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Dynamics of photosynthesis in Eichhornia crassipes Solms of Jiangsu of China and their influencing factors

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  • Jiangsu Academy of Agriculture Sciences

Abstract and Figures

With LI-6400 portable photosynthesis system, the photosynthetic characteristics of artificially cultured Eichhornia crassipes in Jiangsu, China, were monitored from June 1 to November 14, 2009. Both the net photosynthetic rate (Pn) in different positions and light and temperature-response curves of the top fourth leaf were measured in an open-circuit gas channel system in June, July, and August, respectively. The top third to sixth leaves matured with a high Pn in August, 2009. The values of the maximum net photosynthesis (Pmax), light component point (LCP) and apparent quantum efficiency (AQE) of the top fourth leaf of E. crassipes were 34.5±0.72 and 20.25±3.6 µmol m -2 s -1 as well as 0.0532±0.0014, respectively, significantly higher than those in rice and maize. The light-saturation point (LSP) of leaves of E. crassipes was 2358±69 µmol m -2 s -1 , significantly higher than that in rice and much close to that in maize. The natural light intensity and temperatures in Jiangsu are suitable for E. crassipes to rapidly grow but not good enough for it to show the maximum internal photosynthetic capacity from the perspective of photosynthetic physiology, thus resulting in its low biomass in this region.
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African Journal of Biotechnology Vol. 9(43), pp. 7302-7311, 25 October, 2010
Available online at http://www.academicjournals.org/AJB
DOI: 10.5897/AJB10.1087
ISSN 1684–5315 © 2010 Academic Journals
Full Length Research Paper
Dynamics of photosynthesis in Eichhornia crassipes
Solms of Jiangsu of China and their influencing factors
Li Xia*, Zheng Jianchu, Yan Shaohua, Ren Chenggang, Wang Man, Cong Wei, Sheng Jing and
Zhu Puping
Jiangsu Academy of Agricultural Sciences, Nanjing 210014, China.
Accepted 24 August, 2010
With LI-6400 portable photosynthesis system, the photosynthetic characteristics of artificially cultured
Eichhornia crassipes in Jiangsu, China, were monitored from June 1 to November 14, 2009. Both the
net photosynthetic rate (Pn) in different positions and light and temperature-response curves of the top
fourth leaf were measured in an open-circuit gas channel system in June, July, and August,
respectively. The top third to sixth leaves matured with a high Pn in August, 2009. The values of the
maximum net photosynthesis (Pmax), light component point (LCP) and apparent quantum efficiency
(AQE) of the top fourth leaf of E. crassipes were 34.5±0.72 and 20.25±3.6 µmol m-2s-1 as well as
0.0532±0.0014, respectively, significantly higher than those in rice and maize. The light-saturation point
(LSP) of leaves of E. crassipes was 2358±69 µmol m-2s-1, significantly higher than that in rice and much
close to that in maize. The natural light intensity and temperatures in Jiangsu are suitable for E.
crassipes to rapidly grow but not good enough for it to show the maximum internal photosynthetic
capacity from the perspective of photosynthetic physiology, thus resulting in its low biomass in this
region.
Key words: Eichhornia crassipes, photosynthetic characteristics, environmental influencing factors.
INTRODUCTION
Eichhornia crassipes Solms, commonly known as water
hyacinth, is an aquatic plant with a bundle. Because of its
well developed root system, strong reproductive ability,
and ultra strong absorbency, it is widely used for sewage
purification (Hu et al., 2007: Qi et al., 1999). Introduced to
China as a feed, it has recently been applied to a medium
composition for edible fungus and methane fermentation
and has become one of the important resources in
modern low-carbon eco-agriculture (Zhou et al., 2005).
Known as one of the fastest-growing plants, E. crassipes
is native to the Amazon basin, including such countries
*Corresponding author. E-mail: jspplx@jaas.ac.cn. Tel:
00862584390361. Fax: 00862584390322.
Abbreviations: PAR, Photosynthetic active radiation; P,
photosynthetic rate; Pmax, maximum photosynthesis; AQE,
apparent quantum efficiency; Pn, net photosynthetic
rate;LCP,light component point;LSP,light saturation point.
such as Brazil, Argentina and Peru, but is now found
through most areas between 32.3° north and south
latitudes (An and Li, 2007). At 25 ~ 35°C, it grows at an
alarming rate and can reach 10 to 60 million trees in 8
months. Conditions permitting, a single plant may
produce 140 million trees per year, covering a water
surface of 140 hm2 with a fresh weight of 28 000 t, a
testimony to its reproductive ability and diffusivity (Wang
and Wu, 2004).
There are eight species of E. crassipes, but only the
one with little genetic differences is currently found in
China as indicated by the cytological and molecular
genetic analysis. Since it was introduced from Brazil (Wang
and Wang, 1988; Ren et al., 2005), its high biomass
might be more related to its habitat that enjoys high light
intensity and temperatures. In terms of sewage purify-
cation, it is exceedingly difficult for E. crassipes to
achieve the maximum biomass for large-scale use if
artificially planted and bred, particularly in the open Taihu
Lake (Dou et al., 1995). Therefore, how to maximize its
dry matter accumulation at Taihu would become a hot
topic for modern low-carbon eco- agriculture (Chen et al.,
2008).
Photosynthesis refers to the process in which inorganic
substance is converted into organic substance and,
simultaneously, solar energy is fixed into plant energy in
vivo, which is the basis of dry matter production in green
plants. It was said in an early report that the biomass of
E. crassipes was influenced by certain environmental
conditions (Wang and Zhang, 1996). For example,
compared with alligator alternanthera, E. crassipes has a
higher leaf area index and chlorophyll content, but it is
sensitive to low temperatures (Li et al., 1995). Further
results showed that its growth speed and adaptability
were related more with external environmental conditions
(Li and Wang, 2007). However, the characteristics of its
photosynthesis in terms of photosynthetic active radiation
(PAR) and temperatures in Taihu Lake remain rarely
studied. In this study, with the leaves of E. crassipes
grown in Jiangsu as the materials, the photosynthetic
characteristics, including the changes over the year and
at different stages of its growth, were investigated.
Furthermore, when E. crassipes reached the maximum
photosynthetic rate in the year (in August, 2009), its
photosynthetic characteristics in response to essential
environmental factors, such as light intensity, temperature
and humidity, were systemically measured, and the indexes
of the photosynthetic characteristics were thoroughly
analyzed. The above mentioned study revealed the
physiological mechanism of its fastest growth by its
photosynthetic characteristics and found out key environ-
mental factors that influenced its photosynthetic production
and dry material accumulation in Jiangsu, which might
help enhance its local artificial stocking and provide refe-
rence for its efficient, large-scale use for pollution control
in the Taihu Lake Basin.
MATERIALS AND METHODS
Materials
E. crassipes plants were collected between June 1 and November
14, 2009, from ponds in Jiangsu Academy of Agricultural Sciences.
The plants grew at the initial stocking volume of 2 k g per m2 in a 2
m2 plot surrounded with bamboo fences. When the biomass
reached 25 kg per m2, the uniform plants (a robust single-branch, 7
± 3 leaves, the top second leaf’s petiole length of 20 ± 5.2 cm, and
white fibrous roots) were selected to measure the photosynthesis
indexes twice per month with 10 repetitions for each measurement.
The seeds were provided by Jiangsu Academy of Agricultural
Sciences. The japonica r ice cultivar was Kitaake (Oryza sativa L.),
and the corn cultivar was Nongda 108 (Zea mays L), both selected
as materials in Nanjing, Jiangsu in 2009. Before being sown, the
seeds were sterilized in 5% H2O2 for 5 min, soaked in water for 24
h, and incubated at 35°C for 48 h. Seedlings at similar st ages of
development were transplanted into pots (5 hills per pot, 1 s eedling
per hill) and grown in an outdoor net-room. A completely
randomized design with five replicates was employed. The
temperature averaged from 21 to 27°C, with a daily difference of
7.1 to 8.7°C. Chemical fertilizer (2.0 g N, 1.6 g P2O5, and 1.4 g K2O)
was applied per plot as the basal dressing and 1.0 g N as the top
dressing at tillering and booting stages, respectively. The soil was
Xia et al. 7303
paddy soil.
Methods
Fluctuations in air temperature
The tested plants were measured between June 1st and November
14th, 2009, in Nanjing. The air t emperature, including the highest,
lowest, and average temperature, during that period was recorded
systematically.
Photosynthetic rate (P) measurement
The P of intact rice leaves to varying irradiances was monitored
with a Li-Cor 6400 (Lincoln, Nebraska, USA) at 25°C according to
the method proposed by Li et al. (2002). The gas source was
compressed air (a CO2 concentration of 350 µmol mol-1), and the
light source was the halogen light s ource. Varying irradiances to the
leaf surface were obtained by adjusting the distance between the
light source and the leaf chamber. A layer of circulating water bet-
ween leaves and the light s ource was maintained for heat insulation
(25°C and relative humidity of 60%).The P to varying irradiances (0,
50, 100, 150, 200, 400, 600, 800, 1000, 1200, 1400, 1600, 2000,
2200, 2400, 2600 and 2800 µmol.m-2 s) was measured, respec-
tively. The photosynthetic rate at each PAR was surveyed with 4 to
6 repetitions. The curves of photosynthetic light response were
obtained by measuring the steady rates under different PARs.
According t o the method proposed by Li et al. (2006a), the
curves of photosynthetic temperature response were obtained by
measuring the steady rates at different temperatures (15, 20, 25,
30, 35, 40 and 45°C). According to the method proposed by Li et al.
2006b), the photosynthetic humidity response curves were obtained
by measuring the steady rates at the relative humidity between 0
and 60% in the atmosphere.
Statistical analysis
All results reported here are the mean values of replicates. Data
were subjected to the analysis of variance ( ANOVA) with the
Statistical Package for the Social Sceinces (SPSS) 17.0 (Statistical
Graphics Corp., Princeton, NJ)
RESULTS
Photosynthetic characteristics of E. crassipes during
2009 in Jiangsu, China
The daily air temperature, including the highest, lowest
and average temperature, during the experiment was
recorded systematically (Figure 1A). Annual photosynthetic
characteristics of E. crassipes in Jiangsu took on the
“bell-shaped” characteristics (Figure 1B); the maximum
photosynthesis (Pmax) was low in June, increased in
July, peaked in August, fell in September, and then drop-
ped drastically in October and November, which were
same to the apparent quantum efficiency (AQE), an index
reflecting the plant’s ability to use light energy during 0-
200 µmolm-2s-1.
Furthermore, their light saturation point and compen-
sation point in July and early October (Figure 1C) were
7304 Afr. J. Biotechnol.
A
AA
A
0
5
10
15
20
25
30
35
40
27- May-
09
16- Jun-
09
06- Jul -
09
26- Jul -
09
15- Aug-
09
04- Sep-
09
24- Sep-
09
14- Oct -
09
03- Nov-
09
23- Nov-
09
Dat e
Ai r t emper at ur e( ℃)
Max ai r t emper at ur e ℃
Mi n ai r t emper t ur e ℃
Aver age ai r t emper at ur e ℃
B
BB
B
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16- Jun-
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04- Sep-
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24- Sep-
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14- Oct -
09
03- Nov-
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23- Nov-
09
Dat e
Max phot osynt het i c
r at e( μ mol • m
- 2
• s
- 1
)
0
0. 01
0. 02
0. 03
0. 04
0. 05
0. 06
0. 07
Appar ent quant um
ef f i ci ency
Maxi mum net
phot osynt hesi s( Pmax)
appar ent quant um
ef f i ci ency( AQE)
C
CC
C
0
400
800
1200
1600
2000
2400
2800
27-
May- 09
16-
Jun- 09
06-
Jul - 09
26-
Jul - 09
15-
Aug- 09
04-
Sep- 09
24-
Sep- 09
14-
Oct - 09
03-
Nov- 09
23-
Nov- 09
Dat e
Li ght - sat ur at i on poi nt
μ mo l m
- 2
s
- 1
0
40
80
120
160
Li ght - component
poi nt ( LCP) ( μ mo l m
- 2
s
-
1
Maxi mum net phot osynt hesi s( Pmax)
l i ght component poi nt ( LCP)
Figure 1. The changes in the maximum net photosynthesis (Pmax), light component point (LCP), apparent quantum efficiency
(AQE) and light-saturation point (LSP) of leaves in E. crassipes and the air temperature of this period in natural conditions.
Xia et al. 7305
Table 1. Comparison of photosynthetic parameters of leaves among E. crassipes, typical C3 plants, rice (Oryza
sativa L.) and typical C4 plants, maize (Zea mays L) in Jiangsu Province.
Parameter E. crassipes Rice Maize
Light-saturation point [µmo l m-2s-1] 2358±69.00 1641±32.00 2550±37.00
The maximum photosynthesis rates [µmo l m-2s-1] 34.50±0.72 19.56±0.62 30.36±0.42
Light compensation point [µmo l m-2s-1] 20.25±2.60 38.56±3.60 29.75±2.80
Apparent quantum efficiency 0.0522±0.0014 0.0269±0.0011 0.0427±0.0012
found to be more suitable to show a high photosynthetic
productivity for higher Pmax and a wider range of
luminous intensity use. Their photosynthetic characteristics
and local air temperatures, especially the lowest ones, in
2009 were closely correlated. From mid-October to
November, when the air temperature became lower than
15°C, both the Pmax and the AQE fell obviously.
Net photosynthetic rate (Pn) of E. crassipes at
different stages of leaf development in Jiangsu
As shown in Figure 2, from July to September, the Pn of
E. crassipes at different stages of leaf development grew
in the youngest central leaf, but it was low in the
outermost leaf. Among them, the Pn of the youngest
central leaf became lower, but it was the lowest in the
outermost leaf due to senescence, because the flowering
season of E. crassipes in Jiangsu is between July and
August. Interestingly, it could be seen that the Pn of the
leaf nearest to the flower in the flowering season was
higher than that of the youngest central leaf, but obviously
lower than those of other mature ones, thus, suggesting
that some photosynthetic matter might be used partially in
blossoming and seed breeding.
Therefore, the photosynthetic ability of its leaf was
determined more by the intrinsic stages of the leaf’s
growth. But the number of the leaves that performed the
photosynthetic function and the Pn of the leaves were a
bit different in different months: 4-6 leaves in July, 3-8
leaves in August, 2-8 leaves in September, which were
actually closely related with the air temperature.
Photosynthesis characteristics of the functional leaf
in E. crassipes
The light curve of photosynthesis of leaves in E.
crassipes
PAR was one of the dominant environmental factors for
photosynthesis. The curve of photosynthetic rate to PAR
could reflect the plant’s ability to use light energy.
According to the curve of photosynthetic rate to PAR in E.
crassipes, many indexes, such as the LCP, LSP, AQE,
and Pmax, could be determined. As shown in Figure 3A,
function in response to light intensity was a typical
parabolic graph, which expressed the equation:
y=-7×10-6x2 + 0.0304x + 1.2869, R2=0.977*
Furthermore, during the range of weak light intensity (0-
200 µmolm-2s-1), its AQE was 0.0522 (Figure 3B),
indicating its strong ability to use light when there was a
low light intensity. When light intensity grew, the photo-
synthetic rate also increased to its peak accordingly. Its
LSP was up to 2458±69 µmolm-2s-1 and the light-
saturated photosynthetic rate was 34.50±0.72 µmolm-2s-1.
Moreover, it did not fall until 2800 µmolm-2s-1. Therefore, it
was easy to see that E. crassipes could not only adapt
itself to a wide range of light intensity but also exhibit
higher photosynthetic capability at a high light intensity.
The photosynthesis of E. crassipes in response to
temperature
The growth and purifying function of E. crassipes are
largely subject to the influence of temperatures. As
shown in temperature curves of its leaves’ photosyn-
thesis (Figure 4), at the atmospheric CO2 concentration,
the change of its photosynthesis in response to tempe-
ratures was in a bell-shaped graph, and the optimum
temperature was between 30-35°C. Its photosynthetic
rate decreased when the temperature was beyond the
range at 15°C, while the photosynthetic rate was 28.5%
at 30 and 45°C, 57.1% at 30°C. Obviously, these results
showed that its photosynthesis was better adapted to high
temperatures, which was also an important physiological
basis to determine the temperature range for the natural
growth of E. crassipes.
The photosynthesis of E. crassipes in response to
humidity
In Figure 5, the photosynthetic rate was negatively
correlated with the absolute value of relative humidity in
both the leaf chamber (Figure 5A) and the atmosphere
(Figure 5B), and there was a significantly positive cor-
7306 Afr. J. Biotechnol.
0
6
12
18
24
30
I nver t ed 1
I nver t ed 2( l eaf under
t he Fl ower )
I nver t ed 3
I nver t ed 4
I nver t ed 5
I nver t ed 6
I nver t ed 7
Net phot osynt het i c r at e
Pn
(µmol . m
- 2
s
- 1
)
Leaf posi t i on
Nanj i ng Jul y- 2009
Nanj i ng August -2009
0
6
12
18
24
30
I nvert ed 1(l eaf under
t he Fl ower )
I nvert ed 2
I nvert ed 3
I nvert ed 4
I nvert ed 5
I nvert ed 6
I nvert ed 7
I nvert ed 8
I nvert ed 9
Leaf posi t i on
Net phot osynt het i c rat e
Pn
( μ mol . m
-2
s
-1
)
Nanj i ng Sept ember- 2009
0
6
12
18
24
30
I nver ted 1
I nver ted 2
I nver ted 3
I nver ted 4
I nver ted 5
I nver ted 6
I nver ted 7
I nver ted 8
I nver ted 9
Net phot osynt het i c rat e
Pn
( μ mol . m
-2
s
-1
)
Figure 2. The changes in net photosynthetic rate of leaves at different positions from July to September, 2009.
Xia et al. 7307
Nanj i ng August - 2009
- 10
0
10
20
30
40
0 500 1000 1500 2000 2500 3000
Phot osynt het i c phot o f l ux densi t y
( PPFD) ( μ mo l m
- 2
s
- 1
)
Phot osynt het i c
r at e( μ mo l m
- 2
s
- 1
)
Nanj i ng August -2009
- 4
- 2
0
2
4
6
8
10
0 50 100 150 200
250
Phot osynt het i c phot o f l ux densi t y
( PPFD) ( μ mol . m
- 2
s
- 1
)
Phot osynt het i c r at e( μ
mol . m
- 2
s
- 1
)
A
B
Figure 3. The response curve of PPFD for photosynthesis of the leaves in Eichhornia crassipes
relation between the changes in relative humidity in the
leaf chamber and those in the atmosphere (Figure 5C).
Furthermore, as indicated in Figure 5D, the coefficient of
correlation between the stomata conductance and the
relative humidity was even higher. It showed that the
larger the relative humidity difference between inside and
outside the leaf chamber, the more conducive it was to
stomata opening, leading to more atmospheric photo-
synthetic substrates, such as CO2 and H2O, into the leaf
and consequently a higher photosynthetic capacity.
Comparison of photosynthetic indexes among E.
crassipes, the C3 plant, rice, and the C4 plant, maize
In order to facilitate the visual assessment of the photo-
synthetic capacity of E. crassipes, the light-photo-
synthesis curve is shown in Figure 6 by simultaneous
determination of photosynthesis of leaves of the C3 plant,
rice, and the C4 plant, maize in the region. Through
EXCEL mapping, a series of photosynthetic indexes were
obtained and shown in Table 1. It could be seen that
7308 Afr. J. Biotechnol.
0
5
10
15
20
25
30
35
15 20 25 30 35 40 45
Photosyntheric rate
P[µmol.m
-2
.s
-1
]
Air Temperture[
]
Figure 4. The response curve of temperature for photosynthesis of the 1eaves in E.
crassipes.
y = -0.1104x + 13.696
= 0.595
0
5
10
15
20
0
10
20
30
40
50
60
Pho to synthetic rate
Pn(µmo lm
-2
s
-1
)
Relative humidity in atmosphere(%)
y = - 0. 1395x + 16. 294
R
2
= 0. 4837
0
5
10
15
20
0
10
20
30
40
50
60
Rel at i ve humi di t y i n l eaf
Chamber ( %)
Phot osynt het i c r at e
Pn( μ mol . m
- 2
s
- 1
)
y = 0. 0126x + 0. 024
R² = 0. 9403
0
0. 1
0. 2
0. 3
0. 4
0
5
10
15
20
25
St omat al conduct ance
Gs ( mol . m
- 2
. s
-1
)
Di f f er ence of humi di t y bet ween
l eaf chamber and at mospher e( %)
y = 0. 4158x + 5. 2639
R
2
= 0. 8004
0
5
10
15
20
0
5
10
15
20
25
Di f f er ence of humi di t y bet ween
l eaf chamber and at mospher e( %)
Phot osynt het i c r at e
Pn( μ mol . m
- 2
s
- 1
)
Figure 5. The response curve of humidity for photosynthesis of the leaves in Eichhornia crassipes.
Xia et al. 7309
- 7
- 2
3
8
13
18
23
28
33
38
0 400 800 1200 1600 2000 2400
Phot osynt het i c r at e µ mol . m
- 2
. S
- 1
Phot osynt het i c phot o f l ux densi t yPPFD( µmol . m
-
2
. s
- 1
)
Ei chnomi a
cr assi pes
r i ce
Mai ze
Figure 6. Then response curves of PPFD for the 1eaves among Eichhornia crassipes ,typical C3
plants, rice (Oryza sativa L.) and typical C4 plants maize (Zea mays L) in Jiangsu Province.
although E. crassipes was a C3 plant, it showed a Pmax
and light saturation points higher than those of the typical
C3 plant, rice, and similar to those of the typical C4 plant
maize.
Furthermore, the AQE in E. crassipes was higher than
that in maize. These results suggested that E. crassipes
had not only a high photosynthetic capacity but also a
wide range of photosynthetic ecology (20.25 ± 3.6-2358 ±
69 µmolm-2s-1).
DISCUSSION
Mechanism of the high photosynthetic capacity of E.
crassipes in Jiangsu
Photosynthesis in plants would change along with the
environment, including illumination, air temperature, CO2
concentration, and the relative moisture. It is one of the
physiological processes most sensitive to internal and
external factors (Wu et al., 2009). Therefore, the changes
of the photosynthetic indexes can represent the res-
ponses of most plants to environmental factors, thus
directly reflecting the differences in their patterns of
physiological and ecological adaptation to the environ-
mental factors. The LSP and LCP of the leaves would
indicate that the requirements of plants for
photosynthesis are within the range of the highest and
lowest light intensity. For example, most sun plants have
a LSP as high as 1500-2000 µmolm-2·s-1, and a light
compensation point around 50-100 µmolm-2·s-1, but
shade plants usually have a lower LSP, and a LCP as
low as 20 µmolm-2 s -1 (Jiang et al., 2004). In this study,
the results show that E. crassipes in Jiangsu is a typical
sun plant that has photosynthetic characteristics of
tropical plants (Jiang and He, 1999).
Most interestingly, the LCP of E. crassipes in Jiangsu
has been found to be much lower compared with that of
rice and maize, and its LSP is higher than that of rice and
close to that of maize. There is obviously a broad
ecological niche of photosynthesis of E. crassipes in this
region, showing that it has the good adaptability to
different light environments by enhancing its light use
efficiency in case of the low light intensity and increasing
the Pmax in case of the high light intensity. These unique
photosynthetic characteristics could promote the maximal
use of sunlight to synthesize organic substances and the
rapid accumulation of dry matter, thus, bringing about a
faster growth and a higher accumulation of dry matter
than the C4 plant sugarcane (Yan et al., 1994).
At the same time, it leaves also has a broad scope of
photosynthetic responses to temperatures, which is also
between 30-35°C. Thus, it is helpful to bring into playing
the photosynthetic capacity at different air temperatures.
7310 Afr. J. Biotechnol.
Structurally, E. crassipes in Jiangsu has a short stem,
with leaves and the root nearly attached to each other. It
has a high transpiration rate, indicating a short photo-
synthate distance between the leaves and the root (An
and Li, 2007). As for the aquatic environment, a higher
relative humidity is also helpful to the stomatal opening,
bringing more photosynthetic substrates, CO2 and H2O,
into the photosynthetic apparatus.
On the whole, for E. crassipes in Jiangsu, these
internal and external factors are undoubtedly the impor-
tant physiological basis of its higher photosynthetic
capability than the typical C3 plant paddy rice and the
typical C4 plant maize. The intrinsic mechanism of the
high photosynthetic capacity, especially under high light
intensity of E. crassipes in this region is yet to be studied
thoroughly on either the ultra-structural or the biochemical
level.
Analysis of main environment factors for the growth
of E. crassipes in Jiangsu
With a favorable environment, E. crassipes would repro-
duce extremely fast. The mother plant can produce a new
generation of plants through the stolon within 5 days
(Harward and Harley, 1998). Under the temperatures in
this study, the light saturation point of the mature leaves
in E. crassipe reached up to 2358 µmolm-2s-1, but the
light intensity was not good enough for them to show the
maximum photosynthetic capacity despite this region
boasts of the rather favorable sunlight and temperature
conditions. In summer, however, the climate in Jiangsu
would be subjected to the influence of land, sea and the
monsoon, which often brings high winds or torrential
rains, and it is therefore more cloudy or rainy with low
light intensity. Therefore, even if the solar radiation
reaches the peak in this region, usually in July or August,
the maximum light intensity at the sunny noon would not
be higher than 1400 µmolm-2s-1 (Li, 1990). The
comparison of the light and temperature conditions
required for its higher photosynthetic ability and the
limited solar radiation in Jiangsu showed that the key
factor restricting E. crassipes growth in the region has
always been the photosynthetic limitation (such as
stomatal limitation), which may be the main reason that
impedes its intrinsic high photosynthetic capacity and
finally affects its dry matter accumulation.
Temperature is also a key environmental factor that
determines its growth and physiological states. Studies
have shown that E. crassipes can usually live at tempe-
ratures not lower than C. If the water temperature
drops to the freezing point, it will die within a few hours. If
the air temperature is not lower than C, it can survive
the winter. 39-40°C are the highest air temperatures for
its growth. But when the water temperature is above
35°C for 5 - 6 h, its growth would be severely inhibited,
resulting in yellow or wilted leaves (An et al., 2007).The
results in this paper further show that the optimal tempe-
rature for its photosynthesis is between 30-35°C,
indicating a high consistency between the temperature
for its most vigorous growth and that for its maximal
photosynthetic ability. In fact, E. crassipes grows in
Jiangsu from early April to mid-October, at which time,
the average air temperature is between 21.5-23.5°C. It
can be seen that the air temperature in this region is
suitable for its rapid growth, but not good enough for its
maximal photosynthesis, so it limits its largest dry matter
accumulation to a certain extent.
In conclusion, the natural light intensity and tempe-
rature conditions in Jiangsu are suitable for E. crassipes
to rapidly grow, but not high enough for it to reach the
maximal intrinsic photosynthetic capacity, resulting in its
low biomass in this region. In future, when E. crassipes is
bred with the extensive adaptability to light and tempe-
rature conditions, it would be beneficial for it to make
good use of the local light and temperature to achieve the
maximum photosynthetic capacity, which is one of the
decisive issues for its high-yield cultivation in the region.
ACKNOWLEDGEMENTS
The author are grateful both to the National scientific and
technological support projects (2009BAC63B01) and the
National Natural Science Foundation of China (NSFC,
No: 30871459) for their financial support. The authors
express their great thanks to anonymous reviewers and
editorial staff for their time and attention.
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Article
Full-text available
The current study was designed to test the concerning strategy of water hyacinth (Eichhornia crassipes (Mart.) Solms) to UV-B. In this study, we evaluated the short-term effect of UV-B radiation (short-term UV-B radiation, S-UV-B) on water hyacinth under the natural conditions of Nanjing, China (118°46′E, 32°24′N, 30 m above sea level) with supplemental ultraviolet-B (12 W m⁻² above ambient). The growth characteristics and the photosynthetic performance of water hyacinth leaves exposed to UV-B were assessed by measuring net photosynthetic rate, the specific fluorescence parameters including maximal fluorescence (Fm), efficiency of photosystem II (Fv/Fm), and JIP-test parameters. Water hyacinth was tolerant to 1-h UV-B doses over 25 days, maintaining a stable dry weight after treatment. Conversely, plants showed elongation of roots and a decrease in ramet numbers. These changes in growth were closely related to a physiological protection strategy consisting of a higher ability to dissipate extra light energy, strong antioxidative abilities, higher phosphoenolpyruvate carboxylase (PEPC) activity, and stable ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) activity, as indicated by the stable net photosynthetic rate and reduced inhibition of reactive oxygen species content. After the 3-h dose of UV-B, dry weight decreased significantly, as the above-mentioned protective strategy could not cope with the oxidative damage arising from these treatments. The study concludes that S-UV-B is a potent stimulating factor in increasing the concentrations of defense compounds and antioxidants in water hyacinth to optimize its performance under stress.
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Genetic variation within and between 34 populations of Eichhornia crassipes (water hyacinth) in China was surveyed using random amplified polymorphic DNA (RAPD) markers. A total of 1009 individuals were analysed, for which 12 RAPD primers amplified 69 reproducible bands, with 22 (32%) being polymorphic. The percentage of polymorphic loci (p) within a population ranged from 4.4% to 17.4%, and the mean Nei's gene diversity (H e) was 0.046 ± 0.0145, indica-ting a low genetic diversity of E. crassipes in China. Each population contained at least four RAPD pheno-types (genotypes), and the same particular genotype was invariably dominant in all the populations sam-pled. The mean proportion of distinguishable geno-types was 0.29. Analysis of molecular variance revealed a large proportion of genetic variation (83.9%) residing within populations and a slightly larger proportion (88.1%) within localities, indicating a low genetic differentiation of E. crassipes populations, both locally and regionally. Human-mediated dispersal, vigorous clonal growth, and a generally low level of sexual reproduction were thought to be responsible for such a pattern of genetic structure., random amplified polymorphic DNA. REN M-X, ZHANG Q-G & ZHANG D-Y (2005) Random amplified polymorphic DNA markers reveal low genetic variation and a single dominant genotype in Eichhornia crassipes populations throughout China. Weed Research 45, 236–244.
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The most important floating aquatic weeds (FAWs) are Eichhornia crassipes, Salvinia molesta and Pistia stratiotes. E. crassipes and P. stratiotes reproduce sexually. All three species reproduce asexually. E. crassipes and S. molesta have particularly high growth rates. All can form dense mats and growth rates are increased by high nutrient levels and temperatures. Spread between continents and watersheds is largely the result of human activities. Spread within watersheds is mostly via floating propagules. FAWs are known to affect water resource management, the continued existence of human riverine and wetland communities, and conservation of biodiversity. Waterways can be blocked, and the efficiency of irrigation and hydro generation impaired. People are affected by reduction of the fish catch, inability to travel by boat and consequent isolation from gardens, markets and health services, and also changes in populations of vectors of human and animal diseases. Biodiversity can be reduced and conservation value affected. It is proposed that rational application of physical, chemical and biological control of FAWs, and reduction of nutrient input should be part of every strategy for the sustainable management of wetlands.
To study the nature and mechanisms of resistance of rice plants to chilling stress, the effects of low temperature treatment (8 degrees C) on the photosynthetic rate and some important compounds forming redox cycles were measured. The rice varieties used are two japonica rice varieties, i.e., Taipei 309 and Wuyujing; three indica rice varieties, i.e., IR64, Pusa and CA212; and one intermediate type, i.e., Shanyou 63. Three types of varieties were studied by comparing. The light intensity-photosynthesis curves, CO2-photosynthesis curves, primary photochemical efficiency (Fv/Fm), active oxygen species (AOS) (O2*- and H2O2), glutathione (both oxidized and reduced forms) and ascorbate contents in their six-week old seedlings were measured before and after chilling treatment. The results showed that relative to the rice varieties chilling tolerance such as Taipei 309 and Wuyujing, the sensitive ones indica IR64, Pusa and CA212 exhibited a stronger inhibition of maximum photosynthetic rate (Pmax) (Figs.1 and 2) and a decrease in Fv/Fm (Fig.3), which led to the accumulation of AOS (Fig.6). It was found that the glutathione disulphide (GSSG) content in glutathione pool and that of dehydroascorbate (DHA) in ascorbate pool of the leaves of these sensitive ones under chilling were induced to increase obviously (Table 3). The correlation coefficient between the increases in GSSG, DHA and the decrease of Chl content were -0.701**, -0.656** respectively (Table 4). This indicated that the regeneration of reduced glutathione (GSH) and ascorbate was inhibited, resulting in accumulations of AOS and the reduction of Chl content (Fig.4) and the inhibition of photosynthetic activity (Fig.1 and Fig.2). The changes in japonica Taibei 309 and Wuyujing were small. And the changes in indica hybrid were lying between the above-mentioned types. Particularly, the ratio of AsA/DHA and GSH/GSSG (Fig.7) showed similar changes as those in Chl content (Fig.4). The correlation coefficient among Chl content and AsA/DHA, GSH/GSSG were 0.811**, 0.728** respectively (Table 4), significant at 0.01 probability levels. The levels of AsA/DHA and GSH/GSSG ratio in rice leaves may be the physiological indexes associated with the sensitivity to chilling in rice varieties.
The ecological characteristics of water hyacinth. Water Fisheries
  • An
  • Xl
  • Li
An XL, Li T (2007). The ecological characteristics of water hyacinth. Water Fisheries, 27: 82-84.
Utilization of Energy Research in water hyacinth
  • G Y Chen
  • Z Zhen
  • X X Chou
Chen GY, Zhen Z, Chou XX (2008). Utilization of Energy Research in water hyacinth. Jiangsu Agric. Sci. (3): 5-9.
How do flowing aquatic weeds affect wetland conservation all development? How can these effects be minimized? Wetland Ecol
  • Harward
  • Gw
  • Harley
  • Kls
Harward GW, Harley KLS (1998). How do flowing aquatic weeds affect wetland conservation all development? How can these effects be minimized? Wetland Ecol. Manage. 5: 215-225.