Urticaceae

Key takeaways

Urticaceae belongs to science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Urticaceae to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Urticaceae from memory before moving on to harder problems.

Reference excerpt

The Urticaceae are a family, the nettle family, of flowering plants. The family name comes from the genus Urtica. The Urticaceae family includes a number of well-known and useful plants, including nettles in the genus Urtica, Ramie (Boehmeria nivea), māmaki (Pipturus albidus), and ajlai (Debregeasia saeneb). The family includes about 2,625 species, grouped into 53 genera. The largest genera are Pilea (500 to 715 species), Elatostema (300 species), Urtica (80 species), and Cecropia (75 species). Cecropia contains many myrmecophytes. Urticaceae species can be found worldwide, but most species are found in tropical ecosystems, especially tropical Asia.

Description Urticaceae species can be herbs (e.g. Urtica, Parietaria), shrubs(e.g. Pilea), hemi-epiphytes, or, rarely, trees (Dendrocnide, Cecropia). Their leaves are usually entire and bear stipules. Urticating hairs are often present. Stinging trichomes on the leaves break upon contact, imbedding a sharp tip into animal skin which is filled with an irritating liquid. This liquid consists of compounds such as histamines and acetylcholines that create an irritating skin reaction. These urticating trichomes are an herbivory defense against primarily mammals, but also defend against invertebrate herbivory as well.

Urticaceae flowers are typically unisexual, with rare cases of functionally hermaphroditic flowers. Pistillate flowers have superior pseudomonomerous ovaries extending to one style. This family has a gynoecium with two carpels, and a perianth of four to five. Urticacids explosively release their pollen when their urticaceaous stamens dry in the heat, causing the filaments to straighten and the anthers to release pollen in a swift motion. Plants are then wind-pollinated. Fruits are achenes.Additional characteristics represented by members in the family are leaves with cystolith or silicone accumulation. Some members exhibit latex presence only in the bark as an anti-herbivory defense. While the stings delivered by Urticaceae species are often unpleasant, they seldom pose any direct threat to health, and deaths directly attributed to stinging are exceedingly rare; species known to cause human fatalities include Dendrocnide cordata and Urtica ferox.

Uses Many members of Urticaceae are cultivated and foraged worldwide for various uses, including food, medicines, and to create tools. Some notable species include:

Pouzolzia mixta (soap nettle), is used as a culinary herb, made into rope, and is a source of traditional medicine in several southern African countries. Urtica angustifolia, which grows throughout eastern Asia, is an important traditional Chinese medicine plant. Cecropia obtusa, Laportea aestuans, and Urera baccifera are all species used as anti-inflammatory and diabetes medicine in Brazil. While Urtica dioica stinging hairs cause inflammation, the plant has been used to treat a large variety of medical issues, including, but not limited to: arthritis, gout, anemia, and eczema.

Diseases The Urticaceae are subject to many bacterial, viral, fungal, and nematode parasitic diseases. Among them are:

Bacterial leaf spot, caused by Xanthomonas campestris which affects Pellionia, Pilea, and other genera. Anthracnose, a fungal disease caused by Colletotrichum capsici which affects Pilea. Myrothecium leaf spot, a fungal disease caused by Myrothecium roridum which affects plants throughout the Urticaceae, as well as other angiosperms Phytophthora blight, a water mold disease caused by Phytophthora nicotianae which affects Pilea Southern blight, a fungal disease caused by Athelia rolfsii which affects both Pellionia and Pilea

Fossil record The fossil record of Urticaceae is scattered and mostly based on dispersed fruits. Twelve species based on fossil achenes are known from the Late Cretaceous of Central Europe. Most were assigned to the extant genera Boehmeria (three species), Debregeasia (one species) and Pouzolzia (three species), while three species were assigned to the extinct genus Urticoidea. A Colombian fossil flora of the Maastrichtian stage has yielded leaves that resemble leaves of the tribe Ceropieae. In the Cenozoic fossil leaves from the Ypresian Allenby Formation preserve distinct trichomes, and have been attributed to the Tribe Urticeae in the fossil record. The leaves had originally been identified as Rubus by earlier workers on the Eocene Okanagan Highlands, but Devore et al (2020) interpreted the preserved hairs along the stem and major veins as stinging trichomes, rather than simple hairs or thorns.

Taxonomy

Classification The APG II system puts the Urticaceae in the order Rosales, while older systems consider them part of the Urticales, along with Ulmaceae, Moraceae, and Cannabaceae. Urticaceae is a monophyletic group.

Phylogeny Modern molecular phylogenetics suggest the following relationships (see also ):

Tribes and genera

Image gallery

References

Further reading Pignatti, Sandro (1982). Flora d'Italia (in Italian). Bologna: Edagricole. ISBN 978-88-506-2449-2. Friis, Ib (1989). Urticaceae. Flora of tropical East Africa. Rotterdam: A.A. Balkema and the Royal Botanic Gardens, Kew. ISBN 978-90-6191-352-8.

External links

Stevens, P. F. "Angiosperm Phylogeny Website, Version 13". Missouri Botanical Garden. continuously updated.

Illustrations

Worked examples

Example 1 — a first encounter with Urticaceae

Start with the simplest possible case. Write down what Urticaceae claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Urticaceae before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Urticaceae ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Urticaceae

In research: Urticaceae appears in science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Urticaceae in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Urticaceae is common in secondary-school and first-year university syllabi. It links to neighbouring topics Rosid families, Taxa described in 1789, Urticaceae, so understanding it makes those chapters shorter.
In everyday life: Look for Urticaceae outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

How to study Urticaceae in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Urticaceae means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Urticaceae out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Urticaceae in simple terms?

The Urticaceae are a family, the nettle family, of flowering plants. The family name comes from the genus Urtica.

Why does Urticaceae matter?

Because it connects several science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Urticaceae?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Urticaceae.