Current issue: 55(2)
Scots pine (Pinus sylvestris L.) is a resilient, wide spread species. This paper reports on the xylem and phloem cell formation process, before and after, the species was put under artificial stress by stem girdling. Microcore method was applied to a healthy control group and a standing group of girdled trees within an 80-year-old pine forest for two consecutive growing seasons (2013 and 2014). The stem girdling was applied in the middle of the first growing season (July 2013). Cambial activity timings (onset and cessation of cell division), cell formation intensity, cell differentiation, and the dynamics of the annual radial increment in the stem were analyzed. Cambial activity was inhibited and eventually ceased below the stem girdling immediately after the removal of the strip. Therefore, no latewood tracheids were formed. However, above the stem girdling and in the control trees, cell formation and tissue differentiation continued until the end of the growing season, with the girdled trees moving at a less intensive pace but for a longer period of time. During the following growing season (2014), the cambial zone was reactivated only above the stem girdling, not below, and eventually the girdled trees died. In 2014, the onset of the cambial activity was delayed and the division rate of the cells was slower in the girdled trees. Furthermore, the girdled trees formed less phloem cells than the control trees.
The curly-grained trait of Betula pendula Roth is inheritable, but it is persumably not question of only one Mendelian gene since, for instance, there are a number of different types of curly-birch. The progeny obtained from controlled crossing between two curly-birch individuals do not all posses the curly-grained trait.
Plantlets were produced from adult curly-birch (Betula pendula var. carelica). Murashige and Skoog’s medium was used as the culture medium. Growth was initiated on a medium containing 1 mg/l BAP. Bud formation was induced using a medium containing 10 mg/l BAP and 0.2 mg/l NAA. Development of shoots was achieved on a medium containing ½ x Murashige and Skoog’s macrominerals and sucrose, 1/1 x Murashige and Skoog’s microminerals and vitamins, and 0.5 mg/l BAP and 0.5 mg/l IAA. The medium used for inducing root formation was the same as above, but without any growth regulators. The results indicate that adult deciduous trees can be best propagated through tissue culture when the least differentiated cells, i.e. the initial cells of the promeristem, are used as the startin material. The axillary buds provide easily available study material which can be prepared with little difficulty and are continuously renewed.
The PDF includes a summary in Finnish.