Supporting Information for Tozzi, Easlon and Richards
Interactive effects of water, light and heat stress on photosynthesis in Fremont cottonwood
Supporting Information Figure S1. Photographs of Fremont cottonwood seedlings at <10, 30
and >90 days since germination. Cotyledons and young leaves are nearly horizontal, while
mature seedlings have leaves that are nearly vertical. To simulate the leaf orientation of young
seedlings, leaf restraints were used to hold leaves of older seedlings vertically (as a control) and
horizontally (as a treatment). Further, see Supporting Information Table S1 for data from the
leaf orientation experiment.
md (MPa)
4d 3d
C
A
8
BC
16 c
A (mol CO2 m-2 s-1)
10
ABC

= -1.36 (Leffler et al. 2000)
cav
 = -1.50 (Pockman et al. 1995;
50
-1.5
Leffler et al. 2000)
A
B
6
C
d
32
AB
14
28
A
AB
12
24
B
BC
B
20
C
10
e
iWUE (mol mol-1)
-1
A
A
-2
2d
-1.3
b
0d
Cc & Ci (Pa)
a
-1.1
E (mmol H2O m s )
Supporting Information for Tozzi, Easlon and Richards
Interactive effects of water, light and heat stress on photosynthesis in Fremont cottonwood
0.1
0.3
0.5
gs (mol m-2 s-1)
B
75
60
B
45
A A
30
0.1
0.3
0.5
gs (mol m-2 s-1)
Supporting Information Figure S2. (a) Midday leaf water potential (Ψmd), (b) transpiration
(E), (c) assimilation (A), (d) chloroplast and intercellular [CO2] (closed circles represent Cc &
open circles represent Ci), and (e) intrinsic water-use-efficiency (iWUE=A/gs) for plants also
described in Fig. 2 and Table 1. Plants went 0- (blue), 2- (green), 3- (black) and 4- (red) days
without water. Leaf temperature (28.6°C ± 0.5), RH (32.5% ± 1) and PPFD (1000 μmol m-2 s-1 ±
1) were held constant during measurements; data are means ± SE (n=3-5). The safety margin
between the measured Ψmd, and previously measured Ψcav or Ψ50 for Fremont cottonwood was
small (Pockman et al. 1995; Leffler et al. 2000).
-2
-1
ETR (mol electrons m s )
Supporting Information for Tozzi, Easlon and Richards
Interactive effects of water, light and heat stress on photosynthesis in Fremont cottonwood
a
0d
180
1d
150
120
2d
90
3d
0600
0930
1200
1500
-2
-1
ETR (mol electrons m s )
Solar Time
180 b
120
60
0
0
500 1000 1500 2000
PPFD
-2
-1
-2
-1
ETR (mol electrons m s )
(mol photons m s )
120 c
100
80
60
40
25
30
35
40
45
TL (C)
Supporting Information Figure S3. Electron transport rate (ETR) from (a) diurnal
measurements (solar time) for plants that went 0 (solid line, open circles), 1 (long dashed line,
open upside-down triangles), 2 (medium dashed line, open triangles) and 3 (dash dot dot line,
open squares) days without water; and (b) light and water-stress interactions measurements
(PPFD), and (c) leaf temperature and water-stress interactions measurements (TL) for plants that
went 0 (solid line, open circles) and 3 (dash dot dot line, open squares) days without water. Data
are means ± SE (n=3-5).
Supporting Information for Tozzi, Easlon and Richards
Interactive effects of water, light and heat stress on photosynthesis in Fremont cottonwood
Supporting Information Table S1. Midday leaf temperatures (TL) of restrained leaves for the
0-day control and 3- or 4-day water-stressed plants. To simulate the leaf orientation of young
seedlings, leaf restraints were used to hold leaves of older seedlings vertically (as a control) and
horizontally (as a treatment); data are means ± SE (n=6). See Supporting Information Fig. S1 for
photographs of plants <10, 30 and >90 days old.
Ambient air temperature (°C):
Dry soil surface temperature (°C):
Days without
Leaf Orientation
water
Day 3
32.9 ± 0.7
Day 4
35.0 ± 1.1
51.5 ± 1.3
51.3 ± 1.5
TL
TL
0
Horizontal
28.7 ± 0.6b
32.1 ± 0.4b
0
Vertical
28.2 ± 0.3b
30.5 ± 0.6c
3-4
Horizontal
31.0 ± 0.7a
34.3 ± 0.6a
3-4
Vertical
28.6 ± 0.7b
31.2 ± 0.2c