Water caltrop

Water chestnut (Trapa natans )

The water chestnut (Trapa natans ) as the unrelated Eleocharis dulcis type also called water chestnut, a species within the family of Lythraceae is ( Lythraceae ). It occurs in temperate and subtropical regions of Europe, Africa and Asia. This one-year water plant that is threatened with extinction in Germany and since 1987 is protected.

Description

The water chestnut is a deciduous, annual herbaceous plant. It occurs in stagnant water and is available in 30 to 60 centimeters depth anchored in the ground. Their petioles have floats so that the fan-shaped leaves float like a rosette at the water surface. However, the leaves appear only in June on, in autumn they turn red and then die.

The flowering period extends from July to August. Your inconspicuous flowers are white and radial symmetry. It develops a dark brown, hard-shelled fruit that is reinforced with two, often at four ends with sharp thorns with which they can anchor themselves in the bottom of the lake and contains a white core which consists to 20% of starch.

Ecology

The water chestnut is a summer annual plant. This hydrophyte or floating-leaf plant roots with a 1-3 meter long, anchor -like fortified by the fruit stalks in the mud. The stomata are on the upper side. There are also zipfelige submerged leaves without stomata. To find acid separates glands, which are interpreted as a defense mechanism against water Animals on the underside of leaves as the stem. There are arranged in pairs Nebenwurzlen with four rows of green, photosynthetically active lateral roots.

Ecologically flowers are nectar - leading " Small funnel flowers". Self-pollination prevails.

The fruits are single-seeded, drupe -like, enclosed to maturity of the enlarged flower axis nuts. The flap-like sepals were thorn-like to four ( rarely two ), barbed occupy appendages transformed that serve to anchor the soil later. There is swimming spreading, Velcro instead spread by water birds and humans spread, causing the plant to Kulturflüchter and cultural relic was. Fruit ripening is from September to October. The seeds are heat to germinate and have even no endosperm. Of the two cotyledons of a starch serves as memory and remains in the fruit, the other is scale-like occurs with the seed stalks from the fruit. In his armpit arise next to a side shoot two later detaching, vegetative propagation serving Beiknospen.

Occurrence

The water chestnut is found in the Mediterranean region, Central and Eastern Europe, and Central and South Asia, Taiwan, Japan and in Central Africa.

The preferred habitat is low in calcium, but nutrient-rich and warm summer backwaters, humus sludge lakes and ponds. It is found almost exclusively in the lowlands in heat- favored regions.

In Germany, water chestnut was formerly widespread, it suggests, among other finds at Federseemuseum. Matthew Praetorius reported in 1690 still of large deposits in East Prussia. 1962 Horst Koehler called in the practical gardening book Linkehner the lake at Tapiau in East Prussia as one of the last "German" occurrence. In Baden- Württemberg there are two stocks of the Rhine Little Constance and Rußheimer Old Rhine, in Bavaria in Scheyern monastery, in Brandenburg on the Old River Spree, which leads into the Schwieloch and in Saxony -Anhalt in Schönitzer lake. The water chestnut is as endangered in Germany in the Red List of Threatened Species.

Use

Archaeological investigations are particularly in Eastern Europe large amounts of water nuts, demonstrating the extensive use in the diet at least since Neolithic times. In the environment of the Upper Swabian pile dwellings around the Federseemuseum they obviously have formed neolithic an important food source.

The fruit of the water chestnut is edible, but must be heated in order to reduce the toxicity. In Japan, the plant hishi (菱) and was also used in folk medicine, a medical effect is, however, not yet been demonstrated clearly scientific.

Others

At the surfaces of the water chestnut Riesendarmegel ( F. buski ) of man and the pig is transmitted by means of its cercariae in Southeast Asia. By raw consumption of aquatic and marsh plants, various other parasites can be transmitted.

The nearly tetrahedral, hard-shelled fruits of water chestnut remain mostly lie upwards when they are thrown with a tip. This property Japanese Ninja made ​​their advantage and scattered the fruits behind when they were pursued by enemies. It was extremely painful to step on these natural crow's feet with the then usual straw sandals. Also beechnuts were used by ninjas in a similar manner.

2011, the water chestnut in Austria, Germany and Switzerland to the water plant of the year was chosen.

System

There are described several varieties of the species Trapa natans L.:

• Trapa natans var bispinosa ( Roxb. ) Makino ( Syn: Trapa bispinosa Roxb. )
• Trapa natans var inermis Mao
• Trapa natans L. var natans
• Trapa natans var rubeola Maxim. f viridis Sugimoto