We investigated the cambium activity and the dynamics of wood formation in young Aleppo pine trees (Pinus halepensis Mill.) from the Jarafuel and Maigmo sites in Spain. We measured wood increment in young trees in 2005, and compared the results to those for mature trees from the same sites, gathered from parallel studies. The samples were taken between February 22, 2005 and February 8, 2006 in Jarafuel, and between February 18 and December 27, 2005 in Maigmo. We used a rotary microtome to produce 132 permanent slides to observe the cross-sections of the cambial zone, and the developing xylem growth ring. We made hystometrical analyses, carried out with a light microscope, and the image analysis system. We then determined the number of cells in the cambium (CC), and wood cells (tracheids) in the process of postcambial growth (PC), and the formation of secondary wall (SW) as well as the mature tracheids (MT). In Jarafuel, the cell division began on March 25, 2005, when we observed the first PC cells. The first SW and MT cells were formed from March 25 to June 11, 2005. In Maigmo, the cell division in the cambial zone started on April 4, 2005. The first SW and MT cells occurred between April 4 and June 14, 2005. We found out that in both sites in 2005, cell production was stronger in young trees than in mature ones. In Jarafuel, young trees produced on average 34 tracheids per radial row, while mature trees produced only 12. In Maigmo, the cambium cell production was poor for both young and mature trees. The growth ring in young trees in 2005 had only 6 cells, while the annual ring 2005 was not formed in mature trees.
|
