Plants and salt
Salt is important for other living organisms like plants and animals as well. For example, there are salt-tolerant plants, called halophytes, which grow in high-saline environments. Various animal species have evolved to regulate their bodies' salt balance.
Plants that tolerate salt
Salt and its world have many surprises in store – but sometimes a second look is needed to discover them. Plants that tolerate salt or halophytes are a good example. They populate sea coasts, saltmarshes and marshland, salt deserts and saliniferous springs. These masters of survival still flourish in salt concentrations of over 0.5% thanks to various physiological strategies. Glands that excrete salt, extreme water storage (succulence) and filtration in the roots are typical examples of how these plants have adapted. An opportunistic lifestyle can also be successful. Plants of this sort complete their life cycle and form seeds before the salt concentration in their tissue reaches the lethal level.
Intense sunshine, major fluctuations in temperature and droughts create harsh living conditions for littoral plants, similar to those in high mountain areas, deserts and polar regions. Many salt-tolerant plants are therefore dwarfed, or they may grow in clumps with small, leathery, fleshy or hairy leaves.
These examples will give you more insights into the variety of halophytes. Each of these plants is representative in its own particular way.
Gold coin or Mediterranean beach daisy (Asteriscus maritimus L.)
The perennial gold coin or Mediterranean beach daisy (Asteriscus maritimus L.) becomes conspicuous when it blooms in spring and its vibrant yellow blossoms carpet the coastal rocks of the Mediterranean Sea. Otherwise, this plant (a member of the composite or asteraceae group of plants) is unremarkable. The dwarf shrub is woody at the base with narrow leaves and rough hairs in the upper part. These features enable it to withstand wind, heat, radiation and dryness.
Spiny rush (Juncus acutus)
Grasses, sedges and rushes number among the typical flora found on beaches, in swamps and flat areas near coasts. They are often utilised as “pioneer” plants for land reclamation, for fodder or litter in agriculture, or as building materials (reeds are an example of this). Seen from a distance, they resemble one another. However, grasses, sedges and rushes are not related. For our illustration, we have selected the spiny rush (Juncus acutus). Like the very similar Juncus maritimus, it populates the Mediterranean coasts.
Sea grape (Coccoloba uvifera)
The sea grape (Coccoloba uvifera), a member of the knotweed family, is often the only source of shade on desolate sand beaches in Central and South America, and in the Caribbean. It grows into an evergreen tree with multiple trunks and can reach heights of up to 8 metres. The sea grape is resistant to wind and salt, and it is both useful and decorative. It provides fruits that can be eaten and utilised, as well as firewood and dye. Popular medicine makes use of the roots to treat diarrhoea, and the bark is a remedy for throat inflammations.
Buck’s horn plantain (Plantago coronopus)
The buck’s horn plantain (Plantago coronopus) likes to populate sandy and rocky areas on central European coastlines. Its appearance and distribution mark it out as a plant that tolerates salt. However, even laymen will recognise that it is related to the native ribwort and broad-leaved plantain.
Mangrove forests (Rhizophora mangle)
Mangrove forests (Rhizophora mangle) lend a special fascination to tropical coasts and river estuaries, not only as unique habitats but also as backdrops for adventurous filming and travel. Mangroves flourish in salty and brackish water, and they have no problems in coping with alternating tidal movements. We have selected R. mangle, the most widespread and important species. It supplies reddish wood from which tanning agents can be extracted, or which can be used to produce charcoal. The seeds are propagated in a very unusual way. They germinate on the parent plant, fall into the water and remain caught in holes in the silt (as if they were planted with a dibble).
Glasswort (Salicornia perenne)
The glasswort (Salicornia perenne) is known as a plant used in salads. This popular member of the goosefoot family of shrubs is related to spinach. The glasswort is a fleshy, salt-tolerant plant that resembles asparagus; it is frequently native to European coastlines, mud flats and saltmarshes. It is also planted for land reclamation purposes.
Saltmarsh sand spurry (Spergularia salina)
The sea spurry or saltmarsh sandspurry (Spergularia salina) is a member of the carnation (or pink) family. This inconspicuous low-growing plant flourishes on sea coasts and saliniferous ground in Europe, North Africa and the Near East. It produces white or pale pink blossoms between April and September.
Tamarisk (T. africana Poir.)
The genus of tamarisks includes some 80 species of deep-rooted trees and bushes that produce foliage. Their native territory stretches from the Mediterranean to China and they are often found in desert regions. They are planted along coastlines as windshields. Some of them are medicinal plants or sources of dye. Desert peoples have valued manna (Tamarix mannifera) since biblical times. The illustration shows the African tamarisk (T. africana Poir.) which flourishes along rivers, on flat coasts and in the sand dunes of the Mediterranean region, North Africa and the Canaries. It is also cultivated as a decorative plant and a roadside tree.
Beach morning glory (Calystegia soldanella L.)
The beach morning glory (Calystegia soldanella L.) is a relative of our own field bindweed. It seeks out warm coastal regions around the world for its habitat. It creeps across sand, rocks and dunes. Its vibrant evergreen and fleshy foliage and its clusters of bright pink- and white-striped flowers make it a favourite of beachcombers.
Illustrations: Heinrich Bäbler
