Journal of Experimental Botany, Vol 50, 1769-1778, Copyright © 1999 by Oxford University Press
H Haggman, A Jokela, J Krajnakova, A Kauppi, K Niemi and T Aronen
This is the first report on Scots pine (Pinus
sylvestris L.) somatic embryo plants regenerated and growing in
a greenhouse. The present work focused on improving somatic embryogenesis
of the species by studying the factors affecting culture induction.
Developmental stage of explants that were immature female gametophytes,
including the zygotic embryos with suspensor tissues, was investigated in
detail. The genetic background of the material, cold treatments (14 d, 1 or
2 months at +5
ARTICLES
Somatic embryogenesis of Scots pine: cold treatment and characteristics of explants affecting induction
Punkaharju Research Station, The Finnish Forest Research Institute, Finlandiantie 18, FIN-58450 Punkaharju, Finland; Department of Biology, University of Oulu, PO Box 3000, FIN-90401, Oulu, Finland; Department of Forest Genetics and Tree Breeding, Forest Research Institute, TG Masaryka 22, SK-96022 Zvolen, Slovak Republik; Corresponding author; Fax: +358 15 644 333; E-mail: hely.haggman@metla.fi
C) of cones including
explants, as well as the plant growth regulator composition of the
initiation medium, were also examined. When initiation of somatic
embryogenesis was successful, the zygotic embryos in the explants were
either proembryos or early embryos. Cold treatment of the cones had no
significant effect on induction, nor were there any differences among the
treatments with different duration, thus improving the practical
applicability of the culture technique. The explants in cold-stored cones
probably retained their initiation capacity due to the conversion of starch
to sugars. This was observed as decreased number and size of starch grains
in the megagametophytes compared with the controls. The seed family and the
medium significantly affected induction success, the medium with auxin (9.1
or 13.6
M 2,4-dichlorophenoxyacetic acid) and
cytokinin (2.2
M 6-benzylaminopurine) being
better than the medium with cytokinin (5
M 6-benzylaminopurine)
alone. The significance of the genetic background of the explants and the
initiation medium indicate that it might be possible to improve the
initiation rates by using explants from controlled crossings between
competent genotypes, and by developing more specific media for important
seed families.Keywords: Pinus
sylvestris, vegetative propagation, zygotic embryo,
megagametophyte, histochemistry
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