| Structural variation in the nucleus and organelle during endosperm development in rice (Oryza sativa L.) was systematically investigated with light-, transmission electron microscopy. The main results were as follows:1. Amyloplast had many ways of genesis and patterns of proliferation in endosperm cell of rice. Amyloplast might be formed either directly from proplastid or following dedifferentiation of mitochondria, endoplasmic reticulum (ER), annulate lamella (AL) in endosperm cell. These organella showed monomorphic development. There were five different patterns of amyloplast proliferation (amyloplast being formed from amyloplast). The budding, constricting, forming the middle plate of amyloplast were common patterns of amyloplast proliferation, which resulted from the actions of the outer membrane, the inner and outer membrane, the inner membrane respectively. The double membrane vesicle, which was produced by budding of the outer membrane of amyloplast, accumulated starch to form new amyloplast. The double membranes of amyloplast invaginated and the inner membrane dilated to form new amyloplast in the amyloplast.2. Formation of protein body in the endosperm cell. Rapid proliferation of the rough endoplasmic reticulum (RER) and the formation of protein body in endosperm cell were initiated 5 days after flowering. There were two kinds of protein bodies (PBs): FBI and PBII, their protein was all synthesized in RER, but they were formed differently. FBI occurred by two patterns of storage protein accumulation in the cisterna of RER and the circular RER. Two patterns of formation of PBII were noticed. In one of them, the storage protein deposited onto some regions of the inner surface of the big vacuole and new protein bodies were formed by a budding off process of the vacuole. In the other pattern, storage protein accumulated in small vacuole. At late stage of protein body development, the fragments of RER formed circular RER, then turned into vesicles and small PBs. Abundant RER was present around the PBs during protein deposition. RER derived vesicles were involved in the transport of protein from the site of synthesis (RER) to the site of accumulation.3. ER was greatly active in endosperm development, which showed that it had many functions. ER took part in cell wall material deposition during endosperm cell construction. ER rounded up matrix forming endocytic vacuole. ER cisterna swelling and accumulating starch developed into amyloplast. ER took part in protein synthesis and deposition, played a core role in protein body formation. ER swelled at the end to formmany vesicles. ER was associated with the plasmodesmata, helped transporting nutrients at the development and differentiation stage.4. Relations between plasmalemma invagination and nutrient transportation. The plasmalemma of endosperm cell showed invagination with developing and differentiating. Some vesicles and many endoplasmic reticulum elements were associated with the plasmodesmata. Plasmalemma appeared undulated, but occasionally pocketable and variable in size with conspicuous invaginations. Some invaginations were separated from plasmalemma to form sacs in the peripheral cytoplasm. Some spherical inclusions appeared in the intercellular space, the plasmalemma invaginations and the sacs. H+-ATPase localization showed high enzymic activity in the plasmalemma and vesicles beside the plasmalemma. Activity of acid phosphatase was observed in the vacuole, the intercellular space and its vesicular contents. The plasmalemma and sacs in the peripheral cytoplasm exhibited high activities of glucose-6-phosphatase (G6Pase).5. Degeneration of starchy endosperm nucleus. With the development of starchy endosperm cells, several distinct morphological features of PCD existed in nucleus, such as deformation of nucleus, condensation of chromatin, swelling of perinuclear space, disruption of nuclear envelope, and leakage of nuclear matrix. DNA ladder showed that there were some smear large DNA fragments in nucleus whereas...
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