Interactive Effects of Polylactic Acid with Different Aluminum Concentrations on Growth, Pigment Concentrations, and Carbohydrate Accumulation of Azolla

7 Pages·1997·3.7 MB·English

by  Tomas Ayala-Silva

American Fern Journal 87(4):120-126 (1997)
Acid with
Different
of Polylactic
Interactive Effects
Pigment
on Growth,
Aluminum
Concentrations
and Carbohydrate
Concentrations,
AzoUa
Accumulation
of
and Safaa Al-Hamdani^
ToMAS Ayala-Silva
University,
Department of Biology, Jacksonville State
AL
36265-9982
Jacksonville,
Abstract.—The interactive effects of 1 1^ polylactic acid (PLA) v^ith alu
tJig
mg 1^ AzoHa carohniana chlorophyll, caroter
and on growrth,
16
of
2, 4, 8,
growth was decreased
were examined. AzoIIa
accumulation
carbohydrate
wh
was pronounced
minum Furthermore, the growth reduction less
concentration.
Chlorophyll a and b concentrations were decreased in plants
present.
g
and 16
of 4 mg 1- and higher. Polylactic acid reduced the influence of Al concentrations of 4, 8,
mg and carotenoid concentrations were decreased as Al concen-
on chlorophyll a Similarly,
b.
1 '
mg 1^
was
growth media. Anthocyanin concentration increased at 4.0
trations increased in the
PLA. carbohydrate
PLA with without In general,
Al without and higher Al concentrations or
at
growth media,
PLA. absence Al from the treat-
was pronounced in the presence of In the of
less
and carotenoid
ment with PLA resulted in an increase in plant growth, chlorophyll,
1 ^JLg 1 1
damaging
Aluminum an important component of the effects
(Al) toxicity
is
not
and Rueter (1987) reported that acid rain
of acid rain in rivers lakes. et al.
only increased soluble Al concentration, but also changed the affinity of
total
organic and inorganic complexes with metals. Sprenger and Mcintosh (1989)
submerged
and
showed Al concentrations were elevated in both water
that
Luronium natans
Raf.)
macrophytes {Ranunculus ololeucos Lloyd,
aquatic
J.
1^
According Stanley an addition of 92 |xmol
in acidified waters. to (1974),
50% Myriophyllum
medium growth
Al well-buffered inhibited of the root of
to
spicatum
L.
pH
and
The toxicity of Al depends upon a number of factors, including
Aluminum
increases
and toxicity
organic matter content (Tan Binger, 1986).
pH Of
below because increases considerably. the different
solubility
a 5
at its
AP^ one found freshwater at a
species of Al, the only significant that is in
is
pH shown with
Al has been to interfere
of 4 or less (Poleo, 1995). In general,
enzymes governing the
with
cell division, decrease respiration rates, interfere
and
de-
wall
deposition of polysaccharide in cell walls, increase cell rigidity,
crease the uptake and transport of water and several elements including Ca,
K
Mg, and
in plants (Foy 1978).
et
P, al.,
was by
The growth regulator
earliest recorded use of lactic acid as a plant
whom
Author correspondence should be addressed.
to
'
AYALA-SILVA & AL-HAMDANI: EFFECTS OF ALUMINUM ON AZOLLA
121
who
Blumenthal and Meyer
(1924), observed callus formation from carrot
slic-
exposed
es to lactic acid. In response to growth-inhibitory levels of heavy
metals, plants synthesize metal-binding phytochelatins to detoxify excess met-
(Kinnersley, Biostimulants such have
als 1993). as polylactic acid properties
common
in with phytochelatins and could be employed heavy metal
as a de-
Aqueous
toxifier (Kinnersley, 1993). lactic acid contains polymers of lactic
acid which promote growth some and
in plants unicellular algae (Kinnersley,
was
1993). This study designed to evaluate the interactive effects of polylactic
mg
aluminum
acid 1"^) with different concentrations and 16 1')
(1 |xg (2, 4, 8,
on Azolla growth, chlorophyll, carotenoid and anthocyanin content and
car-
bohydrate
and Methods
Materials
were grown Hoag-
Cultures of Azolla caroliniana Willd. in a diluted
(1:40)
pH
land solution (Hoagland and Arnon, 1938) Plants were placed in a
at 6.0.
m
growth chamber with 14 h photoperiod 220 |xmol s^ photosynthetic
a at ^
A
± was
photon and 2400
flux density, temperatures of 25 1°C. total of plants
selected and placed into 250 ml Erlenmeyer flasks (12 flasks per
arbitrarily
treatment). The flasks contained 125 ml diluted (1:40) Hoagland solution (pH
of 3.8), and received 20 plants. The treatments were Al concentrations of 0, 2,
mg
1^ polymer
and 16 with and without the presence of 1~^ dissolved
4, 8, 1 \xg
method
was prepared following the of Kinnersley
L-lactic acid. Polylactic acid
Aluminum was form AlK(SOJ,.12H20. The
supplied the of
in
et (1990).
al.
PLA
concentration of was selected based on the earlier finding that the highest
PLA 1^ and
Azolla growth was obtained concentration of (Ayala-Silva
1
at ixg
and
Al-Hamdani, Azolla was grown the above conditions for 14 days
1997). at
the growth medium was changed the end of the week. At the end of
at first
randomly
the second week of treatment, the plants from six selected flasks of
mea-
and carbohydrates
each treatment were used dry weight nonstructural
for
were used
each treatment
The remaining of
surements. plants in the six flasks
and anthocyanin determinations.
for chlorophyll a and carotenoid
b,
Dry Weight.—Samples were oven dried 48 h 70°C and the dry weight
for at
-20°C subsequent
was The samples were then stored for
recorded. dried at
carbohydrate
analysis.
was
Chlorophyll/Carotenoid Content.—Each sample (0.10 g fresh weight)
ml
N,N-dimethylfor-
placed 10 ml per treatment) containing 5 of
in a vial
(6
h and
mamide (N,N-DMF). The samples were stored in the dark at 4°C for 36
and
procedures of Inskeep
following the
assayed spectrophotometrically
was determined spectrophoto-
Bloom
concentration
carotenoid
(1985). Total
was
N,N-DMF and concentration calcu-
metrically from the extraction, total
Doong
lated using the formula of et al. (1993).
were homogenized
weight
Anthocyanin Content.—Samples of 0.10 g fresh
1% HCl The homogenates were then
in ml methanol containing (v/v).
5 of
VOLUME NUMBER
AMERICAN FERN JOURNAL:
87
i
of and different co
|xg
1 1 1 '
by
filtered and absorbance of the extracts determined spectrophotometrically
method
the of Mancinelli
(1990).
Carbohydrate Determination.— samples
Carbohydrate analysis of the plant
was conducted following a procedure slightly modified from that outlined by
powder and 100-
Samples were ground
Chatterton et (1987). into a fine a
al.
mg
500 portion was placed in a sealed vial and used for the determination of
soluble sugars, starch, and total nonstructural carbohydrates (TNC) as reported
by Wilson and Al-Hamdani
in detail (1997).
Statistical Analysis.—This experiment was repeated twice and analyzed
sta-
tistically as a randomized complete block design (Steel and Torrie 1980). This
design ensured that observed differences in plant performances were largely
due among conducted
to treatments rather than variation blocks (experiment
Mean
F
had
at different times). separations for the treatments that significant
> ANOVA
values were on
(P 0.05) in the tests the basis of the least significant
difference (LSD) and
test (Steel Torrie, 1980).
Results and Discussion
After, 14 days, growth of AzoUa was decreased as the aluminum concentra-
mg
were The was ^ which
tions increased. exception that of 2 Al, in the
1
PLA
The
presence of did not significantly decrease Azolla growth (Table
1).
highest growth reduction was documented grown 16.0
(58.8%) plants
for at
mg
PLA
1-1 Al in the absence of (Table Aluminum was shown to interfere
1).
with cell division, decrease respiration rates, interfere with enzymes governing
and
the deposition of polysaccharide in cell walls, increase cell wall rigidity,
decrease the uptake, transport, and use of water and several elements includ-
K PLA
ing Ca, Mg, P, and in plants (Foy et 1978). The presence of in the
al.,
media had no
significant influence on Al on plant growth the ex-
effects at
AYALA-SILVA & AL-HAMDANI: EFFECTS OF ALUMINUM ON AZOLLA
Table
2. Interactive effects of polylactic acid (PLA) c
tions of aluminum (mg on chlorophyll a (Chi chlorophyll h
') a),
1
LSD =
concentration
in Azolla. Least Significant Difference value
f
Chi a Chlfo
mg
Treatment wt wt Caroienoid Anthocyanin
g M-gg
' fr. ' fr.
PLA)
Control (without Al and 7.53 5.49 72.39 2.00
PLA
8.32 6.15
PLA
2.0 Al with 7.42 5.29 65.52 2.90
5.14 62.08 2.93
PLA 6'31
4.0 Al with 4.40
PLA
4.0 Al without 5.81 3.98 63.81 3.72
PLA
8.0 Al with 3.17 2.13 37.44
ii'go
PLA
16.0 Al with 2.76 2.14 32.30 17.28
PLA
16.0 Al without 30.33
LSD
(0.05) 4.00 3.40 1.42
LSD
5.30 4.60 7.89 1.90
(0.01)
PLA
amined Al However, absence caused
concentrations (Table in the of Al,
1).
significant increase in Azolla growth. Furthermore, the reduction of growth as
when PLA was
influenced by Al concentrations was pronounced present.
less
Aqueous lactic acid containing polymers of lactic acid was reported to pro-
mote growth in a variety of plants and unicellular algae (Kinnersley, 1993). In
found 1000 polymer
earlier studies, Kinnersley et (1990) that |xg of the
al. 1 ^
duckweed
biomass
L-lactic acid resulted in a significant increase plant in
[Lemna minor an was accompanied by an increase in chloro-
effect that
L.),
phyll accumulation.
grown
Chlorophyll a and b concentrations were decreased in plants at Al
mg
concentration of 4 ^ and higher (Table In the absence of Al fi-om the
2).
1
PLA and
growth medium, concentration of chlorophylls a b (Ta-
increased the
was by
Azolla increased
ble Similarly, the concentration of carotenoid in
2).
PLA
the presence and decreased as Al concentrations increased in
of
1 |xg
1 '
growth media
the
(Table
2).
unknown. However,
The actual mechanism of action of polylactic acid is
documented
here
the increase plant growth and chlorophyll concentration
in
enhancing plant nutrient assimila-
for Azolla could be due to polylactic acid
found polylactic acid stimu-
that
tion or utilization. Kinnersley et al. (1990)
On
growth Lemna reduced nutrient media. the other hand, the
lated of in
many
well-documented
have been in
Al with mineral nutrients
interactions of
shown
been
For example, Al has to interfere
plant systems in the recent past.
and and
with the uptake and accumulation of certain nutrients the transport
Mn, and Zn
Mg, Na, Cu,
use of essential elements, including N, P, K, Ca, Fe,
heavy
of metals, plants
(Balakumar response elevated levels
1991). In to
et
al.,
excess metals. Biostimu-
detoxify
synthesize metal-binding phytochelatins to
and
phytochelatins
have properties similar to
lants such as polylactic acid
(Kinnersley, 1993).
could employed heavy metal detoxifiers
be
as a
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AMERICAN FERN JOURNAL:
87
4
Total nonstructural
61.42 355.50
300.85
17.50
92.78 395.37
PLA
16.0 Al without
LSD
(0.05)
LSD
(0.0
1)
mg
Anthocyanin concentration was increased the Al concentration of 4.0
at
PLA
1"^ without the presence of and higher Al concentrations with or with-
at
PLA
out (Table The highest increase in anthocyanin concentration (879%)
2).
mg
was obtained plants grown 16 1"^ Al without PLA. Anthocyanin
for at
measurements
induction in Azolla has not been yet extensively studied. These
may
provide an opportunity formation biomass and chlorophyll
to relate to
its
Many
formation. aquatic plants possess anthocyanins. These pigments are pro-
duced
in response to various stress-related factors such as high light intensity,
Haug
high temperatures or nutritional limitations (Doong 1993). (1984)
et
al.,
suggested that anthocyanins are capable of chelating Al. This indicates that
Azolla increased anthocyanin synthesis as mechanism of detoxifying Al.
Sucrose concentration of Azolla increased with the increase in Al concen-
tration in the growth media (Table However, sucrose concentration was not
3).
among same when PLA was
significantly different the Al concentrations pres-
mg
The was grown 1^ which
ent. exception for plants 16 Al, in the con-
at
was
centration of sucrose increased by 36.6% in comparison to that of the
same was
concentration in the absence of PLA. Starch accumulation in Azolla
increased as Al concentrations were increased in the growth media (Table
3).
However, this increase in starch accumulation was less distinct in the presence
PLA
PLA.
of In addition, influenced reduction in starch accumulation in
mg
grovm
plants at Al concentrations greater than 2 1"^ in comparison to that
obtained of plants grown the same Al concentrations the absence of PLA.
at in
TNC
were
Similar results obtained for the with the exception that in the ab-
PLA
sence of Al, resulted in an decrease in total nonstructural carbohydrates
(TNC)
accumulation (Table This should not be interpreted as Al causing
3).
an increase in carbohydrate synthesis. Rather, most likely resulted from a
it
An
reduction in carbohydrate utilization. increase in carbohydrate accumu-
lation in response to Al was also found to take place in Salvinia minima Baker
AYALA-SILVA & AL-HAMDANI: EFFECTS OF ALUMINUM ON AZOLLA
125
and
(Gardner Al-Hamdani,
1997). Schroll (1978) observed metal
that toxicity
inhibited photosynthesis than Roy
less overall plant growth. Furthermore,
et
(1988) reported that Al decreased and
al. respiration carbohydrate
utilization.
Lower
rates of carbon assimilation and a decrease in yield are associated with
carbohydrate accumulation
in several plant species (Azcon-Bieto
1983).
It
seems
likely, therefore, that Al caused an increase carbohydrate accumu-
in
growth was
lation as plant decreased.
shown
In conclusion, study has Al when
this that toxic to Azolla plants
is
mg
provided
concentrations higher than most
at 2 ^ In cases, polylactic acid
1
reduced the damaging effects of aluminum. This may be due binding
to of
polylactic acid with Al, resulting in a lower effective Al concentration within
plant
cells.
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