biology

Rehmannia

Rehmannia is a biology topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Rehmannia rather than just read about it. In short: Rehmannia is a genus of seven species of flowering plants in the order Lamiales and family Orobanchaceae, which is native to China and Japan. It has been placed as the only member of the monotypic tribe Rehmannieae, but molecular phylogenetic studies suggest that it forms a clade with Triaenophora.

Key takeaways

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

Reference excerpt

Rehmannia is a genus of seven species of flowering plants in the order Lamiales and family Orobanchaceae, which is native to China and Japan. It has been placed as the only member of the monotypic tribe Rehmannieae, but molecular phylogenetic studies suggest that it forms a clade with Triaenophora. Contrary to the vast majority of the taxa of Orobanchaceae, Rehmannia is not parasitic.

Systematics

Etymology Rehmannia is named for Joseph Rehmann (1788–1831), a physician who worked in St. Petersburg.

Homonymy The name "Rehmannia" has also been given to a genus of Jurassic ammonites of the family Reineckeidae.

Classification The genus was included in the family Scrophulariaceae or Gesneriaceae in some older classifications. The current placement of the genus is in neither Scrophulariaceae s.s. nor Plantaginaceae s.l. (to which many other former Scrophulariaceae have been transferred). Earlier molecular studies suggested that its closest relatives were the genera Lancea and Mazus, which have been included in Phrymaceae. Subsequently, it was found that Rehmannia groups with Triaenophora, and both taxa are jointly the sister group to Lindenbergia and the parasitic Orobanchaceae. A 2016 classification of flowering plants, the APG IV system enlarged Orobanchaceae to include Rehmannia, making it one of the few genera in the family, along with Lindenbergia, not to be parasitic.

Species list As of February 2025, Plants of the World Online accepted seven species:

Uses Sometimes known as Chinese foxglove due to its superficial resemblance to the genus Digitalis, the species of Rehmannia are perennial herbs. The plants have large flowers and are grown as ornamental garden plants in Europe and North America, and are used medicinally in Asia.

Traditional Chinese medicine

Known as dìhuáng (地黄) or gān dìhuáng (干地黄) in Chinese, R. glutinosa is used as a medicinal herb for many conditions within Chinese traditional formulations. It is the main ingredient in a mixture called si wu tang (four substance decoction) along with Dang gui, Chinese peony (bai shao yao), and Ligusticum striatum (chuan xiong) that is considered a fundamental medicine to support making blood. When two ingredients, peach (tao ren) and safflower (hong hua), are added, it is called tao hong si wu tang (four substance decoction with peach pit and safflower), which is used in traditional chinese medicine for fatigue.

Chemical constituents Rehmannia contains the vitamins A, B, C, and D, as well as other compounds, such as catalpol, an iridoid glycoside.

References

External links Media related to Rehmannia at Wikimedia Commons

Illustrations

Worked examples

Example 1 — a first encounter with Rehmannia

Start with the simplest possible case. Write down what Rehmannia claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In biology, 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 Rehmannia 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 Rehmannia 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 Rehmannia

In research: Rehmannia appears in biology 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 Rehmannia 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: Rehmannia is common in secondary-school and first-year university syllabi. It links to neighbouring topics Dietary supplements, Medicinal plants of Asia, Orobanchaceae genera, so understanding it makes those chapters shorter.
In everyday life: Look for Rehmannia 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.

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How to study Rehmannia in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Rehmannia 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 Rehmannia out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Rehmannia in simple terms?

Why does Rehmannia matter?

Because it connects several biology 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 Rehmannia?

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 Rehmannia.