Abstract:

As an important natural resource, trees have giant environmental, social, and economic values. The growth stress of trees can be generated by the interaction between cells and cell layers during wood growth and maturation. For trees, growth stress is necessary for stems and branches to grow vertically or at a constant angle. And in response to gravity, light, snow, and slope, trees are prone to produce reaction wood with high growth stress to maintain or adjust their posture. Growth stress has a great effect on the structure, chemical components, and processing of wood. Exploring the distribution and generation mechanisms of growth stress is of great significance to directional cultivation, understanding biological structure and function, the processing and utilization of wood-based materials, and the exploration of new biomimetic materials. Many researchers have attempted various experiments and simulations to discover the origin of growth stress. Different hypothetical mechanisms have been proposed in the literature based on the results of the growth stress level, microstructure, genes, chemistry, hormones, and properties. However, due to the complexity and diversity of tree structure, there are still many divergences in the generation mechanisms of growth stress. With the development of plant science and the improvement of research technology, researchers’ understanding of the growth stress is evolving. In this paper, the biomechanical effect and the testing methods of growth stress in trees were introduced, and some mainstream theories about the origin of growth stress were summarized. The general hypothetical mechanisms of growth stress generation and some special mechanisms targeted reaction wood were discussed to identify which are inconsistent with current knowledge. In conclusion, reviewing the generation mechanisms is helpful to completely understand the growth stress in trees and it can provide the theoretical basis for further research on the mechanism, the study on the variation of wood structure and properties, and the fine utilization of wood. And the exploration of the growth stress generation mechanisms can provide a solid foundation for optimization measures to the loss caused by the growth stress and biological improvement and cultivation of planted forest.

Key words: growth stress, generation mechanism, reaction wood, tension wood, compression wood