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Cai Shumei 蔡 树 美

Phosphorus Absorbing Efficiency Discrepancy

of Duckweed under Different Influence Factors

Dept. of Bioscience & Biotechnology

Yangzhou University

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Backgrounds

In Vitro Experiment

Results & Discussion

Conclusions

Outline

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Backgrounds

Harm of Water Eutrophication ：

滇池蓝藻暴发

Muddy Water Appearance;

Bad Smell;

Dangerous Microcystins;

Dying of Aquatic Organisms. 太湖鱼类死亡

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Phosphorus!!!

Phosphorus!!!

Nitrogen

Nitrogen

Water Eutrophication

Water Eutrophication

……

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PhosphateAbsorption

Mechanism of plants’ Phosphorus Absorption

MembraneTransport protein

MembraneTransport protein

Ion channelIon channel CarrierCarrier

Diffusion

Activetransport

MO I

H+-ATPaseH+ATP+H2O

ADP+Pi

OH-+ ADP

H2O

PhosphateCarrier

OH-

H2PO4-

HPO42-

PO43-

H2PO4-

Ion channelIon channelIon channelIon channelIon channelIon channel CarrierCarrierIon channelIon channel CarrierCarrierIon channelIon channel CarrierCarrierCarrierCarrierIon channelIon channel CarrierCarrier

MembraneTransport protein

MembraneTransport protein

CarrierCarrier

MembraneTransport protein

MembraneTransport protein

Ion channelIon channel CarrierCarrier

MembraneTransport protein

MembraneTransport protein

Ion channelIon channel CarrierCarrier

MembraneTransport protein

MembraneTransport protein

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Advantages of Duckweed for Phosphorus-Containing Wastewater Treatment

Strong Phosphorus Absorptive Capacity;

Fast Growth Rate;

Easy for Reaping;

High Protein Animal Feed;

No Secondary Pollution.

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In Vitro Experiment

Factors affecting Pi uptake rate :

• Genotype ；

• Photon flux density ；

• Temperature ；

• pH;

• Phosphorus concentration.

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25 ℃

3000 lx

20 Fronds

Hoagland’s E-Medium culture

Cultivate Parameters:

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Duckweed genotypes

Lemna

Spirodela

Wolffia

Results & Discussion浮萍属

芜萍属

紫萍属

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Duckweed Size

L: Lemna S: Spirodela W: Wolffia

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Genotypes Biomass increase（ g）

Total Pi uptake（ mg）

Pi uptake rate(mgPi/gFW)

L. aequinoctialis 3.197±0.327aA 3.382±0.010aA 1.066±0.112aA

S. oligorrhiza 1.684±0.037bB 3.312±0.003bB 1.967±0.045bB

S. polyrrhiza 1.663±0.063bB 3.336±0.005cC 2.008±0.077bB

Tab.1 Phosphorus absorbency comparison of different duckweed genotypes

The English capital letter and lowercase expressed the mean difference is significant at the .01 and .05 level in the treats.

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Fig.1 The relationship between pi uptake rate and its concentration in solution

（ a: L. aequinoctialis ， b: S. oligorrhiza ， c: S. polyrrhiza ）

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

0 0.5 1 1.5 2 2.5 3

外Pi浓度（mmol/L）

吸收

速率

（μm

ol/g 鲜

重•h

r ）

a0.0

1.0

2.0

3.0

4.0

0 0.5 1 1.5 2 2.5 3

Pi mmol / L外 浓度（ ）

b0.0

1.0

2.0

3.0

4.0

0 0.5 1 1.5 2 2.5 3

外Pi浓度（mmol/L）

c

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Genotypes Kinetic Equation R2 Km(μmol/

L)

Vmax(μmol/

gFW•hr)

L. aequinoctialis

S. oligorrhiza

S. polyrrhiza

I=5C/ (1.25+C)

I=7.698C/ (2.186+C)

I=9.606C/ (2.695+C)

0.971**

0.966**

0.987**

1.250

2.186

2.695

5.000

7.698

9.606

Tab.2 Kinetic parameters of Pi uptake by different genotypes of duckweed

**: the siginificant were at 1% level.

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Fig. 2 Ultrastructure of chloroplasts in mesophyllic cells of different duckweed genotypes

a b c

（ a: L. aequinoctialis×18500 ， b: S. oligorrhiza×26500 ， c: S. polyrrhiza×26500）

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1. 0

1. 5

2. 0

2. 5

3. 0

3. 5

4. 0

10 20 30

培养时间（天）

ACP

U/gprot

酶活

力（

）

L. aequi noct i al i sS. ol i gorrhi zaS. pol yrrhi za

Fig. 3 ACP activities of different duckweed genotypes

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Spriodela had a higher phosphorus uptake capacity, though

it’s growth rate was lower than the Lemna;

Phosphorus uptake kinetics in duckweed were in accord with

the Michaelis-Menten equation;

Conclusions

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The Km value for Pi uptake of Lemna aequinoctialis was less

than that of Spirodela oligorrhiza and Spriodela polyrrhiza,

making it a better candidate for treating wastewater with a

lower Pi concentration；

The Vm value of phosphorus uptake by Spriodela polyrrhiza

was higher than that of the other two genotypes , which

might lead to a better performance of Spriodela polyrrhiza in

purifying wastewater with a higher Pi concentration;

Conclusions

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Compared with Lemna, leaf chloroplast morphology of

Spriodela promoted the export of assimilation products;

ACP activity of Spriodela was higher than that of Lemna,

which also indicated Spriodela may have a higher

phosphorus uptake capacity.

Conclusions

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