Developmental Genetics of Plastid Populations
Spirogyra provides an outstanding example of plastid division closely and inseparably connected to cell division, except for occasional breaks (Hill 1916, Lewis 1925) or furcations of chloroplasts (see, for instance, Kasanowsky 1913). The chloroplasts might be passively cut in two by the new cell wall, as assumed by Klopfer (1934), or they might withdraw from the wall, showing some kind of active division, as held by Mühldorf (1951). There is no cyclic variation of chloroplast numbers in vegetative cells of Spirogyra. A readjustment of the time of cell division (normally at about midnight) to another time of the day (Strasburger 1880) definitely entrains a readjustment of the time of chloroplast “division”. The highly complicated chloroplast of Surirella is likewise cut in two by the daughter valves (Karsten 1928). Løvlie and Bråten (1968) report a similar division in Ulva.
KeywordsSugar Beet Guard Cell Mesophyll Cell Basic Number Extra Chromosome
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