704 Colchicine 



elongation. The volumes oi cells Ironi a c-tiinior are about the same 

 as the volumes of elongated cells in untreated roots. '^- Therefore, the 

 direction of growth is modified, but not necessarily the total amoimt 

 of expansion. •'- 



Cells of the cortex liccome inllatcd."" This leads to a swelling at 

 the particular place along the root. Longitudinal and cross sections 

 of treated and untreated roots within five or six layers of cells show 

 where the change occurs, and reveal particularly the difference in 

 the shape of individual cells. These comparative studies confirm the 

 opinion that direction of gro^vth is altered when colchicine is j^rcs- 

 ent. The action is not iniiquc for colchicine. Growth-promoting 

 substances, as naphthaleneacetic acid (NAA) and indolebutyric acid, 

 induce tumors.^'- ^^' ^^- ■*-• -"■ ''' 34, 44, 79, si, 59, ei Acenaphthene, another 

 compound that has a c-mitotic potential, may cause tumors on roots. ^^^ 

 Not all compounds that create tumors arrest mitosis. In fact, certain 

 phytohormones that do not stop mitosis may induce root tip enlarge- 

 ments. I'he idea of an autonomy of c-mitosis and c-tumors gains sup- 

 port from these general observations with several chemicals. ^- 



Specific thresholds below which no tumors form, are demonstrable 

 for colchicine. Concentration specificity is shown also by NAA.^^ If 

 t^vo solutions, colchicine and NAA, are combined, the threshold con- 

 centration docs not change. *i There is no evidence that two solutions, 

 each capable of inducing tumors alone, will in combination lower 

 the threshold value. Thus, the mechanism for creating the tumor 

 may be different for these particular substances. ^^^ The threshold 

 changed, however, when sulfonamide (2 per cent prontosil) was 

 added to colchicine. •• •■'•' 



The combined solutions of ???r5o-inositol and colchicine prevented 

 the usual j^roduction of a c-tumor with roots of AUhim.^^ Apparently 

 this antagonism by ///^,90-inositol operates at 19°C. since a repetition 

 at 26°C. did not reveal such antagonism.-*^' The critical role of tem- 

 perature is seen in pollen tube enlargements, where the maximum 

 width induced by colchicine occurs only at a sj)ecific temperature. ^-''^ 

 Above or below that optinumi the pollen tubes are close to normal 

 dimension in spite of the same concentration of colchicine present in 

 each test. 



Venom from bees was demonstrated to have an antagonistic action 

 upon the formation of root timiors by colchicine."'-' The specific dif- 

 ferences between kinds of j)lants was also shown. Tomatoes were 

 more sensitive than wheat seedlings. .\ ()9 per cent reduction of 

 tumors was obtained for tomatoes and 47 per cent with wheat."^^- ^^ 



Ethyl alcohol changes the c-mitotic ihreshold for Allium root cells 

 from 0.006 per cent, when colchicine alone is used, to 0.01 per cent 

 if alcohol (O.T) per cent) is added. If tlie concentration of alcohol is 



