CHAPTER 11 



The Experimental Polyploids 



11.1: 1937 — Beginning of a New Era in Polyploidy 



Colchicine replaced practically all the techniques used to double 

 the number of chromosomes in plants. The procedure was new and 

 could easily be fitted to many different kinds of plants. Within a 

 short time geneticists became convinced that a very useful tool had 

 been discovered, because colchicine methods were more effective and 

 more suitable for making polyploids, plants with additional sets of 

 chromosomes, than any formerly used. 



Immediate and wide universal interest in colchicine developed 

 among botanists, as shown by the rapid rise in popularity that fol- 

 lowed closely upon the announcements of chemical induction of 

 chromosomal doubling.'^' 12.52,53.62 \ ^ew era in polyploidy investi- 

 gations began in 1937, the year the colchicine method was discov- 

 ered.36. 72 



Soon the advantages of colchicine became clear. One out of 600 

 cotton plants treated by "heat-shock" became polyploid (1:600), but 

 colchicine procedures applied to a comparable group yielded 50 poly- 

 ploids from among 100 (1:2) of the cotton plants surviving the 

 chemical treatment. ^ Similarly the superiority of colchicine was dis- 

 covered by workers at the chromosome laboratory, Svalof, Sweden, 

 where up to the time colchicine was introduced, elaborate heat- 

 shock machinery, with refrigeration controls, had been used to double 

 the number of chromosomes.^^ Swedish botanists soon discovered that 

 such complicated equipment was no longer necessary.^*' A rapid 

 change-over to colchicine took place.-**. 3. 8-'i4, 16, 20, 21. 23, 25, 20. 3... 32, 4i. 



43, 46, 51, 50, 54, .50, 57, 58, 59, 63. 64, 05, 60, 69, 70, 73, 74 TllC Switcll tO Colchi- 

 cine in Sweden and elsewhere was so fast that it appeared that the 

 colchicine "fad" in research had arrived.'-' -^ 



As we mentioned in Chapter 2, colchicine was not the first chemi- 

 cal to be tried and used for doubling of chromosomes. Other chemi- 

 cals, heat-shock methods,!^ production of callus tissue,'**^ and other 



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