Colchicina

T H E EFFECT OF COLCHICINE O N ROOT
M ITOSES I N ALLIUM
BY

ALBERT L EVAN

H I L L E S H ~ G ,LANDSKRONA, SWEDEN

A

FTER BLAKESLEE nd AVERY ( 1937) h ad made the sensational
a
discovery of the induction of chromosome doubling by colchicine
treatment it became a question of prime importance to investigate the
cytological mechanism causing this doubling. It has long been known
thatcolchicine acts disturbingly on the normal course of mitosis
(DIXON,1905). DUSTIN(1934) and LITS ( 1934) regarded colchicine as
a very active agent for increasing the numher of mitoses in a tissue
( a ,poison caryoclasique,). LUDFORD( 1936), however, came to the
conclusion that the increase in the number of the mitoses after colchicine
treatment was due to an ,accumulation of arrestedmitoses)) rather than
to a stimulation process. He attributed this effect to a ,failure of t he
mitotic spindle to form and function in the normal manner)). NEBEL
a nd RUTTLE( 1938), who first studied the effect of colchicine on plant
cells (stamen hairs of T radescantia), arrived at a similar result.
The material of the experiments dealt with in the present paper
consists of root tips of Allium fistulosum and Cepa. Root tips of
A. fistulosum were secured from bulbils that had overwintered in the
field, while in the case of A . Cepa large bulbs were used, The f istulosum
form used had a hybrid chromosome garniture, consisting of somatically
15 medially attached chromosomes and 1 typical fistulosuni s1 ( LEVAN,
1936, Fig. 1 b ). The Cepa f orm had the chromosomes characteristic
ofthis species, v iz. 14 medially and 2 subterminally attached chromosomes (LEVAN,1. c., Fig. 1 a ) .
The experiments were arranged in the following way. Bulbs with
rapidly growing root tips, O , . s l , o cm in length, were immersed for exposure into colchicine solutions during periods of different length. Root
tips were then fixed at certain intervals after the transfer of t he bulbs
from thecolchicine solutions into pure water. The fixations were made
in NAVASHIN nder air evacuation. The material was embedded and
u
u
cut into transverse and longitudinal sections, the former being 20 ,
in thickness, the latter 20-30 p . T he slides were stained in gentian
violet, some also in ,lichtgriin,.

4i2

A LBERT LEVAN

I . DESCRIPTION O F THE TYPICAL COURSE OF T HE

C-MITOSIS,
Inthe first series of experiments the conditions were the following:
Concentrations of colchicine: 0,125, O,%, 03, 1,0, 2,o % .
Exposure times: 7, 15, 30 min., 1, 2, 24, 72 hours.
Fixing took place: 0, 15, 30 min., 1, 3, 6, 12, 24, 48, 72 hours after
finishing the colchicine treatment.

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a

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Pi i
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b

e

C

f

h

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d

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j

k

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rn

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IP

Fig. 1. The first stages in the development of the c-pairs. - x 3900.

I

T he effect of colchicine on the course of mitosis is entirely specific,
and the modification in mitotic’ behaviour will be abbreviated B Cmitosis,. The c-mitosis can be referred to one single moment, u iz. a n
inactivation of the spindle apparatus connected with a delay of the
division of the centromere. Theeffect thus produced may be expressed
as a completion of the chromosome mitosis without nuclear o r cellular
mitosis.
The prophase stages take place normally: the chromosomes divide,
condense, and assume metaphase appearance. They are, however, not
arranged into an.equatoria1 plate. Instead they are all the time
scattered over the cell in a diakinesis-like manner. This condition lasts

473THE EFFECT OF COLCHICINE

for a long time after-the disappearance of the nuclear membrane. The
halves of each chromosome are seen to be coiled around each other in
a relational spiral (Fig. 1 a -h). This spiral is then slowly uncoiled, and
during this process the chromosomes assume a whole series of shapes
exceedingly characteristic of the c-mitosis and never occurring norm.ally. At...