96 



Colchicine 



Just how tar this accumulation can continue with hope for re- 

 versibility to normal was answered by an elaborate test that required 

 a series extending over a long time. About 500 chromosomes is the 

 upper limit beyond \vhich no recovery can be expected, Inii 128 and 

 (il make the most rajjid rccoverx to bipolar spindle. -^-^ 



Lethal or toxic effects have been disregarded, but the drug has a 

 gro^vth-dcpressing influence if shoot gro^vth is the index. Hie effects 



Xv- • '.<•■• 



^t:- 



V vxi - 



/ 











/^■■' 





Fig. 3.9 — Allium root cell treated with 0.05 per cent colchicine 32 hours, then fixed and 

 stained with iron alum haemotoxylin. The lower cells show chromosomes around the 

 pseudospindle. Shortened mitochondria do not penetrate the area of the pseudospind!e. 

 Large restitution amoeboid nucleate ceil not in c-mitosis. (Adapted from Mongenot, 1942) 



of the poison may be expressed in giowih differences between treated 

 and control plants. Controls had leaf shoots 34 cm. long on the 

 se\enth day; .01 per cent of the treated j^lants grew to 15 cm. (about 

 one-half), and 0.1 per cent of the plants \vere reduced one-lourih, to 

 8 cm.''-'' 



j.cV— 2; Rccox'cry in (ininutls. Recovery anahses in animals pre- 

 sent difficulties not met in jjlant cells because animal cells are not able 

 to survive as long.-'^' ^'^^ """^ A c-mitotic dose frequently becomes lethal 

 to the animal, an effect that precludes recovery. Another difficulty is 

 the \ariation in toxicity between animals as ^vell as the dilierences 

 when dealing with warm-blooded and cold-blooded animals, and/or 

 tissue cultures. •^■^' '^^ 



