Trees (2004) 18:136–144 DOI 10.1007/s00468-003-0292-9 ORIGINAL ARTICLE Paweł Kojs · Wiesław Włoch · Aleksandra Rusin Rearrangement of cells in storeyed cambium of Lonchocarpus sericeus (Poir.) DC connected with formation of interlocked grain in the xylem Received: 27 February 2003 / Accepted: 29 July 2003 / Published online: 30 September 2003  Springer-Verlag 2003 Abstract The history of cellular events in the storeyed cambium of Lonchocarpus sericeus (Poir.) DC was analysed on the basis of changes in the cell arrangement in successive layers and strata of axial parenchyma in the xylem. The mechanism of formation of the regular interlocked grain was investigated. Inclination of fusiform cells changes intensively whereas height and position of storeys in the successive layers of axial parenchyma are constant. As a result, new contacts between cells are formed by means of the intrusive growth of ends of cells belonging to one storey between the tangential walls of cells of the neighbouring storey and unequal periclinal divisions, which give a new shape to the initials. The concept of intrusive growth between the radial walls of the fusiform initials in the formation of xylem with interlocked grain should be revised on this basis. Keywords Storeyed cambium · Intrusive growth · Unequal periclinal division · Interlocked grain · Lonchocarpus sericeus Introduction Studies on storeyed cambium date back to the beginning of the twentieth century. Initially, research on the structure of this tissue was focused not on the mechanisms of its formation or rearrangement, but on mechanisms of its maintenance during the increase of the cambial surface (Bailey 1920). It was concluded that maintenance of the storeyed structure of cambium was closely related to the longitudinal anticlinal divisions of the initial cell which produced two daughter initial cells of equal length (reviewed in Iqbal and Ghouse 1990), and to the lack of intrusive growth after the division (reviewed in Larson 1994). These concepts lasted until the 1970s, when studies on the storeyed structure of cambium were resumed in connection with the research on the domain pattern and wave-oscillatory phenomena in the cambium (Hejnowicz and Zagórska–Marek 1974; Zagórska–Marek 1975; Włoch and Zagórska-Marek 1982; Włoch and Bilczewska 1987). The history of cambium is recorded in the cell arrangement of xylem and phloem cells; it may be reconstructed from a series of tangential sections (Hejnowicz 1961, 1964, 1968; Hejnowicz and Krawczys- zyn 1969; Pyszyn ´ski 1972; Włoch 1976, 1985, 1987; Włoch et al. 2001, 2002). The continuous analysis of cellular events in the successive layers of xylem in broad- leaved trees is not possible due to the intrusive growth of fibres and vessel members, which heavily disturbs the original arrangement of the cambial cells. However, it is possible to analyse the history of cambium on the basis of changes of the cell arrangement in the successive layers and strata of axial parenchyma. Parenchymatous cells do not grow intrusively during differentiation and hence their arrangement reflects the arrangement of cells in the cambium at the moment of formation of the layer in question. The layer of terminal parenchyma is formed in the xylem of the most broad-leaved trees, especially in those living in temperate zones, at the boundaries of annual increments at the end of the season of cambial activity. The comparison of cellular events in the subsequent layers of terminal parenchyma allows the reconstruction of changes occurring during a certain period of life of a tree. Such an analysis is possible only when the derivatives of the same cambial cell in successive layers of axial parenchyma can be located. The changes of cellular arrangement in the annual P. Kojs · W. Włoch ( ) ) · A. Rusin Botanical Garden—Centre for Biological Diversity Conservation of the Polish Academy of Sciences, ul. Prawdziwka 2, 02–973 Warsaw 76, Poland e-mail: wwloch@us-edu.pl W. Włoch Department of Biophysics and Cell Biology, Silesian University, ul. Jagiellon ´ska 28, 40–032 Katowice, Poland P. Kojs International School of Education and Culture—Polish College, Silesian University Branch in Cieszyn, ul. Bielska 62, 43–400 Cieszyn, Poland