4.3 Physical mechanisms of grain yield penalty caused by WL4
We found that the greatest reductions in grain yield occurred when
waterlogging treatment was applied close to heading, even though the
duration of waterlogging was very short (WL4; Fig. 2). This finding is
in line with previous results (de San Celedonio et al., 2014; Setter &
Waters, 2003). For WL4, lower grain yield was attributed lower grain
weight and to a lesser extent, lower kernels per spike. In this
treatment, waterlogging caused premature leaf senescence in waterlogging
sensitive genotypes. It has been reported that reduced leaf greenness
coincides with lower stomal conductance (Araki, Hamada, Hossain, &
Takahashi, 2012), photosynthetic rate (Hossain et al., 2011) and
water-soluble carbohydrates (Araki et al., 2012). Assimilate from
photosynthesis and remobilization of culm residual water-soluble
carbohydrates reserves are important for grain filling in crops (Kamran
et al., 2020; Schnyder, 1993). Therefore, reduced carbon assimilation
rates and lower remobilization of culm reserves in waterlogged plants
may have resulted in lower grain growth rate during the grain-filling
period of WL4.