One or more of the lateral meristems, which are located at each base of each leaf but attached to the stem node, is stimulated by hormones to produce female flower parts. In corn each node of the modified lateral meristem includes two ovules, one of which degenerates. The ovule diploid cell undergoes meiosis, initially producing 4 monoploid nuclei but three degenerate, leaving a megaspore cell with one monoploid (haploid) cell. This single set of 10 chromosomes on hybrid plants represents a random mix of chromosomes from each of the hybrid plant’s parents. Thus, just as with pollen, there is a minimum of 1028 different sets of genetics among the ovules on a single plant.
The nucleus of the megaspore cell undergoes three successive mitotic divisions resulting in 8 nuclei and a total of 7 cells. Most important of these is the egg cell with a single monoploid nucleus and a large central cell with 2 monoploid nuclei. The central cell is destined to become the endosperm after pollination. Two of the other cells (called synergid cells) adjacent to the egg cell apparently produce attractants to guide the pollen tube to the egg cell. A small opening, called a micropyle, at the tip of the embryo sac, is conveniently located where the silk is attached to the ovule. This composes the embryo sac of the female.
This development process continues in the 500-1000 ovules a few weeks before pollination. Environment and genetics of the hybrid plant influences the actual number of ovules that develop.
About Corn Journal
The purpose of this blog is to share perspectives of the biology of corn, its seed and diseases in a mix of technical and not so technical terms with all who are interested in this major crop. With more technical references to any of the topics easily available on the web with a search of key words, the blog will rarely cite references but will attempt to be accurate. Comments are welcome but will be screened before publishing. Comments and questions directed to the author by emails are encouraged.