Potential of calcium silicate to mitigate water deficiency in maize

Transcription

1 DOI: BASIC AREA - Artil Potntil of lium silit to mitigt wtr fiiny in miz Dougls José Mrqus, Mozrt Mrtins Frrir, Alln Klyngr Silv Loto 3, Wllington Alvs Frits, Jinto Assunção Crvlho, Ewrton Dillis Frrir 3, Frnno Brotto *. Univrsi José o Rosário Vllno - Ful Agronomi - Alfns (MG), Brzil.. Univrsi Frl Lvrs - Dprtmnto Ciêni o Solo - Lvrs (MG), Brzil. 3. Univrsi Frl Rurl Amzôni - Instituto Ciênis Agráris - Prgomins (PA), Brzil.. Univrsi Estul Pulist Júlio Msquit Filho - Instituto Bioiênis - Dprtmnto Quími Bioquími - Botutu (SP), Brzil. ABSTRACT: Th im of this stuy ws to vlut th potntil of lium silit to mitigt th ffts of wtr fiiny in miz plnts yil. A ompltly rnomiz ftoril sign, onsisting of fiv omintions of lium silit (, 5, 5, 75, n %) n fiv iffrnt soil moistur lvls (3, 7,, 3, n %), ws opt. Th following prmtrs wr vlut: soil mtri potntil, xylm wtr potntil, silion onntrtion, lf ry wight, n ry mss proution. Mtri potntil monitoring onfirm tht th irrigtion pths mploy rsult in iffrnt nvironmnts for miz plnt vlopmnt uring th xprimnt. Confirming th hypothsis of th stuy, t th lowr irrigtion pths, th miz proution hs ompni th inrs in lium silit us s orrtiv up to th proportion of 5%. Ths rsults init tht silion mitigt th impt of wtr fiiny in miz plnts n inrs th xylm wtr potntil. Ky wors: Dry mttr, irrigtion, silion, strss. INTRODUCTION Th worl popultion is inrsing, spilly in th poorst n most vulnrl ountris of th Thir Worl, whr foo proution is insuffiint to mintin this growing popultion us thy liv in mrginl griulturl rs hrtriz y wtr n nutrint fiiny (Gihl n Wirén ; Rokström n Flknmrk ). Th vlopmnt of strtgis to ru wtr strss in ri n smiri rgions is sustinl ltrntiv to mitigt th ngtiv impts of glol limt hngs. In viw of th omplxity of rought strss, only n pproh tht will onsir soil-plnt-nvironmnt intrtions my gnrt rlvnt knowlg tht n us in th nr futur to gurnt sustinility. Th onitions for th vlopmnt of miz rops wr unfvorl throughout Brzil in 3, sin th rin ror uring rop yl prio ws not suffiint to rplnish soil moistur lvls. Furthrmor, tmprturs ontinu to high, ft whih ontriut to th mintnn of high rts of vpotrnspirtion. As onsqun, mny miz fils in 3 r lry unr th fft of wtr strss, ruing th rop yil potntil (Boltim Agromtorológio Smnl ). Th srity of wtr rsours in onjuntion with glol wrming hs xrt ngtiv ffts on th plnt s griulturl tivity ovr th lst tn yrs (IBGE ). In this rspt, lins of rsrh fousing on th unrstning, hvior n improvmnt of ultivt spis in rspons to inqut nvironmntl situtions hv ptur sustntil rsours n gin mor visiility (Stnsth ). Th inrs in tmprtur u to glol wrming my us losss in miz grin yils of R$ 7. illion lry in numr tht oul ris to R$ illion in 7. Th most pssimisti pritions stimt tmprtur inrs of to 5. C until, n th most optimisti ons stimt n inrs of. to 3. C until (Ass n Pinto ). *Corrsponing uthor: rotto@i.unsp.r Riv: Spt., 5 Apt: D. 7, 5 Brgnti, Cmpins, v. 75, n. 3, p.75-5, 75

2 D. J. Mrqus t l. In Brzil, out % of th miz plnt r, orrsponing to pproximtly.5 million htrs, is fft y rought, rsulting in proution loss of ths rops of mor thn 3.7 million tons. In spifi yrs n pls, rought my vn l to totl proution loss (Durãs t l. ). In orr to mitigt th ffts of ioti n ioti strss, silion xrts svrl spifi funtions (Moro t l. 5), n its sorption y plnts hs svrl nfits, protting ginst slin strss, mtl toxiity, wtr fiit, rition mg, high tmprtur n frost n rgulting nutrint ln. Ths nfiil ffts r ttriut to th high umultion of sili in plnt tissus (M ). Th mhnisms us y plnts in situtions of strss inlu th tivity of nzyms involv in th prottion ginst oxitiv strss, suh s tls, suproxi ismuts, proxiss, n glutthion. Th im of th prsnt stuy ws to vlut th fft of lium silit s n option to mitigt wtr strss in miz rops. MATERIAL AND METHODS Th xprimnt ws rri out t th Dprtmnt of Soil Sin of th Frl Univrsity of Lvrs, Mins Gris, Brzil (lt S; long 5 W; 95 msl), unr grnhous onitions. Ss of Z mys L. (v. BR ) wr us, whih r pt to th onitions of Brzil, hrtriz y plnt hight of. m, r lngth of. m, n yil of 5.5 t h (Emrp 3). Th soil of th rgion is lssifi s R Ltosol-Oxisol (Emrp ).For soil physio-hmil hrtriztion (Tl ), th following propritis wr trmin: ph in wtr (:.5), P n K y Mhlih- xtrtion, Mg n Al xtrtl y M KCl solution, P in th quilirium solution oring to Álvrz t l. (), n lvl of orgni mttr oring to Ann (95). Th soil grnulomtry ws trmin y th piptt mtho. A ompltly rnomiz ftoril sign onsisting of fiv orrtiv omintions (, 5, 5, 75, n % of lium silit init for liming of this soil) n fiv iffrnt soil moistur onitions (3, 7,, 3, n % of mount nssry for wtr rplnishmnt in this soil), with four rptitions, ws us. Th volum of h pot ws 5 L. Tl shows th mounts of lium silit (CSiO 3 ) n lium ront (CCO 3 ) prsnt in th iffrnt omintions. Aitionlly, lium ws ppli in th form of lium hlori (CCl ) to ln th mount of this lmnt in th trtmnts. Aftr trtmnt pplition, th soil ws inut for 5 ys. Mro n mironutrint frtiliztion (Tl 3) ws rri out s sri y Novis t l. (99). Th Chmil omposition of th soil ftr th orrtiv ssoitions is summriz in Tl. Th wtr rtntion urv (Figur ) ws us to wtr hrtriztion of th soil, n t wr ppli in th formuls θ =.5 [ + (. Ψ m ).757 ] n Ψ m = [/α (/m) /n], in grmnt with vn Gnuhtn (9), whr θ is th humiity urrnt (m 3 m 3 ), Ψ m is th tnsion in soil (kp), α, m, n n r prmtrs link to qution justmnt in th mol propos y vn Gnuhtn. Th fil pity ws stimt y qution θ i = (θ s θ r ) [ + /m] m + θ r, s propos y Dxtr (), whr θ i is th humiity in inflxion point of th urv (m 3 m 3 ), θ s is th humiity of sturtion (m 3 m 3 ), n θ r is th humiity rsiul (m 3 m 3 ). Th vlu of humiity lult in fil pity of this stuy ws.35 m 3 m 3 to tnsion of kp. Tl. Chmil n physil ompositions of th soil us in this stuy. ph Chmil P K Si Zn Cu Mn S B F EP C Mg Al H + Al T m V (mg m 3 ) (mg L ) (mmol m 3 ) (%) Physil Sn (%) Silt (%) Cly (%) OM (g kg ) pH in wtr (:.5), P n K y Mhlih- (Bortolon n Ginllo ) xtrtion, Mg n Al xtrtl y M KCl solution (Thoms 9); P in th quilirium solution (EP) oring to Álvrz t l. (); lvl of orgni mttr (OM) oring to Ann (95). Th soil grnulomtry ws trmin y th piptt mtho (Dy 95). T = Ction xhng pity t ph 7.; m = Aluminum sturtion inx; V = Bs sturtion inx (Olsn n Wtn 957). 7 Brgnti, Cmpins, v. 75, n. 3, p.75-5,

3 Silion ting to mitigt wtr fiiny Tl. Amounts of CSiO 3, CCO 3, n CCl us in iffrnt ssoitions. Assoition (%) CSiO 3 (g pot ) CCO 3 (g pot ) CCl (g pot ) Tl 3. Nutrints, rommn mounts, n sours us in frtiliztion in this stuy. Nutrint Conntrtion (mg kg pr soil) Sour N 3 NH H PO P 3 KH PO K KH PO S K SO Mg MgSO 7H O B.5 H 3 BO 3 Cu 7.5 CuSO 5H O Mo.5 (NH ) MO 7 O H O Zn.5 ZnSO 7H O Tl. Chmil omposition of th soil ftr th orrtiv ssoitions. Corrtiv Msurmnts ssoitions CSiO 3 CCO 3 P K EP C Mg Al H + Al T m V OM ph (%) (mg m 3 ) (mg L ) (mol m 3 ) (%) (g kg ) ph in wtr (:.5), P n K y Mhlih- (Bortolon n Ginllo ) xtrtion, Mg n Al xtrtl y M KCl solution (Thoms 9); P in th quilirium solution (EP) oring to Álvrz t l. (); lvl of orgni mttr (OM) oring to Ann (95). Th soil grnulomtry ws trmin y th piptt mtho (Dy 95). T = Ction xhng pity t ph 7.; m = Aluminum sturtion inx; V = Bs sturtion inx (Olsn n Wtn 957). Ψ m (kp),,... θ (m 3 m 3 ).3..5 Figur. Wtr rtntion urv for R Ltosol us in th xprimnt. θ = volumtri wtr ontnt (m 3 m 3 ). Th soil ws irrigt whn th soil wtr tnsion rh vlu of kp t h irrigtion pth (3, 7,, 3, n % of th pth nssry for wtr rplnishmnt in this soil). All msurmnts wr m ily t 5: PM, n soil moistur mtrs (Wtrmrk, mol SS-5) wr instll to quntify th mtri potntil (Figur ) only t th thr highst tnsions (3, 7, n % of il pth). Th wtr volum nssry for irrigtion ws lult y th qution: V = (θ f θ trt ) V soil, whr V is th wtr volum to ppli (ml), θ f is th wtr ontnt t fil pity (m 3 m 3 ), θ trt is th wtr ontnt in th trtmnt (m 3 m 3 ), n V soil is th soil volum (ml). Brgnti, Cmpins, v. 75, n. 3, p.75-5, 77

4 D. J. Mrqus t l. Th ltril onutivity (EC) of th sturt pst xtrt ws trmin s sri y Rihrs (95). Dry mss ws trmin y rying th lvs of miz plnts in n ovn with vntiltion t C until onstnt mss ws otin. Th xylm wtr potntil (Ψ w ) ws msur in fully xpn lvs unr light twn 5: n :3 AM n twn : n : PM, orrsponing to th prwn n miy potntil, rsptivly. Th wtr potntil ws msur with n nlogu plnt moistur systm (Sky Instrumnts, mol SKPM 5/5), whih is s on thnil prssur hmr (Sholnr t l. 9), oring to th prour y Turnr (9). Dt wr sujt to nlysis of vrin. Whn signifint iffrns wr osrv, th Sott-Knott tst ws ppli t p >.5 lvl of rror proility (Stl t l. ). Stnr rrors wr lult for ll mns. All sttistil prours wr rri out using th SAS softwr (SAS Institut 99). RESULTS AND DISCUSSION Figur illustrts th soil mtri potntil t for n ftr irrigtion orrsponing to 3% (Figur ), 7% (Figur ) n % (Figur ) of th rommn irrigtion pth, whil Figur shows th mtri potntil rings otin with th Wtrmrk snsor for irrigtions orrsponing to 3 n 7% of th rommn pth (Figurs,) n th tnsiomtr (% of th rommn irrigtion pth). Bfor irrigtion, th highst rings of soil wtr tnsion wr otin for th trtmnt pplying 3% of th rommn irrigtion pth (Figur ), rnging from 9 to kp. Th tnsion rings rng from to 3 kpa for th pplition of 7% (Figur ) n from 5 to 5 kpa for th pplition of % (Figur ). Th tnsion grint show th sm trn ftr irrigtion; howvr, whn % of th rommn irrigtion pth ws ppli, th soil () () Mtri potntil (kp) Mtri potntil (kp) () Mtri potntil (kp) Irrigtion tim (ys) Irrigtion tim (ys) Mtri potntil (kp) () Bfor irrigtion Aftr irrigtion 3% 7% % Figur. Mtri potntil of soil wtr for n ftr using it for irrigtion pth of 3% (), 7% (), % () n monitoring of th mtri potntil of soil wtr using th Wtrmrk snsor for th pth irrigtion (3 n 7%) n th pth onsir il for tnsiomtr (%) (). 7 Brgnti, Cmpins, v. 75, n. 3, p.75-5,

5 Silion ting to mitigt wtr fiiny wtr tnsion rmin in th rng of 5 to 3 kp, vlu lowr thn th tnsion t fil pity ( kp), i.. th mount of wtr ppli t this pth inrs soil moistur to lvl ov its fil pity. As n sn in Figur, soil wtr tnsion vri oring to th mount of wtr ppli. Th highst tnsion rings wr otin whn 3% of th rommn irrigtion pth ws ppli, follow y 7 n % of th rommn pth. Th stuy of Rsn t l. () srvs s rfrn of th wtr onitions prviling in th stuy r, whih show potntil of 7 kp in Brzilin Crro unr summr onitions n in th smiri rgion t ny tim of th yr, n of 3 kp uring th wintr. It pprs, thrfor, s it ws th ojtiv of th prsnt stuy, tht wtr pplition orrsponing to 3 n 7% of th rommn irrigtion pth inu wtr fiit onitions. This fiit ws muh mor pronoun whn only 3% of th rommn pth ws ppli. Th vrition in ltril onutivity s funtion of th intrtion twn irrigtion pth n proportion of lium silit is shown in Figur 3. Eltril onutivity tn to rs s th mount of wtr ppli inrs, irrsptiv of th proportion of lium silit. Th highst EC vlus wr osrv with th pplition of 3% of th rommn pth, follow y rution to hlf whn 7% of th rommn pth ws ppli. Th lowst vlus wr osrv with th pplition of 3%. Ths rsults show tht th smllr irrigtion pth sms to inrs th onntrtion of slts in soil, with onsqunt inrs in th osmoti potntil of th soil solution. Soil sliniztion n rsult in nutritionl isorrs, inuing ntgonisti rltionships twn nutrints in th plnt, whih signifintly rus rop yils (Grttn n Griv 999). Ths intrtions n lso our twn nutrints in th soil solution, ffting nutrint vilility. Suh intrtions inlu ntgonism, omptitiv n nonomptitiv inhiition n synrgism, vnts tht n hng th ynmis twn tions in th lvs n roots of plnts. Curtro n Frnánz-Muñoz (99) osrv rution in th ry mss of tomto stms, lvs n roots unr onitions of slinity. Th high onntrtion of ions in soil n l to n imln in th wtr n ion potntil t th soil-plnt intrf n n toxi to th plnt, thus ffting its growth n phytomss proution (Ash t l. ) u to th EC (S m ) EC (S m ) EC (S m ) EC (S m ) EC (S m ) y =.x.x +.9 (R =.9*) % Clium silit 5% Clium silit y =.5x.x (R =.99*) % Clium silit y =.7x.5x + 5. Irrigtion (%) 5% Clium silit y =.x.55x +. (R =.9*) 75% Clium silit y =.x.7x (R =.9*) (R =.95*) Figur 3. Soil solution ltril onutivity (EC) s funtion of iffrnt irrigtions in h proportion of lium silit. Brgnti, Cmpins, v. 75, n. 3, p.75-5, 79

6 D. J. Mrqus t l. rution in th sorption of minrl nutrints suh s potssium, lium n mngns (Lutts t l. 999). Figur shows th xylm mtri potntil (Ψ w ) of miz lvs t 3 ( n ) n 75 ( n ) ys ftr plnting oring to th iffrnt proportions of lium silit n irrigtion pths. At 3 n 7% of th rommn irrigtion pth (Figur ), pur lium silit ws suprior thn othr proportions tst. Howvr, whn irrigtion ws inrs to, 3 n % of th rommn pth, th proportion of 5% lium silit ws suprior for rings prform twn 5: n :3 AM. In ontrst, for rings prform twn : n : PM, trtmnt with pur (%) lium silit ws suprior t 3, 7 n 3% of th rommn irrigtion pth, whil % lium silit provi suprior rsults only t % of th rommn pth (Figur ). At 75 ys ftr plnting (Figur ), in th morning (5: to :3 AM), pur lium silit (%) ws suprior for pplition of 3 n 7% of th rommn irrigtion pth. Ths pths r onsir to limiting. Howvr, whn irrigtion ws inrs to, 3 n %, th pplition of % lium silit ws suprior ompr to th othr irrigtion pths. Rgring Ψ w, trmin twn : n : PM (Figur ), for pplition of 3% of th rommn irrigtion pth, th lium silit proportion of 5% provi th highst Ψ w ompr to th othr proportions for th sm trtmnt. Howvr, whn th irrigtion pth ws inrs proportionlly, th pplition of pur lium silit (%) ws suprior to th othr proportions tst. In th prsn of wtr fiit, th plnts us rought tolrn mhnisms suh s osmoti justmnt, in whih th ll sors wtr n mintins th prssur potntil t qut lvls. Th rution in th osmoti potntil in rspons to wtr fiit my () Prwn xylm wtr potnil (MP) Miy xylm wtr potnil (MP) () () Prwn xylm wtr potnil (MP) Miy xylm wtr potnil (MP) () Irrigtion pth (%) Irrigtion pth (%) % 5 % 5 % 75 % % Figur. Xylm wtr potntil (ψ w ) in Z mys (v. BR) 3 ( n ) n 75 ( n ) ys ftr plnting, pning on irrigtion, in iffrnt proportions (, 5, 5, 75, n %) of lium silit. Brgnti, Cmpins, v. 75, n. 3, p.75-5,

7 Silion ting to mitigt wtr fiiny th rsult of th pssiv umultion of soluts s onsqun of hyrtion of th ll or of tiv umultion of soluts; howvr, only th lttr n onsir osmoti justmnt (Ptks t l. ). Approximt lf Ψ w vlus of.5 MP r onsir to qut for goo vlopmnt of miz n sorghum, whil vlu of. MP inhiits photosynthsis n lf growth n.5 MP is th wilting point (Slh n Triu 997; Klr n Porto 99). Aout 95% of th wtr sor y th plnt is us to mintin th thrml ln through trnspirtion. Figur 5 illustrts th trn in lf ry mss proution s funtion of inrsing irrigtion pth for h lium silit proportion. As n sn, lf ry mss inrs with inrsing mount of wtr ppli t th iffrnt irrigtion pths, irrsptiv of th proportion of lium silit. Th trn in ry mss proution oring to irrigtion pth t ll proportions of lium silit n sri y qurti funtions. Lf ry mss rhs mximum vlus with th pplition of 3% of th rommn pth n tns to lin thrftr. Aoring to Mlvolt t l. (997), wtr strss rus lf ry mss proution n rop yil. This rution pns on th xtnt to whih th wtr fiit hs fft th rs of photosynthti tivity n on th rt n gr of rovry ftr th sstion of wtr strss. Consiring th wtr strss onitions inu y th irrigtion pths of 3 n 7%, th lium silit proportions of 5, 75 n % promot th highst proution of lf ry mss. Ths t r importnt sin thy mphsiz th nfit of silion in mitigting wtr strss in miz rops. Th us of th silit-lim omintion, notly th proportion of 5%, monstrt th omplmntrity of ths orrtivs, sin lium silit hs lowr nutrliztion powr thn lim, whih is mor solul. Plnt spis vry in thir pity to sor n umult silion in tissus n n lssifi oring to th prntg of SiO in ry mttr: () umultor plnts ontining mor thn % SiO, whih inlus mny grsss suh s ri; () intrmit plnts with n SiO ontnt rnging from % (rls, sugrn, n fw iotylons); () non-umultor plnts ontining lss thn % SiO, whih inlus most iotylons suh s ns (M n Tkhshi ; Hoson t l. 5). Ths iffrns in silion Lf ry mttr (g plnt ) Lf ry mttr (g plnt ) Lf ry mttr (g plnt ) Lf ry mttr (g plnt ) Lf ry mttr (g plnt ) % Clim silit y =.5x +.7x +. (R =.95*) 5% Clim silit y =.x +.7x + 9 (R =.97*) 5% Clim silit y =.5x +.7x (R =.9*) 75% Clim silit y =.x +.79x + 9. (R =.75*) y =.7x +.3x +. (R =.7*) Irrigtion (%) % Clim silit Figur 5. Lf ry wight of miz plnts (v. BR ), pning on irrigtion, in iffrnt proportions (, 5, 5, 75, n %) of lium silit. Brgnti, Cmpins, v. 75, n. 3, p.75-5,

8 Silion ontnt grin of miz (g kg ) Silion ontnt orno (g kg ) Silion ontnt r strw (g kg ) D. J. Mrqus t l. umultion hv n ttriut to th ility of roots to sor this nutrint (Tkhshi t l. 99), ut th xt mhnism is not fully unrstoo. Figur shows th onntrtions of silion in th stm (), lf (), r husks (), o () n grins () of miz oring to th proportion of lium silit for h irrigtion pth. In gnrl, Si onntrtions in th lf n r inrs with inrsing irrigtion pth, irrsptiv of th proportion of lium silit. In th stm, o n grins, Si onntrtions i not vry twn th irrigtion pths us. Th iffrnt proportions of lium silit in th orrtiv i not fft Si onntrtions in miz stm, o or grins. Most intriguingly, th highst Si onntrtions wr osrv in th stm t 3% of th rommn irrigtion pth, in os t 3% of th rommn pth n in grins in th sn of silit in th orrtiv. On th othr hn, th prsn of lium silit in th orrtiv h positiv ffts on Si onntrtions in lvs n rs. At ll irrigtion pths, Si onntrtions wr ssoit with highr proportions of lium silit. Th grtr Ψ w (Figur ) of miz lvs my xplin th highr silion ontnt of lvs whih inrss th ffiiny of gs xhngs. Ths rsults gr with thos of Hshmi t l. (), who suggst Si to n lmnt tht onfrs grtr rsistn to ioti n ioti strss in plnts. Figur 7 omprs grin proution twn th iffrnt proportions of lium silit oring to irrigtion pth. As gnrl trn, proution inrs with inrsing irrigtion pth. At 3% of th rommn irrigtion pth, highr proution ws osrv for lium silit proportions of 5, 75 n %. In ontrst, t 7% of th rommn pth, grin proution ws highr for th proportions of 5 n 75% lium silit. Ths rsults init tht silion mitigt wtr fiit in miz plnts grown unr wtr strss. For pplitions of, 3 n % of th rommn irrigtion pth, no signifint iffrns in miz proution wr osrv t th iffrnt lium silit proportions tst. In ri, n inrs in grin proution hs n osrv ftr pplition of lium silit, prtiulrly whn th plnts wr xpos to lowr mounts of wtr vill in soil. Thus, th lowr th fil pity of soil, th grtr th rspons of plnts to silion (Moro t l. 5). Th H SiO monomr is th silion ompoun prsnt in th liqui phs of soil in th Silion ontnt stm (g kg ) Silion ontnt lf (g kg ) Figur. Silion onntrtion in th stm (), lf (), r husks (), o () n orn grin () for th iffrnt irrigtion lvls n proportions of silit lium Irrigtion (%) % 5 % 5 % 75 % % Brgnti, Cmpins, v. 75, n. 3, p.75-5,

9 Silion ting to mitigt wtr fiiny Grin proution (g plnt ) Irrigtion (%) % 5 % 5 % 75 % % Figur 7. Grin proution in miz plnts (v. BR ) xpos to fiv orrtiv ssoitions (, 5, 5, 75, n % of lium silit) n fiv irrigtion pths. whih, y ruing trnspirtion (Dtnoff t l. ), lowrs th wtr rquirmnts of plnts. This n xtrmly importnt for plnts growing in tropil soils, whr thy r sujt to ry splls. Photosynthsis plys n importnt rol in rop proution (Wullshlgr n Oostrhuis 99), sin grin yil is potntilly influn y th urtion of th rohyrt umultion rt (Crfts-Brnnr n Ponlit 99). Aoring to Jorn (93), wtr fiit onitions n fft th us of rohyrts silly y ltring th ffiiny t whih photossimilts r onvrt for th vlopmnt of nw prts of th plnt. Wtr fiit uss hngs in rohyrt prtitioning insi th plnt, whih rsults in th vlopmnt of pttion n rsistn mhnisms y th plnts. ph rng of to 9 (Mrshnr 995), whih is sor y plnt roots in pssiv or tiv mnnr mit y spifi mmrn trnsportrs. Mny stuis hv n onut in n ttmpt to ttr pt rops to rgions with limit wtr rsours n to mk thm mor tolrnt to iity (vn Rij t l. 99). Howvr, th yil of spis unr strss lgs hin thir proution potntil, inluing miz, whih is poorly tolrnt to wtr fiit (Silv t l. 9) n whos ultivtion in th smiri rgions of northstrn Brzil is of th utmost importn not only to irtly mt th foo rquirmnts of th popultion, ut lso for th rgionl gro-inustry. Th sorption of Si hs nfits for rops, inluing n inrs in loging rsistn n in photosynthti tivity. Silion is hmil lmnt involv in physil funtions tht rgult vpotrnspirtion n is l to form mhnil rrir ginst fungl n tril invsion of th plnt, s wll s pst inst ttk (Cost t l. 9). This prottiv fft is minly ttriut to th position of Si in th form of morphous sili (SiO nh O) in th ll wll. Th umultion of silion in th stomt ls to th formtion of oul lyr of utiulr sili, CONCLUSION Mtri potntil monitoring onfirm tht th irrigtion pths mploy rsult in iffrnt nvironmnts for miz plnt vlopmnt uring th xprimnt. Confirming th hypothsis of th stuy, it ws foun tht th smllr wtr pths of miz proution wr proportionl to th inrs in lium silit os to th rtio of 5%. Ths rsults init tht silion mitigt th wtr fiit in miz plnts grown unr wtr strss n inrs th xylm wtr potntil. ACKNOWLEDGEMENTS This work ws support through rsrh grnt for D. J. M. y th Coornção Aprfiçomnto Pssol Nívl Suprior (CAPES, Brsíli, Brzil). W lso thnk th Conslho Nionl Dsnvolvimnto Cintífio Tnológio (CNPq, Brsíli, Brzil) for finnil support. REFERENCES Álvrz V., V. H., Novis, R. F., Dis, L. E. n Olivir, J. A. (). Dtrminção uso o fósforo rmnsnt. Soi Brsilir Ciêni o Solo, 5, Ann, P. (95). Sur l osg rpi u ron orgniqu s sols. Annls Agronomiqus,, -7. Ash, F., Dingkuhn, M. n Dorffing, K. (). Slinity inrss CO ssimiltion ut rus growth in fil-grown, irrigt ri. Plnt n Soil,,. Ass, E. n Pinto, H. S. (). Aquimnto glol nov gogrfi proução gríol no Brsil. São Pulo: Emrp; Cpgri. Brgnti, Cmpins, v. 75, n. 3, p.75-5, 3

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