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RESEARCH PRODUCT

Cell Cycle in Potentially Dedifferentiating Cereal Mesophyll Protoplasts Cultured in vitro. I. Abnormalities in Cycle Kinetics

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Summary Protoplasts isolated from immature and mature mesophyll of wheat and oats were cultured in vitro . The potential progression from G1 (G0) to G2, through mitosis and cytokinesis was analysed. The degree and speed of progression through the cell cycle depended on the species and the state of maturity of the tissue from which the protoplasts were derived. In all the protoplast populations that were tested at least initiation of DNA synthesis was detected by labelling nuclei with the thymidine-analogue, bromodeoxyuridine (BrdU). Protoplasts derived from mature leaf tissue of wheat appeared to be recalcitrant to reach G2. Wheat protoplasts derived from immature leaf tissue appeared to progress slowly from G1 to G2 and they were incapable of mitosis. Protoplasts of oats showed mitosis. Progression through cytokinesis, if occurring, appeared to be sluggish, particularly in protoplasts derived from mature leaf tissue. Sustained cell division was not observed. The results are discussed in the context of coordination and regulation of the cell division cycle in plants and the recalcitrance of cereals in tissue culture.