what the heck makes a legume a legume??

Question

Every dictionary I've ever looked this word up in just says that it is a plant such as a pea or this or that. This is not a definition it is an example.
Every other dictionary makes use of a circular definition: a plant that produces a leguminous seed. I was told by an authority (and authorities are never supposed to be wrong, right?) that definitions are never supposed to use the word (or root word) that is being defined IN the definition.
So WHAT is a legume??

Answer 1

The term legume has two closely related meanings in botany, a situation encountered with many botanical common names of useful plants, whereby an applied name can refer to either the plant itself, or to the edible fruit (or useful part). Thus, "legume" can be:

* The common name for plant species in the Family Fabaceae (or Leguminosae);
* The name of a type of fruit, characteristic of leguminous plants:

A legume is a simple dry fruit which develops from a simple carpel and usually dehisces (opens along a seam) on two sides. A common name for this type of fruit is a "pod", although pod is also applied to a few other fruit types. Well-known plants that bear legume fruits include alfalfa, clover, peas, beans, lupins and peanuts. A peanut is not a nut in the botanical sense; a peanut is an indehiscent legume, that is, one whose pod does not split open on its own.

Legumes are noteworthy for their ability to fix atmospheric nitrogen, an accomplishment attributable to a symbiotic relationship with certain bacteria known as rhizobia found in root nodules of these plants. The ability to form this symbiosis reduces fertilizer costs for farmers and gardeners who grow legumes, and means that legumes can be used in a crop rotation to replenish soil that has been depleted of nitrogen.

Legume seed and foliage has a comparatively higher protein content than non-legume material, probably due to the additional nitrogen that legumes receive through nitrogen-fixation symbiosis. This high protein content makes them desirable crops in agriculture.

Farmed legumes fall into two classes: forage and grain.

* Forage legumes, like alfalfa, clover and vetch, are sown in pasture and grazed by livestock.
* Grain legumes are cultivated for their seeds, and are also called pulses. The seeds are used for human and animal consumption or for the production of oils for industrial uses. Grain legumes include beans, lentils, lupins, peas and peanuts.

The term is derived from the French word "légume" (which, however, has a wider meaning and refers to any kind of vegetable).

Freshly-dug peanuts (Arachis hypogaea)

Answer 2

It seems that you are genuinely interested in knowing the answer . So I will make more efforts to give that to you. First we will look at the basic botany required for the answer to be truly meaningful and then we will look at the question itself. So the answer will be a long one, bear with me!

Basic Botany

1) The Female reproductive part in a flower is called Gynoecium and it is made up of the individual members called Carpels. Gynoecium may have one to many carpels. The number is constant for any given species.

2) A single carpel is again distinguished in to three parts viz. stigma (to receive the pollen during pollination); Style ( to raise the stigma up ) and the OVARY which holds ovules inside.
After pollination and fertilization it is the OVARY and OVARY only that turns in to a FRUIT and the ovules turn in to SEEDS.

3) The OVARY can be one chambered or many chambered. It can hold a single ovule/seed or many ovules/seeds. It can be prominently seen (Superior ovary) or located below the level of the other floral parts
( Inferior ovary.)

4) The wall of the OVARY becomes, obviously, the wall of the fruit or PERICARP ( CARP= fruit; PERI=around)

5) PERICARP may be dry and not distinguishable in to many part or it can be fleshy as in tomato and mango. So a fruit can a dry or fleshy depending upon the nature of the pericarp alone.

6)If the pericarp breaks on its own automatically to release the mature seeds the fruit is Dehiscent.
If it is not so then the fruit is Indehiscent ( All fleshy fruits are Indehiscent fruits) Many, but not all , dry fruits are Dehiscent.( To Dehisce = To break open ).

Why Legume is a Legume ?

A fruit to be classified as a LEGUME, must fulfill the following criteria-- :

It develops from a monocarpellary gynoecium ( That is only one carpel in the flower.)……..1.

The ovary must be superior and having only one chamber. ( Unilocular; Loculus = chamber)..2

The pericarp must be dry and dehiscent…………………………… 3.

When it breaks open , it should do so along the two opposite seams or sutures on the fruit
So as to form, on dehiscence, two valves……………………………………………………..4.

All pulses and beans fulfill the above criteria and are legumes.

Groundnut is an exception to the rule as it follows all the conditions except the last one .
This is because it develops below the soil surface and seeds cannot be dispersed.

Answer 3

A legume is a plant in the pea family.

Your next question of course is "What is the pea family?" That's a much more difficult question since it relies on the definition of "family". The simplest answer is that a plant 'family' is a group of plant species that all share similar characteristics. In the case of the pea family, all species have very similar flower structure.

The longer answer depends on your understanding the way living things are classified based on their morphology (i.e. the shapes of flowers, fruits and leaves). Look up "Linnean taxonomy" in wikipedia if you want to know more (see link).

Answer 4

legume is the name givn to that family of vegetables which makes you fart