biology

Job's tears

Job's tears 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 Job's tears rather than just read about it. In short: Job's tears (Coix lacryma-jobi), also known as adlay or adlay millet, is a tall grain-bearing perennial tropical plant of the family Poaceae (grass family). It is native to Southeast Asia and introduced to Northern China and India in remote antiquity, and elsewhere cultivated in gardens as an annual.

Key takeaways

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

Reference excerpt

Job's tears (Coix lacryma-jobi), also known as adlay or adlay millet, is a tall grain-bearing perennial tropical plant of the family Poaceae (grass family). It is native to Southeast Asia and introduced to Northern China and India in remote antiquity, and elsewhere cultivated in gardens as an annual. It has been naturalized in the southern United States and the New World tropics. In its native environment it is grown at higher elevation areas where rice and corn do not grow well. Job's tears are also commonly sold as Chinese pearl barley, though true barley belongs to a completely different genus. There are two main varieties of the species, one wild and one cultivated. The wild variety, Coix lacryma-jobi var. lacryma-jobi, has hard-shelled pseudocarps—very hard, pearly white, oval structures used as beads for making prayer beads or rosaries, necklaces, and other objects. The cultivated variety Coix lacryma-jobi var. ma-yuen is harvested as a cereal crop, has a soft shell, and is used in traditional medicine in parts of Asia.

Nomenclature Job's tears may also be referred to under different spellings (Job's-tears, Jobs-tears). The crop is also known by other common names in English, such as adlay or adlay millet. Other common names in English include coix seed, gromwell grass, and tear grass. The seeds are known in Hindi as Vaijanti (वैजंती), Baijanti (बैजंती) or Vaijayanti (वैजयंती), in Chinese as yìyǐ rén (薏苡仁), where rén means "kernel", and also described in Latin as semen coicis or semen coicis lachryma-jobi in pharmacopoeic literature.

Taxonomy The species, native to Southeast Asia, was named by Carl Linnaeus in 1753 with the epithet as a Latin translation of the metaphorical tear of Job. As of February 2015, four varieties are accepted by the World Checklist of Selected Plant Families:

Coix lacryma-jobi var. lacryma-jobi Widely distributed throughout the Indian subcontinent to peninsular Malaysia and Taiwan; naturalized elsewhere. The involucres are ovoid, bony and glossy. It has hard shells and is used as beads in crafts. Coix lacryma-jobi var. ma-yuen (Rom.Caill.) Stapf South China to peninsular Malaysia and the Philippines. The varietal name is eponymous after General Ma Yuen or Ma Yuan (馬援) who according to legend learned of the plant's use when he was posted in Cochin China (or Tonkin, in what is now Vietnam), and brought the seeds back to China to be cultivated. The involucres are elliptical, striate and soft. Coix lacryma-jobi var. puellarum (Balansa) A.Camus Assam to Yunnan (China) and Indochina. It is the smallest among the Indian species, with only 4mm in diameter of the seeds. It is used for ornament as well. Coix lacryma-jobi var. stenocarpa Oliv. Eastern Himalayas to Indochina. Job's tears—along with Coix in —was formerly placed in the Maydeae, now known to be polyphyletic. It has cylindrical, longer than broad involucres. It is widely used as beads for ornaments.

Morphology

Job's tear is a monoecious grass which is broad-leaved, loose-growing, branched and robust. It can reach a height between 1.20 m to 1.80 m. Like all members of the genus, their inflorescences develop from a leaf sheath at the end of the stem and consist partly of hard, globular or oval, hollow, bead-like structures. Job's tear seeds differ in color, with the more soft-shelled seeds being light brown and the hard-shelled forms having a dark red pericarp. The hardened "shells" covering the seeds are technically the fruit-case or involucre (hardened bract), with the bract also referred to as "capsule-spathe" or "sheathing bract" by some past botanical works. These shells cover the bases of the flowers (inflorescences) which are male and female racemes/panicles; the male racemes project upright and consist of overlapping scale-like spikelets, with yellow stamens that pop out in-between, and there are one or two yarn-like stigmas drooping from the base.

Proteins Job's tears – as with Coix in general – produces its own variety of α-zein prolamins. These prolamins have undergone unusually rapid evolutionary divergence from closely related grasses, by way of copy-number changes.

History Job's tears is native to Southeast Asian countries, namely India, Myanmar, China, and Malaysia. Residue on pottery from a Neolithic (late Yangshao Culture) site in north-central China shows that Job's tears, together with non-native barley and other plants were used to brew beer as early as ca. 3000 BC. Job's tears were already introduced to Japan (and probably cultivated alongside rice) in the Early Jōmon Period, corroborated by finds in Western Japan (Chūgoku region), e.g., from studies of phytoliths in the Asanebana Shell Midden (朝寝鼻貝塚) (ca. 4000 BC) in Okayama Prefecture. And further east in Japan, the plant has been found at the Toro site, Shizuoka Prefecture dating to the Yayoi Period. Remains of Job's tears have been found in archaeological sites in northeastern India, dating to around 1000 BC. It was introduced to the subtropical area in India from the east Himalayan belt. A number of scholars support the view it has been in cultivation in India in the 2000–1000 BC period. The wild varieties have hard-coated seeds. Job's tear was one of the earliest domesticated crops. Domestication makes the seed coat become softer and easier to cook. In China, the current cultivation of Job's tears mainly occurs in Fujian, Jiangsu, Hebei, and Liaoning provinces. The cultivation of Job's tears spreads out to temperate areas in North and Northeast China. The shelled grains exported from China were erroneously declared through customs as "pearl barley", and "Chinese pearl barley" remains an alternate common name so that the grains are sold under such label in Asian supermarkets, even though C. lacryma-jobi is not closely related to barley (Hordeum vulgare). The name "Job's tears" is a calque of Arabic دموع أيوب (dumūʿ ʾAyyūb), the name used by Arab merchants who introduced the plant to Europe in the Middle Ages. They used the pseudocarps for misbaha (prayer beads) and associated them with the account of the suffering of Job (Ayyub) in the Quran, which is derived from the portrayal of Job in the Hebrew Bible's Book of Job.

Uses

Crafts

… excerpt ends here. Continue reading the full article.

Illustrations

Worked examples

Example 1 — a first encounter with Job's tears

Start with the simplest possible case. Write down what Job's tears 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 Job's tears 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 Job's tears 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 Job's tears

In research: Job's tears 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 Job's tears 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: Job's tears is common in secondary-school and first-year university syllabi. It links to neighbouring topics Austronesian agriculture, Cereals, Coix, so understanding it makes those chapters shorter.
In everyday life: Look for Job's tears 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.

Affiliate

Preply — study more efficiently by working with a personal tutor. 50% off.

How to study Job's tears in 20 minutes

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

Frequently asked questions

What is Job's tears in simple terms?

Why does Job's tears 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 Job's tears?

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 Job's tears.