• Photosynthetic sensitivity to drought is a fundamental constraint on land-plant evolution and ecosystem function. However, little is known about how the sensitivity of photosynthesis to non-stomatal limitations varies among species in the context of phylogenetic relationships.
• Using saplings of 10 Eucalyptus species, we measured maximum CO₂-saturated photosynthesis using A-c_i curves at several different leaf water potentials (PSI_leaf) to quantify mesophyll photosynthetic sensitivity to PSI_leaf (MPS), a measure of how rapidly non-stomatal limitations to carbon uptake increase with declining PSI_leaf. MPS was compared to the macroclimatic moisture availability of the species’ native habitats, while accounting for phylogenetic relationships.
• We found that species native to mesic habitats have greater MPS but higher maximum photosynthetic rates during non-water-stressed conditions, revealing a trade-off between maximum photosynthesis and drought sensitivity. Species with lower turgor loss points have less MPS, indicating coordination among photosynthetic and water-relations traits.
• By accounting for phylogenetic relationships among closely related species, we provide the first compelling evidence that MPS in Eucalyptus evolved in adaptive fashion with climatically determined moisture availability, opening further study of this poorly explored dimension of plant adaptation to drought.

README.txt

Read this for explanation of dataset, contact info, and files -- this file goes into specific detail on each column header for each data file.

Eucalytpus species traits.csv

This file contains species-level traits, including mesophyll photosynthetic sensitivity (MSP) trait values and estimated errors for Amax, Vcmax, and Jmax, and several climatic traits of native habitats.

Common Garden Amax.csv

This file contains max photosynthetic rates Amax (both per area m2 and per mass g) estimated with A-ci curves measured during non-stressful water statuses within plants (psi leaf > -1.5 MPa) collected across Eucalytpus species at 4 different common gardens across Victoria, Australia.

Raw Data A-ci curves Greenhouse experiments.csv

Raw gas exchange measurements collected for A-ci curves. This data was used to estimate Amax, Vcmax, and Jmax per area (cm-2). Data includes both raw gas exchange data, and gas exchange after we corrected for diffusion leakage of CO₂ through the IRGA’s leaf gaskets by additionally conducting A-c_i curves on boiled (i.e., photosynthetically inactive) leaves (see our methods, and Flexas et al. 2007). This diffusion corrected gas exchange data is denoted with a ".dc" at the end of the column name (and the diffusion correction for each gas exchange measurment is shown in column "difcor". Water potential of the leaf was measured after the A-ci curve, and presented in column "WP.psi".

Amax Vcmax Jmax estimates.csv

The Amax, Vcmax, and Jmax values estimated from gas exchange measurements (after diffusion correction) collected for A-ci curves. A-ci curves were analyzed using fitaci function from plantecophys package in R (https://cran.r-project.org/web/packages/plantecophys/plantecophys.pdf; Duursma 2015, 2019) to get Vcmax and Jmax and photosynthesis at ci = 6000 and 400 ppm (ACi6000.dc and ACi400.dc). Amax = ACi6000 + Rd.dc. Rn.meas is night respiration measured two hours after sundown the night before A-ci curves were collected. If Rd.dc was calculated to be negative (theoretically impossible), Rn.meas/2 replaced Rd.dc in the calculation for Amax.

Leaf Chemistry.csv

Leaf chemistry of Eucalyptus leaves measured before (initial) and after (final) a severe drought.  Includes d13C, % leaf nitrogen, % carbon, and d15N.

TLP and other PV parameters.csv

Average turgor loss point (TLP) and other parameters estimated from pressure volume curves of 10 Eucalyptus species.

rehydration experiment raw licor data.csv

Gas exchange measurements during the rehydration experiment (A-ci curves taken before a drought, and after being rehydrated post-drought). Water potential measured before and during drought, and after rehydration.

rehydration experiment Amax Vcmax Jmax WP.csv

Parameters of A-ci curves measured before drought and after post-drought rehydration. Water potential and gas exchange at ca = 400 ppm before and during drought, and after post-drought rehydration.

Please see methods of Salvi et al 2021 New Phytologist for more information.