Influence of inoculation with Glomus mosseae or Acaulospora morrowiae on arsenic uptake and translocation by maize

Transcription

1 Influence of inocultion with Glomus mossee or culospor morrowie on rsenic uptke nd trnsloction y mize Wng, Z. H., Zhng, J. L., Christie, P., & Li, X. L. (2008). Influence of inocultion with Glomus mossee or culospor morrowie on rsenic uptke nd trnsloction y mize. Plnt nd Soil, 311(1-2), DOI: /s Pulished in: Plnt nd Soil Queen's University elfst - Reserch Portl: Link to puliction record in Queen's University elfst Reserch Portl Generl rights Copyright for the pulictions mde ccessile vi the Queen's University elfst Reserch Portl is retined y the uthor(s) nd / or other copyright owners nd it is condition of ccessing these pulictions tht users recognise nd ide y the legl requirements ssocited with these rights. Tke down policy The Reserch Portl is Queen's institutionl repository tht provides ccess to Queen's reserch output. Every effort hs een mde to ensure tht content in the Reserch Portl does not infringe ny person's rights, or pplicle UK lws. If you discover content in the Reserch Portl tht you elieve reches copyright or violtes ny lw, plese contct openccess@qu.c.uk. Downlod dte:15. Fe. 2017

2 Plnt Soil (2008) 311: DOI /s REGULR RTICLE Influence of inocultion with Glomus mossee or culospor morrowie on rsenic uptke nd trnsloction y mize Zhen-Hui Wng & Jun-Ling Zhng & Peter Christie & Xio-Lin Li Received: 18 Mrch 2008 /ccepted: 2 June 2008 / Pulished online: 1 July 2008 # Springer Science + usiness Medi.V strct split root device ws designed to ssess the possile role of MF in trnsloction nd detoxifiction of s y mize plnts. Hlf of ech mize root system grew in s-mended or unmended soil nd the reminder ws inoculted with either Glomus mossee or culospor morrowie. Externl mycelium ws collected from third comprtment. Responsile Editor: F. ndrew Smith. Z.-H. Wng : J.-L. Zhng (*) : P. Christie : X.-L. Li Key Lortory of Plnt Nutrition, Ministry of griculture, Chin griculturl University, eijing , Chin e-mil: junlingz@cu.edu.cn Z.-H. Wng : J.-L. Zhng : P. Christie : X.-L. Li Key Lortory of Plnt Soil Interctions, Ministry of Eduction, Chin griculturl University, eijing , Chin Z.-H. Wng : J.-L. Zhng : P. Christie : X.-L. Li College of Resources nd Environmentl Sciences, Chin griculturl University, eijing , Chin Z.-H. Wng Ruer Reserch Institute/Ministry of griculture Key Lortory for Tropicl Crops, CTS, Dnzhou, Hinn, Chin P. Christie griculturl nd Environmentl Science Deprtment, Queen s University elfst, elfst T9 5PX, UK Neither shoot nor root s concentrtions were ffected y inocultion with either fungus. Soil s mendment produced higher s concentrtions in roots in the second comprtment nd in the externl mycelium. The s concentrtions in the mtrix solution of the second root comprtment were lower in mycorrhizl tretments with no differences in solule s in the hyphl comprtments. Mycorrhiz exerted little effect on s trnsloction within plnts ut my hve influenced root s efflux. Deposition of s in externl mycelium indictes possile role of mycorrhizl fungi in the detoxifiction of s in the host plnts. Keywords rusculr mycorrhiz. rsenic. Phosphorus nutrition. Split-root device. Ze mys Introduction rusculr mycorrhizl (M) fungi cn form potentilly eneficil ssocitions with the roots of more thn 80% of terrestril plnts nd there is incresing evidence tht M fungi re importnt components of soil phytoremedition strtegies for hevy metls (Khn et l. 2000) in terms of incresing plnt growth nd nutrient uptke (Smith nd Red 1997) while enhncing metl uptke y plnts or immoiliztion of metls in the soil. In some cses mycorrhizl plnts show enhnced hevy metl(loid) uptke nd root-toshoot trnsport (phytoextrction) in non-hyperccu-

3 236 Plnt Soil (2008) 311: multors nd in few hypercumultors such s Chinese rke fern for s (l gely et l. 2005; Leung et l. 2006) nd erkhey coddii for Ni. In other cses M fungi contriute significntly to hevy metl immoiliztion in the soil (phytostiliztion) eyond the rhizosphere nd therey enhnce phytostiliztion y relesing compounds or inding hevy metl(loids) to chitin in the fungl cell wll. y doing so, M fungi reduce locl metl concentrtions in the soil or sequester the metls in underground prts of the symiont, for exmple in root tissues nd/ or fungl structures. The outcome of mycorrhizl coloniztion on clen-up of contminted soils depends on the plnt fungus hevy metl(loid) comintion nd is lso influenced y soil conditions (Göhre nd Pszkowski 2006). rsenic (s) is uiquitous toxic element nd it hs led to serious helth prolems, especilly in some countries of south si (edin et l. 2002; Mehrg 2004). oth s nd P re tken up vi phosphte trnsporters on the plsm memrne of root epiderml cells (Ullrich-Eerius et l. 1989) ecuse of their similr chemicl ehviour (Mehrg et l. 1994), nd rsente sensitivity is intimtely linked to phosphte nutrition. In mycorrhizl plnts mycorrhiz-induced phosphte trnsporters (Rusch et l. 2001; Hrrison et l. 2002) re exclusively expressed in mycorrhizl roots. The loss of function of the direct uptke pthwy in roots colonized y M fungi cn pprently e complete in some M ssocitions (Smith et l. 2003). s direct uptke y roots declines, its replcement y the mycorrhizl pthwy will depend on the expression of phosphte trnsporters in the externl mycelium of the fungi (Hrrison nd vn uuren 1995; Mldondo-Mendoz et l. 2001). It is therefore ssumed tht mycorrhizl mycelium my perform similr function in s uptke s in P uptke in s-contminted soils. However, microorgnisms cn detoxify rsente y reduction nd efflux of rsenite (Ghosh et l. 1999; Shi et l. 1999; Mukhopdhyy et l. 2000; Mukhopdhyy nd Rosen 2002; Rosen 2002), nd plnts hve lso een shown to hve high cpcity to reduce rsente (Mehrg nd Hrtley-Whitker 2002; Slt et l. 2002; Qugheeur nd Rengel 2003; Dun et l. 2005). Xu et l. (2007) recently reported tht tomto nd rice plnts cn relese s vi their roots. lthough severl studies hve shown enhnced plnt tolernce to s resulting from inocultion with MF (Gonzlez-Chvez et l. 2002; Leung et l. 2006; Chen et l. 2007), elucidtion of the effects of MF on uptke nd trnsloction of s nd direct evidence showing tht mycorrhizl hyphe re involved in the detoxifiction of s re still lcking. In the present study split root device ws used to ssess the possile role of MF in trnsloction nd detoxifiction of s y mize plnts. rsenic tken up y prt of the root system growing in mixture of soil nd snd would e trnslocted to the shoots nd into the prt of the root system colonized y mycorrhizl fungus or into externl hyphe extending into pot comprtment contining glss eds so tht externl hyphe could e collected nd nlysed for s. rsenic concentrtions in the mtrix solution were lso determined. The study ws designed to test the hypotheses tht mycorrhizl coloniztion influences the trnsloction of s nd tht s efflux differs etween mycorrhizl nd non-mycorrhizl plnt roots. Mterils nd methods Experimentl set up The split-root device shown in Fig. 1 ws used. Two comprtments, ( cm) nd ( cm) were used for the growth of two hlves of the split root system of the mize plnt. mixture of soil nd snd (3:1, v/v) ws plced in comprtment nd Perlite ws plced in comprtment. The sustrte in comprtment ws mended with different levels of s nd tht in comprtment ws either mixed with mycorrhizl inoculum or remined uninoculted. Comprtment C ( cm), which ws djcent to comprtment, ws intended for hyphl growth. Glss eds (<1 mm) were used s the sustrte so tht extrmtricl hyphe could e collected nd nlyzed s descried in previous study y Chen et l. (2001). The device ws designed specificlly to investigte the role of rusculr mycorrhizl fungi in mediting s trnsloction nd detoxifiction in the plnts y determining s contents in different plnt prts, nd y mesuring s in the externl fungl mycelium nd in the mtrix solution. ll mterils used s sustrtes were sieved (1.8 mm) nd sterilized y utoclving t 120 C for 2 h prior to the experiment. Comprtments nd were seprted y polyvinylchloride (PVC) plte ( cm)

4 Plnt Soil (2008) 311: cm C 4 cm 4 cm 3 cm Fig. 1 Digrmmtic illustrtion of the split-root cultivtion system. Comprtments nd were seprted y polyvinylchloride (PVC) plte nd comprtments nd C y nylon screen (30 μm mesh). Roots of mize were split into comprtments nd. rsenic ws dded to comprtment nd mycorrhizl inoculum ws dded to comprtment. Comprtment C ws for hyphl growth. The sustrte in comprtment ws mixture of soil nd snd, nd in comprtments nd C were Perlite nd glss eds, respectively. Hyphe re depicted s roken lines nd mize roots s solid lines nd nylon screen of 30 μm mesh size ws used to seprte comprtments nd C. iologicl mteril, growing conditions nd experimentl design Two rusculr mycorrhizl (M) fungi, Glomus mossee (Nicolson & Gerdemnn) Gerd. & Trppe (EG167; Europen nk of the Glomles) nd culospor morrowie Spin & Schenck (EG194) were used s inocul. The two fungi were propgted on the roots of mize plnts in pot culture for 10 weeks. The inoculum consisted of growth medium contining spores together with infected mize root frgments. The experimentl soil ws collected from field locted t Dnzhou city, Hinn province (19 30 N, E), south Chin. The soil hd the following properties: ph 4.69 (soil/wter rtio, 1:2.5), orgnic mtter content 0.46%, NHCO 3 -extrctle P 0.21 mg kg 1, totl s 1.40 mg kg 1 (HNO 3 HClO 4 digest; tomic fluorescence spectrometry). Other mterils used were Perlite (1 4 mm), corse river snd (<2 mm) nd glss eds ( mm dimeter). The glss eds nd corse river snd were cidwshed nd ll of the sustrtes were sterilised y utoclving t 120 C for 2 h nd then ir-dried. Mize (Ze mys L. cv. Nongd 108) ws used s the host plnt. The experiment consisted of rndomized lock design with two fctors: s level in which the sustrte comprising 3:1 (v/v) mixture of soil nd river snd in comprtment ws mended with s t rtes of 0, 75 nd 150 mg kg 1 in the form of N 3 so 4 12H 2 O (roots were not inoculted), nd the mycorrhizl tretment in which roots in comprtment were either non-mycorrhizl or inoculted with G. mossee or. morrowie. Inoculum (50 g) ws mixed with the Perlite in comprtment to produce inocultion tretments nd 50 g sterilized inoculum plus 25 ml mycorrhizl fungl-free filtrte from the inoculum suspension were dded to produce the nonmycorrhizl tretments to provide similr microflor except for the mycorrhizl fungus. There were nine tretments with four replictes, giving totl of 36 oxes. ll tretments received minerl nutrients dded to the soil s sl fertilizers t rtes of 120 mg kg 1 N (NH 4 NO 3 ), 20 mg kg 1 P (CHPO 4 2H 2 O) nd 80 mg kg 1 K(K 2 SO 4 ). The sustrte ws incuted for 3 weeks fter ddition of the solution contining different s concentrtions to llow equilirtion of the dded s. Seeds of mize (Ze mys L.) were surfce sterilized in 10% (v/v) solution of hydrogen peroxide for 10 min. They were pre-germinted for 2 dys t 28 C nd then sown in vermiculite. fter growth for 10 dys, seedlings with one tproot nd eight to ten lterl roots were selected nd trnsplnted in split root chmer with one seedling per ox. The lterl roots were seprted into two equl prts nd then plced in their two respective root comprtments. The tp root ws plced in comprtment to ensure good root growth nd promote mycorrhizl coloniztion. The experiment ws conducted from ugust to Octoer 2006 in glsshouse t the Chinese cdemy of Tropicl griculturl Science (19 09 N, E nd 74 m ove se level), Hinn, south Chin. The temperture ws C without supplementry illumintion. Wter (or one fourth strength Hoglnd's solution when necessry ut with the P concentrtion reduced to one tenth) ws dded to the sustrte in comprtment every 2 dys. Twice ech dy 20 ml one fourth strength Hoglnd's

5 238 Plnt Soil (2008) 311: solution with one tenth P ws dded to the Perlite in comprtment, nd the glss eds in comprtment C were irrigted four times with 10 ml one sixth strength Hoglnd's solution with one tenth P. The wter supply ws controlled y mesuring the wter loss in unplnted control pots. Hrvest nd chemicl nlysis Plnts were grown for 10 weeks nd shoots nd roots were hrvested seprtely nd rinsed twice with deionized wter. Fresh portions (1.0 g) of the root smples were retined for determintion of mycorrhizl coloniztion (Giovnnetti nd Mosse 1980). Externl mycelium ws collected from comprtment C of the inoculted tretments. Dry weights of shoots nd the remining roots nd hyphe were determined fter oven drying t 80 C for 48 h. Shoots, roots nd mycelium were milled nd sieved (20 mesh) prior to chemicl nlysis. The smples were digested with concentrted HNO 3 nd deionized H 2 O (1:1, v/v), followed y 30% H 2 O 2 for s determintion (USEP 1983) or with concentrted HNO 3,H 2 SO 4, nd 30% H 2 O 2 for P determintion (Olsen nd Sommers 1982). s concentrtion ws determined using n tomic fluorescence spectrometer (Model F-610, eijing Ryleigh nlyticl Instruments, Chin), nd P concentrtion ws determined colorimetriclly with spectrophotometer using the stndrd vndiummolydenum yellow method (Murphy nd Riley 1962). The proportions of s in shoots, roots grown in soil nd Perlite were clculted s follows: Shoot s% ¼ðs content in shoot=plnt totl s contentþ100 Soil root s% ¼ ðroot s content=plnt totl s contentþ100 Perlite root s% ¼ðShoot s content=plnt totl s contentþ100 The s content of the mycelium ws not included in the clcultion of totl s content in mycorrhizl plnts ecuse the mycelium contined much less s thn the other plnt prts. s concentrtions in mtrix solutions in comprtments nd C were determined y using in situ uried nion exchnge memrne (EM) (Mllrino nd ti 2005). Sheets of commercilly ville resin-impregnted plstic mteril (Chemicl Plnt, Shnghi, Chin) were cut into strips (5 2 cm). The strips were soked nd wshed in 95% ethnol for 1 h, rinsed with deionized wter, nd then soked in 0.5 M NHCO 3 for 48 h nd during this period the solution ws replced with fresh NHCO 3 t lest four times. The strips were then mintined in deionized wter prior to use. One strip ws completely uried in the sustrte out 2 3 cm elow the surfce of the sustrtes in the three comprtments for 2 h, mintining the sturted sttus of the mtrix solution. The strips were then removed, rinsed with deionized wter, nd shken for 1 h in 20 ml 0.5 M HCl to desor s. The s concentrtions in the desorent solutions were mesured using the sme method s descried ove. The percentge of root length colonized y the mycorrhizl fungi ws estimted rndomly selected root segments. Root smples were cut into 1-cm-long undles, clered in 10% (w/v) KOH t 90 C for min in wter th, rinsed three times nd then stined with Trypn lue t 90 C for 3 5 min, stored in glycerine nd mesured y the gridline-intersect method (Giovnnetti nd Mosse 1980). Sttisticl nlysis Dt were nlyzed using nlysis of vrince (NOV). Pirs of tretment mens were compred using Duncn's multiple rnge test t the 5% level. The SS version 8.02 softwre pckge ws used. Dt re presented in the Tles s men vlues±se (n=4). Results Mycorrhizl coloniztion No root coloniztion ws oserved in roots of nonmycorrhizl plnts. Inoculted plnt roots in comprtment hd % nd % of their length colonized y Glomus mossee or culospor morrowie. The s ddition level did not hve significnt effect on root coloniztion rtes of either fungus ut root coloniztion rtes of oth M species t 75 mg s kg 1 tended to e higher thn t zero s ddition or 150 mg s kg 1. Dry weights of shoots nd roots Shoot dry weights were significntly ffected y s ddition levels ut not y mycorrhizl coloniztion (Fig. 2, Tle 1). Shoot dry weight t 150 mg s kg 1

6 Plnt Soil (2008) 311: shoot dry weight (g) m Root dry weight in soil (g) m Root dry weight in perlite (g) m s ddition level (mg kg -1 ) s ddition level (mg kg -1 ) s ddition level (mg kg -1 ) Fig. 2 Dry weights of Ze mys shoots nd of roots (grown in soil nd Perlite) inoculted with Glomus mossee or culospor morrowie or uninoculted. Error rs: ±SE. Lower cse nd indicte significnt differences mong control nd the two mycorrhiz inocultion tretments t the sme s ddition levels. Upper cse nd indicte significnt differences mong the three mens t different s ddition levels ws significntly lower compred to 0 nd 75 mg s kg 1. The s ddition level nd mycorrhizl coloniztion hd significnt influence on dry weights of roots grown in soil (comprtment ). Root dry weights decresed with incresing s ddition level nd root dry weights of. morrowie-inoculted plnts were lower thn those of G. mossee-inoculted plnts nd controls. Neither mycorrhizl coloniztion nor s ddition level showed ny significnt Tle 1 nlysis of vrince for Figs. 2, 3, 4 nd 5 Significnce due to Mycorrhizl inocultion s level Interction Shoot dry weight ns P<0.05 ns Root dry weight in soil P<0.01 P<1 ns Root dry weight ns ns ns in Perlite Shoot P concentrtion P<0.01 ns ns Root P concentrtion ns P<0.05 ns in soil Root P concentrtion ns ns ns in Perlite Shoot s concentrtion ns P<1 ns Root s concentrtion P<0.05 P<1 ns in soil Root s concentrtion ns P<1 ns in Perlite s concentrtion in P<1 P<1 P<1 soil comprtment s concentrtion in P<1 P<1 P<1 Perlite comprtment s concentrtion in glss ed ns ns ns y nlysis of vrince; ns, not significnt effect on dry weights of roots grown in Perlite (comprtment C). P nd s concentrtions in shoots nd roots Plnt P concentrtions were out % on dry mtter sis nd were presumly sufficient for dequte growth of the host plnts under the experimentl conditions ecuse no symptoms of P deficiency were oserved (Fig. 3). s dditions to comprtment significntly incresed P concentrtions in roots grown in soil ut hd little effect on shoot P concentrtion or Perlite root P concentrtion (Tle 1). Shoot P concentrtion in mycorrhizl plnts ws higher thn in non-mycorrhizl controls mended with s. No significnt difference ws found etween mycorrhizl nd non-mycorrhizl plnts in P concentrtions of either hlf of the root systems regrdless of s ddition level. rsenic concentrtions in shoots nd roots of oth non-mycorrhizl nd mycorrhizl plnts incresed drmticlly s s ddition level incresed (Fig. 4, Tle 1). s concentrtions in roots grown in soil were much higher thn in roots grown in Perlite or shoot s concentrtions. The highest s concentrtion oserved pproched mg kg 1 in nonmycorrhizl roots grown in soil t 150 mg s kg 1 ut the highest s concentrtion in roots grown in Perlite ws only 2.3 mg kg 1. Inocultion with mycorrhizl fungus often hd no significnt effect on s concentrtions of shoots or roots grown in soil (except t 150 mg s kg 1, where root s concentrtions in mycorrhizl plnts grown in soil were significntly lower thn in the controls).

7 240 Plnt Soil (2008) 311: Shoot P concentrtion (%) m s ddition level (mg kg -1 ) Root P concentrtion in soil (%) 1.0 m s ddition level (mg kg -1 ) Root P concentrtion in Perlite (%) m s ddition level (mg kg -1 ) Fig. 3 P concentrtions of Ze mys shoots nd roots (grown in soil nd Perlite) inoculted with Glomus mossee or culospor morrowie or uninoculted. Error rs: ±SE. Lower cse nd indicte significnt differences mong control nd the two mycorrhiz inocultion tretments t the sme s ddition levels. Upper cse nd indicte significnt differences mong the three mens t different s ddition levels s concentrtions in mtrix solution Solule s concentrtions in soil mtrix solution were pproximtely times higher thn in Perlite (Fig. 5). s concentrtions in soil mtrix solution (comprtment ) incresed drmticlly with incresing s ddition level nd t 150 mg dded s kg 1 s concentrtions in soil mtrix solution significntly decresed in G. mossee-inoculted tretments ut incresed in. morrowie-inoculted tretments. s concentrtions in Perlite incresed with incresing s ddition level ut the increse ws more distinct in non-mycorrhizl plnts thn in mycorrhizl plnts. Mycorrhizl coloniztion significntly decresed s concentrtions in Perlite when s ws dded nd there ws no significnt difference etween the two fungi. s concentrtions in the mtrix solution of the glss eds did not differ significntly mong ll tretments regrdless of mycorrhizl inocultion or s ddition level (Tle 1). s concentrtion in externl mycelium s concentrtions in externl mycelium of oth fungi collected from the glss eds incresed gretly with incresing s ddition level. There ws no significnt difference etween G. mossee nd. morrowie inthe s concentrtions in the externl mycelium (Fig. 6). Proportions of s in shoots nd in roots grown in soil nd Perlite Neither mycorrhizl inocultion nor s ddition level hd ny significnt effect on the proportion of s in Shoot s concentrtion (mg kg -1 ) 1.80 m C s ddition level (mg kg -1 ) Root s concentrtion in soil (mg kg -1 ) m C s ddition level (mg kg -1 ) Root s concentrtion in Perlite (mg kg -1 ) m C s ddition level (mg kg -1 ) Fig. 4 rsenic concentrtions of Ze mys shoots nd roots (grown in soil nd Perlite) inoculted with Glomus mossee or culospor morrowie or uninoculted. Error rs: ±SE. Lower cse nd indicte significnt differences mong control nd the two mycorrhiz inocultion tretments t the sme s ddition levels. Upper cse, nd C indicte significnt differences mong the three mens t different s ddition levels

8 Plnt Soil (2008) 311: s concentrtion of mtrix solution in soil comprtment (µg cm -2 ) C m c s concentrtion of mtrix solution in Perlite comprtment (µg cm -2 ) C m m s ddition level (mg kg -1 ) s ddition level (mg kg -1 ) s ddition level (mg kg -1 ) s concentrtion of mtrix solution in glss ed comprtment (µg cm -2 ) Fig. 5 Solule s concentrtions in the mtrix solution in different comprtments of the rhizooxes. Error rs: ±SE. Lower cse, nd c indicte significnt differences mong control nd the two mycorrhiz inocultion tretments t the shoots or roots of mycorrhizl plnts grown in soil or Perlite (Tle 2). rsenic percentges in shoots were mostly etween 6 nd 7% nd the vlues for roots grown in soil nd Perlite were pproximtely 90 nd % respectively. Discussion The split-root device used in the present study llowed us to investigte the long distnce trnsloction of s within the plnts nd the possile role of mycorrhizl hyphe in mediting the process. rsenic ws minly retined in the roots grown in the soil mended with s s shown y the higher concentrtion of s in the roots grown in soil compred to shoot s nd roots grown in Perlite (Fig. 4). The proportions of s in shoots nd in roots grown in soil nd in Perlite were pproximtely 6 7, 90 nd % when s ws pplied (Tle 2), indicting tht s ws trnslocted from the roots grown in the s mended soil to the reminder of the plnt prts. However, s trnsloction seemed to e limited y restricted upwrd trnsport of s from roots to shoots nd retention of s in the roots, which hs een suggested to e n effective mechnism for most nonhyperccumultor plnts to tolerte s (hmed et l. 2006; Leung et l. 2006; Mehrg nd Mcnir 1991). In generl, s(v) is tken up y the phosphte trnsporters in the plsm memrne while rsenite sme s ddition levels. Upper cse, nd C indicte significnt differences mong the three mens t different s ddition levels is tken up vi the quglycerolporin chnnel (Mehrg nd Hrtley-Whitker 2002). s(v) cn e reduced to s(iii) in the plnt roots (Qugheeur nd Rengel 2003; We et l. 2003; Xu et l. 2007). On entering the roots, trnsloction of s within the plnt occurs oth symplsticlly nd ppoplsticlly, with common pthwy from roots to xylem, xylem to leves, nd leves to phloem (Cmpos et l. 2004; Wchupe 1983). Inocultion with G. mossee or. morrowie in the comprtment often hd no significnt effect on s concentrtion of hyphe (mg kg -1 ) C m s ddition level (mg kg -1 ) Fig. 6 rsenic concentrtions in hyphe collected from the glss ed comprtment. Error rs: ±SE. Lower cse nd indicte significnt differences etween plnts inoculted with the two mycorrhizl fungi. Upper cse, nd C indicte significnt differences mong the three mens t different s ddition levels

9 242 Plnt Soil (2008) 311: Tle 2 rsenic percentges in Ze mys shoots nd roots (grown in soil nd Perlite) inoculted with Glomus mossee or culospor morrowie or uninoculted s ddition level (mg kg 1 ) Inocultion tretment Shoot-s% Soil root-s% Perlite root-s% 0 G. mossee 7.25± ± ±0.84. morrowie 5.98± ± ± G. mossee 7.33± ± ±1.32. morrowie 7.57± ± ± G. mossee 9.43± ± ±0.94. morrowie 6.78± ± ±1.99 Dt re mens±sd (n=4) shoot or root s concentrtions (Fig. 4) nd this ws unexpected ecuse n increse in shoot P concentrtion ws oserved in mycorrhizl plnts (Fig. 3). If s (V) ws the min form of s trnslocted within the plnts n increse in shoot s concentrtion would e expected. We therefore ssume tht s is very likely trnslocted minly in the form of s (III) lthough the species of s present in the xylem sp ws not determined. Recently Xu et l. (2007) showed tht s (III) ws the dominnt form in xylem sp of Lycopersicon esculentum nd Oryz stiv. y compring two mutnts of ridopsis thlin, nmely pho1 (P deficient) nd pho2 (P ccumultor) with the wild type, the erlier study y Qugheeur nd Rengel (2003) lso suggested tht s(iii) ws the min s species trnslocted nd s ws likely to e trnslocted vi different pthwy to P. The proportions of P in shoots nd in roots grown in soil nd in Perlite were pproximtely within the rnges of 70 77%, 10 14% nd 10 16%, which ws in mrked contrst to the s distriutions in different plnt prts (Tle 2). lthough s nd P re nlogues nd rsente nd P re tken up y the sme phosphte trnsporters in plnt roots, there is growing evidence to indicte tht s nd P in the plnt follow different metolic pthwys. The process of trnsloction of s within plnts nd the involvement of P in the process require further study. Microes detoxify rsente y reduction nd efflux of rsenite (Ghosh et l. 1999; Shi et l. 1999; Mukhopdhyy et l. 2000, Mukhopdhyy nd Rosen 2002; Rosen 2002). Plnts lso hve high cpcity to reduce rsente (Mehrg nd Hrtley- Whitker 2002; Slt et l. 2002; Qugheeur nd Rengel 2003; Dun et l. 2005), nd recently Xu et l. (2007) found tht tomto nd rice roots rpidly reduced rsente to rsenite while some of the rsente nd rsenite were ctively relesed to the medium when plnts were grown in solution culture. Efflux of s from mycorrhizl nd non-mycorrhizl roots ws lso found in the present study nd s concentrtions in the mtrix solution of mycorrhizl plnt roots were significntly lower thn of nonmycorrhizl roots (Fig. 5). The process nd mechnism y which mycorrhizl plnt roots exude less s is uncler nd remins to e investigted. The presence of s in externl mycelium (Fig. 6) indictes tht s ws trnslocted to the hyphe nd cn e deposited in the externl mycelium. In the literture, prt from the P-medited effect on the improvement of s tolernce in mycorrhizl plnts (hmed et l. 2006; Chen et l. 2007; Xu et l. 2008), exclusion of s out of the roots nd sequestering of s y inding on hyphe nd other fungl tissues in the roots hve often een proposed (Trot et l. 2006; Ultr et l. 2007, ) ut hve not yet een unequivoclly demonstrted except for the oservtion of s efflux from the roots of Cllun vulgris infected with Hymenocyphus erice (Shrples et l. 2000) nd Glomus species hve een found to hve strong inding cpcity for Zn nd Cd (Joner et l. 2000). Our study provides some insight into these spects y showing tht mycorrhizl fungi my lter the efflux of s nd s my e deposited in the hyphe. Recent studies y Ultr et l. (2007, ) lso showed tht different s species occurred in the rhizosphere of mycorrhizl plnts compred with non-mycorrhizl controls. The two rusculr mycorrhizl fungi G. mossee nd. morrowie showed similr ffinities to the roots of mize s indicted y the percentges of root length colonized. side from few exceptions, this

10 Plnt Soil (2008) 311: often led to similr effects of inocultion of these two fungi on plnt growth (Fig. 2), enhnced shoot P nutrition (Fig. 3), decresed s efflux into the sustrte (Fig. 5) nd deposition of s in the externl mycelium (Fig. 6). rod rnge of fungl species, prticulrly those fungi which hve dpted to scontminted sites, should e included to further elucidte the involvement of M fungi in s trnsloction within plnts. In conclusion, our results indicte tht s cn e trnslocted within mycorrhizl mize, possily minly in the form of s(iii). Inocultion with rusculr mycorrhizl fungi my lter the efflux of s from plnt roots nd the deposition of s in the externl fungl mycelium, implying possile role for rusculr mycorrhizl hyphe in the detoxifiction of s in the host plnts. cknowledgments This work ws funded y the Ntionl Nturl Science Foundtion of Chin (Projects nd ), the ritish Council (Project DelPHE 1.64) nd the Scientific Reserch Foundtion for Returned Overses Chinese Scholrs, Stte Eduction Ministry. We lso thnk two nonymous reviewers whose helpful suggestions hve gretly improved the mnuscript. References edin MJ, Feldmnn J, Mehrg (2002) Uptke kinetics of rsenic species in rice plnts. Plnt Physiol 128: hmed FRS, Killhm K, lexnder I (2006) Influences of rusculr mycorrhizl fungus Glomus mossee on growth nd nutrition of lentil irrigted with rsenic contminted wter. Plnt Soil 258:33 41 l gely, Sylvi DM, M LQ (2005) Mycorrhize increse rsenic uptke y the hyperccumultor Chinese rke fern (Pteris vittt L.). J Environ Qul 34: Cmpos V, precid M, Pires F (2004) Phytoremovl of rsenic from soil. Commun Soil Sci Plnt nl 35: Chen D, Christie P, Li XL (2001) modified glss ed comprtment cultivtion system for studies on nutrient nd trce metl uptke y rusculr mycorrhiz. Chemosphere 42: Chen D, Christie P, Zhu YG, Smith F, Xie ZM, Smith SE (2007) The rusculr mycorrhizl fungus Glomus mossee gives contrdictory effects on phosphorus nd rsenic cquisition y Medicgo stiv Linn. Sci Totl Environ 379: Dun GL, Zhu YG, Tong YP, Ci C, Kneer R (2005) Chrcteriztion of rsente reductse in the extrct of root nd fronds of Chinese rke fern, n rsenic hyperccumultor. Plnt Physiol 138: Ghosh M, Shen J, Rosen P (1999) Pthwys of s (III) detoxifiction in Scchromyces cerevisie. Proc Ntl cd Sci U S 96: Giovnnetti M, Mosse (1980) n evlution of techniques for mesuring vesiculr rusculr mycorrhizl infection in roots. New Phytol 84: Göhre V, Pszkowski U (2006) Contriution of the rusculr mycorrhizl symiosis to hevy metl phytoremedition. Plnt 223: Gonzlez-Chvez C, Hrris PJ, Dodd J, Mehrg (2002) rusculr mycorrhizl fungi confer enhnced rsente resistnce on Holcus lntus. New Phytol 155: Hrrison MJ, vn uuren ML (1995) phosphte trnsporter from the mycorrhizl fungus Glomus versiforme. Nture 378: Hrrison MJ, Dewre GR, Liu J (2002) phosphte trnsporter from Medicgo truncult involved in the cquisition of phosphte relesed y rusculr mycorrhizl fungi. Plnt Cell 14:1 17 Joner EJ, riones R, Leyvl C (2000) Metl inding cpcity of rusculr mycorrhizl mycelium. Plnt Soil 226: Khn G, Kuek C, Chudhry TM, Khoo CS, Hyes WJ (2000) Role of plnts, mycorrhize nd phytocheltors in hevy metl contminted lnd remedition. Chemosphere 41: Leung HM, Ye ZH, Wong MH (2006) Interctions of mycorrhizl fungi with Pteris vittt (s hyperccumultor) in s-contminted soils. Environ Pollut 139:1 8 Mldondo-Mendoz IE, Dewre GR, Hrrison MJ (2001) phosphte trnsporter gene from the extrrdicl mycelilum of n rusculr mycorrhizl fungus Glomus intrrdices is regulted in response to phosphte in the environment. Mol Plnt Microe Interct 14: Mllrino P, ti M (2005) Correltion of resin memrne soil phosphorus test with corn yield nd routine soil tests. Soil Sci Soc m J 69: Mehrg (2004) rsenic in rice: understnding new disster for South-Est si. Trends Plnt Sci 9: Mehrg, Mcnir MR (1991) The mechnisms of rsente tolernce in Deschmpsi cespitos (L.) euv nd grostis cpillris L. New Phytol 119: Mehrg, Hrtley-Whitker J (2002) rsenic uptke nd metolism in rsenic resistnt nd nonresistnt plnt species. New Phytol 154:29 43 Mehrg, iley J, redmore K, Ncnir MR (1994) iomss lloction, phosphorus nutrition nd vesiculr rusculr mycorrhizl infection in clones of Yorkshire fog, Holcus lntus L (Pocee) tht differ in their phosphte uptke kinetics nd tolernce to rsente. Plnt Soil 160:11 20 Mukhopdhyy R, Rosen P (2002) rsente reductse in prokryotes nd eukryotes. Environ Helth Perspect 110: Mukhopdhyy R, Shi J, Rosen P (2000) Purifiction nd chrcteriztion of cr2p, the Scchromyces cerevisie rsente reductse. J iol Chem 275: Murphy J, Riley JP (1962) modified single solution method for the determintion of phosphte in nturl wters. nl Chim ct 27:31 36 Olsen SR, Sommers LE (1982) Phosphorus. In: Pge L, Miller RH, Keeney DR (eds) Methods of soil nlysis, Prt 2. Chemicl nd microiologicl properties. mericn Society of gronomy nd Soil Science Society of meric, Mdison, WI, pp

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