Apical cell development

White (1984) used the term module to describe the product of any single apical meristem. In moss gametophytes the apical meristem consists of a single apical cell with three or occasionally two cutting faces. Each cell produced directly by fission from the apical cell develops into a metamer, a unit eventually consisting of one leaf, tissue forming epidermis and cortex, and often... 

Edwards, J.S., Chen, S.W. and Berns, M.W. (1981) Cereal sensory development following laser microlesions of embryonic apical cells in Acheta domesticus. J. Neurosci. 1 250-258. 

Implantation and subsequent placentation is a unique mammalian form of reproduction. A fertilized mammalian egg autonomously develops into a blastocyst, which must be successfully implanted in the uterus to develop further into a fetus. Initial adhesion of the embryo to the uterus occurs via the apical cell membrane of two polarized epithelial cells, the trophoblast of blastocysts, and surface epithehal cells of the endometrium. This adhesion is unique because it is apical-apical adhesion between two epithelial cells, whereas generally apical cell surfaces of epithelia are nonadhesive. 

The formation of the secondary modules reflects the action of several processes controlling the development of the lateral primordia. Each merophyte has the potential to form an apical cell that... 

Where branch primordia are found evenly distributed along the module, but development of primordia into secondary modules is localized or complanate, it can be supposed that the branching pattern seen reflects mechanisms involving control or release of dormancy. The role of auxins, specifically indolyle-3-acelic acid (lAA), in apical donfinance has been shown to be similar to that in vascular plants (see Cooke et al., 2002, for summary), and can be expected to have an important role in the suppression or release from dormancy of branch primordia. For example, if the apical cell of the primary module is producing auxins that suppress development, branch primordia will develop only when they are sufficiently far from the apical cell for the levels of auxin to have dropped to a certain level. Similarly, the density of secondary modules may also reflect auxin control of module development, with branch primordia remaining dormant where the density of secondary modules has reached a local optimum. There is also evidence that lAA can control development of body-plan (i.e., selective development of branch primordia) (Cooke et al., 2002). 

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