Botanical & chemical description of radish

By: Shehzad Ahmad Kang, Department of Plant Breeding and Genetics, University of

Agriculture, Faisalabad, Pakistan- 38040

Corresponding author’s email; shehzadpbg@gmail.com

Introduction

The radish (Raphanussativus) is an edible root vegetable of the Brassicaceae family that was domesticated in Europe in pre-Roman times. They are grown and consumed throughout the world. Radishes have numerous varieties, varying in size, color and duration of required cultivation time. There are some radishes that are grown for their seeds; oilseed radishes are grown, as the name implies, for oil production. Radish can sprout from seed to small plant in as little as 3 days.

The descriptive Greek name of the genus Raphanus means “quickly appearing” and refers to the rapid germination of these plants. Raphanistrum, from the same Greek root, is an old name once used for this genus. The common name “radish” is derived from Latin radix (root). The radish has been used over many centuries.

Although the radish was a well-established crop in Hellenistic and Roman times, which leads to the assumption that it was brought into cultivation at an earlier time. Wild forms of the radish and its relatives, the mustards and turnip, can be found over west Asia and Europe, suggesting that their domestication took place somewhere in that area. However Zohary and Hopf conclude, “Suggestions as to the origins of these plants are necessarily based on linguistic considerations.”

Radishes grow best in full sun and light, sandy loams with pH 6.5–7.0. They are in season from October to January in most parts of Pakistan but now some summer varieties also avaiable. Summer radishes mature rapidly, with many varieties germinating in 3–7 days, and reaching maturity in three to four weeks. Harvesting periods can be extended through repeated plantings, spaced a week or two apart. As with other root crops, tilling the soil to loosen it up and remove rocks helps the roots grow. However, radishes are used in no-till farming to help reverse compaction. Most soil types will work, though sandy loams are particularly good for winter and spring crops, while soils that form a hard crust can impair growth. The depth at which seeds are planted affects the size of the root, from 1 cm (0.4 in) deep recommended for small radishes to 4 cm (1.6 in) for large radishes. Radishes are a common garden crop in the U.S., and the fast harvest cycle makes them a popular choice for children’s gardens. In temperate climates, it’s customary to plant radishes every two weeks from early spring until a few weeks before the first frost, except during periods of hot weather. In warm-weather climates, they are normally planted in the fall.

Botanical Classification

Kingdom              Plantae

Phylum                Angiosperm

Class                    Eudicots

Order                  Brassicales

Family     Cruciferaceae

Genus                 Raphanus

Botanical Name:         Raphanussativus

Radish PlantFloral Diagram

Characteristic Features

  • Habit: Usually annual or perennial herbs.
  • Root: Taproot system.
  • Stem: Herbaceous, erect, branched.
  • Leaves: Simple, alternate, radical or cauline, usually entire, sometimes lobed, petiolate, exstipulate reticulate venation.
  • Inflorescence: Raceme or corymbose raceme.
  • Flower: Ebracteate, pedicellate, mostly actinomorphic, bisexual, heterochlamydeous, dimerous or tetramerous hypogynous.
  • Calyx: Sepals 4, polysepalous, in two whorls of two each imbricate aestivation.
  • Corolla: Petals 4, arranged in single whorl alternating with sepals, polypetalous, often with long claws and spread out to form a cross. Hence, the name cruciform corolla. Valvate aestivation.
  • Androecium: Stamens 6, polyandrous, arranged in two whorls of 4 and 2 (tetradynamous), outer two are short and the inner four are long, anthers bilobed, basifixed, introse.
  • Gynoecium: Bicarpellary, syncarpous, initially unilocular and later bilocular, (formation of pseudoseptum), one or more ovules on parietal placentation, style short, stigma bifid, sometimes bilobed, ovary superior.
  • Fruit: Siliqua or silicula.
  • Seeds: Endospermic

 

Nutritional value of radish

Nutritional value per 100 g (3.5 oz)

Energy 66 kJ (16 kcal)
Carbohydrates 3.40 g
Sugars 1.86 g
Dietary fiber 1.6 g
Fat 0.10 g
Protein 0.68 g
Thiamine (vit.B1) 0.012 mg (1%)
Riboflavin(vit.B) 0.039 mg (3%)
Niacin (vit. B3) 0.254 mg (2%)
Pantothenic acid(B5) 0.165 mg (3%)
Vitamin B6 0.071 mg (5%)
Folate (vit. B9) 25 μg (6%)
Vitamin C 14.8 mg (18%)
Calcium 25 mg (3%)
Iron 0.34 mg (3%)
Magnesium 10 mg (3%)
Phosphorus 20 mg (3%)
Potassium 233 mg (5%)
Zinc 0.28 mg (3%)

Constituents

Phenyl-ethyl isothyocyanite, a pungent volatile oil and an amylclytic enzyme.

Oil of radish and its extraction

Distilling the roots of White radish we can obtain 0.032 to 0.035 per cent volatile oil while the root of black radish gives 0.038 to 0.40 percent of oil.

The chiefly consists of  butylcrotonylisothiocyanatesulphide C9H17NS2 or C9H15NSa compound with a pungent odour and a flavor characteristic of fresh radish. This thiocyanate probably belong to aromatic series of hydrocarbons.

The disagreeable odour of radish oil is caused by the presence of methyl mercaptan. In the volatile oil derived from the green leaves of the radish plant, contain 2-hexen-1-al (leaf aldehyde), 3-hexen-1-ol (leaf alcohol) and small quantities of  n- and isobutyraldehyde and isovaleraldehyde. From the seed of Raphanussativus L. var. albus, Schmid and Karrer isolated sulphoraphene, a mustard oil containing a sulphoxide group.Sulphoraphene occurs in the seed as a glucoside. This compound is a cleavage product of the mustard oil glucoside occurring in the seed.

Uses of radish and its oil

The most commonly eaten portion is the napiformtaperoot, although the entire plant is edible and the tops can be used as a leaf vegetable. It can also be eaten as a sprout.

The bulb of the radish is usually eaten raw, although tougher specimens can be steamed. The raw flesh has a crisp texture and a pungent, peppery flavor, caused glucosinolates and the enzyme myrosinasewhich combine when chewed to for allylisothiocyanate, also present in mustard.Radish leaves are sometimes used in recipes, like potato soup or as a sauteed side dish. They are also found to benefit homemade juices; some recipes even calling for them in fruit based mixtures. Radishes may be used in salads as well as in many European dishes.The seeds of the Raphanussativus species can be pressed to extract seed oil. Wild radish seeds contain up to 48% oil content, and while not suitable for human consumption the oil is a potential source of biofuel. The oilseed radish grows well in cool climates. Radish is an excellent food remedy for stone, gravel and scorbutic conditions. The juice and oil has been used in the treatment of cholelithiasis as an aid in preventing the formation of biliary calculi.

References:

W.Gunkel et.al, 2010.Handbook of essential oils. CBS Publishers & Distributors Pvt. Ltd. New Delhi. (4) 412.

Nonnecke, IbLibner, 1922. Vegetable production. Van Nostrand Reinhold, New York. (1) 339-340.

 

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