season temperature (°C): Mean temperature during the growing season.
- Latitude and Longitude (decimal degrees): Geographic coordinates of each population’s source location.
2.2 Drought Experiment
File: Drought_Experiment.xlsx
This file contains population-level measurements of stomatal and gas exchange traits under two treatments: control (well-watered) and drought (water-limited) conditions in a greenhouse.
Variables:
- Block: Greenhouse bench or position representing an experimental block.
- Sample ID: Unique label for each individual or population sample.
- Pop: Population identifier matching the source population from the field.
- Treatment: Experimental condition (Control or Drought).
- Mean adaxial density (stomata mm⁻²): Mean number of stomata per square millimeter on the upper (adaxial) leaf surface.
- Mean adaxial size (µm): Average stomatal pore length on the adaxial surface.
- Mean abaxial density (stomata mm⁻²): Mean number of stomata per square millimeter on the lower (abaxial) surface.
- Mean abaxial size (µm): Average stomatal pore length on the abaxial surface.
- Adaxial stomatal density / size (µm): Individual-level averages for the adaxial surface.
- Abaxial stomatal density / size (µm): Individual-level averages for the abaxial surface.
- Photosynthetic rate (µmol CO₂ m⁻² s⁻¹): Rate of CO₂ assimilation under experimental treatment.
- Transpiration rate (mmol H₂O m⁻² s⁻¹): Water vapor loss rate under experimental treatment.
- Stomatal conductance (mol H₂O m⁻² s⁻¹): Conductance to water vapor.
- Intrinsic water-use efficiency (iWUE; µmol CO₂ mol⁻¹ H₂O): Ratio of photosynthesis to conductance.
- Mean annual temperature (°C): Mean temperature at the population’s source site.
- Mean annual precipitation (mm yr⁻¹): Mean total annual precipitation at source site.
- Growing season precipitation (mm): Precipitation during the growing season.
- Aridity index (unitless): Ratio of precipitation to potential evapotranspiration.
- Growing season aridity index (unitless): Seasonal version of aridity index.
- Growing season length (days): Length of the growing season.
- Evaporative index (unitless): Ratio of actual to potential evapotranspiration.
- Growing season temperature (°C): Average temperature during growing season.
- Latitude and Longitude (decimal degrees): Coordinates of the source population.
2.3 Greenhouse Environmental Data Main Experiment
File:
Main_Experiment_Greenhouse_Conditions.xlsx
These files record environmental conditions during the greenhouse experiments.
Variables include:
- Date (MM-DD-YYYY): Measurement date.
- Block: Greenhouse bench used for replication.
- Reading: Direct soil moisture reading from Zentra probe.
- Soil_Moisture (%): Percentage volumetric soil moisture content.
- Soil_Temperature (°C): Soil temperature reading.
- Ambient_Light (µmol photons m⁻² s⁻¹): Photosynthetic photon flux density.
2.4 Greenhouse Environmental Data Drought Experiment
File:
Drought_Experiment_Greenhouse_Conditions.xlsx
These files record environmental conditions during the greenhouse experiments.
Variables include:
- Date (MM-DD-YYYY): Measurement date.
- Treatment: Control or Drought condition.
- Drought_1, Drought_2, Drought_3, and Drought_4: Soil moisture (%) readings for four replicate droughted plants.
- Control_1, Control_2, Control_3, and Control_4: Soil moisture (%) readings for four replicate control plants.
- Soil_Temperature (°C): Average soil temperature.
- Light_Availability (µmol photons m⁻² s⁻¹): Photosynthetic photon flux density.
3. Analysis Scripts
The following text-based scripts accompany the dataset and can be run in JMP or R.
Main_Experiment_Stomata_Climate_JMP.txt– Regressions of stomatal traits against climate variables using linear and quadratic models.Main_Experiment_Stomata_Gas_Exchange_JMP.txt– Models gas exchange traits as a function of stomatal traits.Main_Experiment_PCA_JMP.txt– Principal Component Analysis (PCA) of stomatal and gas exchange traits.Main_Experiment_Network_R_Code.txt– R script for constructing plant trait networks (PTNs) using Spearman correlations.Drought_Experiment_ANCOVA_JMP.txt– ANCOVA testing effects of population, treatment, and stomatal traits on gas exchange.Drought_Experiment_PCA_JMP.txt– PCA of stomatal and physiological traits under control and drought treatments.Drought_Experiment_Gas_Exchange_JMP.txt– Regression of gas exchange variables on stomatal traits.Drought_Experiment_Network_R_Code.txt– R script for treatment-specific network analyses.
4. Software Requirements
- Microsoft Excel / LibreOffice / Google Sheets: For viewing and editing Excel data files.
- JMP Pro 16 or later (SAS): For running statistical analyses including ANCOVA, PCA, and regression models.
- R (version 4.2 or higher) and RStudio (optional): For constructing and visualizing trait networks.
- Required R packages: tidyverse, igraph, Hmisc, corrplot, readxl.
5. Workflow Summary
- Open Excel data files to explore raw and summarized measurements.
- Run JMP scripts for parametric statistical analyses (ANCOVA, PCA, and regressions).
- Use R scripts to compute trait correlation matrices and construct trait networks.
- Compare patterns under control and drought treatments to evaluate climate-dependent trait coordination.
6. Interpretation Notes
- Stomatal traits (size and density) reflect structural adaptations affecting CO₂ uptake and water regulation.
- Gas exchange traits represent physiological performance under varying water availability.
- Climate variables describe the environmental origins of populations and are derived from long-term climatic datasets.
- All measurements were taken on fully expanded leaves from greenhouse-grown plants under controlled light and CO₂ levels.