Talk:Tuber

Root tubers versus tuberous roots

Are these two structures analogous botanical terms? Are tuberous roots true tubers?

Root tubers and stem tubers are the same type of storage structure in function but are derived from different tissues and as such have different morphologies. Root tubers and tuberous roots are the same thing, just the way language says thing- roots that have tubers are called tuberous roots while the tubers themselves are root tubers. This article has suffered a lot over the last year and half; when it was divided into two separate articles (Root tubers & Stem tubers) and why is beyond me. It has lost a number of references two. If some one else does not come in response to your tag, I will clean it up and add in a number of references. Hardyplants (talk) 06:39, 4 December 2008 (UTC)

Thanks, if I had enough sources, I would've done the update myself. But botany is not a subject I am very familiar with. I'm more of a cultivator and collector of plants than a true botanist. payxystaxna (talk) 07:56, 4 December 2008 (UTC)

Technically the two parts are very different botanically. The main differences lie in the way the plant "reproduces" (also misleading, as tuberous growth is a cloning process, not reproduction proper). Generally speaking root tubers are simply organs meant to help over-"winter" plants during climactic/environmental extremes--the plants that grow from the buds are from the same plant stem. Stem Tubers, on the other hand, are technically new stems arising from the extension of the old plant--again, meant to assist in the over-"winter"ing of the plant. The differentiation is largely a matter of botanical placement, albeit on a quantified continuum rather than a de facto difference. That said, there is a slight difference in the way the plants perennialize--largely speaking the root tuber exhausts itself and does not create a "new" plant; where as the stem tuber creates a new plant (meaning a new stem crown and new root system). Both tubers "die off" as the plant uses up the resources for aerial growth--the difference is whether the plant is the same stem crown or a new one... —Preceding

This article is inaccurate

Unfortunately, my botany definitions aren't good enough, otherwise I could make all the corrections myself - but for starters, sweetpotatoes are not tubers - they are storage roots. Tubers are modified stems. I believe "tuberous root" is a misnomer.

See the last sentence of the lead section. In botany, it's frequently the case that terms are used differently in different sources, and there are sources that restrict "tuber" to "stem tuber". But equally there are very reliable sources that do not. Thus The Kew Plant Glossary includes both stem and root tubers under "tuber", saying "a swollen root or branch of a root ... (root-tuber)". Peter coxhead (talk) 06:02, 22 August 2015 (UTC)

Terminology

I note that the introduction to the article, violated NPV rules. It used the phrase "some sources" and "treat" in a way that clearly implied that roots are not "real" tubers. No matter what the case. if the definition is in dispute, then this article needs to report both definitions in a neutral way. It should not choose sides. I edited this to make it neutral. Nick Beeson (talk) 12:35, 5 June 2017 (UTC)

I see that another editor has undone your changes; I would have done so too. The lead summarizes the article and does so neutrally: some sources require tubers to be stem-derived; others do not. A source for each view is presented below in the article. Peter coxhead (talk) 13:07, 5 June 2017 (UTC)

This old question has today re-emerged at Cassava, with a fragmentary discussion at Talk:Cassava, followed immediately by a bold edit and a revert. I am not sure that the multiple threads here at Talk:Tuber provide a clear guidance, such as for the case in Cassava. That article says "root tuber" once in the lead; it says the harvested part is the (starchy) root; and image captions and text call the harvested part "tubers", "storage roots", "yuca roots", and just "roots". It is not obvious that any of these uses are actually wrong, but the result is perhaps untidy. Guidance would be appreciated. Chiswick Chap (talk) 07:01, 28 August 2024 (UTC)

Firstly, it's clear that tuber has at least two meanings. As I noted above, the Kew Plant Glossary has two definitions, labelled "1" and "2". (1) is "a thickened branch of an underground stem...", (2) is "a swollen root or branch of a root..." [p. 124]. So to distinguish the two, "stem tuber" and "root tuber" are perfectly reasonable usages. "Tuber" is also used for the storage structure in Cyclamen (see, e.g., here), which develops from the hypocotyl and is more stem-like in some species (e.g. C. persicum), with roots forming only from the bottom, and more root-like in others, with roots forming mainly from the top (e.g. C. hederifolium).

If there is a bias towards tuber meaning one or the other, it may be towards 'stem tuber'. See, e.g., the glossary entry for the Flora of North America here. Peter coxhead (talk) 10:22, 28 August 2024 (UTC)

Many thanks. So, what would be the best thing to do at Cassava? Chiswick Chap (talk) 10:24, 28 August 2024 (UTC)

@Chiswick Chap: right now there are statements like "The harvested part of a cassava plant is the root." I would say no, it's not the whole root. To give an analogy from a perhaps more familiar cultivated plant, when you prepare a carrot, you do so by cutting off the terminal and lateral roots coming from the root tuber: you don't eat them. In the same way, the part of a cassava plant or a sweet potato plant that is eaten is the root tuber, a.k.a. tuberous root. Whether the article uses "tuberous root" or "root tuber" seems simply a matter of personal preference to me, but just "root" is simply wrong. Once it's established what kind of tuber is meant, I would be inclined to just use "tuber". Peter coxhead (talk) 10:39, 28 August 2024 (UTC)

Many thanks, that sounds good and solid; I'll bear it in mind. I think we should wait to see what the other editor has to say before tweaking the text. Chiswick Chap (talk) 11:33, 28 August 2024 (UTC)

Addendum: there may perhaps be a US vs UK difference here, which may explain some of the disagreements. All the UK-based reference books I have on my shelves that have definitions agree that tuber is either a swollen stem or a root, including Stace (2019), New Flora of the British Isles (4th edition). On the other hand, the US-based work Mauseth (2014), Botany : An Introduction to Plant Biology (5th edition) has only the stem definition [p. 672]. It would be interesting to know what some of the American plant editors think (e.g. Plantdrew). Peter coxhead (talk) 14:41, 28 August 2024 (UTC)

Before I start looking at glossaries, the definition I have in my head is that tubers are stem tissue, and that corms, while also stem tissue, are not a subclass of tubers. Cassava is root tissue, but I'm not sure that I know of a more specific word for the harvested structure. Maybe "storage root"? I would consider "root crop" to include tubers and bulbs, so this maybe a case where seeking precision in terminology leaves us with no precise term to use for a particular case (trying to apply precise definitions to "drupe" and "berry" leaves avocado fruits in a limbo with no precise term). I'll look at some glossaries and respond further later today. Plantdrew (talk) 17:02, 28 August 2024 (UTC)

My go-to glossary ("Plant Identification Terminology" by Harris & Harris) defines tuber as "the thickened portion of a rhizome bearing nodes and buds; underground stem modified for food storage". I assume the authors are American (the publisher is American), but haven't been able to confirm. Textbooks I have at hand ("Vascular Plant Taxonomy" by Walters & Keil, "Biology of Plants" by Raven et al.) define tubers as stem tissue. The glossary for Flora of North America defines tubers as "stem segment or thallus outgrowth" and defines tuberous as "resembling a tuber in shape and texture, but not ontogenetically such; esp. roots"

The APWeb glossary has " an underground stem (typically) or roots (then root tuber is best)" (APWeb is maintained by Peter Stevens, who is British).

So there does appear to be difference in US vs UK usage, with the US botanical English not really having a specific term for thickened roots (and I think non-botanists in the US don't really care to distinguish tubers, corms and roots and would use tuber pretty broadly). Plantdrew (talk) 19:11, 28 August 2024 (UTC)

I agree with your interpretation that this is likely to be a US vs UK botany difference. I just grabbed my copy of Flora of Colorado by Ackerfield (1st edition) published by Botanical Research Institute of Texas and she is using a very similar definition in the glossary on page 781. "Tuber. A thick, short, underground stem (e.g., potato)." 🌿MtBotany (talk) 00:05, 29 August 2024 (UTC)

Ok, so we seem to understand the situation now. The issue that remains is what language to use in articles. Since "tuber" is ambiguous internationally, it seems to me that in a botanically oriented description we should always qualify "tuber" as either "stem tuber" or "root tuber" (or use "tuberous root" for the latter). Peter coxhead (talk) 11:16, 29 August 2024 (UTC)

Qualifying is a good idea. There are more than 2000 links to tuber. Some of those are wrong. Colocasia has "The root tuber..."; the storage structure of Colocasia is usually described as a corm. Sagittaria has a link to root tuber (and is mentioned in the root tuber section of this article), although I think the storage structures are also corms (they have clear nodes with the remnants of sheathing leaves).

The majority of the links here are from orchid species. I'm not sure what the orchid structures actually are. It might differ between genera, but I assume it would usually be the same for all species in a genus. Flora of North America's description of Orchidaceae has "roots [...] tuberoid or stolonoid", and "stems [...] thickened as corms or pseudobulbs". Plantdrew (talk) 16:40, 29 August 2024 (UTC)

One of the problems is that nature doesn't come in neat categories, unlike botanical terminology. Consider the orchid genus Ophrys (a special interest of mine). The old Flora of Europe says it has "tubers" without any qualification. The field guides I have use the same terminology. The more scientific work Pedersen & Faurholdt (2007), Ophrys : The Bee Orchids of Europe, calls the structures "tuberoids", glossing this term as "i.e. 'tubers' formed partly from the stem, partly from the root" [p. 13]. Again, the field guides I have describe the underground structures of the orchid genus Dactylorhiza simply as "tubers"; I haven't yet found any detailed analysis of their structure and origin. The Flora of North America says "Roots from base of stem fascicled tuberoids." The FNA glossary entry for "tuberoid" is unhelpful, confused at best: "tuberoid (root-stem) = dropper An axial outgrowth that descends from a bulb and eventually forms a new bulb; esp. in Orchidaceae". Dactylorhiza certainly doesn't have bulbs in the botanical sense, and its "tuberoids" are not "droppers". (Indeed I don't think that any species of orchid has true botanical bulbs – at most pseudobulbs.)

So the orchid articles may only be able to link to "Tuber". Clearly the article needs some more detailed discussion of cases that don't fit neatly into the "stem tuber" / "root tuber" division. Peter coxhead (talk) 06:55, 30 August 2024 (UTC)