Cellular Growth 107 



I 



responses were obtained from colchicine applied to the Avena, Heliaii- 

 thiis, and Pisum tests. ^i"' Colchicine is not a phytohormone, but the 

 basic relation between gro\\th responses shown by tumors and the 

 reactions noted lor phytohormones in causing cell enlargement is not 

 understood. There are numerous cases reported where colchicine 

 (hanged growth rates. 



Resistance to colchicine by cells of Colchiciim was demonstrated 

 under the secticjn dealing with c-mitoses. A similar resistance can be 

 proved with colchicine and tumor formation. Enough species of 

 Colchiciiin were tried to give conclusive proof of a resistance. '^^^ ^^' ^' ^^ 

 Not all plants supposedly containing colchicine are resistant as tested 

 l)\ the tumor test.**^ The resistance shown by tumor experiments is 

 not proof of a c-mitotic resistance, and vice versa. This point was 

 not always apj)rcciatcd because the independence of the two pro- 

 cesses was not understood until specific tests were finished. 



Golden hamsters showed resistance to colchicine under laboratory 

 conditions.'"' This specific resistance may be explained in the follow- 

 ing way: Animals inhabiting regions where Colchician is found 

 Avould come in contact with seeds, fruits, leaves, and corms of the 

 jjlant and would consume amounts of varying strength. Enough col- 

 chicine ^\■ould be present to kill suscejjtible individuals, while others 

 might sinvi\e. Therefore, by selection in nature the hamster may 

 have acquired this specific resistance. 



4.2: Effects of Colchicine on Pollen Tubes, Hair Cells, and Other 

 Parts of Plants 



The number of chromosomes per pollen tube does not increase 

 after c-mitosis in the generative cell.'^"'' ^^~ An enlarged pollen tube 

 is independent of the action of colchicine upon the nucleus. When 

 a pollen grain germinates in artificial media, a tube grows out and 

 away from the grain (Fig. 4.2) . Such filaments are very narrow and 

 elongation of the tube is polarwise. Colchicine decreases the length 

 and increases the width of a tube. An enlargement e\'en greater than 

 the grain itself may occur (Fig. 4.2) . These are the pollen tube 

 tumors. .\ stimulation has been reported when hormones are added 

 to cultures with colchicine. '"^^ i-^*' 



A lateral expansion is comparable to the isodiametric extension 

 of ro(jt oi hyjjocotyl cells. Ihe tubes seem to "bloat" or inHate like 

 balloons (Fig. 4.2F) . Since there is no bursting, the increase must 

 take place by an orderly deposition of cell wall material forming the 

 tube.-^"' Colchicine causes these pollen tube enlargements. AVhen the 

 concentrations are of low dosage, a stimulation is observed. i''"- ''■ 



An interaction between concentration and tempcratme condition 

 \vas expressed in measurements with calculated averages of pollen 



