Belonging to the family Salviniaceae, Salvinia is its genus. Commonly, it is addressed as watermoss. These species are related to the other water ferns such as the mosquito fern, Azolla. Salvinia are heterosporous synthesizing spores of varying sizes.
The stems of Salvinia are dichotomously branched rhizomes expanding horizontally. They are aerenchymatous in nature and protostelic. The leaves are dimorphic and simple, aerenchymatous. The leaves at maturity appear in whorls of three where the blades are round to oblong. The eggbeater shaped hair departs into four branches uniting at the tips.
Abode of Salvinia spp
- Nutrient-rich water entities
- Slow and still moving motion of water bodies such as reservoirs, ponds, rice fields, ponds
- Withstands mild temperatures and salinity
Salviniaceae, the aquatic fern family is placed in the order Hydripteridales consisting of Salvinia, the single genus. All around the world, ten species of Salvinia are known to exist.
These free-floating ferns emerge from the horizontal rhizome just under the surface of water wherein each of the plants is a ramet’s colony. The ramet in turn comprises a node, internode, floating leaves, associated buds and submerged roots.
The root is an altered form of the leaf that poses the functions of a root. Hence, there are no true roots. These structures are finely dissected into various filaments, emerging are hair-like projections along the length. They are critical in absorbing water for the nourishment of the plant.
Morphologically, Salvinia is variable, majorly in responding to the level of crowding and accessibility to nutrients. Both factors are interdependent.
Reproduction and Growth
Since Salvinia has 45 chromosomes, it is pentaploid. It is not capable of carrying out sexual reproduction. Each node supports an order of at least 3 axillary buds which grow successfully under favourable conditions and at least 6 in number responding to damage. Availability of nutrients is the deciding factor for growth rate, the number of axillary buds, and size of the plant. The aspect of growing is apically dominant and advances by the expansion of the axillary and apical buds where the former produce branches. Formation of new plants occurs when older ones decay and break as a result of any damage or senescence.
Growth Affecting Factors
Salvinia has a perennial plant life lacking seasonal periodicity even though seasonal alterations may inflict variations in the growth, for instance, temperature. It has adapted well to the waters with nutritive value and can absorb nutrients at a quicker pace when they are accessible. The section of axillary buds developing is associated with the nitrogen content of the plant. The content of nitrogen rises ensuing the bud-removal by insects and other such agents.
Roots are longer and leaves, larger when the availability of nitrogen is low. Alongside, the rhizome branching is declined and sporocarps occur more often. The content of nitrogen in Salvinia is in the range 0.6-4% dry weight.
The favourable temperature to grow is close to 30 °C. As per research, it was indicated that no growth occurs above 40 °C and below 10 °C. The temperature, however, has no effect on the parts of the axillary buds which expand to give rise to new branches. Plants can be destroyed by frosts but the unfrozen buds and the protected parts survive. Water bodies typically are chiller than the air in summers and warmer in winter as a result of thermal inertia. This facilitates the protection of Salvinia from extreme temperatures.
Initiation of growth of dormant buds allows Salvinia to compensate for the damage to buds. Complete compensation, however, only takes place at the availability of higher levels of nitrogen. Compensatory growth is not induced by the destruction of rhizomes and leaves.
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