干旱胁迫对白桦木材结构和物理特性的影响

Effects of Drought Stress on Wood Structure and Physical Properties of Betula platyphylla

以东北林业大学帽儿山实验林场的白桦(Betula platyphylla)全同胞子代幼树作为研究材料,通过对试验植株的1年生小枝、多年生粗枝和4年生主干木材横截面切片的显微镜观察,以及木质部物理特性的扫描分析,探讨了在不同施肥条件下干旱胁迫对白桦木材结构和物理特性的影响。结果表明:水分亏缺和施肥都会影响白桦的木材结构和物理特性。干旱胁迫下施肥处理:白桦小枝的形成层细胞多,韧皮部较厚,细胞较大;粗枝的形成层及其附近的细胞比较规则;主干韧皮部细胞比较完整,大而整齐,韧皮部厚,形成层及附近有较大的导管细胞。胁迫未施肥处理:小枝的次生韧皮部细胞小且排列无序,数量少;粗枝的形成层及其附近的细胞小,排列形态混乱,形态明显不规则,主干韧皮部细胞明显遭到破坏。胁迫未施肥处理:小枝胞壁率、管孔密度和导管比量在胁迫过程中先升高后降低,中期达到最大值,末期最小;纤维比量的变化趋势与胞壁率、管孔密度和导管比量刚好相反,即在中期最小,末期最大。胁迫施肥处理:小枝的胞壁率胁迫初期最大,胁迫末期最小;管孔密度和导管比量与未施肥对照相反,胁迫末期最大,胁迫中期最小;纤维比量在胁迫中期和末期较大且相近,胁迫初期较小。

An experiment was conducted to study the effects of drought stress on wood structure and physical properties of Betula platyphylla under different fertilization conditions. The materials were from the soft branches, perennial branches and trunk sections of a young full-sib family progeny grown in Maoershan Experimental Forest Farm of Northeast Forestry University. Results showed that the wood structure and physical properties of B. platyphylla were affected by both of water deficit and fertilization. More cambium cells and thick phloem with larger ceils were found in the fertilized current grown branchlet, and the cells of the perennial branches were small, having regular shape and arranging with rules. The thick phloem with complete, larger and regular cells in the trunk and larger vessel elements near the cambium could be seen. There were few and small ceils in the branchlet phloem without fertilization under the stress. The phloem cells of the perennial branches were also small, arranging irregularly and having irregular shape, and the phloem ceils of the trunk were obviously damaged. The cell wall rate, pore density and vessel proportion of the branchlet without fertilization increased firstly and then decreased during the process of drought stress, while the maximum occurred in the mid period of drought stress and the minimum occurred in the late period. The change tendency of fiber proportion was opposite to that of other two wood properties, while the minimum occurred in the mid period and the maximum occurred in the late period. The maximum of the cell wall rate occurred in the initial period and the minimum occurred in the late period for the branches with fertilization under stress. The change tendencies of vessel proportion and pore density were opposite to the non-fertilization treatment, while the minimum occurred in the mid period and the maximum occurred in the late period. The fiber proportion was the highest in the mid period and in the late period, while the minimum occurred in the initial period.