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Old colchicine-induced polyploid materials
of Betula pendula Roth and Betula pubescens Ehrh.
K. Pieninkeroinen T. Valanne
Department of Biology University of Turku, SF-20500 Turku, Finland
pubescens trees, which originated from exten-
Introduction
sive colchicine experiments with different birch
species carried out in Finland (Valanne, 1972).
The members of the genus Betula form a The birches from the experiments are located
particularly significant group of broad- on the island of Seili (60°12’ N, 21 °55’ E), at the
Experimental Station of the Finnish Forest
leaved trees in Eurasia and North
Research Institute, Punkaharju (61 °43’ N,
America. Certain birch species, e.g., B.
29°25’ E), at Päilahti by Orivesi (61°37’ N,
pendula, B. pubescens and B. papyrifera, 24°29’ E) and in the Botanical Garden of the
are valuable sources of wood and great
University of Turku, Ruissalo (60°26’ N, 22°10’
importance is attached to breeding work E). From the materials of Punkaharju, Orivesi
aimed at their economic improvement. and Turku, 50 8. ,nendula and 50 B. pubescens
trees were taken for this study.
Polyploidy induced by colchicine treat-
The chromosome counts carried out
ment in B. pendula and B. pubescens has were
according to the method of H6mm6 and Sarki-
been ieported by Johnsson and Eklundh
lahti (1986), using young leaves. Arnott’s (1959)
(1940), Schrbck (1951) and Valanne method of clearing leaves was used to study
(1972). The rate of growth of induced stomata. For the measurement of wood fibres
Betula polyploids has been observed to be and vessels, wood tissue was macerated ac-
inferior to that of the diploid parental trees cording to the method for broad-leaved trees.
(Johnsson, 1956; Eifler, 1955; 1967). It
has also been reported that triploid B.
pendula trees obtained from cross-pollina-
tion of colchicine tetraploid and diploid Results
trees did not grow faster than the diploid
control plants (Johnsson, 1956). The aim
of this study was to reveal possible breed- The retarding effect of colchicine on the
ing and evolutionary trends in B. pendula of birches is strong. In the
height growth
and B. pubescens. colchicine-induced polyploids, both the
height and the diameter (dbh) were signifi-
cantly smaller than in the colchicine-treat-
ed chromosom;!lly normal trees (Table I).
Materials and Methods
Some diploid B. pendula trees reached a
height of nearly 20 m, while the highest
The material was part of about 2000 individually
polyploids were under 14 m. The colchi-
numbered ca 25 yr old B. pendula and B.
cine treatment caused branching. No sta- In the colchicine polyploids, the wood
tistically significant difference was found in fibres and vessels were statistically signifi-
branch numbers between the groups. cantly longer and the vessels wider than in
the chromosomally normal trees (Table II).
The petioles of polyploid B. pendula
The mean lengths of the fibres and ves-
trees were thicker than those of diploid
sels of polyploid B. pendula were several
containing parenchymatous
more
ones,
tens of micrometres smaller than those of
and vascular tissue. In the tetraploids, the
polyploid B. pubescens. In some B.
cell size of the parenchymatous tissue
pubescens trees with the longest wood
was greater in relation to other cell types
fibres, the mean length exceeded 1 mm.
than in the diploid trees. In the polyploid
The shortest wood fibres were recorded in
trees, the sclerenchymatous tissue around
some diploid B. pendula trees, the mean
the vascular bundle seemed to be more
value being under 0.6 mm.
abundant and its cells often had thinner
walls than in the diploids.
The guard cells of the stomata were
significantly longer in the induced poly- Discussion and Conclusion
ploids than in the colchicine-treated chro-
mosomally normal trees (Table II). The
Retardation of the height groswth is a typ-
lengths of the guard cells of the normal
ical effect of colchicine in the Betula spe-
trees were on an average 70% of those of
cies studied (Table I). This has already
the induced polyploids.
been seen in the initial stages of saplings References
(Johnsson and Eklundh, 1940; Valanne,
1972). On the other hand, the cell size of Arnott J. Leaf Turtox News 37,
(1959) clearings.
colchicine polyploids is greater (Table II),
192-194
and the leaves and leaf organs greater
are
Eifler I. (1955) Künstliche polyploidie-erzeugung
than at the diploid level.
bei Picea abies und Betula verrucosa. Z. Forst-
The chromosome number of a consider- gen. Forstpflanzenzucht. 4, 162-166
able part (33 trees) of the B. pubescens Eifler I. (1967) Anwendungsm6glichkeiten der
material is heptaploid with 7x = and
98, polyploidie-zYchtung in der forstwirtschaft.
Arch. Forstwes. 1 Et, 515-528
only a small number of the trees have the
expected 8x = 112 (6 trees). The large Hbmmb L. & Särfcilahti E. (1986) A method of
counting chromosomes of hardwood trees
proportion of heptaploid trees suggests
using root tips and young leaves. Can. J. For.
that the chromosome set of B. pubescens
Res. 16, 401-403
consists of 42 + 14 chromosomes (3x+ x),
Johnsson H. (’1956) Auto- and allotriploid
and that in the colchicine treatments 42
Betula families, derived from colchicine treat-
chromosomes have been duplicated, ment. Z. Forstgen. Forstpflanzenzijcht. 5, 65-70
while 14 chromosomes are unchanged. In
Johnsson H. & Ek.lundh C. (1940) Colchicinbe-
our experiments with birches of the sub-
metod vid vdxtf6redling av 16v-
handling som
section Nanae (B. glandulosa and B. trad. Sven. Papperstidn. 43, 355-360, 373-377
nana, both 2n = 28, x = 14), no colchicine Schr6ck O. (1951) Stimulierende wirkung des
polyploids have been obtained. In the liter- colchicins bei der keimung und wachstum der
ature, it has been suggested that the B. sdmlinge. Ziechter, 21, 142-149
pubescens genome contains a genome of Valanne T. (1972) Colchicine effects and colchi-
the subsection Nanae (e.g., Walters, cine-induced polyploidy in Betula. Ann. Acad.
Sci. Fenn. Ser. A4 Biol. 191, 1-28
1968). The abundance of trees with
7x 98 occurring in our B. pubescens Walters S.M. (1968) Betula in Britain. Proc.
=
Bot. Soc. Br. lsl. 7, 179-180
material supports this suggestion.
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