two Bamboo Species (Phyllostachys Auresulcata `Spectabilis' and Pleioblastus Excess Copper

Differential Responses of two Bamboo Species (Phyllostachys Auresulcata `Spectabilis'and Pleioblastus Chino `Hisauchii')to Excess Copper

Li Jiang &Gangrong Shi &Yulong Ding &Laiqing Lou &Qingsheng Cai

Published online:13March 2013

#Springer Science+Business Media New York 2013

Abstract Pot experiments were carried out to examine the responses of growth,physiological properties,copper (Cu)absorption and translocation in two bamboo species,Phyllostachys auresulcata ‘Spectabilis ’and Pleioblastus chino ‘Hisauchii ’Two-year old plants with similar size were exposed to excess Cu treatments,in order to demonstrate their Cu tolerance and potential ability of phytoremediation under Cu-polluted soil as biofuel feedstock.Pots were irri-gated with aqueous solutions of Cu in concentrations of 500,1000and 2000mg CuSO 4·5H 2O kg ?1,against the control (tap water).Plant growth,chlorophyll contents,photosynthesis rate,malondialdehyde (MDA)content,Cu concentrations in leave,stem and root,and Cu contents in shoot per pot were measured after transplanted plants were grown under excess Cu treatments for 60days.Two bamboo species had different responses to tolerance and allocation of supplied Cu.As Cu treatments rose,the percentage of senescent shoot and MDA content increased,and the chlorophyll content and photosyn-thetic capacity decreased.Such changes in Hisauchii were more obvious than in Spectabilis.However,number of

emerged shoots did not differ between the two species across four Cu treatments.In the efficiency of decontamination,Hisauchii was more effective than Spectabilis,since either the Cu concentrations in leaves,stems and roots or Cu con-tents in shoot per pot in Cu treatments from 500to 2000mg kg ?1were higher in Hisauchii than in Spectabilis It is suggested that the potential capability of absorbing Cu might cause the different response to cu stress between the two bamboo species.Both bamboo species can be considered to exhibit enough potential to develop in Cu-polluted areas of China as bioenergy resources and phytoremediation plants.

Keywords Bamboo .Bioenergy plant .Copper stress .Phytoremediation

Introduction

Various industrial and agricultural human activities,such as mining,smelting,land application of sewage sludge,use of fungicides containing copper (Cu)to arable lands,etc.,have led to widespread soil contamination with Cu up to potentially toxic conditions.Copper is an essential micronutrient for plant metabolism,but when present in excessive amounts,could lead to inhibition of plant growth by deteriorating plant phys-iological metabolisms [1–4].For example,excess Cu inhibited chlorophyll synthesis and photosynthetic activity [5]caused an increase in MDA (malondialdehyde),damaged cell membranes,and changed reactive oxygen species (ROS)responses [6,7]and other disordered metabolic activities [8–10].Some plant species,especial heavy metal hyper-accumulators,have relatively strong tolerances to heavy met-al,and can be found growing successfully,showing physio-logical adaptation on soils contaminated by metals,where other species or genotypes would fail.Heavy metal hyper-accumulators were proposed as a promising concept for

L.Jiang :G.Shi :L.Lou (*):Q.Cai (*)

College of Life Sciences,Nanjing Agricultural University,Nanjing 210095,People ’s Republic of China e-mail:loulq@https://www.360docs.net/doc/6618182787.html, e-mail:qscai@https://www.360docs.net/doc/6618182787.html,

G.Shi

College of Life Sciences,Huaibei Normal University,Huaibei 235000,People ’s Republic of China

Y .Ding

Bamboo Research Institute,Nanjing Forestry University,Nanjing 210037,People ’s Republic of China

L.Jiang

Key Laboratory of Oasis Ecology and Desert Environment,

Xinjiang Institute of Ecology and Geography,Chinese Academy of Sciences,Urumqi 860011,People ’s Republic of China

Bioenerg.Res.(2013)6:1223–1229DOI 10.1007/s12155-013-9317-4

more than400species,including24species for Cu. However,these hyper-accumulators are known not to be fit for economical use,due to low biomass yield with slow growth rates[11–14].

Developing high biomass energy crops on metal contam-inated soils is now considered a corking solution to these problems[15,16].Bioenergy crops can be used for produc-ing either biodiesel or bioethanol,which is a sustainable option for possibly removing metal pollutants by phytoremediation,i.e.the use of plant systems to absorb and remove pollutant elements fromcontaminated soils [16–18].

Bamboos(more than70genera and about1,000species) occur naturally in tropical,subtropical and temperate re-gions of all the continents in the world(except Europe), from sea level to4000m.The bamboo area in China is more than4million ha and occupies1/4of the world total,and is mostly covered by genus Phyllostachys[19].Bamboo is the largest member of the gramineous family,usually consisting of large,woody perennials;these are widely used for agricultural products,such as fresh edible shoots and ingredients in medicine;for industrial purposes,such as paper-making and building materials;and for ecological protection,such as soil and water conservation and ero-sion control.Some perennials bamboo species are known to have several merits,including high stress tolerance to various factors,high growth and biomass production [20–22].Recently,some researchers reported on the heavy metal tolerance and accumulation in some bamboo species[10,23,24].

In order to develop dual potentials of bamboo species for bioenergy feedstock and phytoremediation activity in Cu-polluted areas,we examined plant growth,physiological properties,Cu absorb,accumulation and translocation abil-ities of two bamboo species(Phyllostachys auresulcata ‘Spectabilis’and Pleioblastus chino‘Hisauchii’in a range of Cu supplies up to excessive rates using pot-soil-culture. Materials and Methods

Experimental Set Up

The soil used in this experiment was collected from the topsoil(15cm below surface)on a wasteland that had been uncultivated for several years,in Pailou Experimental Station of Nanjing Agricultural University in Nanjing (N:32°12′;E:118°28′),China.The soil was removed of impurity,blend homogenized,air-dried and sieved through a 4.0mm sieve prior to use.The pH,organic matter content and Cu content in the soil samples were determined.The soil was clay,neutral(pH=6.47)with9.15g organic matter kg?1 and35.24mgCukg?1.

Uniform plants in3.0±0.1m height and1.5±0.1cm basal diameter for two bamboo species,Phyllostachys auresulcata ‘Spectabilis’and Pleioblastus chino‘Hisauchii’,were care-fully selected from a two-year old bamboo field in Bamboo Research Institute,Nanjing Forestry University.Twenty se-lected plants with10-cm rhizomes for each species were transplanted into a plastic pot(35cm height×35cm diameter) in autumn,with three culms per pot and four replicates for each treatment.Each pot was filled with25kg of already prepared soil and placed randomly on the field located at the Pailou Experimental Station of Nanjing Agricultural University,Nanjing,China.The heavy metal contamination of the soil began the next spring,180d after transplanting. Each pot was accomplished separately,by irrigating every day or as need with aqueous solutions of CuSO4·5H2O at concen-trations of500,1000and2000mgkg?1against the control(tap water)[25].

The pots were arranged in eight-row repetitions(four pots per row,one pot for each treatment and species),according to the completely randomized design with two factors,namely, bamboo species and the heavy metal concentration.

Measurements for Plant Growth,Physiological Parameters and Cu Accumulation

Plant Growth

Plant growth,physiological parameters and Cu accumula-tion were determined after60-day treatment as described below.In the spring,new bamboo shoots emerged from the base of culm,and at the same time,some emerged bamboo shoots senescent(withered away).Thus,number of emerged shoots and senescent shoots were counted,and the percent-age of senescent shoots(%)was calculated as numbers of senescent shoots/numbers of emerged shoots×100. Physiological Parameters

The mature leaves(0.2g)sampled from each plant were extracted in the dark at4°C with5ml80%acetone until color completely disappeared from leaf pieces.Total chlo-rophyll contents were determined by using spectrophotom-eter(UV-Shimazu,Japan)according to the method of Moran(1982)[26].

The net photosynthetic rate(P N),stomatal conductance (g s),and intercellular CO2concentration(C i)were measured by using a portable photosynthesis system(LI-6400,Li-Cor, Lincoln,NE,USA)equipped with light sources consisting of blue-red light-emitting diodes(LI-6400-02B).The mea-surements were conducted at photosynthetic photon flux density(PPFD)of1000μMm?2s?1,leaf temperature of 25°C,and constant CO2of380±5μM(CO2)mol?1in the sample chamber provided with buffer volume.

The malondialdehyde(MDA)content was determined according to the method of Duan et al.[27].Fresh leaves (about0.2g)were homogenized in10mL of10%trichlo-roacetic acid(TCA),and centrifuged at10,000×g for 10min.Then,2ml of0.6%thiobarbituric acid(TBA)in 10%TCA was added to2ml of the supernatant.The mixture was placed in boiling water for30min,and then quickly cooled down in an ice bath.After centrifugation at 10,000g for10min,the absorbance of the supernatant at 450,532,and600nm was determined with a spectrometer. The MDA content(μg g?1)was calculated using the formula: C(μg g?1)=6.45(A532–A600)-0.56A450.

Copper Accumulation

The plants of each treatment were harvested and washed thoroughly with distilled water,separated into roots,stems and leaves,dried at80°C until they reached constant weights.Copper concentrations were determined by ICP-OES(inductively coupled plasma–optical emission spec-trometer,ICP-OES Optima2100DV,Perkin Elmer,US) after digesting the samples with HNO3:HClO4(3:1,v/v) using a microwave laboratory system(Milestone Ethos T, USA).During the analysis of Cu in plants,standard refer-ence material from the National Research Center for Standards,China,was used for quality assurance.The trans-location factor(TF)indicates the plant’s ability to translocate the heavy metal,Cu,from roots to shoots.It was calculated on a basis of dry weight by dividing the metal concentration in shoots over the metal concentration in roots[28]. Statistical Analysis

A completely randomized design was conducted in these experiments with four replicates.Statistical analysis was

carried out using the software SPSS16.0by one-way ANOV A with Duncan’s test(P=0.05significance level)to test the different significance.

Results

Effects of Excessive Cu to Bamboo Shoot Growth

In the spring,number of emerged shoots did not differ significantly between Cu treatments(500,1000and 2000mgkg?1)and the control in either of bamboo species (Fig.1a).However,the percentage of senescent shoots increased significantly with the increase in Cu treatments from500to2000mgkg?1for both species(P>0.05, Fig.1b).The percentage of senescent shoots in Hisauchii tended to be higher than that in Spectabilis,but was not significant at P<0.05.Effects of Excess Cu on Several Physiological Properties Most of the photosynthetic properties tested,net photosyn-thetic rate(P N),stomatal conductance(g s)_and intercellular CO2concentration(C i)decreased with increasing Cu con-centration from0to2000mgkg?1Cu treatments in both bamboo species;especially P N,which decreased significant-ly at P>0.05(Table1).The reduction of P N and g s in Hisauchii tended to be more obvious than in Spectabilis, especially at higher Cu treatments in a range from0to 2000mgkg?1Cu treatments.The C i did not differ signifi-cantly(P<0.05)between the two species across four Cu treatments.

The chlorophyll contents decreased significantly with increasing Cu concentration from0to2000mgkg?1Cu treatments in both bamboo species(Fig.2a).Two bamboo species did not differ significantly in chlorophyll contents at 500mgkg?1Cu treatment,while Spectabilis had

significantly Fig.1Effect of Cu treatment on(a)number of emerged shoots,(b) percentage of senescent shoot in Spectabilis and Hisauchii.The values (mean±S.E.,n=4)having the same letters above the bars are not significantly different at P<0.05,based on Duncan’s test

higher chlorophyll contents than Hisauchii at1000and 2000mgkg?1Cu treatments,where the decreased rates of chlorophyll contents from the control were much higher in Hisauchii than in Spectabilis.

In opposition to the photosynthetic parameters and chlo-rophyll contents,the MDA contents,one of the indices that reflects the degree of membrane lipid peroxidation,in-creased significantly at P>0.05with increasing Cu treat-ments from0to2000mgkg?1in both bamboo species (Fig.2b).However,the increased rate of MDA contents from the control was significant higher in Hisauchii than in Spectabilis across all of the Cu treatments.

Absorption,Accumulation and Translocation of Cu

Most of the Cu concentrations in leaves,stems and roots of the two bamboo species increased significantly as Cu treatment increased from0to500,1000and2000mgkg?1.It is note-worthy that either the Cu concentrations in leaves,stems and roots or Cu contents in shoot per pot were higher in Hisauchii than in Spectabilis,and differed significant at P>0.05 (Table2).In both bamboo species,Cu concentration was highest in roots,followed by stems,and was lowest in leaves. The translocation rate(TF)tended to be higher in Hisauchii (range,0.41–0.49)than in Spectabilis(range,0.24–0.42) across whole Cu treatments.

Although the shoot biomass per pot decreased signifi-cantly as Cu treatment increased from0to500,1000and 2000mgkg?1in both of bamboo species(Fig.3),the Cu accumulation in shoot increased for all Cu treatments(Table2). As shown in Fig.3,the shoot biomass per pot tended to be lower in Hisauchii than in Spectabilis when treated with1000 and2000mgCukg?1;however,the Cu contents in shoot per pot were still higher in Hisauchii than in Spectabilis (Table2),indicating that the amount of shoot Cu removal per pot was higher by shoots of Hisauchii than those of Spectabilis.

Discussion

Bioenergy plants are considered for multitudinous purposes, such as being transformed into energy for heat and electric

Table1Photosynthetic param-eters of Spectabilis and Hisauchii exposed to increasing Cu concentrations.Mean±S.E., n=4

*Different letters in the same column denote significant dif-ferences(P<0.05),based on Duncan’s test Species Cu treatments P N g s C i

(mg kg?1)(μmol m?2·s?1)(mmolH2O m?2·s?1)(μmol mol?1)

Spectabilis0(Control)10.7±0.7b*0.114±0.011b206.8±15.2a 5007.9±0.2c0.058±0.003d141.6±15.3a

1000 5.9±0.2d0.039±0.002d,e116.8±19.9a

2000 4.1±0.1e0.024±0.002e,f123.8±4.2a Hisauchii0(Control)12.9±0.2a0.132±0.003a207.3±5.0a 5008.6±0.6c0.083±0.011c196.5±10.9a

1000 5.6±0.3d0.036±0.002d,e116.8±20.2a

2000 3.0±0.3e0.013±0.004f149.7±49.2

a Fig.2Effect of Cu on(a)chlorophyll content,(b)MDA content of in

leaves of in Spectabilis and Hisauchii.The values(mean±S.E.,n=4)

having the same letters above the bars are not significantly different at

P<0.05,based on Duncan’s test

power production through direct combustion,used as a feedstock for liquid transportation fuel,or gasified and liquefied to produce syn-gas or bio-oil.Several perennial herbaceous grasses have been studied in recent years as potential dedicated cellulose biomass crops[29].Bamboo, a perennial lignified plant,is considered a promising bio-mass for pulping and bioethanol production,due to its rapid growth rate and huge quantity.Recently,it was reported that the bamboo lignin could be easily released after using ad-vanced chemistry and spectroscopic methods[30]. Therefore,it is necessary to research heavy metal,metal-loids and organic pollution tolerance of bamboo plants,for the use of polluted land for bioenergy production.In this study,the response of bioenergy candidate plants to excess Cu was analyzed.

Naturally,the major portion of total soil Cu is insoluble, precipitated or adsorbed on the solid phase.Only about1%to<0.01%of the total soil Cu is dissolved in the soil solution[31].However,in recent decades,enhanced anthro-pogenic activities,such as mining and smelting,combustion of fossil fuels,utilization of fertilizers and pesticides,and disposal of wastes have contributed to the increasing occur-rence of heavy metals,including Cu,in ecosystems[32]. Copper is both a micronutrient for plants and a heavy metal capable of stress induction.The first visible symptom of Cu toxicity for plants is known as the interveinal chlorosis of leaves[33]due to the decreased rate of chlorophyll biosyn-thesis[34,35],since Cu can induce degradation of chloro-phyll through damage of chlorophyll structure and function [36].Photosynthesis has been found to be very sensitive to heavy metal toxicity.A great number of previous investiga-tions have indicated that heavy metal causes a reduction of the photosynthetic performance in plants[37].The parallel change of P N,g s and C i in this study provided evidence that the photosynthetic responses of two bamboo species to excess heavy metal might be mainly due to the alteration of the pigment contents and stomatal conductance under Cu stress.Abiotic stresses could damage plant cells directly or indirectly through the formation of reactive oxygen species (ROS)[7,31,38].The MDA was the main peroxidation product of membrane lipids when plants were subjected to several stresses.Therefore,MDA content was commonly considered a general indicator of lipid peroxidation,as well as stress levels[39,40].Excess Cu led to the increase of MDA content[41].With the increasing concentration of Cu treatments,the increase of MDA content in Hisauchii was more obvious than that in Spectabilis.

Excessive heavy metals,including Cu,are not only harm-ful to plant growth and philological metabolism,but also enter the food chain and therefore do harm to human health [42].Therefore,soil polluted with excessive heavy metals including Cul is not suitable to cultivate any plants that enter

Table2Copper concentration in Spectabilis and Hisauchii exposed to increasing soil Cu treatments

Species Cu treatments Leaves Stem Roots TF*Cu contents (mg kg?1)μg g?1DWμg g?1DWμg g?1DW mg shoot?1pot?1 Spectabilis0(Control)67.6±10.1c**148.5±7.8d447.6±173.9c0.24486.39 500120.8±20.4c349.4±70.4c603.5±110.0b,c0.39998.47

1000194.3±46.9b559.4±87.8b899.3±124.9b0.421361.00

2000357.3±60.9a735.3±39.7a2048.1±303.0a0.261411.64 Hisauchii0(Control)120.3±15.3d213.2±65.5d398.8±32.7c0.41811.24 500303.3±35.6c473.6±173.9c786.4±61.2b0.491726.27

1000583.1±33.6b812.0±103.4b1586.5±67.6b0.432020.45

2000870.4±10.5a1572.8±122.3a2871.8±179.7a0.422922.68

*TF=[Cd]shoot/[Cd]root

**All parameters were measured60days after treatments.Mean±S.E.,n=4.Different letters in the same column denote significant differences P<0.05,based on Duncan’s

test

Fig.3Effect of Cu treatment on shoot biomass in Spectabilis and

Hisauchii.All parameters were measured60days after treatments.The

values(mean±S.E.,n=4)having the same letters above the bars are not

significantly different at P<0.05,based on Duncan’s test

the food chain;instead,it would be good to develop bioenergy plants in such a polluted area.In this research, the higher Cu concentrations were set up to evaluate Cu tolerance of two bamboo species to excess Cu stress.Under highest Cu supply at2000mgkg?1,Cu concentrations tended to be highest at2048.1and2871.8μgg?1DW in roots and735.3and1572.8μg g?1DW in stems for Spectabilis and Hisauchii,respectively.And the highest Cu accumulation achieved at2922.68mg in shoot per pot in Hisauchii was shown.As Callahan et al.(2012)assessed, plants that store metals in their leaves at concentrations toxic to other organisms are known as hyper-accumulators[43]. While none of the bamboo species can fit to hyper-accumulator of Cu in the present study,both bamboo species can be cultivated in areas of heavy metal Cu-contamination for development of potential biomass resources and for phytoremediation by absorbing and accumulating excess Cu from Cu polluted soil.

The mechanisms of Cu uptake are still poorly understood in monocotyledonous species,while those in dicotyledon-ous species,such as Arabidopsis,have been primarily stud-ied[44].Under the same Cu application,significant differences were found between the two bamboo species in uptake,accumulation and translocation of Cu from roots to stems and leaves,while they had high enough capability of Cu uptake compared to the previous results of Collin et al. (2012)[24]and Collin and Doelsch(2010)[45].Mechanisms for high rate and difference of Cu uptake in two bamboo species should be examined further by using as many bamboo species as possible.

So far,it is unknown if are there any negative effects of the bamboo that accumulated abundant heavy metal including Cu to bioenergy conversion,since research on developing bioenergy plants in heavy metal polluted areas is just begin-ning,and mostly has attended to heavy metal tolerance. However,relative research with cooperation between plant scientisst and process engineers is needed for solving the problem of using Cu accumulated plant material as bioenergy feedstock.

Conclusions

Two bamboo species(Phyllostachys auresulcata‘Spectabilis’and Pleioblastus chino‘Hisauchii’)with similar growth traits and morphological characteristics have different responses to excess copper stress in a range from0to2000mgkg?1Cu treatments.The degree of change in several growth and phys-iological properties(the decrease of chlorophyll content and P N,and the increase of the percentage of senescent bamboo shoots and MDA content),reflects that the Cu tolerance was higher in Spectabilis than in Hisauchii.All the different re-sponses to excess Cu stress between the two bamboo species may depend on the degree of lipid peroxidation.On the contrary,either the shoot biomass,Cu concentrations in leaves,stems,roots or Cu contents in shoot per pot were higher in Hisauchii than in Spectabilis under copper stress in a range from0to2000mgkg?1Cu treatments.These results indicate that the capability of Cu absorption and accumulation arehigher in Hisauchii than in Spectabilis.Both Hisauchii and Spectabilis can be considered as candidates to be cultivated in heavy metal Cu polluted areas as potential renewable bioenergy resources,since the examined two bamboo species survived even under highest Cu treatment at2000mgkg?1.It is better to cultivate Hisauchii than Spectabilis as phytoremediation plant in Cu polluted area,since the shoot Cu accumulation was higher in Hisauchii than in Spectabilis. Acknowledgments We thank the financial support from Natural Science Foundation of China(40971296)and the Doctoral Program Foundation of Institutions of Higher Education of China (200900971200038).The authors thank Dr.Mei Chuansheng,the Institute for Advanced Learning and Research,VA,USA,for his sincere advice during correction of the manuscript.

References

1.Liu TF,Wang T,Sun C,Wang YM(2009)Single and joint toxicity

of cypermethrin and copper on Chinese cabbage(Pakchoi)seeds.J Hazard Mater163:344–348

2.Buss W,Kammann C,Koyro H(2012)Biochar reduces copper

toxicity in Chenopodium quinoa Willd.in a sandy soil.J Environ Qual41:1157–1165

3.Cook CM,Kostidou A,Vardaka E,Lanara T(1997)Effects of

copper on the growth,photosynthesis and nutrient concentration of phuseolus plants.Photosynthetica34:179–193

4.Maksymiec W,Bednara J,Bazynski T(1995)Responses of runner

plants to excess copper as a function of plant growth stages:effects on morphology and structure of primary leaves and their chloro-plast ultra-structure.Photosynthetica31:427–435

5.Lidon FC,Ramalho JC,Henriques FS(1993)Copper inhibition of

rice photosynthesis.J Plant Physiol142:12–17

6.Kennedy CD,Gonsalves FAN(1987)The action of divalent zinc,

cadmium,mercury,copper and lead on the trans-root potential and H+efflux of excised roots.J Exp Bot38:800–817

7.Andrade S,Contreras L,Moffett JW,Correa JA(2006)Kinetics of

copper accumulation in Lessonia nigrescens(Phaeophyceae)under conditions of environmental oxidative stress.Aquat Toxicol78:398–401

8.Augus S(1999)Early copper-induced leakage of K+from

Arabidopsis seedlings is mediated by ion channels and coupled to citrate efflux.Plant Phsiol121:1375–1382

9.Demidchik K,Sokolik A,Yurin V(1997)The effects of Cu2+on

ion transport systems of the plant cell plasmolemma.Plant Physiol 114:1313–1325

10.Remans T,Thijs S,Truyens S(2012)Understanding the development

of roots exposed to contaminants and the potential of plant-associated bacteria for optimization of growth.Ann Bot110:239–252 11.Brooks RR,Lee J,Reeves RD,Jaffre T(1997)Detection of

nickeliferous rocks by analysis of herbarium specimens of indica-tor plants.J Geochem Explor7:49–57

12.Baker AJM,McGrath SP,Reeves RD,Smith JAC(2000)Metal

hyperaccumulator plant:a review of the ecology and physiology of

a biological resource for phytoremediation of metal-polluted soils.

In:Terry N,Banuelos G(eds)Phytoremediation of contaminated soil and water.Lewis Publishers,USA

13.Xue SG,Chen YX,Reeves RD,Baker AJM,Liu Q,Fernando DR

(2004)Manganese uptake and accumulation by the hyperaccumulator plant Phytolacca acinosa Roxb.Environ Pollut131:393–399

14.Zhao FJ,Lombi E,McGrath SP(2003)Assessing the potential for

zinc and cadmium phytoremediation with the hyperaccumulator Thlaspi caerulescens.Plant Soil249:37–43

15.Shi GR,Cai QS,Liu QQ,Wu L(2009)Salicylic acid-mediated

alleviation of cadmium toxicity in hemp plants in relation to cadmium uptake,photosynthesis,and antioxidant enzymes.Acta Physiol Plant31:969–977

16.Liu XH,Shen YX,Ding CL,Cai QS(2009)Copper tolerance of

biomass crops Elephant grass(Pennisetum purpureum Schumach), Vetiver grass(Vetiveria zizanioides)and the upland reed (Phragmites australis)in soil culture.Biotechnol Adv27:633–640 17.Shi G,Cai Q(2009)Cadmium tolerance and accumulation in eight

potential energy crops.Biotechnol Adv27:555–561

18.Huo W,Zhuang CH,Cao Y,Pu M,Yao H,Lou LQ,Cai QS(2012)

Paclobutrazol and plant-growth promoting bacterial endophyte Pantoea sp.enhance copper tolerance of Guinea grass(Panicum maximum)in hydroponic culture.Acta Physiol Plant34:139–150 19.Yang YM,Xu JR(1998)Bamboo resources and their utilization in

China.In:Proceedings of the Workshop‘Bamboo Conservation, Diversity,Ecogeography,Germplasm,Resource Utilization and Taxonomy’,Kunming and Xishuangbanna,Yunnan,China,10–17May

20.Gratani L,Crescente MF,Varone L,Fabrini G,Digiulio E(2008)

Growth pattern and photosynthetic activity of different bamboo species growing in the Botanical Garden of Rome.Flora203:77–84 21.Atkinson CJ(2009)Establishing perennial grass energy crops in

the UK:a review of current propagation options for Miscanthus.

Biomass Bioenergy5:752–759

22.Zhou FC(1999)Looking back to bamboo industry for the20th

century,looking forward to bamboo industry for the21th century.J Bamboo Res18:1–4

23.Gui RY,Leng HN,Zhuang SY,Zheng KL,Fang W(2011)

Aluminum tolerance in Moso Bamboo(Phyllostachys pubescens).

Bot Rev77:214–222

24.Collin B,Doelsch E,Keller C,Panfili F,Meunier JD(2012)

Distribution and variability of silicon,copper and zinc in different bamboo species.Plant Soil351:377–387

25.Papazoglou EG,Serelis KG,Bouranis DL(2007)Impact of high

cadmium and nickel soil concentration on selected physiological parameters of Arundo donax L.Eur J Soil Biol43:207–215 26.Moran R(1982)Formulae for determination of chlorophyllous

pigments extracted with N,N–dimethylformamide.Plant Physiol69:1376–1381

27.Duan B,Lu Y,Yin C,Junttila Q,Li C(2005)Physiological

responses to drought and shade in two contrasting picea asperata populations.Physiol Plant124:476–484

28.Baker AJM,McGrath SP,Sidoli CMD(1994)The possibility of in

situ heavy metals decontamitation of polluted soils using crops of metal-accumulating.Resour Conserv Recyl11:41–4929.Digman MF,Shinners KJ,Muck RE,Dien BS(2010)Full-scale

On-farm Pretreatment of Perennial Grasses with Dilute Acid for Fuel Ethanol Production.Bioenerg Res3:335–341

30.Wen JR,Xue BL,Xu F,Sun RC(2012)Unveiling the structural

heterogeneity of Bamboo Lignin by In Situ HSQC NMR Technique.Bioenerg Res5:886–903

31.SauvéS,McBride M,Norvell WA,Hendershot W(1997)Copper

solubility and speciation of in situ contaminated soils:effects of copper level,pH and organic matter.Water Air Soil Pollut100:133–149

32.Boojar MMA,Goodarzi F(2007)The copper tolerance strategies

and the role of antioxidative enzymes in three plant species grown on copper mine.Chemosphere67:2138–2147

33.Taylor GJ,For CD(1985)Differential uptake and toxicity of ionic

and chelated copper in Triticum aestivu.Can J Bot63:1271–1275

34.Pitsikki E,Kairavuo M,Deren F,Aro EM,Tyystjiirvi E(2002)

Excess copper predisposes photosystem II to photo-inhibition in vivo by out competing iron and causing decrease in leaf chlorophy.

Plant Physiol129:1359–1367

35.Pitsikki E,Aro EM,Tyystjiirvi E(1998)Increase in the quantum

yield of photo-inhibition contributes to copper toxicity in vivo.

Plant Physiol117:619–627

36.Prasad MNV,Malec P,Waloszek A,Bojko M,Strzalka K(2001)

Physiogical responses of Lemna trisulcal L.(duckweed)to cadmi-um and copper bioaccumulation.Plant Sci161:881–889

37.Shi G,Liu C,Cai Q,Liu Q,Hou C(2010)Cadmium accumulation

and tolerance of two safflower cultivars in relation to photosyn-thesis and antioxidantive enzymes.Bull Environ Contam Toxicol 85:256–263

38.Strange J,Macnair MR(1991)Evidence for a role for the cell

membrane in copper tolerance of mimulus guttatu Fishex DC.New Phytologists119:383–388

39.Guo TR,Zhang GR,Zhang YH(2007)Physiological changes in

barley plants under combined toxicity of aluminum,copper and cadmium.Colloids and Surface B:Biointerphases57:182–188

40.Peter MA,Karl L,Ruth P(1999)Modification of the lipid-protein

interaction in human low-density lipoprotein destabilizes ApoB-100and decreases oxidizability.Biochem38:3401–3408

41.Luna MC,Gouzalex CA,Tripp VS(1994)Oxidative damage

caused by excess of copper in oat leaves.Plant Cell Physiol 35:11–15

42.Peralta-Videa JR,Lopez ML,Narayan M,Saupe G,Gardea-

Torresdey J(2009)The biochemistry of environmental heavy metal uptake by plants:implications for the food chain.Int J Biochem Cell Biol41:1665–1677

43.Callahan DL,Ute Roessner U,Dumontet V,Livera AMD,

Doronila A,Baker AJM,Kolev SD(2012)Elemental and metab-olite profiling of nickel hyperaccumulators from New Caledonia.

Phytochemistry81:80–89

44.Memon AR,Schr?der P(2009)Implications of metal accumula-

tion mechanisms to phyto-remediation.Environ Sci Pollut Res 16:162–175

45.Collin B,Doelsch E(2010)Impact of high natural soil borne heavy

metal concentrations on the mobility and phytoavailability of these elements for sugarcane.Geoderma159:452–458