''Salsola soda'', more commonly known in English as opposite-leaved

saltwort Saltwort is a common name for various genera of flowering plants that thrive in salty environments, typically in coastal salt marshes and seashores, including: :*''Salsola'' and related genera within subfamily ''Salsoloideae'' :*''Salicornia'' :*'' ...

, oppositeleaf Russian thistle, or barilla plant, is a small (to 0.7 m tall), annual, succulent shrub that is native to the

Mediterranean Basin In biogeography, the Mediterranean Basin (; also known as the Mediterranean Region or sometimes Mediterranea) is the region of lands around the Mediterranean Sea that have mostly a Mediterranean climate, with mild to cool, rainy winters and wa ...

. It is a

halophyte A halophyte is a salt-tolerant plant that grows in soil or waters of high salinity, coming into contact with saline water through its roots or by salt spray, such as in saline semi-deserts, mangrove swamps, marshes and sloughs and seashores. Th ...

(a salt-tolerant plant) that typically grows in coastal regions and can be irrigated with salt water. The plant has great historical importance as a source of

soda ash Sodium carbonate, , (also known as washing soda, soda ash and soda crystals) is the inorganic compound with the formula Na2CO3 and its various hydrates. All forms are white, odourless, water-soluble salts that yield moderately alkaline solutions ...

, which was extracted from the ashes of ''Salsola soda'' and other

plants. Clow, Archibald and Clow, Nan L. (1952). ''Chemical Revolution,'' (Ayer Co Pub, June 1952), pp. 65–90. . Soda ash is one of the

alkali In chemistry, an alkali (; from ar, القلوي, al-qaly, lit=ashes of the saltwort) is a basic, ionic salt of an alkali metal or an alkaline earth metal. An alkali can also be defined as a base that dissolves in water. A solution of a s ...

substances that are crucial in glassmaking and soapmaking. The famed clarity of 16th-century ''cristallo'' glass from Murano and Venice depended upon the purity of "

Levant The Levant () is an approximate historical geographical term referring to a large area in the Eastern Mediterranean region of Western Asia. In its narrowest sense, which is in use today in archaeology and other cultural contexts, it is eq ...

ine soda ash", and the nature of this ingredient was kept secret. Spain had an enormous 18th-century industry that produced soda ash from the saltworts ( ''barrilla'' in Spanish). Pérez, Joaquín Fernández (1998)
"From the barrilla to the Solvay factory in Torrelavega: The Manufacture of Saltwort in Spain,"
''Antilia: The Spanish Journal of History of Natural Sciences and Technology,'' Vol. IV, Art. 1. . Archived at WebCite fro

on 1 March 2008. Soda ash is now known to be predominantly sodium carbonate. In 1807, Sir

Humphry Davy Sir Humphry Davy, 1st Baronet, (17 December 177829 May 1829) was a British chemist and inventor who invented the Davy lamp and a very early form of arc lamp. He is also remembered for isolating, by using electricity, several elements for the ...

isolated a metallic element from

caustic soda Sodium hydroxide, also known as lye and caustic soda, is an inorganic compound with the formula NaOH. It is a white solid ionic compound consisting of sodium cations and hydroxide anions . Sodium hydroxide is a highly caustic base and alkali t ...

; he named the new element "

sodium Sodium is a chemical element with the symbol Na (from Latin ''natrium'') and atomic number 11. It is a soft, silvery-white, highly reactive metal. Sodium is an alkali metal, being in group 1 of the periodic table. Its only stable ...

" to indicate its relationship to "soda". Before "soda" was somewhat synonymous (in U.S. English) with soft drinks, the word referred to '' Salsola soda'' and other

plants, and to soda ash. While the era of farming for soda ash is long past, ''S. soda'' is still cultivated as a vegetable that enjoys considerable popularity in Italy and with gourmets around the world. Its common names in Italian include ''barba di frate'', ''agretti'', and ''liscari sativa'' (short: lischi or lischeri). Of its culinary value,

Frances Mayes Frances Mayes is an American novelist. Her 1996 memoir '' Under the Tuscan Sun.'' was on the New York Times Best Seller list for over two years and was the basis for the film '' Under the Tuscan Sun''. Biography Born and raised in Fitzgerald, Geo ...

has written that "Spinach is the closest taste, but while ''agretti'' has the mineral sharpness of spinach, it tastes livelier, full of the energy of spring."

Description

This annual, succulent plant can grow into small shrubs up to 0.7 m tall (sometimes called subshrubs). It has fleshy green leaves with either green or red stems. The tiny flowers develop from

inflorescence An inflorescence is a group or cluster of flowers arranged on a stem that is composed of a main branch or a complicated arrangement of branches. Morphologically, it is the modified part of the shoot of seed plants where flowers are formed o ...

s that grow out of the base of the leaves near the stem. Robertson, Kenneth R. and Clemants, Steven E. (1997)
''Salsola Soda''
from "Amaranthaceae" chapter, in: Flora of North America Editorial Committee, eds. 1993+. ''Flora of North America North of Mexico.'' 12+ vols. New York and Oxford. Vol. 4, pp. 399–402. .

Distribution

''Salsola soda'' is native in Eurasia and North Africa. Historically, it was well known in Italy, Sicily, and Spain. In modern Europe, it is also found on the Atlantic coasts of France and Portugal and on the Black Sea coast. It has become naturalized along the Pacific coast of North America, and there is concern about its invasiveness in California's salt marshes. It is also reported to be naturalized in South America.

Soda ash and the biology of sodium accumulation

The ashes obtained by the burning of ''S. soda'' can be refined to make a product called soda ash, which is one of the

materials essential to making

soda-lime glass Soda lime is a mixture of NaOH and CaO chemicals, used in granular form in closed breathing environments, such as general anaesthesia, submarines, rebreathers and recompression chambers, to remove carbon dioxide from breathing gases to prevent ...

soap Soap is a salt of a fatty acid used in a variety of cleansing and lubricating products. In a domestic setting, soaps are surfactants usually used for washing, bathing, and other types of housekeeping. In industrial settings, soaps are used a ...

, and many other products. The principal active ingredient is sodium carbonate, with which the term "soda ash" is now nearly synonymous. The processed ashes of ''S. soda'' contain as much as 30% sodium carbonate. A high concentration of sodium carbonate in the ashes of ''S. soda'' occurs if the plant is grown in highly saline soils (i.e. in soils with a high concentration of sodium chloride), so that the plant's tissues contain a fairly high concentration of sodium ions. ''S. soda'' can be irrigated with sea water, which contains about 40 g/L of dissolved sodium chloride and other salts. When these sodium-rich plants are burned, the carbon dioxide that is produced presumably reacts with this sodium to form sodium carbonate. It is surprising to find a higher concentration of sodium than of potassium in plant tissues; the former element is usually toxic, and the latter element is essential, to the metabolic processes of plants. Thus, most plants, and especially most crop plants, are "

glycophyte A halophyte is a salt-tolerant plant that grows in soil or waters of high salinity, coming into contact with saline water through its roots or by salt spray, such as in saline semi-deserts, mangrove swamps, marshes and sloughs and seashores. Th ...

s", and suffer damage when planted in saline soils. ''S. soda'', and the other plants that were cultivated for soda ash, are "

halophytes A halophyte is a salt-tolerant plant that grows in soil or waters of high salinity, coming into contact with saline water through its roots or by salt spray, such as in saline semi-deserts, mangrove swamps, marshes and sloughs and seashores. Th ...

" that tolerate much more saline soils than do glycophytes, and that can thrive with much larger densities of sodium in their tissues than can glycophytes. The biochemical processes within the cells of halophytes are typically as sensitive to sodium as are the processes in glycophytes. Sodium ions from a plant's soil or irrigation water are toxic primarily because they interfere with biochemical processes within a plant's cells that require

potassium Potassium is the chemical element with the symbol K (from Neo-Latin ''kalium'') and atomic number19. Potassium is a silvery-white metal that is soft enough to be cut with a knife with little force. Potassium metal reacts rapidly with atmosphe ...

, which is a chemically similar

alkali metal The alkali metals consist of the chemical elements lithium (Li), sodium (Na), potassium (K),The symbols Na and K for sodium and potassium are derived from their Latin names, ''natrium'' and ''kalium''; these are still the origins of the names ...

element. Tester, Mark and Davenport, Romola (2003). "Na⁺ Tolerance and Na⁺ Transport in Higher Plants,
''Annals of Botany''
91: 503-527. . The cell of a

such as ''S. soda'' has a molecular transport mechanism that sequesters sodium ions into a compartment within the

plant cell Plant cells are the cells present in green plants, photosynthetic eukaryotes of the kingdom Plantae. Their distinctive features include primary cell walls containing cellulose, hemicelluloses and pectin, the presence of plastids with the capab ...

called a "

vacuole A vacuole () is a membrane-bound organelle which is present in plant and fungal cells and some protist, animal, and bacterial cells. Vacuoles are essentially enclosed compartments which are filled with water containing inorganic and organic mo ...

". The vacuole of a plant cell can occupy 80% of the cell's volume; most of a halophyte plant cell's sodium can be sequestered in the vacuole, leaving the rest of the cell with a tolerable ratio of sodium to potassium ions. In addition to ''S. soda'', soda ash has also been produced from the ashes of '' S. kali'' (another

plant), of

glasswort The glassworts are various succulent, annual halophytic plants, that is, plants that thrive in saline environments, such as seacoasts and salt marshes. The original English glasswort plants belong to the genus ''Salicornia'', but today the glass ...

plants, and of

kelp Kelps are large brown algae seaweeds that make up the order Laminariales. There are about 30 different genera. Despite its appearance, kelp is not a plant - it is a heterokont, a completely unrelated group of organisms. Kelp grows in "underwat ...

, a type of seaweed. The sodium carbonate, which is water-soluble, is " lixiviated" from the ashes (extracted with water), and the resulting solution is boiled dry to obtain the finished soda ash product. A very similar process is used to obtain potash (mainly

potassium carbonate Potassium carbonate is the inorganic compound with the formula K2 CO3. It is a white salt, which is soluble in water. It is deliquescent, often appearing as a damp or wet solid. Potassium carbonate is mainly used in the production of soap and ...

) from the ashes of hardwood trees. Because halophytes must also have potassium ions in their tissues, even the best soda ash derived from them also contains some potash (potassium carbonate), as was known by the 19th century. Plants were a very important source of soda ash until the early 19th century. In the 18th century, Spain had an enormous industry producing ''

barilla ''Barilla'' refers to several species of salt-tolerant ( halophyte) plants that, until the 19th century, were the primary source of soda ash and hence of sodium carbonate. The word "barilla" was also used directly to refer to the soda ash obtaine ...

'' (one type of plant-derived soda ash) from saltwort plants. Similarly,

Scotland Scotland (, ) is a Countries of the United Kingdom, country that is part of the United Kingdom. Covering the northern third of the island of Great Britain, mainland Scotland has a Anglo-Scottish border, border with England to the southeast ...

had a large 18th-century industry producing soda ash from kelp; this industry was so lucrative that it led to overpopulation in the

Western Isles The Outer Hebrides () or Western Isles ( gd, Na h-Eileanan Siar or or ("islands of the strangers"); sco, Waster Isles), sometimes known as the Long Isle/Long Island ( gd, An t-Eilean Fada, links=no), is an island chain off the west coas ...

of Scotland, and one estimate is that 100,000 people were occupied with "kelping" during the summer months. The commercialization of the

Leblanc process The Leblanc process (pronounced leh-blaank) was an early industrial process for making ''soda ash'' ( sodium carbonate) used throughout the 19th century, named after its inventor, Nicolas Leblanc. It involved two stages: making sodium sulfate f ...

for synthesizing sodium carbonate (from salt,

limestone Limestone ( calcium carbonate ) is a type of carbonate sedimentary rock which is the main source of the material lime. It is composed mostly of the minerals calcite and aragonite, which are different crystal forms of . Limestone forms wh ...

, and

sulfuric acid Sulfuric acid ( American spelling and the preferred IUPAC name) or sulphuric acid ( Commonwealth spelling), known in antiquity as oil of vitriol, is a mineral acid composed of the elements sulfur, oxygen and hydrogen, with the molecular fo ...

) brought an end to the era of farming for soda ash in the first half of the 19th century.

Cultivation and culinary uses

The Italian name ''agretti'' is commonly used in English to refer to the edible leaves of ''S. soda''; ''barba di frate'' (or friar's beard) is the most common of the Italian names. This plant is not a summer green and should be started early indoors or in autumn. The seed is notorious for poor

germination Germination is the process by which an organism grows from a seed or spore. The term is applied to the sprouting of a seedling from a seed of an angiosperm or gymnosperm, the growth of a sporeling from a spore, such as the spores of fungi, fer ...

at about 30 to 40% standard, much like

rosemary ''Salvia rosmarinus'' (), commonly known as rosemary, is a shrub with fragrant, evergreen, needle-like leaves and white, pink, purple, or blue flowers, native to the Mediterranean region. Until 2017, it was known by the scientific name ''Rosmari ...

. Though the plant is often grown in saltwater-irrigated land in the

, it will grow without salt water. ''S. soda'' is harvested in bunches when small, or cropped regularly to encourage new growth when mature. It is most commonly boiled and eaten as a

leafy vegetable Leaf vegetables, also called leafy greens, pot herbs, vegetable greens, or simply greens, are plant leaves eaten as a vegetable, sometimes accompanied by tender petioles and shoots. Leaf vegetables eaten raw in a salad can be called salad gre ...

; the recommendation is to cook it in boiling water until the leaves soften, and to serve while some bite (crunch) remains (much like

samphire Samphire is a name given to a number of succulent salt-tolerant plants (halophytes) that tend to be associated with water bodies. *Rock samphire, ''Crithmum maritimum'' is a coastal species with white flowers that grows in Ireland, the Unit ...

). It can also be eaten raw; it is said to taste "grassy and slightly salty with a pleasant, crunchy texture". ''Salsola soda'' is sometimes confused with a plant known in Japan as ''okahijiki'' (land seaweed), which is actually the species '' S. komarovii''. The harvested leaves of the two species have a similar appearance.

Phytoremediation

''Salsola soda'' has also been studied as a

bioremediation Bioremediation broadly refers to any process wherein a biological system (typically bacteria, microalgae, fungi, and plants), living or dead, is employed for removing environmental pollutants from air, water, soil, flue gasses, industrial effluent ...

"biodesalinating companion plant" for crops such as tomatoes and peppers when they are grown in saline soils. The ''Salsola soda'' extracts enough sodium from the soil to improve the growth of the crop plant, and better crop yields result despite the competition of the two plants for the remaining minerals from the soil.

References

External links

PLANTS Profile for ''Salsola soda''.
Natural Resources Conservation Service, United States Department of Agriculture. Retrieved 3 November 2006. *Excellen
gallery of photographs
of ''Salsola soda'' (''soude commune'') from Bouches du Rhône region of France. From ''Banque de données Botaniques et Ecologiques'', Universite Aix-Marseille, France. Retrieved 30 November 2006.
''Salsola soda''
listing at website ''Plants for a Future'' (http://www.pfaf.org). Retrieved 7 December 2006. {{Taxonbar, from=Q2713171 Leaf vegetables Amaranthaceae Halophytes Industrial history Phytoremediation plants Plants described in 1753 Taxa named by Carl Linnaeus Barilla plants Flora of Malta