Abstract:

Three-year-old seedlings of loblolly pine (Pinus taeda) were selected as materials in this article. The seedlings were planted in spring and divided into five groups,then were artificially inclined at the angles of 0°,15°,30°,45°and 60° from the vertical. After four months,the anatomical properties and their variation patterns of compression wood changed with the different inclined angles were determined every three month (totally five times). The following conclusions were drawn: 1) With the increase of the inclined angle,the wall thickness of tracheid increased and the outline of the tracheid became round,the intercellular spaces and helical ribs were obvious and increased gradually in all sections derived from the inclined seedlings. 2) With the increase of the inclined angle,the tracheid length decreased firstly and then increased,the minmum value reached at 30°,the tracheid width decreased firstly and then increased,the minmum value reached at 45°,the double wall thickness increased firstly and then decreased,the maximum value reached at 45°.The ANOVA results revealed that there was highly significant effect of inclined angle on the tracheid length,the tracheid width and the double wall thickness. 3) With the increase of inclined angle,MFA increased firstly and then decreased,the maximum value reached at 30°. The ANOVA results revealed that there was significant effect of inclined angle on MFA. 4) With the increase of inclined angle,the proportion of tracheid and ray varied fluctuately,the proportion of resin canal increased firstly and then decreased,the maximum value reached at 30°. The ANOVA results revealed the effect of inclined angle was significant on proportion of the resin canal,but not significant on the proportion of tracheid and ray. 5) From the variation patterns of the different wood anatomical properties at different angles,the leaning angle of 30°-45° was an important turning point for the formation of compression wood and the further study was needed to understand this mechanism.

Key words: artificial inclination, loblolly pine, seedling, compression wood, anatomical properties