| Three-year-old seedlings of loblolly pine (Pinus taede L.) and one-year-old seedlings of poplar I-107(Populus×euramericana cv."74/76")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 three months, the growth character and growth strain of reaction wood area were determined every three month (totally seven times, three months, six month, nine month, twelve months, fifteen months, eighteen months, twenty-one month), after then one seedling was selected as sample every time to measure the wood properties of reaction wood, and observe the characteristics of reaction wood formation. Then the growth character, growth strain, the formation characteristics of reaction wood formation and wood properties according to different inclined angles and inclined persistent time were analyzed, the relationship between growth strain and characteristics of reaction wood formation, the relationship between growth strain and wood properties were analyzed. The following conclusions were draw:1. Studies on growth character of reaction wood induced by artifical inclinationThe height of tree of loblolly pine varied little with inclined angle from three months to twelve months, and then it decreased with the increase of incline angle, the basal diameter of loblolly pine decreased from 0°to 15°and increased from 15°to 60°with the increase of incline angle. There were significant effects of inclined angle on height of tree and basal diameter of loblolly pine.The height of tree and basal diameter of poplar I-107 decreased with the increase of incline angle. There were highly significant effects of inclined angle on height of tree and basal diameter of poplar I-107.2. Studies on growth strain of reaction wood induced by artifical inclinationWith the increase of inclined angle, the growth strain of loblolly pine increased firstly and then keep steady, the maximum value reached at 30°. There was highly significant effect of inclined angle on growth strain of loblolly pine.With the increase of inclined angle, the growth strain of poplar I-107 increased firstly and then decreased, the maximum value reached at 30°, the growth strain at the angles of 45°and 60°were as the same as 30°. There was significant effect of inclined angle on growth strain of poplar I-107.3. Studies on formation characteristics of reaction wood induced by artifical inclinationAlong with the increase of inclined angles, the eccentric growth of loblolly pine became obvious, the eccentric ratio increased firstly and then keep steady, the maximum value reached at 60°, the shape of cross section changed from round to ellipsoidal, there was significant effect of inclined angle on eccentric ratio of loblolly pine.The micros-characteristics of tacheid of vertical stem of loblolly pine as the same as the normal wood structure, with the increase of the inclined angle, the characteristics of compression wood were obvious, 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 especially when the angle was bigger than 30°, and the maximum value of wall thickness reached at 45°.Along with the increase of inclined angles, the eccentric growth of poplar I-107 became obvious, the eccentric ratio increased firstly and then keep steady, the maximum value reached at 45°, then at the angle of 60°, the value as the same as at 30°, the shape of cross section changed from round to ellipsoidal, there wasn't significant effect of inclined angle on eccentric ratio of poplar I-107.Characteristics of cross section view of tension wood of poplar I-107 were: the number of vessels decreased and the diameter of vessels increased along with the increase of inclined angle, the thickness and number of gelatinous increased; the surface of lumen became wavy and the shape of lumen became irregular.4. Studies on wood properties of reaction wood induced by artifical inclination(1) Compression wood of loblolly pineAlong with the increase of inclined angles, the tracheid length of CW area decreased firstly and then increased, the minimum value reached at 30°; the tracheid length of OW area varied fluctuant; the tracheid length of CW was shorter than OW area(except for 0°). There were highly significant effect of inclined angle on tracheid length, but there wasn't significant effect of area on tracheid length.Along with the increase of inclined angles, the tracheid width of CW area increased firstly and then decreased or fluctuated, the maximum value reached at 30°, the tracheid width of OW area varied fluctuant, the tracheid width of CW was smaller than OW area. The lumen diameter of CW area varied fluctuant, the lumen diameter of OW area decreased; the lumen diameter of CW area was smaller than OW area except at 30°. The double wall thickness of CW area and OW area all increased, the double wall thickness of CW area was bigger than OW area. There were significant effect of inclined angle and area on tracheid width, lumen diameter and double wall thickness.Along with the increase of inclined angles, the MFA of CW area increased firstly and then decreased, the MFA of OW area varied fluctuant, and the MFA of CW area was bigger than OW area. There was significant effect of inclined angle and area on MFA.Along with the increase of inclined angles, the proportion of tracheid of CW area and OW area varied fluctuant; the proportion of ray of CW area and OW area varied fluctuant; the proportion of resin canal of CW area and OW area increased from 0°to 30°, and decreased from 30°to 60°; the ruler were absent when CW area compared with OW area. There weren't significant effect of inclined angle and area on proportion of tracheid, proportion of ray and proportion of resin canal, except there was significant effect of inclined angle on proportion of resin canal.Along with the increase of inclined angles, the height of ray of CW area and OW area increased firstly and keep steady, the height of ray of CW area was smaller than OW area; the height of width of CW area and OW area increased firstly and keep steady, the width of ray of CW area was smaller than OW area from 0°to 30°, and the width of ray of CW area was bigger than OW area from 45°to 60°. There were significant effect of inclined angle and area on height of ray and width of ray.Along with the increase of inclined angles, the basic density of CW area increased, the basic density of OW area varied little, and the basic density of CW area was bigger than OW area except at 0°. There wasn't significant effect of inclined angle on basic density, but there was significant effect of area on basic density.Along with the increase of inclined angles, the longitudinal shrinkage of CW area increased, the longitudinal shrinkage of OW area varied fluctuant, and the longitudinal shrinkage of CW area was bigger than OW area, there wasn't significant effect of inclined angle on longitudinal shrinkage, but there was significant effect of area on longitudinal shrinkage.(2)Tension wood of poplar I-107Along with the increase of inclined angles, the fiber length of TW area decreased, the fiber length of OW area increased firstly and then decreased, the fiber length of TW area was bigger than OW area except at 0°. There was significant effect of inclined angle and area on fiber length.Along with the increase of inclined angles, the fiber width of TW area varied little, the fiber width of OW area decreased, the fiber width of TW area was smaller than OW area; the lumen diameter of TW area and OW area all decreased firstly and then increased, the lumen diameter of TW area was smaller than OW area; the double wall thickness of TW area increased, the double wall thickness of OW area increased firstly until 30°, and then decreased, the double wall thickness of TW area was bigger than OW area. There were significant effect of inclined angle and area on fiber width, lumen diameter and double wall thickness.Along with the increase of inclined angles, the vessel diameter of TW increased firstly until 30°, and then decreased, the vessel diameter of OW varied fluctuatant, the vessel diameter of TW area was bigger than OW area at 45°and 60°, and the vessel diameter of TW area was smaller than OW area from 0°to 30°. There was significant effect of inclined angle and area on vessel diameter.Along with the increase of inclined angles, the MFA of TW area decreased, the MFA of OW area increased, the MFA of TW area was smaller than OW area. There was significant effect of inclined angle and area on MFA.Along with the increase of inclined angles, the proportion of vessel of TW area decreased, the proportion of vessel of OW area increased firstly and then decreased, the proportion of vessel of TW area was smaller than OW area except at 0°; the proportion of ray of TW area and OW area all increased firstly and then decreased, the proportion of ray of TW area was smaller than OW area; the proportion of normal fiber of TW area decreased, the proportion of normal fiber of OW area varied fluctuatant, the proportion of normal fiber of TW area was smaller than OW area; the proportion of gelatinous fiber of TW area increased, the proportion of gelatinous fiber of OW area varied fluctuatant, the proportion of gelatinous fiber of TW area was bigger than OW area. There were significant effect of inclined angle, area, interaction influence of angle and area on proportion of vessel, proportion of ray, proportion of normal fiber and proportion of gelatinous fiber.Along with the increase of inclined angles, the height of ray of TW area decreased, the height of ray of OW area varied fluctuated, the height of ray of TW area was bigger than OW area except at 60°; the width of ray of TW area and OW area varied fluctuatant, the width of ray of TW area were bigger than OW area at 15°, 45°and 60°, and the width of ray of TW area was smaller than OW area from 0°to 30°. There were significant effect of inclined angle, area, interaction influence of angle and area on height of ray and width of ray.Along with the increase of inclined angles, the basic density of TW area increased, the basic density of OW area varied fluctuant, the basic density of TW area was bigger than OW area. There wasn't significant effect of inclined angle on basic density, but there was significant effect of area on basic density.Along with the increase of inclined angles, the longitudinal shrinkage of TW area increased firstly, and then decreased, the longitudinal shrinkage of OW area decreased, the longitudinal shrinkage of TW area was bigger than OW area except at 0°. There wasn't significant effect of inclined angle on longitudinal shrinkage, but there was significant effect of area on longitudinal shrinkage. 5. Studies on formation mechanism of reaction wood induced by artificial inclinationThere was significant positive correlation between growth strain and eccentric ratio of loblolly pine and Poplar I-107.For loblolly pine, there was negative correlation between growth strain and tracheid length, there was positive correlation between growth strain and tracheid width, there was positive correlation between growth strain and double wall thickness, there was positive correlation between growth strain and MFA, there was positive correlation between growth strain and proportion of tracheid, there was negative correlation between growth strain and proportion of ray, there was positive correlation between growth strain and proportion of resin canal, there wasn't significant correlation between growth strain and height of ray, there was significant positive correlation between growth strain and width of ray, there was significant positive correlation between growth strain and basic density, there was positive correlation between growth strain and longitudinal shrinkage.For Poplar I-107, there was negative correlation between growth strain and fiber length, there wasn't significant correlation between growth strain and fiber width, there was weak positive correlation between growth strain and double wall thickness, there was weak negative correlation between growth strain and vessel diameter, there was weak negative correlation between growth strain and MFA, there was significant negative correlation between growth strain and proportion of vessel, there was positive correlation between growth strain and proportion of ray, there was negative correlation between growth strain and proportion of normal fiber, there was positive correlation between growth strain and proportion of gelatinous fiber, there wasn't significant correlation between growth strain and height of ray, there was significant negative correlation between growth strain and width of ray, there was positive correlation between growth strain and basic density, there wasn't significant correlation between growth strain and longitudinal shrinkage.
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