Chronic acceleration in plants

Since this subject was last reviewed (at the Symposium on Gravity and the Organism, 1967), relatively little new work on hypergravity effects on plants has appeared. Centrifugation has been used widely for separation of cellular components, but only occasionally as a primary environmental condition. With increasing magnitude of accelerative forces, the following effects have been reported by a number of authors working with many different plants. In the range 2-25 g, auxin transport and geotropic response in coleoptiles are increased and growth is stimulated. From 25 to 500 g, coleoptile growth is reduced and some morphological changes may be seen. At 1000-2500 g, root formation in willow cuttings increases. From 1000 g upward, cytoplasmic stratification occurs and seed germination decreases. Between 200 and 15000 g, chromosome damage has been observed. Algal cell polarity may be reversed at 5000 to 20000 g. Above 30000 g, the response of some cells to gibberellic acid is halted. Permanent morphologic changes in Escherichia coli are produced at 110000 g. Some plant cells have survived 176000 g for 20 hr.