Early maturity is an essential factor determining the persistence of weedy rice by contributing to the escape of its seed from being harvested with the rice crop. Both early flowering and shorter grain-filling stages determine early maturity, and flowering is more plastic than grain filling. © 2017 Society of Chemical Industry.
Early maturity allows weedy rice (Oryza sativa L. f. spontanea) to persist by escaping harvest in paddy fields. A shorter grain-filling period contributes to the early maturity of weedy rice. However, the differences in morphology and endosperm development in the caryopsis between weedy and cultivated rice are largely unexplored. Here, we selected four biotypes of weedy rice and associated cultivated rice (ACR; Oryza sativa) from different latitudes to conduct a common garden experiment. The endosperm development process of the caryopsis was observed by optical microscopy and electron microscopy. Endosperm cell division and starch accumulation rate during grain filling were also measured. The grain development progress in weedy rice was more rapid and earlier than that in ACR. The endosperm development progress of weedy rice was 6 to 8 d earlier than that of ACR. The endosperm cells of weedy rice cellularized earlier and more rapidly than those of ACR, and the starch grains of weedy rice were more sharply polygonal and compactly arranged than those of ACR. The active endosperm cell division period in weedy rice was 4 to 7 d shorter than that in ACR, while the active starch accumulation period of weedy rice was 2 to 8 d shorter than that of ACR. The rapid development of endosperm cells and starch grains leads to the shorter grain-filling period of weedy rice. weedy rice.
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.
Background: Shorter grain-filling period and rapid endosperm development contributes to early maturity in weedy rice (Oryza sativa L. f. spontanea). However, the differences in programmed cell death (PCD) process and anti-oxidative enzymes system in the caryopsis between weedy and cultivated rice are largely unexplored. Main Text: we selected four biotypes of weedy rice and associated cultivated rice (ACR, Oryza sativa) from different latitudes to conduct a common garden experiment. The difference of PCD process between weedy rice and ACR was compared by chemical staining, and the cell viability and nuclear morphometry of endosperm cells were observed by optical microscopy, and anti-oxidative enzymes activity were also measured during grain filling. We found that the PCD progress in weedy rice was more rapid and earlier than that in ACR. The percentage of degraded nuclei of weedy rice were 10%-83% higher than that of ACR. Endosperm cells in weedy rice lost cell viability 2-8 days earlier than that in ACR. The anti-oxidant enzymes activity of weedy rice were lower than that of ACR during grain filling. The ability of weedy rice to scavenge reactive oxygen species is weaker than that of ACR, which may contribute to the rapid PCD process in the endosperm cells of weedy rice. Conclusion: The rapid PCD process and weaker ability to scavenge reactive oxygen species in endosperm cells lead to the shorter grain-filling period of weedy rice.
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