Geoscience Reference
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maximum temperature on crop yields was insignificant. Peng
et al. (2004) provided evidence in support of statements that
decreased rice yields from increased nighttime temperature was
associated with global warming. Temperature and radiation had
statistically significant impacts during both the vegetative and
ripening phases of the rice plant. Welch et al. (2010) concluded
that diurnal temperature variation must be considered when
investigating the impacts of climate change on irrigated rice
in Asia. Higher temperatures can adversely affect rice yields
through two principal pathways, namely (i) high maximum
temperatures that cause—in combination with high humid-
ity—spikelet sterility and adversely affect grain quality, and (ii)
increased nighttime temperatures that may reduce assimilate
accumulation. On the other hand, some rice cultivars are grown
in extremely hot environments, so that the development of rice
germplasm with improved heat resistance can capture an enor-
mous genetic pool for this trait. The results show that high night
temperature compared with high day temperature reduced the
final grain weight by a reduction in grain growth rate in the
early or middle stages of grain filling, and also reduced cell size
midway between the central point and the surface of the endo-
sperm (Morita et al., 2005). In the Philippines, rice production
may decline up to 75% by 2100 because of global warming
and Filipinos will have to settle for meals with little or no rice
unless the government aggressively implements climate change
adaptation programmes (Antiporda, 2013). Transpiration from
rice panicles can help lower the temperature of the panicle,
which is the susceptive organ for high-temperature-induced
spikelet sterility. By increasing the transpiration, the heat dam-
age to the panicle predicted to occur due to global warming
may be avoided. To examine the possibility of genetic improve-
ment in transpiration conductance of intact rice panicles (
g
pI),
we measured
g
pI at the time of flowering in the open field in
21 rice varieties of widely different origins. Thus, the target of
improvement in
g
pI against high-temperature-induced spikelet
sterility should be set at the level of the existing varieties with
the highest
g
pI (Fukuoka et al., 2012). Tao et al. (2008) stud-
ied the impact of global warming on rice production and water
use in China, against a global mean temperature. They found
the median values of rice yield decrease ranged from 6.1% to
18.6%, 13.5% to 31.9% and 23.6% to 40.2% for GMT changes of
1°C, 2°C and 3°C, respectively. Yoshimoto et al. (2010) synthe-
sised a process-based model study in tandem with FACE exper-
iments for studing the effects of climate change on rice yields
in Japan. They found that it not only contributes to reducing
