SEASONAL CHARACTERISTICS OF WOOD FORMATION IN HOPEA-ODORATA AND SHOREA-HENRYANA

Seasonal characteristics of wood formation were investigated using the pinning method in Hopea odorata and Shorea henryana in a natural dry evergreen forest of eastern Thailand. The position of cells having ini tiated S-1-layer formation at the time of pinning was estimated in the zone where cells were directly injured by the pinning and consequentl y destroyed. The position of cambial initials at the time of pinning w as estimated in the zone where cells were indirectly affected by the p inning and continued their physiological activity resulting in the for mation of aberrant cells. Traumatic resin canals were occasionally for med in Shorea. These canals were formed after pinning and could, there fore, not record the exact time of the pinning. Diameter growth of bot h species was greatest in the rainy season and decreased in the dry se ason.