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Effects of low temperature on cambial cells induced by localized heating in Cryptomeria japonica and Abies firma were investigated during winter dormancy in January-February. Localized heating induced cambial reactivation in the stems earlier than natural cambial reactivation. In heated Cryptomeria japonica and Abies firma stems, cambial reactivation occurred after 6 and 2 days of heating, on 14 January 2007 and 15 January 2010, respectively. We stopped the electric heating system just after cambial reactivation in stems. When we stopped the heating system, the minimum atmospheric temperature was about 0°C. After cambial reactivation, due to rapid decrease in temperature, cell contents of cambium became coagulated but nucleus was present in ray cambial cells. After one month, the shrunk cambium produced new deformed tracheids with abnormal cell shape. The results suggest that rapid decrease in temperature just after cambial reactivation might induce temporary damage of cambium that produces deformed tracheids indicating that cambium and its derivatives can response directly to changes in temperature which provides a useful experimental model system for studies of cambial biology and xylogenesis.
Anatomical investigation has been made on the stem of
pigeonpea (Cajanas cajan (L.) Millsp.) at different stages of growth
following the standard paraffin method of microtechnique. The vascular
bundle of the stem are collateral and arranged in a ring. The cambium
initiates in the primary vascular bundle between xylem and phloem at the
basal part of the stem of 3 days old plant. After the formation of fascicular
cambium it gives rise to secondary xylem adaxially and secondary phloem
abaxially. Most of the vessel members are solitary and few are paired
while others are multiple. The solitary vessel members are more in mature
stem as compared to that of the younger stem. The well developed periderm
was found in mature stem. The pith resembles a typical dicotyledonous