FIGURE LEGENDS
Figure 1:Temperature response of
photosynthesis under different light intensities and in leaves of
different maturity. A) photosynthetic efficiency (ɸII),
B) light-induced thylakoid proton motive force (pmf ) estimated by
the ECSt parameter, C) ATP synthase activity
(g H+), D) non-photochemical quenching (NPQ), E)
redox state of primary quinone acceptor (q L), F)v H+/LEF and G) Relative change in thev H+/LEF ratio. Data were normalized to values at
30 °C from Figure 1F. Leaf maturity is indicated by the line type:
dashed line, mature leaves (ML, unifoliate leaves from 12 -day old
seedlings); solid line, young leaves (YL, unifoliate leaves from 4-day
old seedlings). The different colored lines represent measurements at
low (300 µmol m-2 s-1) and high
(1000 µmol m-2 s-1 and 1500 µmol
m-2 s-1) light intensities as
indicated in (A). Grey area represents recovery for at least 1 h. Data
are from cowpea genotype ‘Yacine’. The temperatures reported are the air
temperature in the chamber, which was changed every 2h, although,
measurements were made after at least 1 h under each temperature. Data
are means of 8-14 replicates from 2-3 independent experiments ±1 S.E.
Figure 2: Effects of lincomycin on maximum efficiency of PSII
(FV/FM) under HL (1500 μmol
m-2 s-1) or combined HL and HT
stress. Starting from 1 h after lincomycin treatment, the kinetics of
relative FV/FM are shown for A) GT+HL
and B) HT+HL treatments. Values are expressed relative to the initial
FV/FM values for each day. Leaves were
syringe infiltrated with 0.2 g/L lincomycin or deionized water. Dashed
lines with hollow markers represent lincomycin treatment and solid lines
with filled markers represent mock (water) infiltrated leaves. Line
color indicates the temperature and light intensity treatment. Red =
HT+HL (high temperature + high-light), black=GT+HL (growth temperature +
high-light). For the GT+HL treatment, the temperature was kept constant
(30 °C) throughout the 6 h period whereas the temperature for the HT+HL
are indicated in the colored boxes above the data points. Data are from
young cowpea leaves and the two genotypes (Yacine and 58-77) are used to
show the differences in HL sensitivity which is abolished in HT+HL. The
means of 4 replicates ±1 S.E are shown.
Figure 3: Temperature responses of CO2assimilation-related processes in young leaves of cowpea seedlings under
different light intensities. A) Net CO2 assimilation
(A ), B) Stomatal
conductance (g s) and C) Intercellular
CO2 concentration (Ci). The different
colored lines represent measurements at low (300 µmol
m-2 s-1) and high (1000 µmol
m-2 s-1 and 1500 µmol
m-2 s-1) light intensities as
indicated in the legend in Figure 3B. Grey area represents recovery for
at least 1 h. Data are from young leaves (YL) of cowpea genotype
‘Yacine’. The temperatures reported are the air temperature in the
chamber, which was changed every 2h, although, measurements were made
after at least 1 h under each temperature. Data are means ±1 S.E of at
least 8 biological replicates from 2–3 independent experiments.
Figure 4: Effect of temperature on velocity of rubisco
for carboxylation (vc) and oxygenation
(vo) and electron transport rate in cowpea.A–B) Temperature response of v c andv o in leaves of different maturity and under
light intensities of A) 300 μmol photons m-2s-1 (low light — LL) and B) 1000 μmol photons
m-2 s-1 (high-light — HL). C–D).
The temperature response and light intensity dependence of electron
transport rate measured by chlorophyll fluorescence (ETR) or calculated
from gas exchange (ETRGE). The colors represent the
different parameters as indicated in the y-axes of the leading (far
left) figures. Closed symbols = young leaves (YL), open symbols = mature
leaves (ML). LL Data are means of 6–8 replicates with error bars being
± 1 S.E. Assumptions used in calculating v c andv o are outlined in the Materials and Methods.
Figure 5: Comparison of responses of net CO2assimilation (A) and ETR/4 to internal CO2concentration (Ci) in different light
intensities, O2 levels and temperature in young cowpea
leaves. Response of A and ETR/4 against C i under
low light (300 μmol photons m-2 s-1)
at A–B) 30 °C and C–D) 45 °C respectively. Corresponding measurements
at high light (1000 μmol photons m-2s-1) are shown in E–F and G–H respectively. The
circled points represent the first measurements made under ambient
CO2. Data are means ± 1 S.E of 3–10 biological
replicates from 1–3 independent experiments.
Figure 6: HT treated plants exhibit less photo-inhibitory
quenching under prolonged dynamic and high light conditions. Changes in
A) ɸII, B) Non- photochemical quenching
(NPQ(T)), C) Photo-inhibitory quenching
(q I(T)) and D) the rapidly reversible
(photoprotective) quenching (q E(T)) during a
4-day experiment with corresponding temperature and light intensity
(PAR=photosynthetically active radiation — μmol photons
m-2 s-1) changes indicated in the
top panel of Figure 6A. The color of the lines corresponds to the colors
of the temperature. Dashed line = 58-77, solid lines=Yacine. The suffix
after the genotype names indicates the temperature treatment. Data are
means of 5–8 replicates from 1–2 independent experiments. Measurements
were made at 20 min intervals on days 1 and 4 and at 1 h intervals on
days 2 and 3 using the CCD (charge coupled device) cameras in the DEPI
(Dynamic Environment Photosynthesis Imager) chamber (Cruz et al., 2016).