We analyzed seasonal cambial dynamics and wood formation in Scots pine (Pinus sylvestris) from Moncayo mountain in Spain. Samples were taken from trees growing at 2 altitudes: (1.562 m a. s. l. and 1.179 m a. s. l.). From March 24, 2011 till November 23, 2011 20 samplings were performed at 1 or 2 week intervals. At each sampling date microcores from 6 randomly selected trees were taken at each location. After embedding of samples in paraffin we made 480 permanent slides of cross-sections of cambium, wood and phloem with rotary microtome. Using a light microscope and image analysis system we counted the number of cells in the cambial zone and xylem growth rings, where we analyzed differentiation cells in various phases. In addition we measured the widths of the current and 3 previous xylem rings. At the beginning of the growing season, we observed an increased number of cells in the cambial zone, and formation of the first cells in the phase of post-cambial growth (PC), detected on the lower site on April 14, 2011, and on the
higher site on April 20, 2011. The last PC cells were produced at the end of August 2011. Differentiation of terminal latewood cells was completed by November 8, 2011. At the end of the growing season the dynamics of wood formation was similar on both sites. Average 2011 xylem ring widths were 1086 μm on the lower and 997 μm at the upper site.
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