Lee Kyounghwan, Nah Seung-Yeol, Kim Eun-Soo
Department of Cell and Developmental Biology, University of Massachusetts Medical School, Worcester, MA, USA.
College of Veterinary Medicine, Konkuk University, Seoul, Korea.
J Ginseng Res. 2015 Apr;39(2):135-40. doi: 10.1016/j.jgr.2014.10.001. Epub 2014 Oct 28.
A leaf cuticle has different structures and functions as a barrier to water loss and as protection from various environmental stressors.
Leaves of Panax ginseng were examined by scanning electron microscopy and transmission electron microscopy to investigate the characteristics and development of the epicuticular structure.
Along the epidermal wall surface, the uniformly protuberant fine structure was on the adaxial surface of the cuticle. This epicuticular structure was highly wrinkled and radially extended to the marginal region of epidermal cells. The cuticle at the protuberant positions maintained the same thickness. The density of the wall matrix under the structures was also similar to that of the other wall region. By contrast, none of this structure was distributed on the abaxial surface, except in the region of the stoma. During the early developmental phase of the epicuticular structure, small vesicles appeared on wall-cuticle interface in the peripheral wall of epidermal cells. Some electron-opaque vesicles adjacent to the cuticle were fused and formed the cuticle layer, whereas electron-translucent vesicles contacted each other and progressively increased in size within the epidermal wall.
The outwardly projected cuticle and epidermal cell wall (i.e., an epicuticular wrinkle) acts as a major barrier to block out sunlight in ginseng leaves. The small vesicles in the peripheral region of epidermal cells may suppress the cuticle and parts of epidermal wall, push it upward, and consequently contribute to the formation of the epicuticular structure.
叶片角质层具有不同的结构和功能，可作为防止水分流失的屏障以及抵御各种环境应激源的保护机制。
通过扫描电子显微镜和透射电子显微镜对人参叶片进行检查，以研究表皮角质层结构的特征和发育情况。
沿表皮细胞壁表面，角质层的近轴面存在均匀突出的精细结构。这种表皮角质层结构高度褶皱，并径向延伸至表皮细胞的边缘区域。突出部位的角质层厚度保持不变。这些结构下方的壁基质密度也与其他壁区域相似。相比之下，除气孔区域外，远轴面均未分布这种结构。在表皮角质层结构的早期发育阶段，表皮细胞外周壁的壁-角质层界面上出现小泡。一些与角质层相邻的电子不透明小泡融合形成角质层，而电子透明小泡相互接触并在表皮壁内逐渐增大。
向外突出的角质层和表皮细胞壁（即表皮角质层皱纹）是人参叶片阻挡阳光的主要屏障。表皮细胞外周区域的小泡可能抑制角质层和部分表皮壁，将其向上推，从而有助于表皮角质层结构的形成。
