Cannabis sativa L. - Botany and Biotechnology

from 0.1 to 0.2% during 24 h. The survival rate declined up to 63.33 in plant treated
with 0.2% colchicines for 48 h.

17.3.2 Induction of Tetraploidy inCannabisby Colchicine

Application to Seedling Apical Meristem

Interaction of colchicine concentration and treatment time was significant on
induction of tetraploidy. With increasing treatment time from 24 to 48 h, induction
of polyploidy plants declined. The most of tetraploid plants (43.33%) were pro-
duced in concentration of 0.2% colchicine applied on apical meristems. The most of
the mixoploid plants (13.33%) were observed in apical meristem treatment with a
concentration of 0.1% colchicine for 24 h. Hence, the application of colchicine to
the apical meristems of young seedlings was an effective method for inducing
tetraploidy in the hemp plant. The treatment of apical meristem, the concentration
of colchicine, the duration of exposure, explant type and tissue penetrability should
be evaluated, because these factors have effects on chemical permeation and the
percentage of meristematic cells that successfully increased the number of chro-
mosomes (Allum et al. 2007 ).
Almost all the selected samples on the basis of enlargement of the guard cells of
stomata as possible polyploids forflow cytometric analysis showed changes in
ploidy level. Thus, increasing the size of epidermis cells can be used as an
appropriate criterion for the separation of polyploid plants by colchicine treatment.
Nail polish used to measure the size of stomata guard cells was very efficient and
provided an accurate view of the epidermis.

Table 17.1 Effects of colchicine concentration and duration of treatment on polyploidy induction
in cannabis plants (significant at 0/05%)

Treatment

duration

(h)

Colchicine

concentration

(%w/v)

Number of

seedlings

Treated

Survival

rate^1 (%)

Ploidy

Diploid Tetraploid Mixoploid

24 0 30 100 a* 30 (100)^2 0 (0.0) 0 (0.0)

0.1 30 89.96b 23 (85.15) 0 (0.0) 4 (14.81)

0.2 30 73.33c 9 (40.9) 13 (59.09) 0 (0.0)

Total 90 87.78 62 (78.48) 13 (16.45) 4 (5.06)

48 0 30 100 a 30 (100) 0 (0.0) 0

0.1 30 89.96b 25 (92.59) 0 (0.0) 2 (7.4)

0.2 30 63.33d 11 (57.89) 8 (42.10) 0

Total 90 84.44 66 (86.84) 8 (10.52) 2 (2.63)

(^1) Survival rate was assessed after the shoot tips had been cultured for 60 days
(^2) Data in parentheses are the percentages of diploids, tetraploids or mixoploids
*The same letter means no significant difference
372 H. Mansouri and M. Bagheri