GROWTH OF SOMATIC TOBACCO CELLS IN MICROCULTURE

J ones , L. E. (Oregon State Coll., Corvallis), A. C. H ildebrandt , A. J. R iker , and J. H. Wu. Growth of somatic tobacco cells in microculture. Amer. Jour. Bot. 47(6): 468–475. Illus. 1960.—Somatic cells of hybrid tobacco ( Nicotiana tabacum × N. glutinosa ) grew more than 4 mo. in microcultures in which critical microscopic observations could be made. Microchambers were made aseptically by placing cells in a droplet of medium on a cover slip that was inverted onto a standard microscope slide with a ring of paraffin oil (U. S. P. Heavy Mineral Oil) and 2 coverslip risers. Growth of single cells was good in a medium previously “conditioned” by a mass of growing cells. The cells divided, enlarged, differentiated, and became senescent. Mitosis was timed in somatic cells in microcultures. During prophase the streaming cytoplasm formed distinctive strands suspending the nucleus and then entered a state of “fixed‐tension” in which there was no massflow of organelles. Reversion of the cytoplasm to the usual fluid‐flow condition followed cytokinesis.Senescence and impending death in undisturbed, mature, parenchyma cells were preceded by concatenation of the discrete round‐oval mitochondria into filiform aggregates. A few “giant” parenchyma cells rejuvenated by forming discrete, free‐floating, endogenous cells. When placed in microcultures, the endogenous cells grew into daughter populations that appeared normal.Tobacco cells in microcultures provided a unique experimental material for cytological and cytochemical studies of growth, differentiation, senescence, and rejuvenation in living, somatic, angiosperm cells that were free of artifacts and protected from reactions to shock.