An Examination of the Effects of Ultracentrifugation on the Organelles in Living Root Tip Cells

Bouck, G. Benjamin. (Yale U., New Haven, Conn) An examination of the effects of ultracentrifugation on the organelles in living root tip cells. Amer. Jour. Bot. 50(10): 1046–1054. Illus. 1963.—Excised pea roots were centrifuged at 20,000 g for various periods to determine the speed and order of stratification of living plant organelles; 20,000 g for 24 hr at 6 C seems to produce the most consistent layering with least damage to the organelles or to the root as a whole. The recovery of the cells was then followed to determine how fast and in what order the organelles achieve a random redistribution. Rough endoplasmic reticulum seems slow to stratify in its ultimate position at the centrifugal pole but is among the first of the organelles to reorient after centrifugation. Proplastids, large vacuoles, and the nucleolus are slow to recover from centrifuging, but after 8 hr of recovery only the nucleolus and very large vacuoles show indications of a previous layering. Within 12 hr after removal of the root from the centrifuge, growth (in length) of the whole root could be measured.