DOI: 10.5061/dryad.wdbrv15v4
title: Beyond a single temperature threshold: applying a cumulative thermal stress framework to plant heat tolerance

description: Most plant thermal tolerance studies focus on single critical thresholds,
 which limit the capacity to generalise across studies and predict heat
 stress under natural conditions. In animals and microbes, thermal
 tolerance landscapes describe the more realistic, cumulative effects of
 temperature. We tested this in plants by measuring the decline in leaf
 photosynthetic efficiency (FV/FM) following a combination of temperatures
 and exposure times, then modelled these physiological indices alongside
 recorded environmental temperatures. We demonstrate that a general
 relationship between stressful temperatures and exposure durations can be
 effectively employed to quantify and compare heat tolerance within and
 across plant species and over time. Importantly, we show how FV/FM curves
 translate to plants under natural conditions, suggesting that
 environmental temperatures often impair photosynthetic function. Our
 findings provide more robust descriptors of heat tolerance in plants and
 suggest that heat tolerance in disparate groups of organisms can be
 studied with a single predictive framework.
description: Leaf-level data was collected on plants at the Australian Arid
 Lands Botanic Garden, South Australia, Australia as per methods in the
 manuscript. Leaf F<sub>V</sub>F<sub>M</sub> data
 on collected detached leaves in response to thermal tolerance assays. Leaf
 temperature was collected in situ with thermocouples inserted into the
 leaf epidermis and modeling of leaf and reported air temperatures from the
 Australian Bureau of Meteorology. See the article for more
 details.
description: # Beyond a single temperature threshold: applying a cumulative thermal
 stress framework to plant heat tolerance *R Script and data for:* *Cook et
 al. Beyond a single temperature threshold: applying a cumulative thermal
 stress framework to plant heat tolerance. Ecology Letters, 2024.* Contains
 14 files: (**1) Analyses** - R scripts to replicate analyses and figures
 in the manuscript and supplementary material (4 files total): * TDT
 plants_final.R * Thermal landscapes functions.R * Fig 1.R *
 Neuner_Buchner.R **(2) Datasets** (7 files total): *
 *Cook_Cleandata_R_TD_MmonEsoc2023_FINAL.csv* For thermal tolerance and
 temperature duration analysis Columns: * ID - consecutive row numbers *
 Trial - Trial 1, 2 or 3 * Date tested - Date leaves were tested * Species
 - M.mon, *Myoporum montanum*; E.soc, *Eucalytpus socialis* * Duration -
 (min) temperature stress duration; 5, 10, 15 or 30 min * Temp - (°C),
 temperature of stress; 28, 48, 50, or 52°C * Rep - leaf replicate (1-10) *
 fvfm_0 - dark-adapted, maximum quantum yield (fv/fm) prior tolerance assay
 * fvfm_0-gm - grand mean centered, dark-adapted, maximum quantum yield
 prior tolerance assay * fvfm_on - overnight post assay dark-adapted,
 maximum quantum yield. * *M.mon-highH2O-2_2-5-2017_processed.csv* Leaf and
 air temperature of *M. montanum*. T-type thermocouples (40 gauge) inserted
 into leaves, HOBO loggers, and Port Augusta Arid Lands botanic gardens. HW
 = high water treatment (irrigated), Plants were grown in the ground (red
 sand dune type substrate). Columns: * \#- sequential row record number *
 Date Time * HW_Tleaf1 - leaf rep 1 temperature (°C), irrigated plant *
 HW_Tleaf2 - leaf rep 2 temperature (°C), irrigated plant * HW_Tleaf3 -
 leaf rep 3 temperature (°C), irrigated plant * HW_Tair - air temperature
 (°C) next to leaves * *Tmaxmin.csv* Recorded air temperature for nearest
 Bureau of Meteorology site-18201, AGBoM (2018). Data for the dynamic
 model. Columns: * Code - product number * Station - Bureau of Meteorology
 station number * Year - year of measurement * Month - month in the year *
 Day - day number in the month * Tmax - (°C) maximun air temperature * Tmin
 - (°C) minimum air temperature * Missingrecord_Tmax - 'y' = yes,
 'n' = no. Yes indicates that the blank cell in 'Tmax'
 (Col F) had no temperature record for that day from the weather station.
 See Australian Government, Bureau of Meteorology for their data cleaning
 processes. * Missingrecord_Tmin- 'y' = yes, 'n' = no.
 Yes indicates that the blank cell in 'Tmin' (Col G) had no
 temperature record for that day from the weather station. See Australian
 Government, Bureau of Meteorology for their data cleaning processes. *
 *Airtemp_dfmean_long.csv* Recorded air temperature at the sampling site
 (Ibutton). For Supplementary figure S1. columns: * Day - date of
 measurement * Measurement- mean, min or max temperature * Temp - (°C) air
 temperature * *Rainfall_df.csv* Rainfall from Australian Bureau of
 Meteorology, AGBoM (2018). For Supplementary figure S1. Columns: * Date -
 date of measurement * Rainfall_mm - rainfall in mm * missing_record -
 'y' = yes, 'n' = no. Yes indicates that the blank cell
 in col B (Rainfall_mm) had no rainfall record for that day from the
 weather station. See Australian Government, Bureau of Meteorology for
 their data cleaning processes. * *Cook_T50_selection_data_Mmon.csv*\ Data
 for Supplementary Figure S2. Columns: * Trial - first trial * Date -
 Day/month/year * Species - *Myoporum montanum* * Temp - (°C), temperature
 of stress; 28, 44, 46, 48, 50, or 52°C * Duration - (min) temperature
 stress duration; 5, 10, 15 or 30 min * Rep - leaf replicate (1-10) *
 fvfm_0 - dark-adapted, maximum quantum yield (fv/fm) prior tolerance
 assay. * fvfm_on - overnight post assay dark-adapted, maximum quantum
 yield. * *S1 raw data(FvFm).csv* mean Fv/Fm data for 5 species response to
 temperatures 34 to 64°C and 1min to 512 min. Graciously provided with
 permission from Neuner & Buchner (2023). *Pinus crembra, Picea abies,
 Larix decidua, Kalmia procumbens, Ranun glacialis*. * Table per species
 with treatment duration (minutes) across the top (columns) and temperature
 (°C) down the rows. Values are the percentage loss of Fv/Fm with
 treatment. R code will read this file as is. **(3) text data**- dynamic
 model outputs (3 files; see analysis code) * Survival.txt - row number,
 DATE -date time, ta - temperature (°C), alive * Survival_1.txt - row
 number, DATE -date time, ta - temperature (°C), alive * Survival_2.txt -
 row number, DATE -date time, ta - temperature (°C), alive **References:**
 * AGBoM (2018a). Climate statistics for Australian Locations: Port Augusta
 AERO. Available at: http://www.bom.gov.au/climate/data/stations/2018. *
 Neuner, G. & Buchner, O. (2023). The dose makes the poison: The longer
 the heat lasts, the lower the temperature for functional impairment and
 damage. *Environmental and Experimental Botany*, 212, 105395.