Rootstock is one of several botanical terms that have multiple
definitions. You seem to be referring to the old gardening definition
of rootstock as a synonym for rhizome or underground stem. Using
rootstock as a term for a stem is obviously confusing and therefore
The more useful definition of rootstock is the root bearing part of a
grafted plant. However, even when applied to grafting, rootstock is
somewhat misleading. Less misleading terms are understock or stock. A
stock may consist solely of root tissue. However, a stock is usually
going to consist mostly of root tissue with a small amount of stem
tissue. The stock of a topgrafted fruit tree will contain considerable
stem tissue. A stock may include an underground stem but usually it
will not. About the only plant with tubers that is occasionally
grafted is potato. Tomato is grafted on potato as a novelty or for
I mentioned several botanical sources, not just Websters Dictionary.
You mentioned no sources. Katherine Esau was a well respected plant
anatomist. The root chapter in her textbook, Anatomy of Seed Plants,
2nd ed. says Dioscorea has "storage roots." Maybe Esau, Hortus Third
and the half dozen college botany textbooks I consulted are wrong and
Dioscorea does have tubers and not storage roots as you contend. If
so, where is some published proof of that? I checked Simpson and
Ogorzally (1986) which says there is controversy whether Dioscorea
storage organs represent stem or root tissue.
Terms for modified stems are not uniformly defined and are often
confusing. There seems to be more diversity in underground stems than
can be accomodated by the handful of terms commonly used. Tuberous
root and tuber are particularly confusing terms. The term storage root
seems to be preferred over tuberous root in botany textbooks and is
certainly more accurate.
There are different definitions for tuber. Some authorities restrict
tuber to a swollen underground organ that develops from a rhizome or
stolon. By that definition, tuberous begonia and cyclamen do not
produce tubers although they are commonly called tubers. Cyclamen is
often referred to as a corm as well. Their storage organs develop
mainly from the hypocotyl and have a vertical orientation, not the
horizontal orientation of a "true" tuber. They are sometimes termed
tuberous stems instead (Hartmann and Kester 1983). However, that term
adds additional confusion. The aerial tubers of some Dioscorea species
are also not "true" tubers and are sometimes termed tubercles or
David R. Hershey
Hartmann, H.T. and Kester, D.E. 1983. Plant Propagation: Principles
and Practices. Englewood Cliffs, NJ: Prentice Hall.
Simpson, B.B. and Ogorzally, M.C. 1986. Economic Botany: Plants in Our
World. NY: McGraw-Hill.
"Cereoid+10" <cereoid at prodigy.net> wrote in message news:<uV40a.704$kR2.658 at newssvr16.news.prodigy.com>...
> The term rootsock does not mean the same as true roots. Roostock refers to
> the central body of perennial plants and can be rhizomes, tubers, bulbs,
>> Webster's (which is not a botanical reference anyway) is wrong. The
> rootstock of Dioscorea is a tuber. Often it is fleshy but it can be woody
> and caudiciform. None have tunicated corms.
>> You should look for yourself rather than rely on sources based on second or
> third hand information.
>>> David Hershey <dh321 at excite.com> wrote in message
> news:7039c6ef.0302041326.22733e31 at posting.google.com...> > A rootstock cannot be a tuber because a tuber is a modified stem.
> > A variety of terms are applied to storage structures of Dioscorea.
> > Katherine Esau in her Anatomy of Seed Plants text, Hortus Third,
> > Webster's New Collegiate Dictionary (under yam) and all the college
> > introductory botany texts I checked all say Dioscorea has a storage
> > root or tuberous root. Hortus Third also says D. bulbifera produces
> > aerial tubers, and some Dioscorea species have rhizomes. A few
> > websites even claim some Dioscorea species do have corms.
> > Distinctions between types of modified stems, such as stolons,
> > rhizomes, tubers and corms, are not always clear cut.
> > Reference
> > David R. Hershey
> > "Cereoid+10" <cereoid at prodigy.net> wrote in message
> news:<flA%9.3109$LZ6.1357 at newssvr16.news.prodigy.com>...
> > > Sorry Spammy Davis, Jr. but you have already jumped to wrong conclusions
> > > that does not help.
> > >
> > > The rootstock of Dioscorea is a tuber not a corm. A corm is covered by a
> > > tunic but a tuber is not.
> > >
> > > Dioscorea is a huge genus and even includes a number of cold hardy
> > >
> > > The "Sweet Potato" Ipomoea batatas is a "Morning Glory" with tuberous
> > >
> > >
> > > I Don't Like Spam <nobody at ibm.com> wrote in message
> > > news:1ait3vc1horkuisq67hljgo2v2tia0433s at 4ax.com...> > > > In article <v3rh869esm5ha5 at corp.supernews.com>,
> > > > blair <blair863 at hotmail.com> wrote:
> > > > >I was at somebody's house once and they had a big sprawling plant
> > > > >shaped leaves. They said that they grew it by putting a relative of
> > > > >family into the ground and planting it. Apparently you could also
> plant a
> > > > >yam and grow a different plant as well.
> > > > >
> > > > >Does anyone know what this plant is?
> > > > When I was in college, a friend planted a sweet potato in a pot and
> > > > let it grow. Later she told her room-mate that it was a "heart-shaped
> > > > wandering jew". This was believed until an energetic pet knocked the
> > > > pot over, breaking it, revealing the true nature of the plant. As
> > > > mentioned earlier, sweet potato is in Convolvulaceae, with morning
> > > > glories.
> > > >
> > > > I wouldn't have brought this up, except sitting on my window sill here
> > > > at work is a member of the yam family Dioscoreaceae, _Dioscorea
> > > > macrostachya_, (dormant right now) the leaves of which are very
> > > > similar to the heart shaped leaves of sweet potato. This grows from a
> > > > large corm that is quite interesting in appearance. In nature this
> > > > corm is hidden underground, but when sold as a houseplant, the organ
> > > > is kept above ground for show (some of the larger, older ones resemble
> > > > a tortoise shell, at least if you have an active imagination).
> > > >
> > > > So, before we jump to conclusions about exactly what the plant is,
> > > > there ARE some members of the yam family kept as houseplants that fit
> > > > your description (although, in general, they are a bit pricey, and not
> > > > very common except perhaps through specialty succulent dealers).
> > > >
> > > > Sweet potatoes as sold in the US, often called yams (oh the wonders of
> > > > misleading common names). Ask your friend if they could allow you to
> > > > take a look at the underground stem by brusing away a little soil. If
> > > > it looks like a sweet potato, it probably is. Otherwise, my Dioscorea
> > > > has a THIN, SINGLE, TOUGH twining vine that comes from the TOP of a
> > > > CORM-like structure. If I recall correctly, a sweet potato would
> > > > likely have SEVERAL sprouts coming from a VARIOUS POINTS along a
> > > > HORIZONTAL TUBER, and those sprouts would tend to be more FLESHY or
> > > > SUCCULENT, at least close to the tuber.
> > > >
> > > > Hope this helps.