161
lent and trivalent forms of phosphate ions are not as readily
available to the plants as monovalent phosphate ions (Devlin and Witham 1986). The data of Table 12.11 suggested
that the 40 ppm of the Surf Excel increased the dry weight,
chlorophyll content, and uptake of NPK in the Spirodela
polyrrhiza.
It also emerged from the data that increasing concentration of Surf Excel resulted into a proportional increase in
the pH of the water medium. Thus, despite increased availability of phosphate, probably its ionic forms consistently
changed from monovalent to bivalent and trivalent ions
which proportionally reduced the uptake of NPK in both the
duckweeds at 50 ppm as compared to uptake at 40 ppm of
Surf Excel (Tables 12.9 and 12.11). Moreover, the cells in
the fronds of a Lemna species have proton extrusion pump
at the plasmalemma which is responsible for the energy-dependent component of the membrane potential (Ansari and
Khan 2006b; Novacky et al. 1978a, b; Löppert 1979; Jung
and Lüttge 1980). This pump is responsible for the uptake
of sugars, amino acids, phosphates, nitrates, and perhaps
other inorganic ions by means of H
+
-co transport mechanism
(Ullrich-Eberius et al. 1978, 1981; Fischer and Lüttge 1980;
Böcher et al. 1980; Lüttge et al. 1981).
The findings of the present work also established the
ecological importance and sensitivity levels of the Lemna
minor. Aziz and Mobina (1999) reported that pH 6.0 was
most suitable for two species of Spirodela polyrrhiza and
Spirodelapunctata. The Spirodela polyrrhiza died at pH 4.0.
Both the species of Spirodela grew quite well up to pH 9. In
both the species low pH affected the chlorophyll b formation (Aziz and Mobina 1999). Riis and Sand (1998) found a
direct relationship between macrophyte distribution and pH,
nutrient conditions, and transparency of Danish lakes.
The phosphorus is an important constituent of ATP, ADP,
nucleic acids (DNA and RNA), phospholipids, and proteins.
The meiotic cell division in sexual reproduction and mitotic
cell division in vegetative propagation require greater supply of phosphorus for its binding into required nucleic acids,
phospholipids, and protein. When grown singly, the phosphorus uptake in Lemna minor at 40 ppm of Surf Excel was
almost 23 % higher than the control (Table 12.9). The phosphorus uptake in Spirodela polyrrhiza was 60 % higher (than
the control) at 40 ppm of Surf Excel (Table 12.11).The plants
have specific controls for the uptake of solutes, whether they
have osmotic roles in the cells or the solutes are used as nutrients. The uptake of phosphate depends upon the phosphate
status of the plants (Ullrich-Eberius et al. 1981).
A direct relationship between phytoplankton minima and
maxima was found related with the DO content by a number of workers (Lande 1973; Misra et al. 1975; Saad 1973;
Schindler 1971). As evident from the data of the water quality (Tables 12.10, 12.12) the dissolved oxygen and turbidity of water was impaired to a relatively greater extent by
Spirodela sp. as compared to Lemna sp. Thus, the Spirodela
polyrrhiza modifies the aquatic environment more actively
than the Lemna minor. Such modifications in the environment by component species themselves, results into the succession of community to a higher seralstage. Any change in
the natural quality of water is best reflected in the change in
natural flora and fauna of the aquatic ecosystem (Kulshrestha et al. 1989). The eutrophication reduced the number of
rare species and increased the abundance of meso- to hypereutrophic species specifically Fragilariaberolinensis in
the eutrophic broad area of De NieuwkoopsePlassen in the
Netherlands (Van Dam and Mertens 1993).
In the present work, temperature played important role
in the growth of both the selected duckweed species. The
optimum growth increase was noted at 30 °C temperature.
The temperature of 20 and 30 °C increased the uptake of
NPK specifically of phosphorus. The higher temperatures
adversely affected the chlorophyll content in both the species
eventually the excessive chlorosis and necrosis lead to faster
duckweed mortality. The nitrogen uptake was optimum in
both the species at 30 °C of temperature (Tables 12.15 and
12.17).The chlorophyll concentration was found strongly
linked to the total nitrogen concentration. During summer,
nitrogen concentrations accounted for about 60 % of the
variability in chlorophyll concentration among different
coastal systems (Neilson et al. 2002). It appears that higher
temperature of 40 and 50 °C impaired the nitrogen availability and thereby reduced the chlorophyll content and thus,
caused early disappearance of both the duckweeds by 5th to
9th day from the treatment. The temperature deviations are
believed to impose stresses on plants leading to abnormalities resulting into reduced chances of survival (Ansari and
Khan 2006b; Treshow 1970).
The temperature regulates cell division rate, enzyme activity (Giese 1979), translocation, and synthesis of food material (Devlin and Witham 1986). The development of plant,
metabolic activities, mineral absorption, and water uptake
are strongly temperature dependent (Treshow 1970; Devlin and Witham 1986). The lower temperatures below 10 °C
(Ghosh et al. 1995) have been reported to retard the growth
and productivity of duckweed. The temperature between 20
and 30 °C was found optimum by Hillman (1961). Aziz and
Mobina (1999) found 25–33 °C temperature were optimum
for the growth of two species of Spirodela. The photosynthesis is also dependent upon the enzyme activity which is
reported to be negligible below 10 °C and to be optimum at
30 °C in most of the plant species (Treshow 1970). The role
of several other parameters (viz. direct impact of detergents
on the cell membranes, injuries and leakage of ions out of the
fronds cells) in modifying the responses of both duckweeds
cannot be ruled out. It is suggested that more detailed studies
are needed to have a deeper insight on the physio–morphological responses of the duckweeds.
12 Household Detergents Causing Eutrophication in Freshwater Ecosystems
lent and trivalent forms of phosphate ions are not as readily
available to the plants as monovalent phosphate ions (Devlin and Witham 1986). The data of Table 12.11 suggested
that the 40 ppm of the Surf Excel increased the dry weight,
chlorophyll content, and uptake of NPK in the Spirodela
polyrrhiza.
It also emerged from the data that increasing concentration of Surf Excel resulted into a proportional increase in
the pH of the water medium. Thus, despite increased availability of phosphate, probably its ionic forms consistently
changed from monovalent to bivalent and trivalent ions
which proportionally reduced the uptake of NPK in both the
duckweeds at 50 ppm as compared to uptake at 40 ppm of
Surf Excel (Tables 12.9 and 12.11). Moreover, the cells in
the fronds of a Lemna species have proton extrusion pump
at the plasmalemma which is responsible for the energy-dependent component of the membrane potential (Ansari and
Khan 2006b; Novacky et al. 1978a, b; Löppert 1979; Jung
and Lüttge 1980). This pump is responsible for the uptake
of sugars, amino acids, phosphates, nitrates, and perhaps
other inorganic ions by means of H
+
-co transport mechanism
(Ullrich-Eberius et al. 1978, 1981; Fischer and Lüttge 1980;
Böcher et al. 1980; Lüttge et al. 1981).
The findings of the present work also established the
ecological importance and sensitivity levels of the Lemna
minor. Aziz and Mobina (1999) reported that pH 6.0 was
most suitable for two species of Spirodela polyrrhiza and
Spirodelapunctata. The Spirodela polyrrhiza died at pH 4.0.
Both the species of Spirodela grew quite well up to pH 9. In
both the species low pH affected the chlorophyll b formation (Aziz and Mobina 1999). Riis and Sand (1998) found a
direct relationship between macrophyte distribution and pH,
nutrient conditions, and transparency of Danish lakes.
The phosphorus is an important constituent of ATP, ADP,
nucleic acids (DNA and RNA), phospholipids, and proteins.
The meiotic cell division in sexual reproduction and mitotic
cell division in vegetative propagation require greater supply of phosphorus for its binding into required nucleic acids,
phospholipids, and protein. When grown singly, the phosphorus uptake in Lemna minor at 40 ppm of Surf Excel was
almost 23 % higher than the control (Table 12.9). The phosphorus uptake in Spirodela polyrrhiza was 60 % higher (than
the control) at 40 ppm of Surf Excel (Table 12.11).The plants
have specific controls for the uptake of solutes, whether they
have osmotic roles in the cells or the solutes are used as nutrients. The uptake of phosphate depends upon the phosphate
status of the plants (Ullrich-Eberius et al. 1981).
A direct relationship between phytoplankton minima and
maxima was found related with the DO content by a number of workers (Lande 1973; Misra et al. 1975; Saad 1973;
Schindler 1971). As evident from the data of the water quality (Tables 12.10, 12.12) the dissolved oxygen and turbidity of water was impaired to a relatively greater extent by
Spirodela sp. as compared to Lemna sp. Thus, the Spirodela
polyrrhiza modifies the aquatic environment more actively
than the Lemna minor. Such modifications in the environment by component species themselves, results into the succession of community to a higher seralstage. Any change in
the natural quality of water is best reflected in the change in
natural flora and fauna of the aquatic ecosystem (Kulshrestha et al. 1989). The eutrophication reduced the number of
rare species and increased the abundance of meso- to hypereutrophic species specifically Fragilariaberolinensis in
the eutrophic broad area of De NieuwkoopsePlassen in the
Netherlands (Van Dam and Mertens 1993).
In the present work, temperature played important role
in the growth of both the selected duckweed species. The
optimum growth increase was noted at 30 °C temperature.
The temperature of 20 and 30 °C increased the uptake of
NPK specifically of phosphorus. The higher temperatures
adversely affected the chlorophyll content in both the species
eventually the excessive chlorosis and necrosis lead to faster
duckweed mortality. The nitrogen uptake was optimum in
both the species at 30 °C of temperature (Tables 12.15 and
12.17).The chlorophyll concentration was found strongly
linked to the total nitrogen concentration. During summer,
nitrogen concentrations accounted for about 60 % of the
variability in chlorophyll concentration among different
coastal systems (Neilson et al. 2002). It appears that higher
temperature of 40 and 50 °C impaired the nitrogen availability and thereby reduced the chlorophyll content and thus,
caused early disappearance of both the duckweeds by 5th to
9th day from the treatment. The temperature deviations are
believed to impose stresses on plants leading to abnormalities resulting into reduced chances of survival (Ansari and
Khan 2006b; Treshow 1970).
The temperature regulates cell division rate, enzyme activity (Giese 1979), translocation, and synthesis of food material (Devlin and Witham 1986). The development of plant,
metabolic activities, mineral absorption, and water uptake
are strongly temperature dependent (Treshow 1970; Devlin and Witham 1986). The lower temperatures below 10 °C
(Ghosh et al. 1995) have been reported to retard the growth
and productivity of duckweed. The temperature between 20
and 30 °C was found optimum by Hillman (1961). Aziz and
Mobina (1999) found 25–33 °C temperature were optimum
for the growth of two species of Spirodela. The photosynthesis is also dependent upon the enzyme activity which is
reported to be negligible below 10 °C and to be optimum at
30 °C in most of the plant species (Treshow 1970). The role
of several other parameters (viz. direct impact of detergents
on the cell membranes, injuries and leakage of ions out of the
fronds cells) in modifying the responses of both duckweeds
cannot be ruled out. It is suggested that more detailed studies
are needed to have a deeper insight on the physio–morphological responses of the duckweeds.
12 Household Detergents Causing Eutrophication in Freshwater Ecosystems