前期研究发现适度干旱可以促进降香黄檀心材形成，但其机制尚不清楚。目前树木心材形成机理不明，很难直接围绕其机理与过程开展研究。因此，本项目以心材形成的原料非结构性碳水化合物（NSC）为切入点，探究适度干旱如何影响NSC在韧皮部和木质部间的交换运输及木射线的双向运输等径向转运，为心材形成提供更多原料，间接揭示干旱促进降香黄檀心材形成的机制。以10年生降香黄檀人工林为对象，设置重度、轻度干旱和对照处理，运用13C同位素示踪分析树干韧皮部NSC经交换运输后13C丰度的变化规律，验证适度干旱是否通过加强NSC在韧皮部和木质部间的交换运输，使更多NSC从韧皮部扩散至木质部；并分析树干木质部NSC各组分含量及径向分布，验证适度干旱是否通过增加NSC在内边材和过渡区等深层木质部的积聚及可溶性糖在NSC中的占比，为心材形成提供更多可直接利用的碳原料。研究结果将为降香黄檀人工林高效培育提供理论依据和技术支撑。

We have found that non-lethal drought can promote the formation of heartwood of Dalbergia odorifera, however its mechanism remains unclear. Because the mechanism of heartwood formation is unknown, it is impossible to conduct studies based on the mechanism and process of heartwood formation directly. Non-structural carbohydrates (NSC), the raw materials for the synthesis of heartwood substances, are continuously supplied through radial transport processes such as exchange transport between the phloem and xylem and bidirectional transport in the xylem ray cells. Thus, this study will explore how non-lethal drought can provide more raw materials for heartwood formation by affecting the radial transport of NSC in the stem and reveal the mechanism that explains how drought promotes the formation of heartwood of Dalbergia odorifera. This study will conduct a throughfall exclusion experiment (severe and mild drought) in a 10-year-old Dalbergia odorifera plantation. In order to verify whether non-lethal drought enhances the exchange transport of NSC between phloem and xylem and causes more NSC to spread passively from phloem to xylem, we will analyze the variation in 13C abundance of NSC after exchange transport by using 13C isotope tracer technique. In addition, we will analyze the content and radial distribution of each component of NSC in the xylem of the stem to verify whether non-lethal drought provides more directly usable carbon for the synthesis of heartwood substances by increasing the accumulation of NSC in the inner xylem such as the inner sapwood and transition zone and the proportion of soluble sugars in NSC. These results will provide theoretical basis and technical support for the efficient cultivation of Dalbergia odorifera plantation.