Graham Linda E, Wilcox Lee W
Department of Botany, University of Wisconsin-Madison, Madison, Wisconsin, 53706.
Am J Bot. 1983 Jan;70(1):113-120. doi: 10.1002/j.1537-2197.1983.tb12439.x.
Following fertilization, zygotes of the green alga Coleochaete orbicularis, which are retained on the haploid thallus, first enlarge, then become covered with a layer of vegetative cells. Light microscopy and high-voltage electron microscopy revealed the presence of localized wall ingrowths in vegetative cells adjacent to zygotes. These covering cells resemble the gametophytic placental transfer cells of embryophytes in their morphology, location, and time of development. If Coleochaete cells with wall protuberances function as do placental transfer cells of embryophytes, their presence is evidence that photosynthates may be transported between haploid thallus cells and zygotes. Thus, a nutritional relationship between different phases of the life cycle, similar to that which occurs in embryophytes, may also have evolved in green algae. This first report of putative placental transfer cells in a green alga supports Bower's (1908) ideas concerning the origin of land plant sporophytes and alternation of generations. The presence or absence of cells with wall ingrowths in several species of Coleochaete was correlated with estimates of zygote-plant area ratios.
在受精后，保留在单倍体叶状体上的绿藻圆石莼合子首先会膨大，然后被一层营养细胞覆盖。光学显微镜和高压电子显微镜显示，在合子相邻的营养细胞中存在局部细胞壁内突生长。这些覆盖细胞在形态、位置和发育时间上类似于胚植物的配子体胎盘转移细胞。如果具有细胞壁突起的圆石莼细胞发挥着与胚植物胎盘转移细胞相同的功能，那么它们的存在就证明光合产物可能在单倍体叶状体细胞和合子之间运输。因此，类似于胚植物中发生的生命周期不同阶段之间的营养关系，也可能在绿藻中进化而来。这篇关于绿藻中假定胎盘转移细胞的首次报道支持了鲍尔（1908年）关于陆地植物孢子体起源和世代交替的观点。在几种圆石莼物种中，具有细胞壁内突生长的细胞的有无与合子 - 植物面积比的估计值相关。
