2. Classification
Domain: Eukaryota
Kingdom: Plantae (plants)
Phylum: Spermatophyta (seed plants)
Subphylum: Angiospermae(Comprising flowering plants that
produce seeds enclosed in an ovary)
Class: Monocotyledonae (comprising seed plants that produce an
embryo with a single cotyledon and parallel-veined leaves)
Order: Hydrocharitales
Family: Hydrocharitaceae
Genus: Hydrilla
Species: Hydrilla verticillata
3. Common Name –
water thyme (English)
Kodi paasi (tamil)
Indian star-vine(Sinhala)
Common Alternate Name of hydrilla
Florida eldoa
Water thyme
Poo naachu
Samudra sokh
5. Biology of hydrilla verticillata
Height: Hydrilla is variable in height depending primarily on the depth of the
water
Leaves: The leaves are in whorls of 4 to 8. Individual leaves measure 0.6 to
2 cm long and 2 to 4 mm wide. The margins have 11 to 39 sharp teeth per
centimeter and sometimes spines on the underside along the reddish midrib.
6. Biology of hydrilla verticillata
Flowers: The axial pistillate flowers are 10 to 50 mm long and 4 to 8 mm wide.
The three sepals are whitish in color with three translucent petals. They arise from the tip of the
stem and float on the surface of the water.
The female flower resembles an inverted bell filled with
a bubble.
The free-floating staminate flowers have three whitish to reddish sepals petals.
Both types of flowers are produced singly surrounded by a bract or spathe.
7. Reproduction of hydrilla verticillata
Sexual and Asexual production can occur
Within the group of submerged rooted aquatic macrophytes
Hydrilla verticillata has the greatest reproductive advantage,
because it has the ability to reproduce sexually through two
biotypes, namely through a dioecious system of male and
female flowers in different specimens, and also through the
monoecious system with male and female flowers in the same
specimen.
Pollination occurs on the water’s surface Pollen is released
from free floating male flowers and “caught” by the free
floating female flowers (Cronk and Fennessy, 2001).
8. Subterranean Tubers
• Sometimes buried several centimeters below the surface.
• Can sprout new shoots even after a period of 4 years.
Reproduction of hydrilla verticillata
Vegetative reproduction (Asexual
Reproduction)
• Subterranean tubers
• Axillary turions
• Fragments
Axillary Turions
• Turions form in the leaf axils at the ends of the stems, Turions
abscise and fall into the sediment.
, Over winter and produce new growth in the spring.
Fragmentation
• Spread from lake to lake by boats, Large populations found
adjacent to boat ramps. and Spreads extremely fast
• Total lake coverage can change drastically in just a years time
9. Weediness of hydrilla verticillata
Invasive in its native range
Proved invasive outside its native range
Highly adaptable to different environments
Tolerates, or benefits from, cultivation, browsing pressure, mutilation, fire etc
Tolerant of shade
Highly mobile locally
Long lived
Fast growing
Has high reproductive potential
Has propagules that can remain viable for more than one year
Reproduces asexually
10. The specimens of Elodea come from the monotypic genus Hydrilla of uncertain origin,
however, it is believed that it may have originated in meso-thermal waters of the Asian
continent, it exhibits pantropical distribution hence it has a wide geographical
occurrence, and can be found in naturalized areas of a large number of countries in
Europe, Africa, Australia, North America and South America.
Hydrilla verticillata is found on all continents except Antarctica. This
species is native to Asia, but it is uncertain whether it is truly native to
Europe, Australia and Africa. Hydrilla was first recorded in North
America from 1960 and South America from 2005
World wide Distribution
12. Distribution in SriLanka
Hydrilla verticillata (L.f.) Royle (Hydrocharitaceae) is a native aquatic that has been identified
as an invasive aquatic plant in the Western Province.
(Bambaradeniya, 2001 and 2008).
Hydrilla verticillata is a prevailing weed in the Mahaweli irrigation networks.
A recent conducted survey showed that 60% of the water bodies are infested
with Salvinia, 45% with water hyacinth and 17% with water lettuce (Pistia stratiotes).
(The problem of water weeds in Sri Lanka By Lucky Amarasinghe and Ricardo Labrada)
13. Impact
Hydrilla reproduces amazingly fast, outcompeting native aquatic plants by forming dense
stands that often fill the water column down to 20 feet. The decomposition of plant material in
these dense stands causes reductions in the dissolved oxygen content of water.
The degradation of habitat and alterations in the trophic (food chain) structure of the
ecosystem often reduces fish growth rates and numbers.
Dense stands impede navigation, dramatically reduce recreational opportunities and
tourism, and often block irrigation canals by dramatically slowing the flow of water.
Hydrilla can also interfere with hydroelectricity, by clogging intake pipes and
filters, causing millions of dollars worth of damage at individual hydroelectric
facilities.
14. Uses hydrilla verticillata
Medicinal uses
Two biologically important and structurally novel natural products,otteliones A and B, obtained from
this plant.
Therapeutically hydrilla plant may be used for the following purposes:
1. digestion and gastrointestinal function,
2. improves bloodcirculation,
3. helps in detoxification,
4. Good for neurological health and cardiovascular function
It increasesendurance, help in blood sugar control and strengthens immunity to protect the
body from invaders and slows ageing.
( Little known uses of common aquatic plant, Hydrilla verticillata (Linn. f.) Royle D K
Pal* andS B Nimse)
15. Control In Srilanka
Water hyacinth, one of the worst aquatic weeds in the world, has been intentionally
introduced for ornamental purpose in 1904 and it is widely distributed in Sri Lanka despite its
declaration as a prohibited weed under Water Hyacinth Act in 1909 and subsequently under Plant
Protection Act in 1924. (The problem of water weeds in Sri Lanka By Lucky Amarasinghe and
Ricardo Labrada).
Hydrilla can be controlled by physical, chemical and biological methods, or by a combination of these
methods (integrated weed management).
16. Physical management
options
Removes by use of
machines
Physical barriers
Biological ControlnMethods
Use by Grass Carp
Chemical methods
Bispyribac sodium, is the
recommended for control
the weed by DOA ,Srilanka