Identification of Juvenile Duration and Morphological Changes in Leaves and Stems after Transition to the Adult Phase in Native Trachelospermum in Korea

This study was conducted to determine an index of phase changes in Trachelospermum jasminoides leaf and stem morphology and to identify the timing of the juvenile-to-adult phase transition. Fifty percent of stems showed thigmotropism in the fall of the 5th year after sowing. In May of the 6th year, stems had adult leaves and 33% of the stems bloomed, indicating that the juvenile period for native T. jasminoides requires at least 5 years prior to blooming. As a result of a study targeting 13 regions in Korea to identify changes in the shape of leaves and stems during the juvenile and adult leaf phases, the leaf shape index of juvenile leaves was greater than that of adults in cultivation test districts and most (10) regions. Young leaves were lanceolate with distinct veins, whereas adult leaves were long and oval-shaped, with inconspicuous morphological changes. This study shows that juvenile and adult phases can be distinguished by the thigmotropism of stems, leaf vein pattern, relative size of leaves, and leaf shape index. This identification method could be adapted into an index to discriminate the juvenile and adult phases of the native T. jasminoides. According to a dendrogram and PCA, there was no clustering by region of harvest and the morphological elements in juvenile and adult leaves were similar. In addition, PCA showed that leaf area had the highest contribution rate among the first main components and could be used as an indicator for distinguishing the juvenile and adult phases of native T. jasminoides.