不同类型针阔材树木形成层活动规律与木质部细胞分化差异的研究

In longer term, the utilization of plantation wood is an important way to solve the shortage of wood resources and the tension between wood supply and demand in China. Trees cambium active patterns and their xylem cell differentiation and maturation processes are the foundation of the research on wood formation. Now more attention has been paid to study on trees cambium activities in temperate regions, but very few was found to trees’ in tropical and subtropical regions. Six mainly representative tree species with different wood types planted in subtropical regions of China for industrial wood will be selected to study their wood formation processes and analize their cell anatomical features in this project, which include Pinus Pinus elliottii （Pinaceae）, Taxodium ascendens (Taxodiaceae) , Platycladus orientalis (Cupressaceae ), Zelkova schneideriana (ring-porous wood), Cinnamomum camphora (semi-ring-porous wood), Populus tomentosa (diffuse-porous wood). Their cambium periodicity dividing active patterns, secondary xylem cells seasonal variation, secondary xylem cell numbers accumulated and cell characteristics, cell wall lignin deposition process and distribution patterns and the relationship of wood cell tissues proportion variation to climate factors will be studied in this project. Their anatomical mechanism of vascular cambium growth and development will be exposited. The differences of their cambium dividing activity patterns, cell variate features and their wood formation processes among Pinaceae ,Taxodiaceae, Cupressaceae in coniferous trees and those among ring-porous wood, semi-ring-porous wood and diffuse-porous wood in broad –leaved trees will be compared seperatively.The changes of cell length in cambium periodicity activity and their wood density will be conducted. These results will be used to provide the theory basis for improving wood quality of main tree species’ plantation in subtropical areas and the biological specific directional cultivation of plantation for industrial wood. The consequence of this study is of important significance in the rational utilization of plantation wood and solving the shortage of wood resources in China.

我国木材资源缺乏，供需矛盾紧张，长远之计是利用人工林木材资源。树木形成层活动规律及其木质部细胞分化过程是研究木材形成的基础。温带树木形成层活动规律研究较多，亚热带和热带地区这方面研究甚少。本项目选择亚热带区域不同类型木材树种湿地松（松科）、池杉（杉科）、侧柏（柏科）、榉树（环孔材）、樟树（半环孔材）和意大利杨（散孔材），对其木材形成过程进行系列解剖观察与特性分析，研究其形成层分生活动规律、次生木质部细胞季节性动态变化、次生木质部细胞数量累积特征、细胞壁木素沉积过程与分布、组织比量变化与气候因子的关系，揭示其维管形成层发生发育的解剖学机理，分析其木材细胞长度与木材密度与气象因子间关系，比较针叶树松杉柏三科间和阔叶树环孔材、散孔材和半环孔材间形成层分生活动规律和木质部细胞分化上的差异，探索其木材形成过程，为亚热带地区主要造林树种木材质量的生物改良、定向培育和木材资源的合理利提供科学理论依据.

树木形成层活动及其细胞分化是研究木材形成的基础。本项目选择亚热带不同类型木材树种湿地松、池杉、侧柏和榉树、樟树、杨树为材料，研究其顶端生长点细胞分生活动、形成层发生、形成与分生活动规律、次生木质部细胞时空动态变化及其子细胞数量累积特征、木材细胞形态特征及其组织比量变化与气候因子间的关系，研究其细胞壁形成、木素沉积过程与分布，比较了六个树种间形成层分生活动规律和木质部细胞分化上的差异，揭示其维管形成层发生发育的解剖学机理与木材形成过程。结果表明六个树种形成层年活动规律与气候因素密切相关，呈明显的季节性规律，形成层细胞与木质部子细胞解剖特征之间有一定的相关性。形成层恢复期，细胞中小液泡合并成大液泡，细胞形状变得极不规则，且弦向壁和径向壁明显变薄，内含物含量急剧降低；形成层活动旺盛期，基本看不到内含物的存在，细胞质凝缩在细胞壁周围，呈条带状分布，没有明显的质壁分离。次生壁加厚期，原生质体逐渐瓦解并消失；射线细胞分化过程没有出现原生质体的衰退现象，细胞一直保持生物活性，直到次生壁加厚过程的完成。生长后期形成层活动减弱，内含物重新富积，休眠期内含物又开始积累。次生维管组织活动早期及旺盛期，细胞木质化程度较低，木素首先沉积在角隅处，之后沉积在最先分化出来的细胞壁上。形成层活动后期至休眠期，细胞壁荧光越来越强、分布逐渐均匀，木质化程度高。形成层活动周期中，径向壁都比弦向壁厚。造成木质部细胞体积增大的主要因素的是伸展生长期，这一时期主要是初生壁微纤丝不断沉积。随着分化过程的开始，次生壁S1层微纤丝开始积累在初生壁内侧。次生壁物质首先沉积在细胞角隅处，刚形成的次生壁上，细胞壁物质排列比较疏松，还未发生木质化；之后，CMfs的沉积和木质化同时进行。厚薄细胞次生壁呈现明显三层结构（S1、S2和S3层），射线细胞壁呈现复杂的多层次结构。研究结果为人工林木材形成、生物改良、定向培育和合理利用提供科学理论依据。

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