The potential to use somatic embryos for large-scale propagation of elite genotypes, for integration into breeding programmes and for connecting breeding and mass propagation, is receiving much attention. However, before the methods are applied it is important that the plants regenerated via somatic embryogenesis grow as expected, i.e. as seedlings or cuttings. Growth of somatic embryo plants is under a cumulative in uence of a number of treatments given during the in ×itro phase and during the ex ×itro establishment phase. The aim of this study was to identify treatments with a negative in uence on the subsequent growth of somatic embryo plants of Norway spruce (Picea abies L. Karst.). Based on the results, the time of contact with abscisic acid during somatic embryo maturation and the length of continuous light treatment (CLT) during the rst growth period strongly affect the height growth during two successive growth periods. In both cases longer treatments exerted negative effects. Based on these results a new method was set up, which includes: (1) prematuration treatment of the suspension culture in a growth regulator-free medium, by which the maturation step is synchronized and contracted; and (2) a two-phase germination treatment, rst on a solidi ed medium and then in a liquid medium. This treatment avoids extended CLT during the rst growth period. Another advantage of the two-phase germination treatment is a better root-system development. Somatic embryo plants produced according to this method can be transferred directly from in ×itro conditions to the greenhouse.

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The rooting of hypocotyl cuttings from 20‐day‐old seedlings of Pinus sylvestris L. cultured in vitro is discussed. About 40% of the cuttings cultured on medium lacking activated charcoal produced roots during the first two months. When activated charcoal was added to the medium, either root formation (75% formed roots) or wound tissue growth (95% formed large wound tissues) was stimulated in different experiments. These large wound tissues did not develop any roots. The anatomical changes in the basal part of the cuttings were similar during the first two weeks in all the cuttings studied. A vascular cylinder composed of short tracheids with many pores developed. Thereafter the differentiation process became varied. The amount of wound tissue produced and the time for rooting differed among the cuttings. Tracheid nests which were in contact with the vascular system in the hypocotyl via short tracheids were observed after three weeks. Subsequently, roots developed from the tracheid nests. The longer root formation was delayed, the larger the wound tissue became. Short tracheids were found close to the wound tissue surface. Their ability to adsorb nutrients and water is discussed.

The origin of roots and wound tissue after treatments for induction of roots on hypocotyl cuttings of three‐week‐old Pinus contorta Dougl. ex Loud, is discussed. The cuttings were cultured in vitro and treated with 1.2 μM to 1.5 M IBA (indole‐3‐butyric acid) for 6 h to 10 days. The control, which was not treated with IBA developed a wound tissue from which roots formed. Cuttings treated with IBA developed roots directly from the hypocotyl. Direct rooting was faster than indirect rooting via a wound tissue. Rooting was considered to be optimal if more than 80% of the cuttings rooted within 19 days and half of the cuttings which possessed roots after one month had acquired them within 14 days. This type of rooting was obtained after treatment with either 80 μM IBA for 4 to 6 days or 1.25 to 5.0 mM IBA for 6 h. Suboptimal treatments gave lower rooting percentages and superoptimal treatments resulted in delayed rooting. In IBA‐treated cuttings, large increases in mitotic activity (number of mitoses per mm hypocotyl) were found in the pericycle and parenchyma inside endodermis. However, the control also had similar mitotic activities as the IBA‐treated cuttings but closer to the cut surface. This led us to the conclusion that similar tissues may produce either wound tissue or roots. Almost all roots obtained through direct rooting originated outside resin ducts.

Two S-adenosylmethionine synthetase (SAMS) cDNAs, PcSAMS1 and PcSAMS2, have been identified in Pinus contorta. We found that the two genes are differentially expressed during root development. Thus, PcSAMS1 is preferentially expressed in roots and exhibits a specific expression pattern in the meristem at the onset of adventitious root development, whereas PcSAMS2 is expressed in roots as well as in shoots and is down-regulated during adventitious root formation. The expression of the two SAMS genes is different from the SAMS activity levels during adventitious root formation. We conclude that other SAMS genes that remain to be characterized may contribute to the observed SAMS activity, or that the activities of PcSAMS1 and PcSAMS2 are affected by post-transcriptional regulation. The deduced amino acid sequences of PcSAMS1 and PcSAMS2 are highly divergent, suggesting different functional roles. However, both carry the two perfectly conserved motifs that are common to all plant SAMS. At the protein level, PcSAMS2 shares about 90% identity to other isolated eukaryotic SAMS, while PcSAMS1 shares less than 50% identity with other plant SAMS. In a phylogenetic comparison, PcSAMS1 seems to have diverged significantly from all other SAMS genes. Nevertheless, PcSAMS1 was able to complement a Saccharomyces cerevisiae sam1 sam2 double mutant, indicating that it encodes a functional SAMS enzyme.