PHYTOTOTOXICITY OF PHENOLIC ALLELOCHEMICALS TO AQUATIC
WEEDS WITH REFERENCE TO CONSERVATION, RESTORATION AND
MANAGEMENT OF AQUATIC ECOSYSTEMS
Pandey D. K. and Mishra N.
Physiology Section, National Research Centre for Weed Science (ICAR),
Maharajpur, Jabalpur (M.P.) 482004, India
Phone: 0761-353101 (O); 353934
Fax: 0761-332329
E-mail:
dayapandey@hotmail.com
dkpandey@mantrafreenet.com
The study was aimed at investigating phytotoxicity of allelochemicals viz. o-, mand p- anisic acids; o-, m- and p- coumaric acids; caffeic acid, caffeine anhydrous,
catechol, chloremphenicol and cinnamic acid to six floating aquatic weeds Eichhornia
crassipes Mart Solmns., Salvinia molesta Mitchell, Pistia stratiotes L., Azolla nilotica
Decne., Spirodela polyrhiza L. Schleid. and Lemna pausicostata Hegelm.; and four
submerged weeds - Hydrilla verticillata L. f. Royle, Ceratophylum demersum L., Najas
graminea Del. and Chara sp. The aquatic weeds were allowed to grow in solutions of the
test allelochemicals in a quarter strength standard nutrient medium in plastic containers
outdoors. Biomass of the weeds were monitored after 5 and 10 days. Toxicity of the
allelochemicals varied with species. The chloramphenicol was lethal to Chara sp. at
relatively very low concentration (one- fiftieth the lethal level for other aquatic weeds)
and this has implications on management of the weed using the allelochemical (an
antibiotic) as a circumstantial allelochemic herbicide for an aquatic ecosystem especially
in fisheries. Alternatively, it may be an idea that an organism releasing the allelochemical
at substantial concentration into the medium could be found out for facilitating
management of the weeds especially Chara sp. in aquatic ecosystems. Accumulation of
the allelochemicals may affect conservation, restoration and management of aquatic
ecosystems.
INTRODUCTION
Allelopathy (a term first coined by Prof. Hans Molisch, a German Plant
Physiologist in 1937) is a chemical interaction among plants including microbes. It
involves release of a wide variety of chemicals by a plant into its environment, which are
taken up by a sensitive plant resulting in growth promotion or inhibition (Rice, 1984). In
addition to release of the allelochemicals by a living plant, residue of plants including
microbes, which becomes part of soil or aquatic systems can also liberate the
allelochemicals as such and/or consequent to death and decay involving various
microbial and chemical interactions. The allelochemicals may be released into the
environment variously including volatilisation or exudation from above and/or below
ground plant parts. Allelopathy is a simple phenomenon with complex consequences. A
plant is allelopathic when at least in one instance in nature or in a natural ecosystem or
under field conditions it has unequivocally shown allelopathy (Rice, 1984). An
allelochemical is a plant constituent other than a growth regulator and a nutrient that has
been decisively shown to have caused or is implicated in allelopathy in one or more
instances, usually active at a concentration below 10-4M. Allelopathic potential of plant is
the magnitude of its capacity to cause allelopathy. Allelopathy can be and should be
unequivocally proved when it occurs by showing presence of allelochemicals at
physiologically effective concentration from the substratum and by showing allelopathic
effects of the allelochemicals at a concentration found in the substratum under controlled
conditions (Putnam and Tang, 1986). In general, allelochemicals may promote growth of
the target species at a lower concentration and may inhibit them at higher concentrations.
Thus, allelopathy and allelochemicals may play important roles in restoration,
conservation and management of ecosystems including aquatic ecosystems (Rice, 1984,
Inderjit and Keating, 1999).
Allelochemicals may comprise several classes of plant constituents. These involve
secondary metabolites belonging to various chemical classes including simple acids and
esters, polyacetylenes, long chain fatty acids, alkaloids, benzoic acid derivatives,
cinnamic acid derivatives, coumarins, mono-, di- and triterpenoids, sesquiterpe lactones,
quinones and sulfated compounds, etc. (Kanchan and Jayachandra, 1980, Putnam, 1983;
Rice, 1984; Macias, 1995). Among these, phenolic compounds comprise a wide range of
plant substances possessing in common an aromatic ring bearing one or more hydroxyl
substituents. Phenolic substances are water soluble, frequently occur combined with
sugar as glycosides and are usually located in the cell vacuole. Function of some classes
of phenolic compounds has been well established. For example, lignins are structural
material of cell wall; the anthocyanins as flower pigments, the purpose of other classes is
still speculative (Harborne, 1988). The phenolic compounds have been attributed to have
a role in regulation of growth, and their adverse effects on insect feeding (Rosenthal and
Berenbaum, 1991). The phenolics have been widely implicated in allelopathy including
in aquatic ecosystems.
The secretion and leaching of organic compounds from living aquatic plants, both
macro- and micro-phytes have been frequently observed (Gopal and Goel, 1993). Since
most phenolic compounds are water soluble, their release from dead and decaying tissues
from terrestrial and aquatic origin may result in accumulation at physiologically
significant concentrations, which may show interference in aquatic plants. The effect of
phenolics on growth and metabolism of aquatic macrophytes are poorly understood
(Stom and Roth, 1981). The phenolics at high concentrations may cause injury to algae
and aquatic spermatophytes. Phenolic compounds have been suggested to be principal
active agents in preventing germination in a marshy environment (McNaughton, 1968).
Several phenolic plant constituents including p-hydroxybenzoic acid, vanillic acid,
syringic acid, ferulic acid, p-coumaric acid, salicylic acid, protocatechuic acid and
eugenol have been reported from aquatic plants (McNaughton, 1968; Drost and Doll,
1980; Jangaard et al., 1971; Sanchez et al., 1973; Cheng and Riemer, 1989; Gopal and
Goel, 1993). Investigations have reported phytotoxicity of allelochemicals including
phenolics on several aquatic weeds (Pandey et al., 1993; Pandey, 1994; Pandey, 1996).
Several species have been reported to show allelopathic interactions in aquatic
ecosystems. For example, Eleocharis acicularis or Sagittaria subutata eliminated
Potamogeton sp. Eleocharis sp. showed allelopathic inhibition of several other
macrophytes (Osborn et al., 1954) including Najas guadalupensis (Yeo, 1980). A
compound in leachates of Eleocharis was found toxic to Potamogeton pectinatus and
Hydrilla verticillata (Ashton et al., 1985). Salicylic acid had the maximum potential to
inhibit the sprouting of Hydrilla tubers and subsequent growth of the shoots. Hydrilla
verticillata inhibited Ceratophyllum demersum and Ceratophyllum muricatum
(Kulshreshtha and Gopal, 1983). Myriophyllum suppressed Najas (Agami and Waisal,
1985). Aqueous extracts of Azolla and Potamogeton illinoensis stimulated the growth of
Lemna pausicostata at lower concentration but reduced the growth at higher
concentrations (Sutton and Portier, 1989). Ceratophyllum demersum also contained
allelopathic compounds that negatively influenced other macrophytes (Phillips et al.,
1978). These findings imply that at high density such plants in aquatic ecosystems may
exert chemical regulation on the growth of other plants. Dead and decomposition of plant
and plant parts, and macrophytes and aquatic-terrestrial plant interactions may also
interact with species dynamics in aquatic ecosystems (Gopal and Goel, 1993).
Phenolics are secondary metabolites derived from the aromatic amino acids
synthesised through shikimic acid pathway (Harborne, 1988, Hopkins, 1999). Terrestrial
and aquatic plants release several phenolics directly from their living tissues and/or
indirectly after death and decomposition of the tissues (Rice, 1984). It is likely that these
may get washed or dissolved in water and find their way into aquatic substratum and thus
may affect the aquatic ecosystems. Allelochemicals have been shown to be inhibitory to
aquatic weeds (e.g., Pandey et al., 1993; Pandey, 1994; Pandey, 1996). However, detailed
studies as regard to the response of the aquatic weeds to a range of physiological
concentrations of the allelochemicals have not been undertaken. The study may help in
understanding the effect of accumulation of the allelochemicals in the aquatic ecosystems
on species survival, population dynamics and may have implications of practical
significance for management of the species. Present investigation reports phytotoxicity of
some of the phenolic allelochemicals on six floating and four submerged weeds with
reference to conservation, restoration and management of aquatic ecosystems.
Materials and methods
Six floating species Eichhornia crassipes Mart Solms., Salvinia molesta Mitchell,
Pistia stratiotes L., Azolla pinnata Decne., Spirodela polyrhiza L. Schleid. and Lemna
pausicostata Hegelm.; and four submerged species Hydrilla verticillata L. f. Royle,
Ceratophyllum demersum L., Najas graminea Del. and Chara sp. maintained at the
centre were used in the experiments. Solutions of the allelochemicals viz. o-, m- and panisic acids; o-, m- and p- coumaric acids; caffeic acid, caffeine anhydrous, catechol,
chloremphenicol and cinnamic acid were prepared in a quarter strength nutrient medium.
The nutrient medium (Einhellig et al., 1985) consisted of KH2PO4, 690 mg; KNO3, 515
mg; Ca(NO3)2.4H2O, 1180 mg; MgSO4.7H2O, 500 mg; H3BO3, 2.86 mg; ZnSO4.7H2O,
0.22 mg; Na2MoO4.2H2O, 0.12 mg; CuSO4.5H2O, 0.08 mg; MnCl2.4H2O, 3.62 mg; and
FeCl3.6H2O, 5.4 mg with the final pH adjusted at 6.5 with HCl or NaOH. The
concentrations of the allelochemicals used were control 0.01, 0.05, 0.10, 0.50, 1.00, 2.50
and 5.00 mM. The controls contained the nutrient medium only. Five hundred ml or one
litre or a suitable volume of the treatment medium was poured into a plastic container or
glass beakers with side walls covered with black carbon sheet. Pre-weighed aquatic
weeds were placed in the medium. The containers with aquatic weeds were incubated
outdoors in natural light. Effect of allelochemicals on test plants was monitored and
biomass of the test species was measured 5 and 10 days after initiation of the treatments.
Evapotranspiratory loss of water was replenished daily. All the experiments were
repeated three times. From the 0, 5 and 10 days biomass, % change in biomass over
original value were calculated and the data was analysed for ANOVA.
RESULTS AND DISCUSSION
Results of effects of allelochemical o-, m- and p-anisic acid and o-, m- and pcoumeric acid, caffeic acid, caffeine anhydrous, chloramphenicol and cinnamic acid on
biomass of the ten aquatic weeds studied have been shown in Table 1-10. The
percentage changes in biomass over original value in response to the allelochimicals 5
and 10 days after initiation of the treatment show effect on growth of the test species.
Ortho- and m-anisic acids were lethal to the aquatic weeds at and above 5 mM. However,
p-anisic acid was lethal at 2.5 mM. Ortho-coumaric acid was lethal at varying
concentrations in different species ranging from 1-5 mM. Meta-coumaric acid was lethal
at 5 mM. However, p-coumaric acid was lethal at 0.5-5 mM, depending on the weed
species. Caffeic acid was consistently lethal to all species at 5 mM except to floating
weeds Lemna pausicostata, Azolla pinnata and Spirodella polyrhiza, which withstood
this concentration. Caffeine anhydrous was lethal to submerged weed Eichhornia
crassipes and floating weed Chara sp. at 5 mM and to other floating and submerged
species at 10 mM. Catechol was lethal to all floating and submerged weeds at 5 mM
except for floating weed Pistia stratiotes and submerged weed Chara sp. which were
killed at 10 and 1 mM, respectively. Chloramphenicol was lethal to floating weeds
Eichhornia crassipes, Pistia stratiotes and Salvinia molesta, and submerged weeds
Hydrilla verticillata and Najas sp. at 0.5 mM and to floating weed Lemna pausicostata,
Azolla pinnata and Spirodella polyrhiza, and submerged weeds Najas graminea and
Ceratophyllum demersum at 1.0 mM. However, it was lethal to submerged weed Chara
sp. at and above 0.01 mM. Cinnamic acid was lethal to all floating and submerged weeds
at and above 5.0 mM except for Azolla pinnata, which was killed at 1.0 mM. None of the
allelochemicals tested showed toxicity in the dark for about one day. Light seems to
exacerbate manifestation of the toxicity in all cases. At lethal dose, toxicity in the treated
plants appeared the very next day after initiation of the treatment in o- and m-anisic acid.
In p-anisic acid the toxicity appeared after 3 days. Ortho- and p-coumaric acid showed
toxicity in two days. Meta-coumaric acid showed toxicity after a day at the lethal dose.
Caffeic acids caused toxicity in about two days. Caffeine anhydrous was toxic in about
three days. Catechol and chloramphenicol showed toxicity in about two days. Cinnamic
acid showed toxicity in about three days. Different allelochemicals caused death and
decay of different weeds in different durations ranging from 5-10 days.
Toxicity symptoms did not vary much with the allelochemical. The symptoms of
toxicity of different allelochemicals at lethal dose involved dull green colour, chlorosis,
desiccation of leaves and above water plant parts, and flaccid roots. The flaccid roots and
desiccation of above water plant parts implicate involvement of root dysfunction derived
desiccation and associated physiological changes including massive damage to cellular
membrane integrity and loss of macromolecules decisively killing the treated plants.
Similarly, in submerged species the symptoms including dull green colour, chlorosis,
flaccid plant body and fragmentation implicate damage to macromolecules and excessive
loss of cellular membrane integrity resulting in death of the treated plants at the lethal
dose.
Among all the allelohemicals, chloramphenicol was lethal to the species studied at
much lower concentrations. Chara sp. was most sensitive to this allelochemical with
lethal dose at 0.01 mM. The allelochemical was also lethal to floating weeds Eichhornia
crassipes, Salvinia molesta, Pistia stratiotes, and submerged weed Hydrilla verticillata at
0.5 mM. The lethal dose for floating weeds Lemna pausicostata and Spirodella polyrhiza,
and submerged weeds Najas graminea and Ceratophyllum demersum was at 1.0 mM.
The chloramphenicol was lethal to Chara sp. at relatively very low concentration (one
fiftieth the lethal level for other aquatic weeds) and this has implications on management
of the weed using the allelochemical (an antibiotic) as a circumstantial allelochemic
herbicide for an aquatic ecosystem especially in fisheries. Alternatively, it may be
postulated that an organism releasing the allelochemical at substantial concentration into
the medium could be found out for facilitating management of the weeds especially
Chara sp. in aquatic ecosystems.
Phenolics are widely occurring plant constituents including in aquatic species
(McNaughton, 1968; Drost and Doll, 1980; Jangaard et al., 1971; Sanchez et al., 1973;
Cheng and Riemer, 1989; Gopal and Goel, 1993). Accumulation of phenolics and other
allelochemicals in an aquatic ecosystem due to allelopathy and/or by washing or
dissolution of allelochemicals as a result of death and decay or decomposition of the
plants or plant parts and their residue (Rice, 1984; Gopal and Goel, 1993; Pandey et al.,
1993; Pandey, 1994, 1996) may affect conservation, restoration and management of
aquatic ecosystems. Different species may have different sensitivities to the
allelochemicals. Accumulation of the allelochemicals at higher concentration may
influence growth, population dynamics and survival of more sensitive species first and
then those that are less sensitive ones. Thus, the allelochemical accumulation in an
ecosystem may affect species distribution, shifts and succession, and the biodiversity.
Aquatic ecosystems with accumulation of allelochemicals may necessitate their
management for effective restoration. Allelopathy and/or use of allelochemicals have
potential, that are yet to be explored for application , for selective management of plants
in an aquatic ecosystem. Exploration of such a potential may be rewarding by facilitating
invasive and noxious weed management in an aquatic ecosystem in an eco-friendly
approach.
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Table 1. Effect of o-anisic acid on biomass of aquatic weeds
Treat
ment
(mM)
Percent change in biomass over original value 10 days after initiation of the treatment
Eichhor Pistia
nia
stratio
crassip tes
es
Contro
15.6
142.3
l
0.01
24.6
135.6
Salvi
nia
moles
ta
37.2
Lemna
pausicos
tata
Spirode
lla
polyrhi
za
138.1
Najas
grami
nea
131.3
Azoll
a
pinna
ta
61.6
33.4
Ceratoph
ylum
demersu
m
40.1
Hydrill
a
verticill
ata
43.0
37.9
135.3
63.6
128.6
25.5
39.0
21.8
0.05
15.5
138.9
60.7
111.9
64.3
124.4
26.9
36.0
22.4
0.1
29.6
85.4
79.0
114.0
60.9
109.7
24.9
38.5
23.2
0.5
20.1
107.0
46.0
111.6
57.3
98.9
28.8
32.1
18.4
1.0
.47
56.6
55.4
95.3
60.6
96.8
30.4
39.9
7.90
5.0
-100
-100
-100
-100
-100
-100
-100
-100
-100
10.0
-100
-100
-100
-100
-100
-100
-100
-100
-100
LSD
12.9
36.1
33.24
14.15
10.37 14.34
at
P=0.0
5
Minus 100 % biomass shows death of the treated plants.
9.21
33.59
25.7
Cha
ra
sp.
55.
0
46.
0
72.
2
26.
6
100
.0
54.
16
100
100
20.
65
Table 2. Effect of m-anisic acid on biomass of aquatic weeds
Treat
ment
(mM)
Percent change in biomass over original value 10 days after initiation of the treatment
Eichhor Pistia
nia
stratio
crassip tes
es
Contro
29.1
108.8
l
0.01
18.5
61.1
Salvi
nia
moles
ta
45.4
Lemna
pausicos
tata
Spirode
lla
polyrhi
za
146.9
Najas
grami
nea
144.5
Azoll
a
pinna
ta
72.1
54.4
Ceratoph
ylum
demersu
m
18.7
Hydrill
a
verticill
ata
22.8
54.5
133.5
64.6
142.2
31.0
20.7
28.3
0.05
25.7
94.8
54.1
130.8
64.3
135.1
39.3
25.5
21.8
0.1
10.8
82.8
77.4
125.0
62.1
129.0
21.2
23.8
24.2
0.5
16.9
67.6
83.7
123.5
54.0
132.0
20.0
20.7
15.6
1.0
16.4
-18.5
48.0
111.2
50.8
128.3
19.2
-3.1
6.34
5.0
-100
-100
-100
-100
-100
-100
-100
-100
-100
10.0
-100
-100
-100
-100
-100
-100
-100
-100
-100
LSD
23.8
39.5
45.9
13.0
8.47
9.58
at
P=0.0
5
Minus 100 % biomass shows death of the treated plants.
26.1
40.5
18.8
Cha
ra
sp.
30.
2
20.
8
30.
2
24.
6
15.
8
21.
7
100
100
18.
8
Table 3. Effect of p-anisic acid on biomass of aquatic weeds
Treat
ment
(mM)
Percent change in biomass over original value 10 days after initiation of the treatment
Eichhor Pistia
nia
stratio
crassip tes
es
Contro
29.9
197.0
l
Salvi
nia
moles
ta
105.6
Lemna
pausicos
tata
133.1
Azoll
a
pinna
ta
58.3
Spirode
lla
polyrhi
za
135.0
Najas
grami
nea
32.1
Ceratoph
ylum
demersu
m
46.6
Hydrill
a
verticill
ata
25.4
Cha
ra
sp.
40.
5
0.01
8.0
152.0
68.0
126.4
61.9
127.8
32.6
26.9
21.8
0.05
15.3
184.4
63.5
126.5
68.5
126.8
23.7
31.6
37.0
0.1
17.5
145.9
82.2
114.4
65.2
113.9
25.8
30.5
25.0
0.5
26.3
128.1
107.3
96.9
56.7
104.2
19.9
45.7
21.9
1.0
5.0
12.8
-100
17.9
-100
20.5
-100
106.8
-100
58.5
-100
98.5
-100
-12.5
-100
7.63
-100
-21.2
-100
10.0
13.2
61.6
98.5
10.8
12.6
6.26
54.0
63.3
27.8
22.
6
27.
7
20.
5
16.
6
-1.5
100
58.
2
LSD
at
P=0.0
5
Minus 100 % biomass shows death of the treated plants.
Table 4. Effect of o-coumaric acid on biomass of aquatic weeds
Treat
ment
(mM)
Percent change in biomass over original value 10 days after initiation of the treatment
Eichhor Pistia
nia
stratio
crassip tes
es
Contro
26.9
167.6
l
0.01
36.1
151.8
Salvi
nia
moles
ta
79.3
Lemna
pausicos
tata
Spirode
lla
polyrhi
za
140.5
Najas
grami
nea
130.7
Azoll
a
pinna
ta
66.6
51.5
Ceratoph
ylum
demersu
m
42.9
Hydrill
a
verticill
ata
35.4
56.0
121.4
63.9
123.1
51.1
43.6
36.7
0.05
18.4
163.4
46.0
119.2
58.9
120.3
56.1
40.9
30.8
0.1
20.3
102.1
68.1
114.4
55.3
109.6
58.3
59.3
36.9
Cha
ra
sp.
62.
7
61.
6
58.
3
50.
8
0.5
20.1
144.0
54.4
109.3
57.4
104.5
39.0
21.6
20.8
1.0
15.2
47.1
29.1
101.5
52.7
96.8
-3.5
-6.6
36.1
5.0
-100
-100
-100
-100
-100
-100
-100
-100
-100
10.0
-100
-100
-100
-100
-100
-100
-100
-100
-100
LSD
21.3
40.8
47.7
14.4
6.51
19.4
at
P=0.0
5
Minus 100 % biomass shows death of the treated plants.
63.1
68.4
25.2
36.
7
100
100
100
8.4
7
Table 5. Effect of m-coumaric acid on biomass of aquatic weeds
Treat
ment
(mM)
Percent change in biomass over original value 10 days after initiation of the treatment
Eichhor Pistia
nia
stratio
crassip tes
es
Contro
29.3
85.2
l
0.01
20.7
62.3
Salvi
nia
moles
ta
58.8
Lemna
pausicos
tata
Spirode
lla
polyrhi
za
136.8
Najas
grami
nea
132.7
Azoll
a
pinna
ta
64.3
51.0
Ceratoph
ylum
demersu
m
20.7
Hydrill
a
verticill
ata
31.3
34.2
124.7
60.3
131.6
49.1
28.3
36.4
0.05
14.6
78.3
32.9
119.3
55.6
129.9
49.9
22.5
31.9
0.1
23.3
79.8
43.3
116.6
55.6
130.1
57.3
25.5
31.5
0.5
-34.7
69.6
40.5
108.6
57.3
127.3
50.0
3.46
26.7
1.0
-18.3
26.5
33.0
100.0
54.9
120.9
42.4
-83.3
22.5
5.0
-100
-100
-100
-100
-100
-100
-100
-100
-100
10.0
-100
-100
-100
-100
-100
-100
-100
-100
-100
LSD
at
P=0.0
5
18.2
43.4
52.2
11.6
9.01
8.90
18.2
14.30
12.1
Cha
ra
sp.
36.
3
31.
7
32.
8
25.
5
24.
9
22.
1
100
100
4.4
0
Minus 100 % biomass shows death of the treated plants.
Table 6. Effect of p-coumaric acid on biomass of aquatic weeds
Treat
ment
(mM)
Percent change in biomass over original value 10 days after initiation of the treatment
Eichhor Pistia
nia
stratio
crassip tes
es
Contro
13.1
135.2
l
0.01
29.6
136.0
Salvi
nia
moles
ta
52.2
Lemna
pausicos
tata
Spirode
lla
polyrhi
za
136.9
Najas
grami
nea
124.2
Azoll
a
pinna
ta
65.3
59.6
Ceratoph
ylum
demersu
m
21.5
Hydrill
a
verticill
ata
32.2
61.6
120.3
57.3
134.5
51.9
38.3
22.9
0.05
35.6
140.5
68.7
121.6
53.3
124.1
55.6
30.5
37.8
0.1
32.0
121.1
80.5
115.3
57.3
123.0
44.1
31.0
34.4
0.5
20.7
110.9
54.0
99.2
52.9
121.6
42.8
-27.1
45.5
1.0
-14.7
56.0
-53.1
92.5
51.6
106.6
-100
-100
-56.4
5.0
-100
-100
-100
-100
-100
-100
-100
-100
-100
10.0
-100
-100
-100
-100
-100
-100
-100
-100
-100
LSD
29.67
22.5
50.8
7.61
10.99
13.6
at
P=0.0
5
Minus 100 % biomass shows death of the treated plants.
6.64
40.4
49.8
Cha
ra
sp.
47.
1
45.
6
40.
8
55.
3
100
100
100
100
5.9
4
Table 7. Effect of caffeic acid on biomass of aquatic weeds
Treat
ment
(mM)
Percent change in biomass over original value 10 days after initiation of the treatment
Eichhor Pistia
nia
stratio
crassip tes
es
Contro 110.9
53.5
l
0.01
153.6
95.3
Salvi
nia
moles
ta
122.5
Lemna
pausicos
tata
Spirode
lla
polyrhi
za
97.7
Najas
grami
nea
46.7
Azoll
a
pinna
ta
121.6
15.0
Ceratoph
ylum
demersu
m
24.9
Hydrill
a
verticill
ata
62.5
253.0
105.8
93.0
75.0
17.0
55.2
18.6
0.05
133.3
81.9
119.8
96.5
178.6
116.1
13.0
83.9
64.0
0.1
137.9
89.6
153.8
108.7
177.0
147.9
36.9
40.1
69.7
0.5
89.2
73.7
204.4
98.3
177.5
155.5
22.9
63.1
47.0
1.0
5.0
156.9
-100
47.0
-100
47.5
-100
98.8
-63.2
176.8
-15.3
165.1
62.5
35.3
-100
31.7
-100
57.7
-100
10.0
-100
-100
-100
-100
-100
-100
-100
-100
-100
LSD
72.7
53.7
143.7
59.5
86.0
at
P=0.0
5
Minus 100 % biomass shows death of the treated plants.
23.8
74.5
32.5
Table 8. Effect of caffein anhydrous on biomass of aquatic weeds
Treat
ment
(mM)
Percent change in biomass over original value 10 days after initiation of the treatment
Cha
ra
sp.
7.8
3
26.
7
16.
1
26.
0
16.
1
-4.9
100
100
20.
4
Eichhor Pistia
nia
stratio
crassip tes
es
Contro
97.9
108.1
l
0.01
88.8
92.9
Salvi
nia
moles
ta
78.5
Lemna
pausicos
tata
Spirode
lla
polyrhi
za
138.0
Najas
grami
nea
142.3
Azoll
a
pinna
ta
70.8
45.7
Ceratoph
ylum
demersu
m
38.9
Hydrill
a
verticill
ata
29.3
92.6
137.3
67.7
143.0
39.2
33.2
27.4
0.05
94.5
93.9
48.9
131.0
64.3
134.6
35.4
35.6
26.9
0.1
117.2
58.9
104.1
123.3
60.7
131.0
39.7
52.1
44.3
0.5
73.9
54.6
89.9
121.6
51.1
128.3
60.9
63.6
29.1
1.0
101.2
52.2
56.5
115.3
53.9
117.0
47.4
51.7
26.2
5.0
-100
-100
23.4
109.3
51.9
109.3
41.5
24.2
25.8
10.0
-100
-100
-100
-100
-100
-100
-100
-100
-56.8
LSD
49.6
40.0
57.1
6.33
6.05
10.7
at
P=0.0
5
Minus 100 % biomass shows death of the treated plants.
14.8
36.6
47.7
Cha
ra
sp.
46.
0
68.
1
52.
1
67.
2
17.
7
18.
2
100
100
52.
6
Table 9. Effect of catechol on biomass of aquatic weeds
Treat
ment
(mM)
Percent change in biomass over original value 10 days after initiation of the treatment
Eichhor Pistia
nia
stratio
crassip tes
es
Contro
46.1
111.5
l
0.01
45.0
144.0
Salvi
nia
moles
ta
81.9
Lemna
pausicos
tata
Spirode
lla
polyrhi
za
146.9
Najas
grami
nea
142.5
Azoll
a
pinna
ta
72.4
31.8
Ceratoph
ylum
demersu
m
35.8
Hydrill
a
verticill
ata
49.2
75.0
130.4
69.0
142.2
33.3
16.5
32.9
0.05
55.7
116.7
79.5
126.2
65.10
135.1
30.5
32.9
31.7
0.1
39.5
129.2
38.8
128.4
67.6
129.0
37.1
23.2
56.2
Cha
ra
sp.
55.
4
40.
0
76.
6
38.
3
0.5
-1.5
88.2
9.3
124.6
65.6
132.0
67.7
-2.6
49.1
1.0
-12.7
47.2
-23.1
123.0
63.1
128.3
-20.0
-73.1
-21.4
5.0
-100
-100
-100
-100
-100
-100
-100
-100
-100
10.0
-100
-100
-100
-100
-100
-100
-100
-100
-100
LSD
39.7
79.8
59.9
12.3
5.94
9.58
at
P=0.0
5
Minus 100 % biomass shows death of the treated plants.
66.8
41.4
64.0
25.
0
100
100
100
31.
8
Table 10. Effect of chloroamphenicol on biomass of aquatic weeds
Treat
ment
(mM)
Percent change in biomass over original value 10 days after initiation of the treatment
Eichhor Pistia
nia
stratio
crassip tes
es
Contro
50.6
145.0
l
0.01
64.8
146.5
Salvi
nia
moles
ta
104.7
Lemna
pausicos
tata
Spirode
lla
polyrhi
za
141.2
Najas
grami
nea
142.3
Azoll
a
pinna
ta
69.5
54.7
Ceratoph
ylum
demersu
m
32.8
Hydrill
a
verticill
ata
29.7
81.8
138.7
63.7
135.5
43.0
18.9
24.8
0.05
64.0
181.9
62.9
138.7
59.6
135.8
25.0
30.2
34.0
0.1
26.7
83.6
40.8
140.0
60.6
126.9
29.7
28.6
22.3
0.5
-21.9
47.1
30.3
131.3
59.4
122.5
29.3
13.1
14.3
1.0
-100
-100
-100
137.1
54.1
116.2
33.7
-96.6
-100
5.0
-100
-100
-100
-100
-100
-100
-100
-100
-100
Cha
ra
sp.
26.
6
11.
3
100
100
100
100
-
10.0
-100
-100
-100
-100
-100
-100
-100
-100
-100
LSD
51.1
27.2
44.5
10.1
7.44
6.00
at
P=0.0
5
Minus 100 % biomass shows death of the treated plants.
11.0
11.4
19.4
100
100
6.6
3
Table 11. Effect of cinnamic acid on biomass of aquatic weeds
Treat
ment
(mM)
Percent change in biomass over original value 10 days after initiation of the treatment
Eichhor Pistia
nia
stratio
crassip tes
es
Contro
26.4
87.3
l
0.01
13.7
73.9
Salvi
nia
moles
ta
25.2
Lemna
pausicos
tata
Spirode
lla
polyrhi
za
115.3
Najas
grami
nea
132.8
Azoll
a
pinna
ta
70.3
71.6
Ceratoph
ylum
demersu
m
50.9
Hydrill
a
verticill
ata
90.7
29.7
125.6
59.2
110.5
57.6
26.0
77.2
0.05
20.8
70.2
36.9
127.3
64.3
117.4
67.8
41.2
91.6
0.1
23.1
81.1
37.3
125.6
62.0
112.3
68.8
20.9
64.5
0.5
1.0
27.9
25.7
27.9
55.8
52.1
30.8
127.7
120.3
66.5
-100
105.0
108.4
62.7
50.0
22.7
11.5
-100
-100
5.0
-100
-100
-100
-100
-100
-100
-100
-100
-100
10.0
-100
-100
-100
-100
-100
-100
-100
-100
-100
LSD
19.7
47.0
22.1
8.27
9.07
15.1
at
P=0.0
5
Minus 100 % biomass shows death of the treated plants.
31.6
34.0
41.7
Cha
ra
sp.
55.
0
46.
6
72.
2
26.
6
100
54.
1
100
100
50.
5