Re: Tuber vs. Corm

From: Jonathan Ertelt <jonathan.ertelt at vanderbilt.edu> on 1999.01.14 at 23:19:32(2900) >This question was discussed at some length last fall on a gesneriad growers >listserve - one member found the following definitions on the web: > >On the GardenWeb site (http://www.gardenweb.com/glossary/): > >Corm: The enlarged fleshy base of a stem, bulb-like but solid. > >Tuber: A thickened and short subterranean branch having numerous >buds or eyes and used for food storage. > > > +More >>From the glossary of the Flora of Australia >(http://155.187.10.12/glossary/fl-aust.html): > >Corm: A fleshy, swollen stem base, usually underground, in which >food reserves are stored between growing seasons. > >Tuber: A storage organ formed by swelling of an underground stem >or the distal end of a root > > >>From the University of Illinois extension service >(http://www.ag.uiuc.edu/~robsond/solutions/horticulture/gloss.htm >l): > >Corm: Swollen underground stem tissue. The basal plate is >located on the bottom of the corm; roots develop from this plate. > >Tuber: Short, fat underground stem tissue with growing points, >buds or "eyes" as in a potato. Tubers can be flat, rounded or >irregular in shape. (Sinningia is used as an example of a >tuberous plant) > > >So, from these definitions, it would seem that a corm is ALWAYS >the swollen BASE of a stem. There is a basal plate on the bottom >of a corm from which the roots arise. A bulb is the swelling of >an underground stem (not necessarily the base of an above-ground >stem), and has multiple growing points. > >An additional point that was made, after it was suggested that tubers and >corms may be the same thing (essentially), but having developed from two >different evolutionary lines, was that to the best of the writer's >knowledge, no monocot families had tubers. >While not an expert, my inclination after some thought is to agree until >exceptions can be raised. An interesting side point for someone to >explore. Monocots seem to have either bulbs or corms as their underground >storage units -- dicots have tubers. >Another note, especially significant for aroid growers - corms do not >necessarily have the basal plate located at the bottom--more often than not >with the corm-growth aroids, the roots are coming out above the storage >tissue, not from below. > >Another point, along a different path -- on the subject of bulbils as the >corm offshoots produced at the base or along the stem at leaf axils on some >aroids. My sense is that this is a non-scientific classification, which >means any term goes. The structures are kind of bulb-like (but not >really), therefore, bulbils. Arguing terms of this sort could go on and on >and, well, you get the point. Kind of like ginger root, meaning, of >course, the stem, or even more abstractly, bromeliad "pups," the basal >sidebranch growths that arise along with or immediately following flowering >with most bromeliads most of the time. Are these really pups? And on it >goes. > >Above all, good growing. >- Jonathan

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