Sporogenesis in Conifers

Publisher Summary In a microsporangium there are several hundred sporogenous cells that consequently yield many pollen grains, while in a megasporangium the single tetrad is formed from only one. The term sporogenous cell may then be applied to any destined to give rise to a meiotic cell once the archaesporium has differentiated, the remainder forming the tapetum. The sporogenous cells in both microsporangia and megasporangia undergo a finite number of divisions. The final division gives rise to a spore mother cell or meiocyte within which meiosis takes place. This brings to a close the diploid phase of the life cycle, but the haploid spores subsequently acquire elaborate surface architecture. This chapter focuses on these subjects at greater detail. It is noteworthy that the conifers are generally difficult subjects for study because the reproductive cells of interest are often inaccessible to experimental manipulation and difficult or impossible to isolate. For these reasons the most profitable approach has been an in situ one, using a variety of microscopical techniques.