Endosperm development in Zea mays is characterized by a period of intense mitotic activity followed by a period in which mitosis is essentially eliminated and the cell cycle becomes one of alternating S and G phases, leading to endoreduplication of the nuclear DNA. The endosperm represents a significant contribution to the grain yield of maize; thus, methods that facilitate the study of cellular kinetics may be useful in discerning cellular and molecular components of grain yield. Two mathematical models have been developed to describe the kinetics of endosperm growth. The first describes the kinetics of mitosis during endosperm development; the second describes the kinetics of DNA endoreduplication during endosperm development. The mitotic model is a modification of standard growth curves. The endoreduplication model is composed of six differential equations that represent the progression of nuclei from one DNA content to another during the endoreduplication process. Total nuclei number per endosperm and the number of 3C, 6C, 12C, 24C, 48C, and 96C nuclei per endosperm (C is the haploid DNA content per nucleus) for inbred W64A from 8 to 18 days after pollination were determined by flow cytometry. The results indicate that the change in number of nuclei expressed as a function of the number of days after pollination is the same from one yearly crop to another. These data were used in the model to determine the endosperm growth rate, the maximum nuclei number per endosperm, and transition rates from one C value to the next higher C value. The kinetics of endosperm development are reasonably well represented by the models. Thus, the models provide a means to quantify the complex pattern of endosperm development.Changes in mitosis and DNA content appear to be fundamental events in normal endosperm development in Zea mays (maize) (1, 2). Maize is a major source of food and feed throughout the world. The endosperm makes up '80% of the mature kernel weight. Elucidating the cellular and molecular events that contribute to normal endosperm development may provide a better understanding of the components of grain yield and afford the possibility to manipulate these components to alter grain yield.Maize endosperm begins as a triploid tissue resulting from the union of two polar nuclei and one sperm nucleus. After fertilization, endosperm growth is the result of increases in both cell number and cell size. For the first 4 days after pollination (DAP), the endosperm nuclei divide synchronously without cell wall formation. At 4 DAP, cell walls are laid down, and the tissue changes from a multinucleate, single cell to a uninucleate, multicellular morphology. From this time forward, the nuclear divisions are asynchronous. The mitotic index peaks between 8 and 10 DAP and then plummets (3). AsThe publication costs of this article were defrayed in part by page charge payment. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. §1734 solely to indicate this fact.the mitotic index decre...
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