Nucleus and Chromosomes 



57 





Consequences of c-ii}itoses: polyploidy in plants. The arti- 

 ficial induction ol jjolyploidy by colchicine was not a new discovery 

 in plant science. Doubling of chromosomes was demonstrated in 

 jilant cells as early as 1904.'^- Dining a long and successful teaching 

 career, Professor C. F. Hottes, University of Illinois, repeatedly ovit- 

 lined cytophysiological methods for inducing polyjjloidy in root tip 



12h. 



18 



24 



48 



72 



1j 



1 



■ ■ 



I ■ 



- ■ ■ I 



Fig. 2.12 — Regenerating liver of the rat, after a single injection of colchicine. Schematic 

 drawings of the various types of restitution nuclei: (1) exploded metaphase with scat- 

 tered chromosomes, (2) fusion of some of these chromosomes, (3) micronuclei, (4) fusion 

 of the micronuclei (compare with Fig. 2.4), (5) three nuclei, (6) abnormal mitosis with 

 partially inactive spindle, (7) normal mitosis. The percentages of these types of cell- 

 ular changes at various intervals after colchicine are expressed by the black rectangles. 

 Normal mitoses are only found 72 hours after the injection, and restitution appears to 

 proceed by the fusion of the micronuclei. (After Brues and Jackson) 



cells. Specific polyploid plants were induced by regeneration tech- 

 niques with mosses in 1908 by the Marchals. Later, polyploids were 

 created among the flowering plants by Winkler in 1916 and similar 

 work w^as continued by W'cttstein, Jorgcnsen, Lindstrom and Koos, 

 and Greenleaf from 1924 to 1934. An early suggestion for inducing 

 polyploidy by temperature change was made by John Belling in 

 1925.'' The temperature shock technique was later standardized sue- 



