Leaves of all higher plants have leaves attached to the stem at a place called nodes. Monocotyledons including grasses like corn, have one leaf per node. At the base of the attachment of the leaf is a branch meristematic growing point. Genetics and environment determine whether the meristematic cells at an individual node divide and develop into another stem, some environments such as wide plant spacing with some genetics encourage the lower node buds to develop a branch stem that we call a tiller. Corn was selected from Teosinte plants often had tillers at lower nodes of central stem with many upper plant node buds developing into specialized branches as flowering structures. These became small ears at numerous upper nodes.
Humans selected, over several thousand years, genetics that generally inhibited the growth of most nodal meristems, selecting for plants without nodal branches except for one specialized branch for female flowers at a node convenient for humans use. That branch consisted of leaves surrounding a series of nodes each of which had a female flower in which an embryo was surrounded by specialized tissue and from which a long, specialized tissue extended beyond the leaves. This specialized tissue could be penetrated by corn pollen from other plants or from the other specialized tissue at the top of the plant, the tassel. Each tiny flower within the specialized nodal branch produces its own embryo surrounded by tissues that ultimately, after pollination, develops into a seed within the fruit that we call the kernel. Genetics and environment determine the number of nodes with these specialized buds and the number of flowers within these buds.
Accumulation of heat or day length interact with genetics determine the timing of these ear shoots and environment affect on photosynthesis the number of specialized flowers created within an individual nodal branch we call an ear. Humans have selected genetics concentrating the nodal buds into specialized structures stored with carbohydrates in forms that are convenient for human consumption.
That reminds me, I wonder if the sweet corn in our nursery is ready for eating?
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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.