重金属Cd对一年生直立与倾斜生长杨树解剖特性的影响

以30棵一年生人工林69杨(Populus deltoids Bartr. cv. ''Lux'' (I-69/55))为研究对象，在生长季节将其中的15棵苗木人工倾斜45°，将直立生长和倾斜生长的苗木分别平均分成5组（每组3棵），分别施加0、5、20、50和100 mg·kg^-1的Cd(NO₃)₂，记为C₀、C₁、C₂、C₃和C₄。苗木生长8个月后开始取样，树干按其纵向上的高度分为顶部、中部和基部，倾斜生长分应拉区和对应区对其解剖特性进行测定分析。结果表明：（1）随着土壤中重金属Cd浓度的增加，直立生长下的杨树的纤维长度在C₀、C₁、C₂浓度下大于倾斜生长，C₃、C₄浓度下则小于倾斜生长；在倾斜生长下，C₀与C₄浓度下应拉区纤维长度小于对应区，而C₁、C₂、C₃则相反。在树干纵向分布上，纤维长度为基部＞中部＞顶部。方差分析表明，不同Cd浓度对纤维长度的影响显著，不同区域上影响不显著。（2） 导管长度上，直立生长大于倾斜生长，应拉区的导管长度大于对应区；纵向分布上，在倾斜生长下导管长度为基部＞中部＞顶部。方差分析表明，不同Cd浓度和不同区域对导管长度的影响显著。（3）双壁厚上，C₀、C₁为直立生长小于倾斜生长， C₂、C₃、C₄则与此相反。方差分析表明，不同Cd浓度对双壁厚的影响显著，不同生长方式和高度上影响不显著。（4）微纤丝角上， C₀、C₁、C₂浓度下直立生长大于倾斜生长，C₃、C₄浓度下则相反；倾斜生长下的应拉区微纤丝角小于对应区。方差分析表明不同Cd浓度和不同区域对微纤丝角的影响显著。（5）结晶度上，倾斜生长下应拉区结晶度大于对应区；在纵向分布上，结晶度为基部＞中部＞顶部。方差分析表明，不同Cd浓度和不同区域对结晶度的影响显著。

Effects of heavy metal Cd on anatomical characteristics of one-year-old upright and inclined poplars

Poplar 69 (Populus deltoids Bartr. cv. ''Lux'' (I-69/55)) was selected to study the anatomical characteristics of one-year-old upright and inclined poplars under Cd stress. Thirty seedlings were planted, among which, 15 were artificially inclined by 45°, and 15 were upright planted during the growing season. Five treatments of Cd appli-cation in the soil with 3 repetitions were set for each group, which were 0, 5, 20, 50, and 100 mg·kg-1 in terms of Cd, denoted as C₀, C₁, C₂, C₃, and C₄, respectively. Poplar trunks were sampled longitudinally along the height for the top, middle and base parts after 8 months of the growth. For inclined poplar (IP), each trunk part was further sampled for the tension zone (TZ) and the opposite zone (OZ). The anatomical characteristics were measured and analyzed. The results showed that: (1) With the increase of C_d application in the soil, the fiber length of upright poplar (UP) was greater than that of IP at C₀, C₁, and C₂, but less than that of IP at C₃ and C₄. For IP, the fiber length in TZ at C₀ and C₄ was smaller than that in OZ, while it was opposite at C₁, C₂, and C₃. Longitudinally, the fiber length demonstrated an order as the base > middle > top. ANOVA showed that Cd application had a significant effect on the fiber length, but the difference was not significant between the two zones for IP. (2) The length of the vessel of UP was greater than that of IP, and that in TZ was greater than that in OZ for IP. Longitudinally, the length of the vessel of IP demonstrated an order as the base > middle > top. ANOVA showed that the length of the vessel was significantly