Pea

Key takeaways

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

Reference excerpt

Pea is a pulse or fodder crop, but the word often refers to the seed or sometimes the pod of this flowering plant species. Peas are eaten as a vegetable. Carl Linnaeus gave the species the scientific name Pisum sativum in 1753 (meaning cultivated pea). Some sources now treat it as Lathyrus oleraceus; however the need and justification for the change is disputed. The name "Pea" is also used to describe other edible seeds from the Fabaceae such as the pigeon pea (Cajanus cajan), the cowpea (Vigna unguiculata), the seeds from several species of Lathyrus, and Sturt's desert pea (Swainsona formosa). Each pod contains several seeds (peas), which can have green or yellow cotyledons when mature. Botanically, pea pods are fruit, since they contain seeds and develop from the ovary of a pea flower. Peas are annual plants, with a life cycle of one year. They are a cool-season crop grown in many parts of the world; planting can take place from winter to early summer depending on location. The average pea weighs between 100 and 360 milligrams (1+1⁄2–5+1⁄2 grains). The immature peas (and in snow peas and snap peas the tender pod as well) are used as a vegetable, fresh, frozen or canned; varieties of the species typically called field peas are grown to produce dry peas like the split pea shelled from a matured pod. These are the basis of pease porridge and pea soup, staples of medieval cuisine; in Europe, consuming fresh immature green peas was an innovation of early modern cuisine.

Description

A pea is a most commonly green, occasionally golden yellow, or infrequently purple pod-shaped vegetable, the pod has a length of about 4 to 10 centimeters, the fruit is widely grown as a cool-season crop. The seeds may be planted as soon as the soil temperature reaches 10 °C (50 °F), with the plants growing best at temperatures of 13 to 18 °C (55 to 64 °F). They do not thrive in the summer heat of warmer temperate and lowland tropical climates, but do grow well in cooler, high-elevation, tropical areas. Many cultivars reach maturity about 60 days after planting. Peas have both low-growing and vining cultivars. The vining cultivars grow thin tendrils from leaves that coil around any available support and can climb to be 1 to 2 metres (3 to 7 ft) high. A traditional approach to supporting climbing peas is to thrust branches pruned from trees or other woody plants upright into the soil, providing a lattice for the peas to climb. Branches used in this fashion are called pea sticks or sometimes pea brush. Metal fences, twine, or netting supported by a frame are used for the same purpose. In dense plantings, peas give each other some measure of mutual support. Pea plants can self-pollinate.

Genome The pea karyotype consists of seven chromosomes, five of which are acrocentric and two submetacentric. Despite its scientific popularity, its relatively large genome size (4.45Gb) made it challenging to sequence compared to other legumes such as Medicago truncatula and soybeans. The International Pea Genome Sequencing Consortium was formed to develop the first pea reference genome, and the draft assembly was officially announced in September 2019. It covers 88% of the genome (3.92Gb) and predicted 44,791 gene-coding sequences. The pea used for the assembly was the inbred French cultivar "Caméor". In 2022, a pea pangenome was published.

Taxonomy Carl Linnaeus gave the species the scientific name Pisum sativum in 1753 (meaning cultivated pea). Some sources now treat it as Lathyrus oleraceus, although the need and justification for this change is disputed.

Etymology The term pea originates from the Latin word pisum, which is the latinisation of the Greek πίσον (pison), neuter variant form of πίσος (pisos) 'pea'. It was adopted into English as the noun pease (plural peasen), as in pease pudding. However, by analogy with other plurals ending in -s, speakers began construing pease as a plural and constructing the singular form by dropping the -s, giving the term pea. This process is known as back-formation.

Varieties

Garden peas There are many varieties (cultivars) of garden peas. Some of the most common varieties are listed here, with the number of days they require to reach maturity. PMR indicates some degree of powdery mildew resistance; afila types, also called semi-leafless, have clusters of tendrils instead of leaves. Unless otherwise noted these are so called dwarf varieties which grow to an average height of about 1 m. Giving the vines support is recommended, but not required. Extra dwarf are suitable for container growing, reaching only about 25 cm. Tall varieties grow to about 2 m with support required.

Alaska, 55 days (smooth seeded) Tom Thumb / Half Pint, 55 days (heirloom, extra dwarf) Thomas Laxton (heirloom) / Laxton's Progress / Progress #9, 60–65 days Mr. Big, 60 days, 2000 AAS winner Little Marvel, 63 days, 1934 AAS winner Early Perfection, 65 days Kelvedon Wonder, 65 days, 1997 RHS AGM winner Sabre, 65 days, PMR Homesteader / Lincoln, 67 days (heirloom, known as Greenfeast in Australia and New Zealand) Miragreen, 68 days (tall climber) Serge, 68 days, PMR, afila Wando, 68 days Green Arrow, 70 days Recruit, 70 days, PMR, afila Tall Telephone / Alderman, 75 days (heirloom, tall climber)

Edible-pod peas

Some peas lack the tough membrane inside the pod wall and have tender edible pods, allowing them to be eaten whole. There are two main types:

Snow peas have flat pods with thin pod walls. Pods and seeds are eaten when they are very young. Snap peas (also known as sugar snap peas) have rounded pods with thick pod walls. Pods and seeds are eaten before maturity. The name sugar pea can include both types or be synonymous with either snow peas or snap peas in different dictionaries. The term mangetout (; from French: pois mange-tout, 'eat-all pea') is generally used in British English to refer to the snow pea specifically, but may also refer to a snap pea, especially when used in other contexts. Snow peas and snap peas both belong to macrocarpon group, a cultivar group based on the variety Pisum sativum var. macrocarpum Ser. named in 1825. It was described as having very compressed non-leathery edible pods in the original publication.

Field peas

… excerpt ends here. Continue reading the full article.

Illustrations

Worked examples

Example 1 — a first encounter with Pea

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

In research: Pea appears in chemistry 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 Pea 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: Pea is common in secondary-school and first-year university syllabi. It links to neighbouring topics Botanical taxa named by Carl Linnaeus, Edible legumes, Founder crops, so understanding it makes those chapters shorter.
In everyday life: Look for Pea 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 Pea in 20 minutes

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

Frequently asked questions

What is Pea in simple terms?

Pea is a pulse or fodder crop, but the word often refers to the seed or sometimes the pod of this flowering plant species. Peas are eaten as a vegetable.

Why does Pea matter?

Because it connects several chemistry 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 Pea?

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 Pea.