In: Phyton, 51 Fasc. 2 (2011), S. 231–244, with 2 figures.

Key words: Alignment of cambium, ethephon, Euphorbiaceae, fusiform cambial cells, Hevea brasiliensis, tapping panel dryness, vascular rays.

Summary

PRAMOD S., THOMAS V. & RAO K. S. 2011. Structural and dimensional changes in the cambium of tapping panel dryness affected bark of Hevea brasiliensis. – Phyton (Horn, Austria) 51 (2): 231–244, with 2 figures.

The structural changes associated with the cambium of bark area affected by tapping panel dry-ness (TPD) have been studied in Hevea brasiliensis and compared with those of unaffected bark area of the same tree and that of TPD unaffected (healthy) trees. A number of structural deforma-tions and dimensional changes occurred in the cambial zone cells including the altered cambial ac-tivity in the affected area. The cambium is nonstoried with elongated fusiform initials having ac-tively growing tips enclosing uni or multiseriate rays. The anatomical features of cambium in relation to the structural changes in the affected trees were studied by observing the alignment of cells in the cambial zone. The changes in the cambial zone of affected area of bark include shortening of fusiform cambial cells, increase in the number of cambial rays, number of terminal cell of ray, width of ray and number of cell layers constituting the cambial zone. In the affected bark, fusiform cambial cells underwent transformative division leading to increment in the width and height of cambial rays. While in the TPD affected trees with warty outgrowth, the height of ray cambial cells decreased drastically and showed an increase in their width and density. The effect of ethylene in triggering the structural symptoms associated with TPD has also been studied as the ethephon ap-plication is a common practice in rubber plantations to stimulate the latex yield. In healthy trees, ethephon stimulation enhanced the cell divisions and length of fusiform cambial cells. The stimula-tion on the affected bark resulted in triggering of structural aberrations in the cambial zone cells. The effect of permanently altered cambial activity on the differentiation of laticifier system with respect to TPD has been discussed.