DOI: 10.5061/dryad.4f4qrfjkb
title: Divergence in cold tolerance promotes niche differentiation between diploid and polyploid kiwifruits along an altitudinal gradient in Southwest China

description: Polyploidization is hypothesized to improve the freezing resistance of
 plants in cold regions. However, adaptive strategies and key physiological
 mechanisms involved in the freezing resistant ability of polyploids remain
 unclear. In Actinidia chinensis (kiwifruits), the tetraploids and
 hexaploids occupy higher altitude habitats with colder climates than the
 diploids, providing a study system to investigate mechanisms responsible
 for differentiation in freezing resistance between cytotypes. We
 characterized environmental conditions of their natural distribution
 areas, and measured leaf-level traits of cold damages and water relations
 at typical sites of each cytotype along an altitudinal gradient.
 Polyploids showed lower semi-lethal temperature (LT50) than ice nucleation
 temperature (INT), reflecting a tolerance strategy to cope with freezing
 events in the plateau regions. More negative turgor loss points and larger
 cell elastic modulus of polyploids could help to alleviate damages from
 freezing-induced cell dehydration, thus strengthening their tolerance to
 lower subzero temperatures (lower LT50). The increased supercooling
 capacity of polyploids (lower INT) might correlate with less extracellular
 ice formation due to lower osmotic potential at full turgor, apoplastic
 water fraction and tissue capacitance. Our study uncovers a greater cold
 tolerance in polyploid kiwifruits than diploids, and suggests the
 potential linkage between freezing tolerance and water relations. Taken
 together, such a divergence in stress resistance may underlie the niche
 shift of polyploid plants towards harsh environments.
description: We measured leaf extracellular ice nucleation temperature (INT)
 of three typical cytotypes (2x, 4x and 6x) of kiwifruits. The electrolyte
 leakage and chlorophyll fluorescence measurements were used to assess
 freezing damage on the cellular and chloroplast membranes of detached
 leaves. We obtained the relative electrical conductivity (REC) and
 relative chlorophyll fluorescence (RCF), then got leaf lethal temperature
 at 50 % REC (LT<sub>50</sub>-REC) and leaf semi-lethal
 temperature by RCF (LT<sub>50</sub>-RCF). The determination of
 leaf pressure-volume (P-V) curves and calculation for related parameters
 were obtained using the bench dehydration technique. Five individuals per
 cytotype were used for the above physiological measurements.
description: # Divergence in cold tolerance promotes niche differentiation between
 diploid and polyploid kiwifruits along an altitudinal gradient in
 Southwest China ##
 Abstract These data contents include the primary data that measured by the
 authors. We found that polyploids showed lower semi-lethal temperature
 (LT50) than ice nucleation temperature (INT). More negative turgor loss
 points and larger cell elastic modulus of polyploids could help to
 alleviate damages from freezing-induced cell dehydration. The increased
 supercooling capacity of polyploids (lower INT) might correlate with less
 extracellular ice formation due to lower osmotic potential at full turgor,
 apoplastic water fraction and tissue capacitance. ## Usage notes These
 datasets were included the distribution information of the three cytotypes
 (2x, 4x and 6x) of kiwifruits, leaf-level traits of cold damages and water
 relations at typical sites of each cytotype. Details for each dataset are
 provided in the README file. The datasets included: 1\) locality points
 Number of samples (Code) Cytotype (2x, 4x, 6x) Longitude (E) and Latitude
 (E) of each samples 2\) electrical conductivity of leaves (leaf EC) For
 the three cytotypes (2x, 4x and 6x), electrical conductivity (EC, μS cm-1)
 measurements for the leaf samples (unboiled and boiled samples) under
 different target temperature treatments (20, 0, -5, -10, -15, and -20 ℃).
 3\) leaf relative chlorophyll fluorescence (leaf RF) For the three
 cytotypes (2x, 4x and 6x), chlorophyll fluorescence measurements (the *F*v
 /*F*m value) for the leaf samples under different target temperature
 treatments (20, 0, -5, -10, -15, and -20 ℃). 4\) leaf INT and LT50 For the
 three cytotypes (2x, 4x and 6x), leaf extracellular ice nucleation
 temperature (INT, ℃), leaf lethal temperature at 50 % REC (LT50-REC, ℃)
 and leaf semi-lethal temperature by RCF (LT50-RCF, ℃) were determined. 5\)
 leaf P-V The eight related parameters were obtained from leaf
 pressure-volume (P-V) curves. πtlp (MPa): leaf water potential at turgor
 loss point; πo (MPa): osmotic potential at full turgor; *a*f: apoplastic
 water fraction; Cft (MPa-1): capacitance at full turgor; *C*ft* (mol m-2
 MPa-1): absolute capacitance at full turgor; SWC: saturated water content;
 RWCtlp (%): relative water content at turgor loss point; ε (MPa): bulk
 modulus of elasticity. Additional details are available in the datasets.