Build-up of water reed

The rhizome (rootstock)

Water reed has a widely ramified subterranean part of the sprout, called the rhizome.
The rhizome acts as a fixation of the water reed at the bottom and takes the soil water with the solute mineral nutriments. Essentially that is responsible for the water reed growth. The growth depends on the nutrient reserved by the rootstock. The emerging scions grows during winter up to the ice crust untill the ice crust stops their growth. The scions will grow again, when the ice crust melts. The rhizome has to supply the emerging scions with nutrients and oxygen till the interfusion of the water surface. That means the rhizome acts as a nutrient reserve. If the water surface is saturated, the first air leaves will supply the rootstock with nutrients and oxygen. Since the rootstock is often rooted in a soil with under oxygen, o2 is assimilated by the water and air foliages of the spear and then transported to the deepest ramification of the rhizome. The top of the radix emits the surplus oxygen that causes a symbiosis with deposited germs in the soil. The bacteria utilise the oxygen to dissolve composite nutriments. The rhizome absorbes the dissolved nutrients. In this way water reed can bridge bad hydrological conditions for a certain time. Water reed can also spread by broken rootstocks. The rhizome parts strike root at a preferred position and emerge. The rootstock has a lifetime of more than three years, then the oldest rhizome parts are deceasing and will be replaced with new erudite rhizome scions.

The spear

The stipe is divided by the no protruding knops in several internodal segments and grows up to 1,25 metres to 4 metres (Phragmites communis Trin in Germany). The longest spears emerge in the Iraq (Phragmites australis) with length over 8 metres. The height and the thickness of a spear depend on the development conditions and the size of the water reed scion which pierces the water surface in the spring. The higher the spears, the less water reed extends on a square metre of the rootstock. At a height of 3 metres the average amount of spears amount up to 20-40 pieces per square metre. The number of the internodal segments depends on the water reed class and the height; it often averages from 15 to 25 knops. The spear is straightforward, cylindrical formed, concave and has axial a slightly conical form. The stipe has a clean and luminous surface and a green to yellowish brown colour, which changes during the maturation to yellow. If water reed spears stand constantly in water, they build up a compact and keen silicified wax skin inside the internodal segments. The wax skin waterproofs the cell wall from the inner hollow space.

The hose cover of the spear, called epidermis, is made up of thick walled lignifying cells which consist of two zones: The first zone is composed of standard, lignified cells with thick walls and the second zone is composed of cells with smaller diameter and thicker walls. The base reinforcement which is between the scelorose boundary reinforcement and the concave centre of the spear consists of cells with a bigger diameter. Vascular bundle of the outer circle borders on the outer span of the scelorose flange. The fibre parallels in the internodal segments so that tubes are indefinitely fissionable.

Growth, circulation and reproduction

For the growth and circulation of water reed you can differ two possibilities, the germ growth and the vegetative reproduction through rhizome spread.

The germ growth

The spike shaking by the wind makes the caryopse fall into water. The cayropse swims on the water surface till it germinates at an advantageous place and sprouts (at a water depth of 2-3 mm). After 5-6 days the first foliage forms of the sprout. Now the plant is independent from the reserves of the seed. 3 months later the plant has a size of 20-40 cm. After the formation of 4-6 leaves side sprouts emerge on the base of the primary sprout. The side sprouts grow up to a upturned bow, later the main sprout becomes the rhizome. The main part of the rhizome sprouts uprightly down and generates long adventitious roots. The other rhizome parts grow semi-circular und form new scions. A rhizome bunch of 50-70 cm size with 12-14 parts can grow untill the autumn of the year. The formed spears reach a height of 25-70 cm. In winter the rhizomes grow underneath the ice crust via the water leaves they generated and the nutrients the rhizome stored (for example glucose and starch). In the second year of growth, in which the sympodium spreads, a main rhizome part grows into the depth and creates a new rhizome sections, which grows contrary to the water surface and forms new spears that can reach up to 2m. In third year some of spears blossom. In the fourth year the sympodium generated by the seed has a size of 8 to 10 m and is made up of 400 to 1000 spears. By the years the rhizome ingresses deeper in the soil to generate a compound to the ground water. The dryer the water reed growing area the deeper the rhizome grows in the soil (up to 5 m). The moister the water reed growing area is, the more intense the rhizome grows in the amplitude. The reproduction of the seed is very rare because the germinated semen is pulled out through the least water raise. The growth of water reed is limited by to a constant water depth of 2-2,5 m, because the rhizome cannot provide more nutrients for the growth of the sprouts. A higher water depth can be conquered only by formation of a swimming water reed carpet that is called „plaur”.

Growth from the rhizome

The growth and the spread of water reed is carried out the vegetative way. During the whole year the rhizome tiller builds buds which emerge as new sprouts. The new sprouts are supplied with nutrient reserves from the rhizomes by photosynthesis. That happens perennial, in autumn and winter with a higher intensity. In addition water reed fans out through washing away full blown and broken off rhizome parts. The sprouts can increase with a spread of 3-12 cm daily. Normally water reed grows very fast and has its final extend in 4-5 months. The less spears per square metre grow the bigger and heavier they become. Mainly water reed is growing from April to July (in Europe). If the spear has reached its ultimate height, the walls of the spears start to shrink until the seceding of the leaves. That is caused by the aging of the sclerenchyma fibre and the bulge of the cellulose amount. Under ideal conditions (2 m deep, calm water, under 0,2m/min. flow rate, no waves, soil rich in minerals), solid water reed can grow 30 % per year.