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本研究以6个月巨桉无性系GL1苗木为试验材料,外源施加赤霉素到巨桉茎部,通过组织化学分析其对木质部发育的影响.外施GA3浓度在1.0～1 0.0 mg/L时能够显著促进桉树茎的伸长,外施1.0 mg/LGA3时,新生木质部中纤维细胞数量显著增加,而纤维细胞的直径没有变化,组织化学分析表明木质部细胞的增加主要是通过细胞分裂增加纤维细胞数量的方式,新生木质部导管分子数量和直径并没有显著增加.同时GA3处理会引起新生木质部中S-木质素和G-木质素含量降低,且GA3并不能显著促进巨桉新生木质部细胞中纤维细胞和导管分子的伸长.这些研究说明赤霉素通过调控细胞的分裂和次生细胞壁成分的合成来调控巨桉次生木质部发育.“,”In this study,the stem of a 6-month-old Eucalyptus grandis clone GL1 was treated exogenously with GA3.Chemical and anatomical phenotypes analysis were characterized to uncover the roles of GA3 in secondary xylem formation of E.grandis.Length of shoots significantly increased by exogenously applied 1.0～10.0 mg/L GA3.Meanwhile,number of fiber cells in newly developing xylem clearly increased and diameters of fiber cells showed no significant change,which was mainly through the acceleration of cell division in xylary cells.Moreover,it was indicated that coniferaldehyde (G) units and sinapyl aldehyde (S) units were significantly down-regulated in GA3-treated stems.However,the length of both types of xylary cells (fiber and vessel elements) did not increase significantly after GA3 application.Thus,GA3 showed regulatory roles in the biosynthesis of secondary cell wall components and cell divisions during secondary xylem development in E.grandis.