Secondary abstract: |
Recent studies on wood formation in Slovenia and the present study on differentiation of last formed cells in the xylem growth rings of silver fir (Abies alba) and common beech (Fagus sylvatica) were overviewed. Intact tissue samples containing xylem, cambium and phloem from mature living trees during the 2003 (fir) and 2006 (beech) vegetation periods were collected. Light microscopy and UV-microspectrophotometry were used for analyses. In silver fir, cell divisions in the cambium stopped between 20 August and 3 September 2003. At that time, the cambium consisted of 7-10 layers of cells and the last formed xylem growth ring contained 15 layers of undifferentiated tracheids. The differentiation of terminal tracheids was completed after 5-7 weeks. In beech, the cambial divisions stopped between 25 July and 8 August 2006, when the cambium contained 5-6 layers of cells and the last formed xylem growth ring had 30 layers of undifferentiated fibres. The differentiation of terminal fibres was completed after 4-5 weeks. The differences in composition of lignin and the degree of lignification between species were presented. The presented studies are important for the understanding of tree physiology and productivity, and wood properties. |