Figure legends
FIGURE 1 (a) Partial view of Exp. 1 and Exp. 2 with the drought
and heat stress, with a detail on how the system looked like from inside
the enclosures. (b) Partial view of Exp.3 with the drought and heat
stress, with a detail on how the system looked like from inside the
enclosures. (c) The stage exposed to drought, heat and combined drought
and heat stress for each treatment. (d) The growth conditions in Exp.1.
(e) Processing of maize grains cultivation in vitro in Exp. 2 and Exp.
3. CK, control treatment. DS, drought stress treatment. HS, heat stress
treatment. DHS, combined drought and heat stress treatment.
FIGURE 2 (a) Time courses of average soil water potential and
temperature in Exp. 1 and Exp. 2. (b) Time courses of soil water content
and temperature in Exp. 3. CK, control treatment. DS, drought stress
treatment. HS, heat stress treatment. DHS, combined drought and heat
stress treatment.
FIGURE 3 Schematic diagram of logistic curve (black color),
where W is the kernel weight (mg), K is the final kernel weight (mg), t
is the time after pollination. a, b are coefficients determined by
regression. Phase I: The slow-increase period (d); Phase Ⅱ: The
fast-increase period (d); Phase Ⅲ: The slight-increase period (d).
FIGURE 4 Effects of drought, heat and combined drought and heat
stress around flowering on kernel numbers and 1000-kernels weight at
physiological maturity. (a) The kernel numbers in Exp. 1. (b) The
1000-kernels weight in Exp.1. (c) The 1000-kernels weight in Exp. 2.
Values with the same letter are not significantly different atP <0.05 within the same parameter of each hybrid. Bars
denote the standard error of the mean (n=4). CK, control treatment. DS,
drought stress treatment. HS, heat stress treatment. DHS, combined
drought and heat stress treatment.
FIGURE 5 Effect of drought, heat and combined drought and heat
stress around flowering on grain dry matter accumulation. (a) The
changes of 1000-kernels weight in superior and inferior grains in Exp.
1. (b) The 1000-kernels weight in superior and inferior grains in Exp.
2. Values with the same letter are not significantly different atP <0.05 within the same parameter of each hybrid. Bars
denote the standard error of the mean (n=4). CK, control treatment. DS,
drought stress treatment. HS, heat stress treatment. DHS, combined
drought and heat stress treatment.
FIGURE 6 Effect of drought, heat and combined drought and heat
stress around flowering on leaf area, SPAD and net photosynthesis (Pn;
μmol CO2 m-2 s-1).
(a) The changes of leaf area in Exp.1. (b) The changes of SPAD in Exp.1.
(c) The changes of net photosynthesis in Exp.1. (d) The relationship
between 1000-kernel weight and leaf area reduction at maturity. (e) The
relationship between 1000-kernel weight and SPAD reduction at maturity.
(f) The relationship between 1000-kernel weight and net photosynthesis
reduction at maturity. Values with the same letter are not significantly
different at P<0.05 within the same parameter of each hybrid.
Bars denote the standard error of the mean (n=4). CK, control treatment.
DS, drought stress treatment. HS, heat stress treatment. DHS, combined
drought and heat stress treatment.
FIGURE 7 The soluble sugar content and starch content in
superior and inferior grains under drought, heat and combined drought
and heat stress around flowering. (a) The changes of soluble sugar in
Exp. 3. (b) The changes of starch content in Exp. 3. Values with the
same letter are not significantly different at P<0.05 within
the same parameter of each hybrid. Bars denote the standard error of the
mean (n=4). CK, control treatment. DS, drought stress treatment. HS,
heat stress treatment. DHS, combined drought and heat stress treatment.
FIGURE 8 Enzymes activity related to starch synthesis in
superior grains and inferior grains under drought, heat and combined
drought and heat stress around flowering in Exp. 3. (a) The sucrose
invertase activity in superior and inferior grains. (b) The sucrose
synthase activity in superior and inferior grains. (c) The ADP Glc
pyrophosphorylase activity in superior and inferior grains. (d) The
starch synthase activity in superior and inferior grains. Values with
the same letter are not significantly different atP <0.05 within the same parameter of each hybrid. Bars
denote the standard error of the mean (n=4). CK, control treatment. DS,
drought stress treatment. HS, heat stress treatment. DHS, combined
drought and heat stress treatment.
FIGURE 9 Hormone content in superior grains and inferior grains
under drought, heat and combined drought and heat stress around
flowering in Exp. 3. (a) The ZR content in superior and inferior grains.
(b) The IAA content in superior and inferior grains. (c) The
GA3 content in superior and inferior grains. (d) The ABA
content in superior and inferior grains. Values with the same letter are
not significantly different at P<0.05 within the same
parameter of each hybrid. Bars denote the standard error of the mean
(n=4). CK, control treatment. DS, drought stress treatment. HS, heat
stress treatment. DHS, combined drought and heat stress treatment.
FIGURE 10 A schematic diagram of how drought, heat and combined
drought and heat stress around flowering reduced kernel weigh. CK:
control treatment; DS: drought stress treatment; HS: heat stress
treatment; DHS: combined drought and heat stress treatment. Solid line
indicated superior grain. Dotted line represented the inferior grain.
The three lines from left to right represent DS, HS and DHS stress. The
line thickness represents the influence degree of stresses.