| Geographic Range |
it is widespread all over the world, the northern
border is about the 69th parallel, the southern border is the 55th. |
| Physical Characteristics |
it isn't a true marine plant, but it is considered
a fresh water species with high salinity tolerability. It behaves as an
annual species in habitats subject to drought and to big ranges in the salinity,
while in more stable habitats it behaves as a perennial plant. Some researchers
have observed that perennial species preferably grow in areas subject to
tide conditions that leave plants exposed or covered with water, while annual
plants grow in shallow ponds, where they are less subject to the tide. Plants
in more stable environments are generally taller and have broader leaves;
moreover they have longer flower peduncles so that pollination can take
place over rather than under the water surface; they have a wider and stronger
root system which allows vegetative hibernation. A wigeongrass plant may
have 2-15 nodes on the rhizome. Adventitious roots may be single or clustered;
there may be up to 20 roots at the nodes. The belowground body of the plant
is a rhizome spreading from a single axis with shoots originating at 1 centimeters
one from each other. Rhizomes look from an anatomic point of view like vertical
stems except for the presence of roots instead of leaves. Rhizomes contain
more starch than vertical stems, they are thin and lighter and they are
usually found a few millimetres under the surface. The vascular system in
the rhizomes and in the roots is extremely simple. Plants subject to air
exposure in the intertidal habitats produce fewer shoots, more shoots flowering
at the beginning of the growing season and a smaller production of drupelets
than the plants that remain submerged during the growing season. Before
and during flowering the thin stems of the Ruppia grow quickly producing
several lateral branches that branch again and so on. Stems may be up to
3 meters long, even if average height of this plant in mild waters is 5-20
centimeters. Leaves are small, alternate, with obtuse or acute tips, serrate
or entire margins. The proportion of the leaf area at various depth reflects
adjustments to differences in light caused by turbidity or by the presence
of other plants. The structure of leaf epidermal cells and their chemical
composition vary with water salinity. |
| Notes |
nearly 100% of the belowground biomass of
the Wigeongrass (roots and rhizomes) is usually found in the upper 10 centimeters
of the substrate. In temperate estuaries, where the plant behaves as a perennial,
the dry weight of subaerial parts during peak growth can vary from 76% of
total plant dry weight in extremely shallow sites to only 2% in deeper sites.
This may reflect different strategies for nutrient uptake or survival in
dimly-lit waters. Although sheaths partially protect wigeongrass roots from
dessication and physical damage, the root system is delicate and unable
to penetrate deeply into sediment. This makes the species susceptible to
water turbulence. It produces a huge numbers of underwater flowers about
5-6 weeks after the onset of spring growth. The pollen released by the flowers
rises to the water surface carried by gas bubbles and it is transported
towards the flowers of other wigeongrass plants. Reproduction can occur
sexually (pollen) or asexually (rhizomes). |
| Habitat |
coasts, salt marshes, lagoons, ponds. |
Ruppia
maritima
