The cambial activity and periodicity of secondary xylem and phloem formation have been less
studied in tropical tree species than in temperate ones. Cambium activity is the only source of timber
production. Studies on its activity and xylem formation can provide helpful data for dendrochronology and
possible factors that control tree growth, the yield and quality of wood. Cinnamomum camphora is an important
fast-growing tree for furniture and sculpture wood in South China. Its dynamics of cambial activity was not
reported. During the growth season in 2011, five trees of Cinnamomum camphora plantation were monitored
on the campus of Huazhong Agricultural University in central china (located on 113°41’ to 115°05’ E and
29°58’ to 31°22’ N). Sampling time was from 13, February 2011 to 13, February 2012. Some small stems
of 15–20 cm length were selected to sample in the middle of 2–3 years old health branches in the central
crown of these trees. The observational study found that the cambium of camphor trees was active from
March to October and dormant from November to February. Onset of cambial cell division was observed in
early March, one week after sprouting of new buds. The morphology of the cells and number of cell layers
in the cambium zone varied throughout the year. In early March, cambium reactivated with the rising of
temperature, the cell wall was relative thick. The number of cell layers increased from 2–3 in middle Feb. to
3–5. In June, the number of cell layers in cambium reached the maximum of 5–7 in a radial direction. In mid
March, phloem cells began to differentiate, followed by xylem three weeks later. The number of cell layers
in immature phloem and xylem increased dramatically before mid June and the increment of cell layers in
xylem was almost fifth times of phloem in the differentiating process. The phloem cells mainly stopped
dividing new cells in end of October, but xylem cells were still in the activity a week later. The annual activities
of cambium was in accordance with the air mean temperature change in 2011–2012. The results
showed that the cambial activity and formation of xylem and phloem were related to the environmental
factors, especially the temperature.
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