Am J Bot. 1997 Sep;84(9):1192.
Stems of Eulychnia (a genus of six to nine species of candelabriform or arborescent cacti) have a parenchymatic cortex with two distinct regions. The outer chlorenchymatic layer is characterized by a conspicuous parallel striping, whereas the inner cortex region devoid of chlorophyll has a coarsely granular aspect. Stem samples from nine accessions, collected in the field or taken from cultivation, were studied from resin-embedded microtome sections and maceration. Two different forms of lignified sclereids were found dispersed in the cortex and the pith. The sclereids of the outer palisade-like cortex layer are distinctly elongated and strictly oriented at right angle to the stem surface, whereas those of the inner cortex and pith are globular or subglobular and conspicuously enlarged compared with the surrounding parenchyma cells. The ontogeny of the sclereids was studied from stem samples of different ages. Formation of the secondary cell walls starts only after cell growth is completed. A screening of numerous South American cacti for the presence of idioblastic sclereids showed that these structures are unique for the genus Eulychnia. Finally, functional aspects of the sclereids are shortly discussed. It is assumed that the sclereids contribute to the mechanical support and reinforcement of the plants.
茎的 Eulychnia （一个属的 6 至 9 种的烛台状或乔木仙人掌）有一个薄壁组织的皮质与两个不同的区域。外层的绿色组织层的特点是明显的平行条纹，而没有叶绿素的内层皮质区具有粗糙的颗粒状外观。从野外采集或栽培的 9 个标本的茎样本，从树脂包埋的切片和浸出物进行研究。在皮质和髓中发现两种不同形式的木质化厚壁组织细胞分散。外层栅栏状皮质层的厚壁组织细胞明显拉长，并与茎表面成直角严格定向，而内层皮质和髓的厚壁组织细胞呈球形或近球形，与周围的薄壁组织细胞相比明显增大。从不同年龄的茎样本中研究了厚壁组织细胞的发生。次生细胞壁的形成仅在细胞生长完成后才开始。对大量南美仙人掌进行的针对同型厚壁组织细胞存在的筛选表明，这些结构是 Eulychnia 属所特有的。最后，简要讨论了厚壁组织细胞的功能方面。据推测，厚壁组织细胞有助于植物的机械支撑和加固。
