DOI: 10.5061/dryad.rn8pk0p8v
title: Mesophyll photosynthetic sensitivity to leaf water potential in Eucalyptus: A new dimension of plant adaptation to native moisture supply

description: 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-ci curves at several different leaf water
 potentials (PSIleaf) to quantify mesophyll photosynthetic sensitivity to
 PSIleaf (MPS), a measure of how rapidly non-stomatal limitations to carbon
 uptake increase with declining PSIleaf. 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.
description: 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 &gt; -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
 CO<sub>2</sub> through the IRGA’s leaf gaskets by additionally
 conducting <i>A-c<sub>i</sub></i> curves on boiled
 (i.e., photosynthetically inactive) leaves (see our methods, and Flexas
 <i>et al.</i> 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.