DOI: 10.5061/dryad.cz8w9gjbg
title: Acclimation of thermal tolerance in juvenile plants from three biomes is suppressed when extremes co-occur

description: Given the rising frequency of thermal extremes (heatwaves and cold snaps)
 due to climate change, comprehending how a plant’s origin affects its
 thermal tolerance breadth becomes vital. We studied juvenile plants from
 three biomes: temperate coastal rainforest, desert, and alpine. In
 controlled settings, plants underwent hot days and cold nights in a
 factorial design to examine thermal tolerance acclimation. We assessed
 thermal thresholds (Tcrit-hot and Tcrit-cold) and thermal tolerance
 breadth (TTB). We hypothesised that: 1) desert species would show the
 highest heat tolerance, alpine the greatest cold tolerance, with temperate
 species intermediate; 2) all species would increase heat tolerance post
 hot days and cold tolerance after cold nights; 3) combined exposure would
 broaden TTB more than individual conditions, especially in the desert and
 alpine species. We found that biome responses were minor compared to the
 responses to the extreme temperature treatments. All plants increased
 thermal tolerance in response to hot 40°C days (Tcrit-hot increased by
 ~3.5°C) but there was minimal change in Tcrit-cold in response to the cold
 -2°C nights. In contrast, when exposed to both hot days and cold nights,
 on average plants exhibited an antagonistic response in TTB, where cold
 tolerance decreased and heat tolerance was reduced, and so we did not see
 the bi-directional expansion we hypothesised. There was, however,
 considerable variation among species in these responses. As climate change
 intensifies, plant communities, especially in transitional seasons, will
 regularly face such temperature swings. Our results shed light on
 potential plant responses under these extremes, emphasizing the need for
 deeper species-specific thermal acclimation insights, ultimately guiding
 conservation efforts.
description: <em>Title: </em>Methods for Assessing Thermal
 Tolerance in Plants from Different Australian Biomes
 <em>Summary: </em>This study compared the responses
 of plants from temperate rainforest, alpine, and desert biomes in
 Australia to hot days and cold nights using temperature-dependent
 increases in chlorophyll a fluorescence. For each biome, eight species
 were selected based on seed availability and family representation. Seeds
 were obtained from conservation seed banks, sown, and grown under common
 conditions in glasshouses. Some species were purchased from
 nurseries. A fully factorial experimental design was
 used with three biomes, eight species per biome, five replicates, and four
 temperature treatments (control, hot days, cold nights, and a combination
 of hot days and cold nights). Experiments were conducted in growth
 chambers, and plants were exposed to the temperature regimes for five
 days. Leaf temperatures were monitored using thermocouples.
 Thermal tolerance assays were performed on days three and five of
 the experiment using Maxi Pulse Amplitude Modulating (PAM) systems. Leaf
 discs were placed on Peltier plates and subjected to cooling (-25°C) and
 heating (65°C) ramps. The critical temperatures during heating (Tcrit-hot)
 and cooling (Tcrit-cold) were defined as the breakpoint between the slow
 and fast-rise phases of basal fluorescence.
description: # Acclimation of thermal tolerance in juvenile plants from three biomes is
 suppressed when extremes co-occur
 [https://doi.org/10.5061/dryad.cz8w9gjbg](https://doi.org/10.5061/dryad.cz8w9gjbg) ## Thermal tolerance data This Excel file contains the data from the paper 'Acclimation of thermal tolerance in juvenile plants from three biomes is suppressed when extremes co-occur' Test Whether the metric was tcrit hot, tcrit cold, or thermal tolerance breadth (TTB) ID Not a true ID, but gives you the date, block, plate a or b, and what test it was Block Replicate group of species from 1-5. Smaller plants were in blocks 2 and 4 sp Species name combined with what treatment it went in Plant_ID ID that tells you the block number, species, and treatment Species Species name Measurement_Day If plants were measured on day 3 or day 5 Biome Which biome: temperate, desert or alpine Treatment The treatment type: warming, cooling, combination or control Warming Either yes or no: e.g. control would be no but heatwave would be yes Cooling Either yes or no: e.g, control would be no, and heatwave would be no PAMID The area of interest recorded on the PAM to get F0 values (not unique and not useful in analysis at this point) Tcrit Derived from tcrit extraction script in R Tmax Derived from tcrit extraction script in R NT Calculated from thermocouple temperature output when an exothermic reaction occurs (release of heat during ice formation) and tells you the time/temp when ice formed TTB Tcrit hot minus tcrit cold gives you the thermal tolerance breadth (TTB) Growth_Form Type of growth form the plants are Delta_Tcrit Tcrit of treatment minus the control treatment Type The treatment combination type: warming, cooling, combination or control NA = failed tcrit or missing data due to error