Abstract
Shorter grain-filling period and rapid endosperm development endow weedy rice (WR) with early maturity compared to cultivated rice (CR). However, the role of the cytological features and antioxidative enzyme system during grain development are largely unexplored. We selected four biotypes of WR and their associated cultivated rice (ACR) types from different latitudes to conduct a common garden experiment. The difference in the cytological features of endosperm between WR and ACR was compared by chemical staining, and the cell viability and nuclear morphometry of endosperm cells were observed by optical microscopy. Furthermore, antioxidative enzyme activity was measured during grain filling. Anatomic observation of endosperm shows that the development process of endosperm cell in WR was more rapid and earlier than that in ACR. The percentage of degraded nuclei of WR was 2–83% more than that of ACR. Endosperm cells in WR lost viability 2–6 days earlier than those in ACR. The antioxidant enzyme activity of WR was lower than that of ACR during grain filling. The ability of WR to scavenge reactive oxygen species (ROS) was weaker than that of ACR, which may contribute to the rapid cytological process in the endosperm cells of WR. The rapid cytological process and weaker ability to scavenge ROS in endosperm cells may contribute to early maturity in WR.
Highlights
Weedy rice (Oryza sativa L. f. spontanea, weedy rice (WR)) has become one of the most harmful weeds in paddy fields worldwide (Azmi and Karim, 2008; Burgos et al, 2014; Kraehmer et al, 2016; Zhao et al, 2018, 2020)
Morphological and statistical results of starch endosperm cell nuclei of WR and associated cultivated rice (ACR) at 3, 5, 7, and 9 days post anthesis (DPA) are shown in Figures 1, 2
After DAPI staining, 100% of the nuclei of the endosperms of FIGURE 1 | 4,6-Diamidino-2-phenylindole staining of endosperm nucleus in weedy and cultivated rice. (A1–A4): weedy rice from Taizhou, TZWR; (B1–B4): cultivated rice from Taizhou, TZCR; (C1–C4): weedy rice from Yangzhou, YZWR; (D1–D4): cultivated rice from Yangzhou, YZCR; (E1–E4): weedy rice from Maoming, MMWR; (F1–F4): cultivated rice from Maoming, MMCR; (G1–G4): weedy rice from Dandong, DDWR; (H1–H4): cultivated rice from Dandong, DDCR
Summary
Weedy rice (Oryza sativa L. f. spontanea, WR) has become one of the most harmful weeds in paddy fields worldwide (Azmi and Karim, 2008; Burgos et al, 2014; Kraehmer et al, 2016; Zhao et al, 2018, 2020). WR has many morphological and physiological characteristics related to weediness, such as a rapid growth rate, high phenotypic plasticity, early maturity, seed shattering, long seed dormancy, and longevity, which facilitate seed dispersal and persistence in paddy fields (Azmi and Karim, 2008; Burgos et al, 2014; Dai et al, 2014, 2017; Zhao et al, 2018, 2020) These characteristics contribute to its competitive advantage over CR in rice production areas globally (Delouche et al, 2007)
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