The number of chromosomes (x) for Picea abies is 12. Tetraploids and mixoploids occur very rarely in nature. Artificial triploids and aneuploids were obtained after treating the seeds with colchicine (ILLIES 1951/52) or X rays (BEVILACQUA and VIDAKOVIC1963, SIMAK et al. 1968). The relative length of the metaphase chromosome, which is used for idiogram (karyogram) construction, is 70-130 (Bialobok and Bartkowiak 1967, TERASMAA 1971,1972). The longest one is almost twice as long as the shortest. The ten pairs of homologous chromosomes are metacentric. The relative length of the chromosome arms is 1.0-1.7. Two other chromosomes (numbers 9 and 12) are submetacentric. Their centromeres lie near the end of one of the arms. The relative length of the arms is 1.8-2.1. A secondary contraction, the cleaving of small fragments of chromosomes (satellite or trabant), occurs in five chromosomes: numbers 2, 3, 5, 6, and 10 (Fig. 6.13).

Other researchers claim that the number of satellite chromosomes in P. abies is much fewer, and that some of the "satellites" may be artifacts arising during the cytological tissue preparation (Bialobok and BARTKOWIAK 1967, Gabrilavichyus 1972). It seems that some of the satellites may have gone unnoticed owing to the treatment of the studied material with colchicine, which causes the chromosome to contract for easier counting, and that some secondary contractions on slides were not visible. This is confirmed by the fact that in interphase nuclei, the number of nucleoli is always ten or fewer (TERASMAA 1972). Chromosomes with satellites participate in nucleoli restitution.

Figure 6.13. Karyogram of Picea abies (Terasmaa 1971)

chromosome numbers from the longest to shortest one; a-b - relative lengths of the chromosome arms

Alina Hejnowicz, Polish Academy of Sciences, Institute of Dendrology, Kornik.

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