A STUDY ON THE ROLE OF CALCIUM IN XYLEM DEVELOPMENT AND COMPRESSION WOOD FORMATION IN TAXODIUM DISTICHUM SEEDLINGS

Abstract

One-year-old Taxodium distichum seedlings were decapitated and attached to plastic tubing for ‘force feeding’ of liquid media containing different levels of calcium regulating chemicals. The decapitated stems were either vertically placed or tilted at an angle of 45° to be gravitationally stressed. After an eight-week period of culture, diameter growth occurred at 1–3 cm below the cut ends and a large quantity of compression wood cells had differentiated on the lower side of tilted stems that were fed with a modified WPM control medium. However, the application of EGTA, a calcium chelating agent, and LaCl3, a calcium channel blocker, at concentrations of 20 or 50 mM and 1.0 mM, respectively, inhibited the formation of compression wood and the wall thickness of tracheid cells. The results suggested an involvement of calcium in the gravi-stimulated compression wood formation of conifers.