Khaled Mguis 1, 2, 3 *, Ali Albouchi 2, Ayda khadhri 1, Mejda Abassi 2, Mbarka Yakoubi-Tej 4, Asma Mahjoub 3, Zeineb Ouerghi 1 and Nadia Ben Brahim 3

Transcription

1 AJCS 6(5): (212) ISSN: Ajustments in lef wter reltions of wil whet reltive Aegilops geniult Roth. n whet (Tritium urum Desf.) plnts grown in slinity grient Khle Mguis 1, 2, 3 *, Ali Alouhi 2, Ay khhri 1, Mej Assi 2, Mrk Ykoui-Tej 4, Asm Mhjou 3, Zeine Ouerghi 1 n Ni Ben Brhim 3 1 Unit of Physiology n Biohemistry of Slt tolerne of Plnts, Deprtment of Biology, Fulty of Sienes of Tunis, University Tunis El Mnr, 292 Tunis, Tunisi 2 Unit of Agrosylvopstrolism, INERGREF, University of Crthge, Hei krry Street, 28 Arin, Tunisi 3 Botni lortory, INRAT, Hei krry Street, 28 Arin, Tunisi 4 Deprtment of Biology, Fulty of Sienes of Tunis, University Tunis El Mnr, 292 Tunis, Tunisi *Corresponing uthor: k_guigis@yhoo.fr Astrt In orer to stuy slt effet on wil n ultivte whet, three essions of Aegilops geniul Roth. (wil whet) from Ain Zn, Zghoun, n Sitl n vriety of Tritium urum L. (ultivte whet) were grown in greenhouse n trete with ifferent slinity levels. Lef growth, wter reltions, n proline n sugr ontents were mesure for eh plnt t the reproutive stge n nlyze using SAS softwre. T. urum n the three essions of A. geniult respone to sline stress y eveloping voine n tolerne mehnisms. The voine mehnisms took ple t the morphologil n physiologil levels. Morphologilly, reution of lef numer n length were oserve, whih re onsiere s mehnisms tht regulte wter loss vi trnspirtion. Tolerne mehnisms inlue osmoti justment, erese of lef ell elstiity, n n inrese of poplst wter ontent. This stuy showe high vriility in these hrteristis, whih is minly relte to see geogrphil origins. It ws lso oserve tht Sitl ession ws the lest ffete y the impose slt stress (57% t mm) while Ain zn ws the most ffete (84% t mm). Keywors: Aegilops geniult, osmoti justment, P-V urve, slinity, wter reltions, whet. Arevitions: LL, Per-flg lef length; LN, Lef numer; DW, lef ry weight; g s, Stomtl onutne; Ψ p, Pre-wn potentil; Ψ m, Miy wter potentil; AWC, Apoplsti wter ontent ; OA, Osmoti justment; ε mx, Moulus of elstiity; Ψ π, Osmoti potentil t full turgor; Ψ π, Osmoti potentil t turgor loss point; RWC, Reltive wter ontent t loss point. Introution Slinity is omplex environmentl onstrint tht presents two min omponents: n osmoti omponent ue to the erese in the externl osmoti potentil of the soil solution n n ioni omponent linke to the umultion of ions tht re toxi t high onentrtions (minly N + n Cl - ). The umultion of these elements les to erese in essentil nutrient (e.g, potssium n lium) uptke (El-Bssiouny n Bekhet, 1). The most rop speies in the worl re glyophytes; hene, they o not grow uner high soil slinity (Ko et l., 5). However, with n inresing foo emn from the growing humn popultion, the nee to evelop slttolernt rop vrieties is neessry. Therefore, it is ompulsory to ientify the egree of slinity tolerne within rops n their wil-type reltives. Durum whet represents only 8% of totl whet proution ut 8% is growing uner Meiterrnen limtes (Monneveux et l., ). In these regions, slinity onsierly limits its yiel sine its effet is lwys reinfore y those of rought n het. Consequently, speil efforts shoul e me to inrese ioti stress tolerne in this speies (Monneveux et l., ). The genus Aegilops is losely relte to Tritium (Vn Slgeren, 1994). A growing interest hs een evelope in the reent yers to exploit Aegilops spp s importnt geneti resoures for whet improvement (Frooq et l., 1996; Zhriev et l., 1). Aegilops geniult Roth. (= A Aegilops ovte L.) is n nnul, selfing llo-tetrploi speies (2n = 4x = 28) with MU genome (Vn Slgeren, 1994). This speies grows in Meiterrnen regions hrterize y ry summer seson with high temperture n high irrine. As mny other wil speies, they n limte to these onstrints y esping, voiing, or tolerting it (Colmer et l., 6). Plnts my e sujete to environmentl stresses tht versely ffet growth, metolism, n yiel (Lwlor, 2). Their egrees of tolerne vry gretly not only etween speies ut lso etween vrieties. Genotypi ifferenes in rought tolerne oul e ttriute to the ility of plnts to grow (Turtol et l., 6). A thorough unerstning of the physiologil sis of suh ifferene in stress tolerne oul e use to selet or rete new rop vrieties le to inrese proutivity uner suh onitions. A lrge numer of environmentl stresses, suh s rought, slinity, n low temperture my limit rop growth n proutivity y imposing osmoti stress on plnts. Slt stress ereses plnt growth n proutivity y slowing the rte of ell ivision n expnsion minly through loss of turgor, whih results in eline of the wter sttus omponents of the plnt ells (Nvrro et l., 7; Mguis, 21). To ope with this prolem, plnt ells must rejust their osmoti potentil to prevent wter losses either y n uptke of inorgni ions from the externl solution or y e novo synthesis of numer of metolites terme omptile solutes euse 768

2 they o not interfere with iohemil retions (Bohnert et l., 1995). These metolites inlue rohyrtes suh s mnnitol, surose, oligos-hries, nitrogen-ontining ompouns, n mino is. The funtion of omptile solute umultion is often ssoite with osmoti justment y lowering the osmoti potentil (Ψ π ) to improve wter uptke ginst the externl grient (Bohnert et l., 1999). The erese in osmoti potentil (Ψ π ) n result either from simple pssive solute onentrtion resulting from ehyrtion or from net solute umultion. It hs een pointe out tht only the ltter n e regre s tive osmoti justment (Morgn et l., 1991). In mny plnts, net umultion of osmotilly tive solutes llows turgorepenent proesses to ontinue to some extent uner wter stress onitions. Furthermore, tolerne to wter efiits n e improve y inresing intrellulr solute onentrtion y ion uptke (Sholner n Hmmel, 1965). The resulting erese in osmoti potentil llows mngroves to sustntilly lower their xylem wter potentil elow tht of sewter n mintin positive wter uptke y roots (Sholner n Hmmel, 1965). Turgor is known to ply n importnt role in lef physiology (Pssiour, 1994). A positive turgor is neessry to sustin lef growth (MDonl n Dvies, 1996). Turgor mintenne is ffete y hnges in oth osmoti n elsti properties of lef tissue (Dle, 1988). Osmoti potentil t full turgor (Ψ π ) s well s t turgor loss point (Ψ π ) erive from pressure-volume urves hve prove to e relile inies of the osmoti justment ility in plnts (Arms n Kuiske, 1994, Livingston n Von, 1992; Tn n Hogn, 1995). However, the hnges in tissue elstiity re relte to ell turgor, ell imensions, n symplst solute ontent. A numer of reserhes explore wter reltions n osmoti n elsti justment of ifferent rops uner sline stress (Roriguez et l. 5; Nvrro et l., 7). The speifi ojetives were: (1) to evlute lef growth in three essions of A. geniult (Ain zn, Zghoun, n Sitl) n vriety of T. urum (Chili) uner experimentl slinity onentrtions from to mm NCl; (2) to nlyse lef wter reltions; (3) to etermine osmolyte (proline n totl sugrs) ontents in response to inresing externl slinity; n (4) to selet the most tolernt ession in orer to improve whet vrieties. This stuy erive forms prt of lrge whet improvement progrm in Tunisi tht fouses on the use of A. geniult to expn geneti vriility n evelop lternte plnt types through n unerstning of physiologil proesses tht re responsile for its tolerne to slt, rought, n high temperture. Results Vrine nlysis revele highly signifint speies; popultion n tretment effets (Tle 2). Popultion effet ws signifint in ll trits (leves growth, stomtl onutne, wter reltions n osmolytes ontents). Inee the fourteen trits showe signifint ifferene (P <.5) etween Aegilops essions n whet vriety initing high level of geneti vriility (Tle 2). This inlue three lef growth (LL, LN n DW), stomtl onutne (g s ), eight wter reltions trits (Ψ p, Ψ m, Ψ π, Ψ π, OA, RWC, ε mx n AWC) n solute onentrtions (proline n totl solule rohyrtes). The fourteen prmeters were signifintly ffete y the slt tretments (P <.5). Popultion X tretment intertions were lso etete for ll trits exept Apoplsti wter ontent (AWC) initing vrile performne of popultions in ifferent slt levels Lef growth n iomss For ll sline levels, the length of pre-flg lef showe ler ifferene etween the three Ae.geniult essions n urum whet vriety (Tle 3). Inee, whet plnts present the most elevte lef length ompre to the Ae.geniult plnts. Ae. geniult Sitl ession presente the most elevte lef length n Ain zn popultion isplye eh vlue. The lef length ereses progressively with inresing stress (Tle 3). However, t mm NCl, preflg lef length ws reue to 67, 58, 5 n 55% for Ain zn, Zghoun, Sitl n whet vriety (Chili) respetively ompre with the plnts ontrol. Inresing NCl reue signifintly lef numer. However, the reution epene on the NCl level. In ft, t mm, lef numer ws reue to 78, 67, 56 n 68 % for Ain zn, Zghoun, Sitl n whet vriety (Chili) respetively, ompre with the plnts ontrol. In three Ae. geniult essions n whet vriety slinity inue erese in the totl lef iomss (Tle 3). However, ler ifferenes were note etween whet n Ae geniult, n etween Aegilops essions. At the reproutive stge, totl lef iomss ws reue t mm NCl y 8, 72, 66 n 77 % for Ain zn, Zghoun, Sitl n whet vriety (Chili) respetively, ompre with the ontrol. Stomtl onutne Miy stomtl onutne (g s ) in pre-flg lef ws similr mong the three Aegilops essions in the ontrol, ut g s in this tretment ws higher in the Whet vriety `Chili`. g s erese progressively with inresing slt onentrtion (Fig. 1). Inee, t mm these ereses of g s were 89; 82; 77 n 85% for Ain zn, Zghoun, Sitl n whet vriety `Chili` respetively. Wter reltions Pre-wn lef wter potentil (Ψ p ) n Miy lef wter potentil (Ψ m ) of the pre-flg lef of ll Ae. geniult essions n whet vriety were reue to similr extent y slinity. Ψ p n Ψ m in ontrol were lower in the whet vriety thn in Aegilops essions (Fig. 2). However, the effet of slinity on Ψ p n Ψ m ws similr with the two speies. An inresing NCl tretment le to erese Ψ p n Ψ m. Uner slt stress Ain zn ession h the highest lef wter potentil, ompre Zghoun n Sitl. However, whet h the lest vlues of Ψ p n Ψ m. At mm, Ψ p rehe -,87, -,95, -1,9 n MP n Ψ m ws -2.76, -2.87, n MP respetively for Ain zn, Zghoun, Sitl n whet vriety (Chili). Osmotique potentil t the loss point (Ψ π ) n t the full trugor (Ψ π ) of the pre-flg lef in the three essions of Ae. geniult n ultivr of whet erese signifintly with inresing of onentrtions of NCl (Figs. 3, ). In ft, Ψ π n Ψ π showe similr vlues in the plnts ontrols of Ae. geniult essions n whet vriety. However, from 5 Mm NCl, the height inrement in Sitl ession ws lower thn Ain zn. Ae. geniult essions n whet n e rrnge in 769

3 Tle1. Aessions of Aegilops geniult Roth. n hrteristis of sites of origin. Coe es essions Site Provine Altitue (m) Rinfll (mm) Biolimti re AZ Ain Zn Kroumirie Su-humi Z Zghoun Dorsle Uper semi ri S Sitl Centre Uper ri Tle 2. Summry of nlysis of vrine for 1 growth, wter sttut, n gs exhnge trits of three Ae. geniult Roth essions `Ain zn, Zghoun n Sitl` n urum Whet vriety `Chili` grown uner ifferent slinity levels (, 5,,, mm) t Arin, Tunisi. Prmeters Ar Popultion (Pop) Soures of vrition Tretment Pop & Tr (Tr) Growth prmeters Per-flg lef length LL 74.93** 21.7** ** Leves numer LN 27.34** 12.94** ** Totl leves ry weight DW 4.31** 31.45**.45** Gs exhnge prmeters Stomtl onutne g s.63**.327**.12** Wter reltions Pre-wn potentil Ψ p ** **.598* Miy wter potentil Ψ m 1.6** 68.58** 1.95** Apoplsti wter ontent AWC ** 78.28** 9.55 ns Osmoti justment OA.28**.771**.3* Moulus of elstiity ε mx 1.119** 5.657**.159*** Osmoti potentil t full turgor Ψ π.43**.33**.38** Osmoti potentil t turgor loss point Ψ π.892**.775**.31** Reltive wter ontent t loss point RWC 61.14** ** 1.987** Solute umultions Solule rohyrte 73.76** ** 7.37** Proline 81.4** ** 9.7** F-proilities re inite y symols, ns = non signifint ifferenes t.5. * = signifint ifferene t p <.5. ** = signifint ifferene t p <.1. the following orer on the se of osmoti potentil: `Ain Zn`> `Zghoun` > whet > `Sitl`. The lower vlues of Ψ π (Fig. 3) showe n osmoti justment (OA) in stresse rther thn in ontrol plnts. In the three essions of Ae. geniult n whet ultivr, OA inrese with inresing of NCl onentrtions (Fig. 3). However, ler ifferenes etween Ae. geniult n whet were note. For ll slt level, the higher vlues of OA ws notie in Sitl n the lower in Ain Zn. Whet ultivr n Zghoun ession showe intermeiry ehviours. In three essions of Ae. geniult n whet, the reltive wter ontent t the turgor loss point (RWC ), the volumetri moulus elstiity (ε mx ) n the poplsti wter ontent (AWC) inrese signifintly with n inrese of slinity (Figs. 3, e, f). Nonetheless ler ifferenes were oserve etween essions of Ae. geniult n ultivr of whet. In ft, for ll NCl onentrtions, the higher vlues of RWC n ε mx otine in Ain Zn ession n the lower in Sitl (Figs. 3, e). In ontrst, Sitl showe the gretest inrement of AWC n Ain Zn the lest. Whet ultivr n Zghoun ession showe intermeiry ehviours (Fig. 3f). Osmolytes umultion Proline n totl solule rohyrtes onentrtions in ontrol weren t ifferent etween Ae. geniult n whet. The slt stress provoke mrkely umultion of proline n totl solule rohyrtes. However, from mm NCl, strongly iffere etween popultion (Tles 2 n 4). In ft, the highest ontents were reore in Sitl followe y Zghoun, whet n finlly Ain Zn. Disussion Sustntil vrition ws oserve in our stuy for trits relte to the pttion of Ae. geniult Roth n whet to slt stress. However, eh popultion ehve ifferently uner the influene of ifferent slt tretments. The vrition mong speies n essions for growth leves, wter reltion n orgni solutes ws minly expline y geogrphil origin, suggesting tht those trits re minly onstitutive n result from nturl pressure seletion exerte y the limti onstrints (Tle 2). Although t were otine from plnts grown in pots, the result n e relte to in situ performne. Sitl ession, whih is etter pte to nturlly ourring slt stress, ws more tolernt to experimentlly n impose slt experiment stress thn Ain Zn n Zghoun essions. Ain Zn ws the most sensitive to the slt stress. Growth of oth speies (whet vriety n the three Aegilops geniult Roth essions) erese with n inresing slt stress s inite y efore-flg lef length, lef numer n totl leves ry weight (Tle 3). This ws oserve in other speies, suh s whet (Mhr et l., 3; Munns et l., 3; El-Bssiony et l., 5) n Olive (Gui et l., 1996). The results reporte y Munns n Rwsn (1999) in whet showe tht sline stress generlly ppers y wek growth, reution of re n numer of leves n n elertion of senesene of the mture leves. Besies, Crmer n Qurrie (2) in mize note tht slt stress reue the evelopment of the 77

4 Ψp (MP) Ψm (MP) gs (mol CO2 m-² s -1 ) -,5-1 -1,5 -,5-1 -1,5-2 -2,5-3 -3,5,35,3,25,2,15,1,5, 5 NCl (mm) A Zn Sitl Zghoun Fig 1. Stomtl onutne (gs) of three Ae. geniult essions `Ain zn., Zghoun n Sitl` n urum Whet vriety `Chili` grown uner ifferent slinity levels (, 5,,, mm NCl) the t re men vlues of four replitions with three mesurements per replite n vertil rs re LSD.5. NCl (mm) Blé 5 A zn Zghoun Sitl whet NCl (mm) 5 A zn Zghoun Sitl whet Fig 2. () Pre-wn (Ψ p ) n () miy (Ψ m ) lef wter potentil for three Ae. geniult essions `Ain zn., Zghoun n Sitl` n urum Whet vriety `Chili` grown uner ifferent slinity levels (, 5,,, mm NCl) the t re men vlues of four replitions with three mesurements per replite n vertil rs re LSD.5. erils prts y inhiition of the pprition of new leves. The oserve reution in plnt iomss might e ue to omintion of slow growth n evelopment s result of osmoti stress (Shni n Ben-Gl, 5). Nonetheless, the reution in lef re n e onsiere s voine mehnisms minimising wter losses when stomt re lose n whih hppens to mny speies uner osmoti stress (Blum 1986; Své l., 1994; Ruiz-sháhez et l., ). Uner sline onition it is known tht the reution in totl lef re n e expline y erese in lef turgor, hnges in ell wll proprieties or erese photosynthesis rte (Frno et l., 1997). In our onitions, it oul e ue to ell wll hnges n erese in the photosynthesis rte, euse Ψ π vlues re reue (Figs. 3, ) n the net ssimiltion rte erese (Mguis, 21). Inee, t the reproutive stge, slinity stress mrkely inhiite the lef wter potentils (Ψ p n Ψ m ), the stomtl onutne (g s ) n the osmoti potentil (Ψ π n Ψ π ). Similr results were foun on whet (Rivelli, 2), Plntgo ronopus (Koyro, 6), Arutus uneo (Nvrro et l., 7). The highest Ψ p n Ψ m ws foun in Ain zn ession s well s in the tow uthor essions of Zghoun n Sitl. Low vlues were foun in whet (Fig. 2). For instne, the existene of ifferene etween Ψ p n Ψ m vlues suggeste tht some reovery in lef wter potentil took ple uring the night. In three essions of Ae. geniult n whet, stomtl onutne erese (Fig. 1) proportionlly Ψ m (Fig. 2) with n inrese of NCl, whih n inites tht sline stresse plnts hve pity to fvour wter sorption n to onserve. For instne the strong orreltion (r 2 =.98, p <.1) whih ws oserve etween gs n Ψm (Fig. 4) suggeste tht lef wter potentil ws the min ftors inuing stomtl losure. However, stomt lose uner slinity in response to soiltolef hemil signls (Jmes et l., 2, LeNole et l. 4), lef wter potentil (Nvrro et l., 7) or lef speifi hyruli onutivity (Shultz, 3). On the other hn, the grul losure of the stomt in slt stress over wie rnge of Ψm my e importnt to mintin some level of photosynthesis (Své l., 1994). The erese Ψπ Contriutes to mintin positive ell turgor t lower wter potentils. Nonetheless, the reue Ψπ oul e ttriute to osmoti justment following eprture from pure wter to the ehyrtion of tissues n / or n tive umultion of solutes. The first hypothesis n e epte s lower Ψπ (Fig. 3) is ompnie y n inrese RWC (Fig. 3) n the seon hypothesis will e isusse lter. The oserve shrp erese in lef osmoti potentil t full turgor (Ψπ ) in trete plnts of three Ae. geniult n whet inite the ility of those plnts to evelop osmoti justment uner sline onitions (Fig. 3). However, the retion of those plnts ws ifferent. Uner ll NCl onentrtions, Sitl ession showe high umultion of osmoti ompouns n lso with the mehnisms of physiologil pttion to rought followe y Zghoun ession n whet whih showe intermeite ehvior. The highest Ψπ were otine from Ain Zn ession (Fig. 3).The osmoti justment whih ours through slt umultion in plnt uner sline stress is less energeti n emning thn the justment of inorgni ions n orgni solutes my perform osmoti justment (Netono et l., 4; Munns et l., 6), proline n glyine etine (Yng et l., 199). In the three Ae. geniult essions n whet the effet of sltiness ours y high umultion of solule rohyrtes n proline in leves (Tle 4). Thus, uner ifferent slt tretments, the highest umultions of solule sugrs n proline were showe in Sitl ession n the 771

5 Tle 3. Pre-flg lef length (LL) in m of the tgge tillers, leves numer (LN, numer of leves emerge in prinipl tiller) nt totl leves ry weight (DW) (men ± SE., n = 8) of three Ae geniult essions `Ain zn, Zghoun, Sitl` n one urum Whet vriety `Chili` grown uner slt stress (, 5,,, mm) onitions. Slinity levels Ae Ain Zn Ae Zghoun Ae Sitl Whet LL mm 9.21 ± ± ± ± mm 6.5 ± ± ± ± 1.4 mm 4.92 ± ± ± ± 2.9 mm 3.72 ± ± ± ± 1.92 mm 2.99 ± ± ± ± 2.17 LN mm 9 ± 1 9 ± 1 9 ± 1 12 ± 2 5 mm 6 ± 1 8 ± 1 8 ± 1 9 ±1 mm 4 ± 1 5 ± 1 6 ± 1 7 ± 1 mm 3 ± 1 4 ± 1 5 ± 1 5 ± 1 mm 2 ± 1 3 ± 1 4 ± 1 4 ± 1 Lef DW mm 3.86 ± ± ± ±.93 5 mm 2.73 ± ± ± ±.52 mm 1.67 ± ± ± ±.48 mm 1.18 ± ± ± ±.31 mm.78 ± ± ± ±.47 Tle 4. Solute onentrtions in leves (men ± SE., n = 4) of three Ae geniult essions `Ain zn, Zghoun, Sitl` n one urum Whet vriety `Chili` grown uner slt stress (, 5,,, mm) onitions. Slinity levels Ae Ain Zn Ae Zghoun Ae Sitl Whet Proline ontent (µmol. g -1 MS) mm 1.5 ± ± ± ± mm ± ± ± ± 1.47 mm ± ± ± ± 2.22 mm ± ± ± ± 1.77 mm ± ± ± ± 2.45 Solule rohyrtes (µmol. g -1 MS) mm ± ± ± ± mm ± ± ± ± mm ± ± ± ± mm ± ± ± ± mm ± ± ± ± lowest umultions were reore in Ain Zn, while Zghoun n whet showe intermeite umultions. Nevertheless, the Strong reltionships oserve etween umultion of proline n the erese of Ψ π (r 2 =.92, p <.1) n etween inreses of totl rohyrtes n ereses of Ψ π (r 2 =.96, p <.1) suggeste the involvement of those elements in mintining the osmoti lne (Figs. 4, ). Similr effets hve een reporte in mny speies suh s, whet (Rivelli et l., 2; Tmussi et l., 5), sorghum (Netono et l., 4), Arutus uneo (Nvrro et l., 7). The slt stress inue signifint erese in lef ell elstiity (tht is, the ulk moulus of elstiity, ε mx, inrese) in the three Ae. geniult n whet (Fig. 3e). An inrese in ε mx, tene to enhne reltive wter ontent t zero turgor (RWC). However, osmoti justment ompenste for this effet. Inrese ε mx onomitnt with osmoti justment is n effetive mens of ounterting the negtive effets of osmoti stress on wter lne (Nvrro et l., 7). An inrese in ε mx (stiffness) is expete when the ell wlls eome more rigi or thiker (Stuiver et l., 1978; Kuiper, 1984). This inrese is oserve to e higher in the tolernt ession (Sitl) followe y Zghoun, whet, n Ain Zn. The greter stiffness of the ell wll, given n equl erese in ell volume, will e responsile for the rop in wter potentil. These sltiness relte hnges in tissue elstiity of three Ae. geniult n whet ession le to n ltertion in the reltionship etween turgor pressure n ell volume whih might ontriute to slinity tolerne. Similr results were showe in whet (Rivelli et l., 2), in Cornus stolinifer (Jennifer n Sylvi, 4), Arutus uneo (Nvrro et l., 7). On the other hn in fourth popultions (three Ae. geniult essions n whet ultivr), the slt stress lso provoke signifint inrese in poplst wter ontent (AWC) ompre with ontrols vries with the ultivr or ession n the intensity of stress (Fig. 3f). Inresing wter reserve of poplst omprtment oul e ttriutle to thiker ell wlls or reues ell volume (Cutler n Rins, 1978) y umultion of mterils suh s hemiellulose (Rsio et l., 1992) n slts (Chorro et l., 1993). For instne, Wter poplst protets tissues ginst wter loss from symplst (Tyree n Jrvis, 1982) n this seems to prove tht in whet n Ae. geniult, the inrese of poplst wter plye role in mintining or inresing the turgiity. This ehvior woul hve uffer role uring the instlltion of wter efiit to preserver wter symplst. In onlusion, the Ae. geniult essions provies germplsm tht hs the potentil of rop improvement; it elongs to the wil speies. Wil relte speies hve een onsiere until now muh more s soures of resistne to pests n iseses thn s soures of iversity permitting eep moifition of rhiteture n physiology of the 772

6 Fig 3. Wter reltion prmeters erive from P-V urve nlysis: () the osmoti potentil t zero trugor (Ψ π ), () the osmoti potentil t full trugor (Ψ π ), () the osmoti justment (OA), () the reltive wter ontent t the turgor loss point (RWC ), (e) the volumetri moulus elstiity (ε mx ) n (f) the poplsti wter ontent (AWC)of three Ae. geniult essions `Ain zn., Zghoun n Sitl` n urum Whet vriety `Chili` grown uner ifferent slinity levels (, 5,,, mm NCl) the t re men vlues of four replitions with three mesurements per replite n vertil rs re LSD.5. ultivte speies. There re initions tht Ae. geniult Roth n ontriute useful genes for slt tolerne (Monneveux et l., ). Systemti pprohes to inrese the level of ioti stress tolerne require the evlution of geneti vriility in Ae. geniult Roth gene pool, within n mong essions. In this stuy, lrge vrition for sltstress tolerne ws foun within essions. Single popultion suh s Sitl or Ain zn or Zghoun tht exhiit rih growth n wter reltions iversity my provie vlule resoures for trits of gronomi importne. The slt-stress tolernt ientifie in the Ae. geniult essions n whet vriety `Chili` my e omine with reeing lines exhiiting high yiel potentil. Genotypi nlysis in the omintion with physiologil stuies is require to estlish whether the slt-stress-tolernt lines re similr, i.e. the sme mehnisms. If ifferent mehnisms re ientifie there will e potentil for reomining these for further improvement. Mterils n methos Plnt Mterils The three A. geniult essions originte from Ain Zn, Zghoun, n Sitl (Tle 1) were ollete on lrge rnge of limti onitions n t ifferent ltitues. The 773

7 gs (mole m -2 s -1 ) Proline ontent (µmol.g -1 MS) Solule rohyrtes, µmol.g -1 MS ,4,3,2,1 y = -,1613x +,522 R 2 =,98*** 5 5 Ψm (MP) Ain Zn Sitl -1-1,5-2 -2,5 5 Zghoun whet Fig. 4. Reltionship etween lef onutne (gs) n miy lef wter potentil (Ψ m ) of three Ae. geniult essions `Ain zn., Zghoun n Sitl` n urum Whet vriety `Chili` grown uner ifferent slinity levels (, 5,,, mm NCl) the t re men vlues of four replitions with three mesurements per replite n vertil rs re LSD Ain Zn Sitl Zghoun whet ,25-1,5-1, ,25 Ain Zn Sitl 5 Ψπ (MP) Zghoun -3 y = 123,14x - 152,79 R 2 =,92*** Blé ,25-1,5-1, ,25 Ψπ (MP) y = 99,728x - 24,491 R 2 =,96*** Fig 5. Reltionships etween umultion of proline n osmoti potentil t full trugor (Ψ π ) n etween totl solule rohyrtes n osmoti potentil t full trugor (Ψ π ) of three Ae. geniult essions `Ain zn., Zghoun n Sitl` n urum Whet vriety `Chili` grown uner ifferent slinity levels (, 5,,, mm NCl) the t re men vlues of four replitions with three mesurements per replite n vertil rs re LSD.5. -3,5 urum whet vriety (Chili) ws provie y the Cerel Lortory of the Ntionl Institute of Agronomi Reserh of Tunis (INRAT). It is n ol n preoious vriety tht hs high length verge (12 m). It slows lte (2 ys fter moern one) n low yieling. Furthermore, it is suseptile to loging ys to heing n it is one of the most nient slt-tolernt vrieties (Mmouri et l., 1998). Growing onitions Experiments were rrie out uring (9-21) in greenhouse t the INRAT in Arin (Northest Tunisi t 1 m ove se level). See sowing ws performe in pots of 28 m of imeter n 25 m of height. The pots were fille with mixture of 5% lom n 5% sn. After replenishment of the pots, 1 sees per pot were sowe in homogeneous wy to epth of 2-3 m, n fter emergene (7 ys), seeling numer per pot ws reue to 6. During the first seven ys, pots were wtere ily with tp wter while ing the neessry volume to ring soil to its fiel pity. Therefter, pots were wtere twie week. Slt tretment strte when the seeling h pproximtely 3 to 4 leves (4 weeks fter sowing). Soium hlorie ws e in four onentrtions: 5,,, n mm. Prior to slt tretment, nutrient solution ws supplie inste of wter. The nutrient solution ws prepre oring to Ms et l. (1986). Pots were irrigte t eh stge of plnt evelopment with nutrient solution. The experiment ws set up s ompletely rnomize esign of five slt levels, four popultions (three Aegilops essions n one urum whet vriety) n four replites. Eh pot (six seelings) ws onsiere s one replite. Hene, eh tretment ontine 24 seelings per ession or vriety. Mesurements Mesurements were me t intervls of 6 or 7 ys etween 6: n 8: h, eginning t the heing stge (16 weeks fter emergene) n ontinuing uring the flowering one. Lef growth prmeters The pre-flg lef length (LL) in "m" of the tgge tillers n lef numer (LN, numer of leves emerging from the prinipl tiller) of Aegilops essions n the urum whet vriety were mesure. After hrvest, leves were seprte n rie for 3 ys t 7 C for ry-weight (DW). Mesurements were tken from eight plnts (2 plnts per replite) per popultion n per tretment. Stomtl onutne Stomtl onutne (g s, mol m -2 s -1 ) ws mesure t miy for similr numer n type of leves s for lef wter potentil using stey-stte promoter (LI 16, LI- COR In.). Lef wter reltions Wter potentil Lef wter potentil ws mesure pre-wn (6: m) (Ψ p ) n t miy (Ψ m ) for one mture lef of the tgge tillers (pre-flg leves) per plnt n per replite (n = 4 mesurements per tretment) using pressure hmer (Soil Moisture Equipments Corp., Snt Brr, CA, USA) following the reommentions of Turner (1988). 774

8 Pressure-volume (P-V) urves P-V urves were etermine using the Sholner pressurehmer tehnique (Sholner n Hmmel 1965). The P-V urves of eh lef were otine y expressing the reltionship etween reltive wter ontent (RWC) vlues n the reiprols of the mesure wter potentils (-1/Ψw). Osmoti potentil t full turgor (Ψ π ) ws estimte vi liner regression of t in the stright-line region of the P-V urve. Osmoti potentil t the turgor loss point (Ψ π ) ws erive from the RWC n -1/ Ψw oorintes respetively of the first point in the stright-line region of the P-V urves (Ptks n Notskis 1999). The osmoti justment (OA) ws efine s the ifferene in Ψ π etween stresse n ontrol plnts. OA = (Ψ π ) stresse - (Ψ π ) ontrol The poplsti wter ontent (AWC) or interellulr wter is estimte from the extension of the liner prt to the xis (OX) (Girm n Krieg, 1992). It tells out the no isple wter (Rithie n Roen, 1985). The reltive wter ontent t the turgor loss point (RWC ) ws otine from the extension of the intersetion of urve n liner portions (Wilson et l., 1979). The volumetri moulus elstiity (ε) ws lulte s the slope of the reltionship etween turgor pressure n RWC (Ptks n Notkis, 1999). ε mx = (Ψ t Ψ t ) x (1- AWC) / (1- RWC ) Reltive wter ontent (RWC) ws etermine on three to four fully expne leves. Leves were exise efore wn, weighe freshly (FW) n ple in vils to rehyrte in the rk for 2 h. Preliminry experiments h inite tht full rehyrtion ws omplete fter 18 h. The next morning, lef turgi weight (TW) ws mesure n then leves were rie t 8 C for 48 h n ry weight (DW) ws etermine. The RWC ws lulte from the eqution: RWC = [(FW - DW)/(TW - DW)]. Osmolytes ontents Proline ws etermine following the ninhyrin metho esrie y Btes et l. (1973), using L-proline s stnr. Proline in the test smples ws lulte from stnr urve prepre ginst L-Proline (5-3 µg, from MERCK KGA): (y =.59x -.14, R 2 =.99). The ontent of totl solule rohyrtes in the stuie smples ws etermine oring to M Crey et l. (195) n Stu (1963), using gluose s stnr. From the stnr urve, the onentrtions of solule rohyrtes in the test smples were lulte (y =.95x -.299, R 2 =.979). Sttistil Anlysis The experiment ws omplete rnomize esign onsisting of five slinity tretments, four popultions (three Aegilops essions n one urum whet vriety) n four replites. The t were nlyze using pproprite proeures of the SAS softwre 6.12 (Khwrizmi Center, Tunis version 1998). Anlysis of vrine (ANOVA) ws performe with the sttistil progrm Minit (Minit In.; College Prk), involving two levels of lssifition (slinity n popultion) with intertions. A Dunn s multiple rnge test ws rrie out to etermine if signifint (P <.5) ifferene ourre etween essions n tretments. Referenes Arms MD, Kuiske MD (1994) Synhronous hnges in tissue wter prmeters of mture folige from wellwtere n perioilly roughte tree seelings. J Exp Bot 45: Btes LS, Wlren RP, Tere ID (1973) Rpi etermintion of free proline for wter stress stuies. Plnt n Soil 39: Blum A (1986) Slinity resistne In: CRC (e): Plnt Breeing for Stress Environments. Press, Bo Rton Bohnert HJ, Nelson DE, Jensen RG (1995) Apttion to environmentl stresses. Plnt Cell 7: Bohnert HJ, Su H, Shen B (1999) Moleulr mehnisms of slinity tolerne. In: Shinozki K, Ymguhi-Shinozki K ( ets) Moleulr Responses to Col, Drought, Het n Slt Stress in Higher Plnts. Lnes RG Compny. Aust. TX Chorro P, Ortiz A, Cer A (1993) Growth, wter reltions n solute omposition of Phseolus vulgris L. uner sline onitions. Plnt Si 95: Colmer TD, Flowers TJ, Munns R (6) Use of wil reltives to improve slt tolerne in whet. J Exp Bot 57: Crmer GR, Qurrie SA (2) Asisi i is orrelte with the lef growth inhiition of four genotypes of mize iffering in their response to slinity. 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