Tuyển tập các báo cáo nghiên cứu về sinh học được đăng trên tạp chí lâm nghiệp đề tài: Preliminary study on phloemogenesis in Norway spruce: influence of age and selected environmental factors. | JOURNAL OF FOREST SCIENCE 57 2011 5 226-232 Preliminary study on phloemogenesis in Norway spruce influence of age and selected environmental factors G. Vichrová H. Vavrcík V. Gryc L. Mensík Faculty of Forestry and Wood Technology Mendel University in Brno Brno Czech Republic ABSTRACT The process of phloem formation in Norway spruce Picea abies L. Karst. was analysed during the growing season 2009 in Rajec-Nemcice locality Czech Republic . The research series consisted of research plots with 34 and 105 years old spruce monocultures. The formation of phloem cells was determined by the examination of small increment cores taken once a week. Cross-sections of tissues were studied under a light microscope. Cambium activation was observed on 9 April both in young and old trees. On the same date the first newly formed cells of early phloem were observed in old trees but in young trees one week later. Although the time of early phloem formation was 14 days longer in old trees there were no large differences in the numbers of formed cells. The beginning of the longitudinal axial parenchyma formation was determined in young trees on May 14. In old trees this activity was seen a week later. The influence of air temperature and soil moisture was also analysed in relation to phloemogenesis. Keywords cambium environmental factors influence of age light microscopy Norway spruce Picea abies phloem formation The growth of multicellular organisms is seen as the increase in an individual s volume conditioned by the creation of new cells. This leads to an irreversible process of the expansion of plant dimensions. Secondary growth is referred to as radial growth and is conditioned by cambial activity Larson 1994 Prochazka et al. 1998 . The cambium is a secondary meristem which divides the phloem cells centrifugally and xylem cells centripetally Zimmermann Brown 1971 Larson 1994 . Cambial activity and secondary growth in temperate regions are periodic alternating periods of growth with
