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Rootless Duckweed, Spotless Watermeal
Wolffia arrhiza

3.2 Vulnerable

name of participantsBased on: "The Red Book of Israeli Plants - Threatened Plants in Israel" by Prof. Avi Shmida, Dr. Gadi Pollack and Dr. Ori Fragman-Sapir
Update Time: Aug. 21, 2023, 4:32 p.m.

Wolffia arrhiza
can be eaten after cooking and is very rich in proteins, carbohydrates, fats
and vitamins. It is also used as fish food. The species, like other species in
the
Lemnaceae family,
is also a good fodder plant, especially given its high protein content. It is also
effective in purifying wastewater.

Wolffia arrhiza is found today only
in the Golan. In the past, it was collected in the Sharon, from the
Batih Pond, northeast of Hadera, where it is
now extinct. In the Golan, it was observed during last 25 years at 20 sites in
springs and ponds, especially in the central Golan. Hyman (1981, and pers.
comm.) reported several sites of
W. arrhiza in the Zavitan
Stream basin at altitudes of 350-900 meters.

Water surface of
ponds, puddles and fresh water canals. Sometimes grows together with species of
Lemna. According to Hyman (1981)
Wolffia
arrhiza
is a major component of the “Lemna gibba - Wolffia
arrhiza

plant association typical of slow flowing streams in the
Golan. L. gibba is usually dominant in the spring, and as water
temperature rises, or possibly due to the reduced flow,
W. arrhiza
develops and dominates the water surface. The appearance of
W. arrhiza
is probably related to well-lit, open bodies of water, and according to Hyman
(1981) only in places with flowing water. Nevertheless, it was also found in standing
water, such as the Sumka Reservoir in the northern
Golan Heights. As a rule
W. arrhiza plants float in
open water where there are no other rooted aquatic plants, but it occasionally appears
in shallow streams with slow flowing water, which are generally dominated by Nasturtium
officinale
and Apium nodiflorum, with
W. arrhiza plants
scattered in semi-shaded conditions between them.

·        
The
major threat to
Wolffia arrhiza populations is the drying
of ponds and springs in the Golan Heights, resulting from impounding water in
reservoirs  and the decline in water levels.
Trampling by cattle in puddles and ponds damages the plants.

·        
The
populations are fragmented and several kilometers apart, according to the
location of the water sources. Population density fluctuates seasonally and
annually: sometimes the water surface area is almost completely covered (together
with
Lemna gibba)
and at other times, only a few plants are found.

·        
The
species is very common in the world, and is not globally endangered. 

Ponds and springs in the Golan should be protected and trampling
by cattle should be prevented.
Wolffia arrhiza
should be reintroduced and naturalized in wetlands in the Sharon, such as the
Ya'ar or Dora ponds. 

Wolffia arrhizais is distributed
over extensive areas in the Old World: throughout Europe, the western Mediterranean,
the Maghreb countries, the Black Sea countries, equatorial Africa, India,
Malaysia, the Philippines and Australia. In the Middle East, it grows only in
Israel and northern Iran.

Wolffia arrhiza is
a floating aquatic plant, the smallest flowering plant in the world. Its distribution
is currently limited only to the Golan, where it is threatened by the reduction
of flow in springs resulting from water impoundment in reservoirs and trampling
by cattle. Reintroduction and naturalization of
W. arrhiza
in the Sharon should be considered.

 

היימן, ר.1981. הצומח של מקווי המים בגולן. עבודת גמר,המחלקה לבוטניקה, האוניברסיטה העברית, ירושלים.
ויזל, י. וליפשיץ, נ. (1971). צמחי מים בישראל. הוצאת רשות שמורות הטבע.

name of participantsBased on: "The Red Book of Israeli Plants - Threatened Plants in Israel" by Prof. Avi Shmida, Dr. Gadi Pollack and Dr. Ori Fragman-Sapir

Current Occupancy Map

Current occupancy map for observations per pixel
1000 squre meter pixel 5000 squre meter pixel 10000 squre meter pixel
number of observations 0 0 0
in total pixels 0 0 0

FamilyLemnaceae
ClassificationOn the endangered species list
EcosystemMediterranean humid
ChorotypeMulti-regional, Northern and Tropical
Conservation SiteEn Sumka in the Enot Orvim Nature Reserve

Rarity
1
2
6
Vulnerability
0
4
4
Attractiveness
0
0
4
Endemism
0
0
4
Red number
1
3.2
10
Peripherality 0
IUCN category DD EW EX LC CR EN VU NT
Threat Definition according to the red book Vulnerable
1 (2) districts
Disjunctiveness: Medium
0.0% of protected sites

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