|
| |
|
Interesting plant species
The water chestnut (the water caltrop) Trapa natans
It is an ornamental aquatic plant, very popular with "ponders" but extremely rare in the wild - on the verge of extinction.
The water chestnut is an annual plant, which means that the whole life cycle (germination, growth, flowering and fructification) is limited to one vegetation season, after which it dies and sinks onto the bottom; only its fruit winter. The decorative floating leaves are arranged in rosettes (up to 50 cm in diameter) and joined with the roots by means of a long filamentous stalk. In late summer big, nut-like seeds appear on the underside of a rosette, which are provided with four long, sharp barbed spines. Their inside, rich in starch and is edible after cooking (they are sometimes served in Chinese restaurants). In many countries various species of the genus Trapa were even cultured on purpose as foodstuff. The water chestnut is a protected species and very rare in the Polish flora - it is known to occur at only 40 locations. They are concentrated mainly in submontane basins: the O¶więcim and the Sandomierz Basins and on the Silesian Lowlands. It is regarded as a critically endangered species and has been entered in the Polish Red Data Book of Plants. In the O¶więcim Basin the water chestnut has survived only thanks to numerous fish ponds and the fishing industry thriving here. Currently around 30% of its population is situated in this area. But even here the water chestnut, once very common, has now survived only in several dozen basins, within eight fish-farming pond complexes; and only in a few places (mainly on the Przeręb farm near Zator) it is in good condition and covers many hectare areas. As the passive conservation hasn"t produced desired results so far, and yet other water chestnut sites are disappearing, the Earth Society made an attempt at active protection of the species. A project aimed at rebuilding the water chestnut population at locations where it used to occur in the past, has been carried out since 2002. The reintroduction has been successful in ten water bodies, which however are not used for any industrial purposes. These water bodies are mainly Vistulan cut-offs and also some basins in the Historic Park in Pszczyna, and Lake Paprociańskie in Tychy. In spite of the fact that the water chestnut is an endangered species, it becomes very expansive in favourable conditions. Impressive rosettes covering a pond surface with a compact layer slow down the process of the water warming up; and when they sink onto the bottom in autumn, they considerably speed up shallowing of the basin. That is why the water chestnut is a very troublesome and undesirable species in ponds from an industrial point of view. In warmer European and Asian countries, and first of all in America, the plant is even sometimes called "water blight", as it causes trouble completely overgrowing local waterways.
|
| |
|
|
