CRITICAL OSMOTIC, IONIC AND PHYSIOLOGICAL INDICATORS OF SALINITY TOLERANCE IN COTTON (GOSSYPIUM HIRSUTUM L.) FOR CULTIVAR SELECTION

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1 Pk. J. Bot., 42(3): , 21. CRITICAL OSMOTIC, IONIC AND PHYSIOLOGICAL INDICATORS OF SALINITY TOLERANCE IN COTTON (GOSSYPIUM HIRSUTUM L.) FOR CULTIVAR SELECTION M. FAROOQ HUSSAIN MUNIS 1, LILI TU 1, KHURRAM ZIAF 2, JIAFU TAN 1, FENGLIN DENG 1 AND XIANLONG ZHANG 1, * 1 Ntionl Ky Lortory of Crop Gnti Improvmnt, Huzhong Agriulturl Univrsity, Wuhn, Hui 437, PR Chin 2 Collg of Hortiultur n Forstry, Huzhong Agriulturl Univrsity, Wuhn, Hui 437, PR Chin. *Corrsponing uthor E-mil: xlzhng@mil.hzu.u.n Tl.: ; fx: Astrt Slinity ffts th grmintion, growth n ultimtly th yil of otton (Gossypium hirsutum L.) whih mns rlil trits for th vlution n sltion of slt tolrnt ultivrs. Hr, tn mjor osmoti, ioni n physiologil prmtrs hv n stui to istinguish th fft of slinity in two iffrnt ultivrs of otton. Plnts wr grown in hyroponi systm n xpos to iffrnt slinity lvls of NCl follow y its rovry unr non slin onitions. Dt ws ror t thr iffrnt stgs i.., for strss, ftr strss n ftr rovry for omprtiv stuy. Rovry ssy prov to vry hlpful in xtrting rlil rsults. Both ultivrs show signifintly iffrnt rspons to N + n K + umultion n phnotypilly slt tolrnt ultivr (Cokr 312) umult lss N + n mor K + in omprison with susptil (Simin 3). Drs in lf r, s grmintion n sling growth wr lso onlusiv to iffrntit ths ultivrs. W lso foun othr physiologil prmtrs lik rltiv lf wtr ontnt (RLWC), plnt frsh-wight (PFW), plnt ry-wight (PDW), rltiv growth rt (RGR) n stomtl hvior s goo initors of slinity ut oul not fin thir signifint rol to iffrntit two losly rlvnt ultivrs rgring slinity tolrn. Our stuis rvl tht prolin umultion n hlorophyll onntrtion r not signifint to us s urt initors to hrtriz th snsitivity of otton ultivrs to slinity. W foun post-rovry nlysis to vry usful in unrstning th rol n hvior of iffrnt initors of slinity. Introution Cotton is mjor rop wily grown in mor thn 8 ountris for fir n oil purposs. It is pl in mortly slt tolrnt group of plnt spis (Ashrf, 22). Unr fil onitions, slin soils n inu stunt growth of otton. Lvs of slt fft otton plnts r smllr n rk lu grn in olor thn th norml lvs n th plnts xhiit pprns similr to moistur strss onitions. Aoring to urrnt survy, mor thn 8 million htrs of ln throughout th worl r slt fft (Anon., 28). Slinity ffts plnt mtolism y isturing physiologil n iohmil prosss of plnts u to ioni n osmoti imlns whih rsults in th rution of plnt growth n proutivity (Munns, 25). Plnts lso hv pt svrl mhnisms to op with ths strss onitions. For slt tolrn, rtin inorgni ions lik K + n N + n orgni osmolyts lik prolin ply ky rols. Plnts n prott thmslvs from slt toxiity y mintining highr K + ontnt n K + /N + rtio (Khn t l., 29) n/or orgni soluts (Roriguz t l., 1997). Slt tolrn hs lso n rport to irtly rlt with th umultion of prolin (Munns n Tstr, 27).

2 1686 M.F.H. MUNIS ET AL., Lik othr osmolyts, prolin umultion is propos to rspons of N + omprtmnttion in vuols y tonoplst N + /H + ntiportrs tivity. If N + n Cl r squstr in th vuol of ll, orgni soluts tht r omptil with mtoli tivity (lik prolin) umult in th ytosol n orgnlls to ln th osmoti prssur of th ions in th vuol (Munns, 25). Grmintion n rlist vlopmntl stgs r vry ritil whih mks s grmintion ssy nssry for th ssssmnt of th rspons of ultivr unr strss nvironmnt. Th impt of slt strss hs lso n orrlt with som morphologil n physiologil trits lik rution in frsh n ry wight (Chrtzoulkis & Klpki, 2), hlorophyll ontnts (Zif t l., 29) n stomtl losur (Zhu, 21). Th n to spify istintiv rlil initors for slting slt tolrnt gnotyps (lins/vritis) of ommrilly importnt rops (Ashrf & Hrris, 24) provok us for this stuy. Th im ws to (1) sort out rlil osmoti, ioni n physiologil initors of slinity in otton, (2) to stuy rovry of otton rop ftr slt strss, n (3) to iffrntit two ultivrs rgring slt snsitivity. Mtrils n Mthos Plnt mtril: W slt two ultivrs of otton, (Cokr 312 n Simin 3) to s th fft of slinity on s grmintion n plnt growth. Both ultivrs r plnt unr iffrnt soil onitions us thy r ky ultivrs for somti mryognsis (Zhng t l., 21; Khn t l., 26) with Amrin n Chins origin, rsptivly. Ss of h ultivr wr ot n surf striliz with.1% (w/v) quous mruri hlori (HgCl 2 ) solution for 1 minuts n thn wsh four tims with striliz istill wtr. Ths striliz ss wr ultur in 1 ml flsks (four ss pr flsk) h ontining 15 ml of hlf-strngth MS (Murshig & Skoog, 1962) mium for grmintion n kpt t 28 C with 14/1 h (light/rk) photoprio for 8 ys. Hyroponi systm for slt strss: Eight ys ftr grmintion, slings wr trnsfrr to th Styrofom supports n pl on hyroponi tnks ( ft) ontining hlf strngth Hogln s Solution (Hogln & Arnon, 195) with onstnt rtion. Plnts wr grown on hlf strngth Hogln s solution without strss untill th mrgn of 3-4 tru lvs n thn xpos to, 5, 1, 15 n 2 mm onntrtion of NCl in th Hogln s solution y ing NCl to th nutrint solution in 5 mm inrmnts vry 24 h, until th finl onntrtions wr rh. Nutrint solution ws hng wkly. Aftr 21 ys strss, ll plnts wr provi with hlf strngth Hogln s solution (without slt) for thr wks for rovry ssy. S grmintion n sling growth: To hk s grmintion prntg n sling lngth unr slt strss onition, 2 ss of h vrity wr sown in hlfstrngth MS mi with, 5, 1, 15 n 2 mm NCl onntrtion. Grmintion prntg ws lult 1 ys ftr sowing. A s ws onsir grmint t th mrgn of th ril (Chrtzoulkis & Klpki, 2). Avrg lngth of slings ws msur in ntimtrs ftr tking n wshing sling out of mi. Prolin stimtion: To nlyz th umultion of prolin unr slt strss, iffrnt plnt tissus inluing sling roots, plnt roots n plnt lvs wr wigh n fr prolin ontnt ws trmin oring to stnr protool (Bts t l., 1973).

3 CRITICAL INDICATORS OF SALINITY TOLERANCE IN COTTON 1687 K +, N + nlysis: Th ri root n lf smpls wr groun to powr n thir K + n N + ontnts wr trmin oring to Xu t l., (26). Chlorophyll onntrtion/stimtion: Th hlorophyll ontnts wr trmin oring to Arnon (1949). Frsh lvs wr xtrt with 8% ton, ntrifug n sorn of th suprntnt ws r t 645 n 663 nm using sptrophotomtr (DU 8 UV/Visil Sptrophotomtr, Bkmn Coultr, In. USA). Lf rltiv wtr ontnt: Lvs wr ollt from th plnts n wigh s frsh mss (FM). Ths wr flot in istill wtr for 24 hours until fully imi, n thir turgi mss (TM) ws ror. Smpls wr thn pl in vuum ovn t 8 C for 48 hours to otin ry mss (DM). Lf rltiv wtr ontnt ws lult s: LRWC (%) = [(FM-DM)/(TM-DM)] 1. Plnt iomss n rltiv growth rt: Four plnts of h ultivr wr slt rnomly n tgg. Frsh wights of ths slt plnts for n ftr strss n ftr rovry wr ror. Rltiv growth rt ws lult oring to Evns (1972). For ry wight, rnomly thr plnts wr slt ftr strss n rovry stgs, ovn-ri t 65 C for 1 wk n ry wight ws ror. Lf r: Aftr strss, 5 plnts unr h strss trtmnt wr slt rnomly n lf r of th iggst lf from h plnt ws trmin y using LI-31C Ar Mtr (LI-COR Biosins, LI-COR, in. Linoln, Nrsk, USA) n vrg. Stomtl hvior: Siz n onition of stomt on th lvs, ftr 21 ys of strss ws osrv on trnsprnt nil vrnish lf imprssion unr mirosop (DM25, Li, Wtzlr, Grmny) t 4 mgnifition n imgs wr photogrph. Exprimntl ly out n sttistil nlysis: Th xprimnt ws li out in ompltly rnomiz sign with 3 rplits, h hving t lst 4 plnts. Th t wr sujt to two wy nlysis of vrin (slinity ultivr) using Sttisti (vrsion 5.5 ) n mns wr ompr y DMR tst (p<.5). Rsults Grmintion n sling lngth is fft y slinity: Both two ultivrs of otton show vrition in s grmintion prntg t 1 mm n highr slinity lvls. Consirl loss in grmintion prntg ws ror t 1 mm NCl onntrtion in Simin 3 (25% rs) whil for Cokr 312 it ws t 15 mm NCl (2% rs). At highst slinity lvl (2 mm NCl), grmintion ws 7% in Cokr 312 n 6% in Simin 3. Inrsing slt onntrtion impos grul lin in sling lngth in oth ultivrs (Fig. 1 n 2A). Avrg sling lngth of Simin 3 ws mor thn Cokr 312 in th sn of slt strss ut t h slinity lvl, it ws osrv lss thn Cokr 312 (Fig. 1 n 2A). Aumultion of orgni n inorgni soluts: Slinity inrs N + ontnt n rs K + ontnt s wll s K + /N + rtio in th roots of slings, 1 ys ftr

4 1688 M.F.H. MUNIS ET AL., sowing in oth ultivrs (Tl 1; Fig. 2B-C). Comprtiv stuis rvl high N + ontnt, low K + ontnt n low K + /N + rtio in Simin 3 in omprison with Cokr 312 uring sling growth. At 5 mm NCl strss, 5.79 n 6.49 fol inrs in N + ontnt whil 29.79% n 21.47% rs in K + ontnt ws osrv in Cokr 312 n Simin 3, rsptivly. At 2 mm NCl onntrtion in nutrint solution, Simin 3 h 1.18 tims highr N + ontnts thn Cokr 312, in th sling roots whil K + ontnts of Cokr 312 wr 1.61 tims mor thn Simin 3 (Fig. 2B-C). Sm kin of hvior ws osrv in th lvs n roots of oth ultivrs ftr trting thm t iffrnt slinity lvls for 21 ys. Mximum N + lvls (24.87 mg/g DW n mg/g DW) wr osrv t 2 mm NCl in Cokr 312 n Simin 3, rsptivly. In roots, thr ws n rupt inrs in N + in Cokr 312 n Simin 3 t 5 mm NCl lvl of slinity (Fig. 3A2). Thr ws slow rs in K + ontnt in th lvs n roots of oth ultivrs n thy show signifint iffrns in K + umultion in roots t 2 mm NCl with Cokr 312 ontining 1.41 tims mor K + ontnt thn Simin 3 (Fig. 3B2). In th lvs, 44.1% n 34.85% rs in K + ontnt ws ror in Cokr 312 n Simin 3, rsptivly t 2mM NCl (Fig. 3B1). In oth ultivrs, stp fll in K + /N + rtio ws osrv with th inrs of slinity (Tl 1). Minimum K + /N + rtio in oth ultivrs ws ror t 2 mm NCl in ll thr tissus (sling roots, plnt lvs n plnt roots). Signifint iffrns in K + /N + rtio twn Cokr 312 n Simin 3 wr lso osrv in ll plnt prts (Tl 1). Rovry ssy prov usful in inrsing K + /N + rtio in th lvs of oth ultivrs trt t 5 n 1 mm NCl. Roots of Cokr 312 show signifint inrs in K + /N + rtio ftr rovry from 5, 1 n 15 mm NCl whil Simin 3 just mng signifint inrs in K + /N + rtio in th plnts trt t 5 n 1 mm NCl lvls of slinity (Tl 1). Enognous lvl of prolin inrs in oth ultivrs unr inrs slinity lvls. Prolin umultion ws mor in Cokr 312 ( µg/g FW) thn Simin 3 ( µg/g FW) t 2 mm NCl uring sling growth (Fig. 2D). A shrp inrs in prolin ontnts ws osrv t 5 mm NCl in th lvs of oth ultivrs whil thr ws omprtivly grul inrs in prolin ontnts in roots (Fig. 3C1-C2). In Cokr 312, mximum prolin ws msur ( µg/g FW) t 15 mm NCl in roots whil lvs umult mximum prolin t 1 mm ( µg/g FW) t pr with 2 mm NCl (18.9 µg/g FW). In Simin 3, prolin pil up mor in lvs t 5 mm NCl ( µg/g FW) with signifint flutution in th susqunt slinity lvls. On th othr hn, mximum prolin in roots (17.27 µg/g FW) ws osrv t 2 mm NCl. Post-strss plnt rovry prolin stimtion rvl signifint rs in prolin Cokr 312 Simin 3 Fig. 1. Slings of two otton ultivrs, grown on hlf-strngth MS mium t iffrnt slinity lvls. Two onsutiv slings rprsnt on of th fiv slinity lvls, whih vry s, 5, 1, 15 n 2 mm NCl onntrtions, from lft to right.

5 CRITICAL INDICATORS OF SALINITY TOLERANCE IN COTTON 1689 A B Fig. 2. Sling lngths (A), N + (B), K + (C) n prolin ontnt (D) msur in sling roots, 1 ys ftr s sowing t iffrnt slinity lvls. Sm lttrs (,,,,, f n g) init non signifint iffrn t p<.5 y DMR tst. Vrtil rs rprsnt stnr rror of mns (n=3). N + ontnt (mg/g DW) Prolin ontnt (ug/g FW) K + ontnt (mg/g DW) Sliing lngth (m) K + ontnt (mg/g DW) A1 C CPR S SPR Pr Strss Pr Strss Lf Pr Strss B1 C1 C NCl onntrtion (mm) Cokr 312 Simin 3 f Cokr 312 Simin NCl onntrtion (mm) fg fg N + ontnt (mg/g DW) K + ontnt (mg/g DW) Prolin ontnt (ug/g FW) Fig. 3. N + (A1, A2), K + (B1, B2) n prolin ontnt (C1, C2) in th lvs n roots of two ultivrs unr iffrnt slt strss lvls. C: Cokr 312, CPR: Cokr 312 post rovry, S: Simin 3, SPR: Simin 3 post rovry. Vlus follow y th sm lttrs (,,,,, f n g) r not signifintly iffrnt from h othr whil strisks () on CPR n SPR r init signifint post rovry iffrn from th sm lvl of slinity t p<.5 y DMR tst. (n=3). N + ontnt (mg/g DW) Prolin ontnt (ug/g FW) D A2 Pr Strss Pr Strss Root i h f gh fg NCl onntrtion (mm) Pr Strss B2 C2 Cokr 312 Simin Cokr 312 Simin NCl onntrtion (mm) f g Cokr 312 Simin 3 Fig. 4. Efft of iffrnt slinity lvls on lf r. Lvs t, 5, 1, 15 n 2 mm NCl slinity r pl from lft to right rprsnting two iffrnt ultivrs of otton.

6 169 M.F.H. MUNIS ET AL., Tl 1. K + /N + rtio in th sling roots, plnt lvs n plnt roots of Simin 3 n Cokr 312 unr fiv slt trtmnts (n=3). NCl K + /N + K + /N + Plnt tissu Cultivr (mm) (Post Strss) (Post rovry) Cokr Sling root Simin f f ** Cokr ** f.79 Plnt lf ** Simin ** g h ** Cokr ** ** Plnt root ** Simin ** f.61 In h of thr tissus (sling root, plnt lf n plnt root), th vlus rprsnt y th sm lttr r not signifintly iffrnt from h othr whil strisks (**) in K + /N + post rovry olumn init signifint post rovry iffrn t tht prtiulr lvl of slinity t p<.5 oring to th DMR tst. Sling Root: roots of slings 1 ys ftr s grmintion on MS mium, Plnt Lf n Plnt Root: lvs n roots of plnts grown in Hogln s solution for NCl strss n rovry h ontnt in th roots of oth ultivrs sujt to 1, 15 n 2 mm NCl strss (Fig. 3C1-C2), whil ftr rovry from 5 mm NCl, Cokr 312 h non-signifint inrs n Simin 3 show signifint rs in prolin ontnts lik othr slinity lvls (Fig. 3C2). In th lvs, rovry ssy us signifint rs in prolin umultion t 1 mm n 2 mm NCl in Cokr 312 whil in Simin 3 thr wr non signifint hng in prolin ontnt t ll slinity lvls xpt signifint inrs t 2 mm NCl onntrtion (Fig. 3C1).

7 CRITICAL INDICATORS OF SALINITY TOLERANCE IN COTTON 1691 A D Rltiv Growth Rt Plnt Dry Wt (g/plnt) fg fg C CPR S SPR g h B Plnt Frsh Wt (g/plnt) E Chlorophyll (mg/g FW) Pr Strss f 4 g 4 2 h Pr St rs s NCl onntrtion (mm) NCl onntrtion (mm) NCl onntrtion NCl (mm) Lf Ar (m ) Fig. 5. Physiologil hngs unr slt strss in two ultivrs of otton. C: Cokr 312, CPR: Cokr 312 post rovry, S: Simin 3, SPR: Simin 3 post rovry. Vlus follow y th sm lttrs (,,,,, f, g n h) r signifintly similr whil strisks () on CPR n SPR r init signifint post rovry iffrn from th sm lvl of slinity t P<.5 y DMR tst. Numr of rplits r thr (for A, C n F), four (for B n D) n fiv (for E). C F RLWC (%) A B C D Fig. 6. Visul osrvtion of inrs in numr n rs in siz of stomt t 4 mgnifition. A n C rprsnt stomt in th plnts t mm NCl whil B n D show stomt t 2 mm NCl in Cokr 312 n Simin 3, rsptivly. Moultion of morphologil n physiologil trits: Inrs in slinity ru lf r in oth ultivrs (Fig. 4). In omprison with ontrol ( mm NCl), thr ws signifint rution in lf siz t 1 mm NCl in oth ultivrs ut it ws mor prominnt in Simin 3 thn Cokr 312. At 2 mm NCl strss, 7.94% n 81.17% rution in lf r ws foun in Cokr 312 n Simin 3, rsptivly (Fig. 5E). Inrs slinity lso us rution in plnt frsh wight (PFW) n plnt ry wight (PDW), whih onsquntly fft rltiv growth rt (Fig. 5A-C). At 2 mm NCl onntrtion, ultivr Cokr 312 show 62.8% n 61.4% whil Simin 3 xhiit 69.3% n 75.1% rution in PFW n PDW, rsptivly, in omprison with ontrol (Fig. 5A-B). During rovry prio, Cokr 312 mng to inrs PFW

8 1692 M.F.H. MUNIS ET AL., signifintly in th plnts prviously xpos to 5 mm n 1 mm NCl slinity ut Simin 3 just isply signifint PFW inrs t 5 mm NCl strss (Fig. 5B). During rovry ssy, oth ultivrs show sm hvior of inrs in PDW in th plnts trt t 5 n 1 mm NCl onntrtion ut signifint rs in PDW ws osrv in th plnts of Simin 3 sujt to 2 mm NCl strss (Fig. 5A). Rltiv growth rt (RGR) rs signifintly n Simin 3 xhiit ngtiv growth rt t 15 mm n 2 mm NCl. In Cokr 312, RGR ws lso ngtiv t 2 mm NCl initing rs in PFW t ths slinity lvls (Fig. 5C). Chlorophyll ontnts flutut t iffrnt lvls of slinity in oth ultivrs (Fig. 5D). Mximum hlorophyll ontnts (1.39 mg/g FW n 1.42 mg/g FW) wr hiv t 5 mm n 1 mm NCl slinity in Simin 3 n Cokr 312, rsptivly. Cokr 312 xhiit signifintly highr hlorophyll ontnts thn Simin 3 t 1 n 15 mm NCl. In oth ultivrs, rovry ssy h no signifint influn on hlorophyll ontnts. A grul rs in rltiv lf wtr ontnts (RLWC) ws osrv with inrs in slinity (Fig. 5F). Thr ws 23.8% n 3.8% rs in RLWC in Cokr 312 n Simin 3, rsptivly t 2 mm NCl slinity lvl. Rovry trtmnt i not fft RLWC in oth ultivrs. W lso osrv rs in stomtl siz n inrs in its frquny in oth ultivrs t iffrnt lvls of slinity whih ws mor prominnt t 2 mm NCl (Fig. 6). Disussion Slinity is on of th mjor yil limiting ftors in otton. With slinity thrshol lvl of 7.7 S m 1, otton is lssifi s slt-tolrnt rop ut its tolrn vris grtly mong gnotyps (Ashrf, 22). In this stuy, w vlut iffrnt ioni, osmoti n physiologil initors of slinity to hk thir rol in th sltion of otton ultivrs unr slt strss onitions. W foun ru s grmintion % n sling growth unr slt strss in oth ultivrs. Similr rsults hv lry n rport in otton (Chhr t l., 28). Our omprtiv stuis rvl tht Cokr 312 umult lss N + n highr K + ontnt thn Simin 3 whih my rson of gnotypi iffrns mong ultivrs (Mloni t l., 21). This ioni ln is min rson for strss tolrn us N +, Cl - n K + r th prinipl inorgni soluts unr slt strss onitions (Roriguz t l., 1997) n th mintnn of K + n N + homostsis is vry ruil unr slt strss (Zhu, 23). This rs in N + my u to th omprtmnttion of N + us vuolr squstrtion of N + not only lowrs N + onntrtion in th ytoplsm ut lso ontriuts to osmoti justmnt to mintin wtr uptk from slin solutions. Othr orgnlls, suh s plstis n mitohonri, my lso umult som N + n thus ontriut to th ovrll sullulr omprtmnttion of N + (Zhu, 23). High N + ontnt, low K + ontnt n low K + /N + rtio in Simin 3 in omprison with Cokr 312 unr slt strss onitions rvls it slt susptil vrity. This lso onfirms K + /N + rtio s rlil inx of slinity in otton. Slt Strss inrs th lvl of prolin in oth ultivrs whih hs lry n rport in otton unr slin onitions (Mloni t l., 21). Aumultion of orgni soluts (lik prolin) in highr onntrtions hs n rport to non-toxi to ytoplsmi funtions, llowing turgor mintnn n/or prottion of mromolulr struturs (Ashrf & Hrris, 24). W foun inrs prolin ontnt unr slin onitions ut thr ws grt flutution t iffrnt slinity lvls in oth ultivrs whih my rlt to th vrition in th onntrtion of K + n othr omptil soluts us its inrs pns on th onntrtion of othr soluts (Munns & Tstr, 28). On th sis of our rsults, w onlu tht prolin is prou in otton lvs n roots in rspons to slt strss ut this rspons n not onsir

9 CRITICAL INDICATORS OF SALINITY TOLERANCE IN COTTON 1693 s isrt ritrion to slt ultivr for slt rsistn. Som othr stuis (Lutts t l., 1999; Munis t l., 21) lso ngt th rliility of prolin s n initor of slinity. Thr ws grul rs in plnt frsh wight, plnt ry wight n lf r in oth ultivrs with inrsing slinity. This rs in growth might rson of too muh N + in th solution whih rsults in ly mturity of th rop (MConnll t l., 28). Drs in lf r ws signifint mong ths two ultivrs whih my hlpful in iffrntition n sltion of ttr ultivr. This rs in lf r my ttriut to th umultion of N + n othr inorgni soluts us th ultivr Cokr 312, showing mor rsistn to rs in lf r, umult lss N + thn othr on (Simin 3). Rution in plnt frsh wight n plnt ry wight hs n rport y Zif t l., (28), whih strngthn our rsults. Both ultivrs show signifint rs in RLWC t iffrnt slinity lvls ut w foun non-signifint iffrns within ultivrs t th sm lvl, whih onlu tht RLWC is n initor of slinity ut it ws not goo nough to iffrntit otton ultivrs us in our xprimnt. Lf hlorophyll ontnts wr inrs in oth ultivrs unr strss ut this flutution in hlorophyll ontnts ws not squntil. Furthrmor, rovry ssy i not rvl ny signifint inrs in th hlorophyll ontnts. In onlusion, hlorophyll ontnt ws not foun s goo prmtr, u to unvn vrition in hlorophyll onntrtion t iffrnt slinity lvls in oth ultivrs. Inrs numr of stomt with rs in thir siz unr slt strss is possily u to rs in sp flow n turgiity of gur lls in rspons to slt strss in orr to mintin thir wtr sttus (Roinson t l., 1997). Thus, on th sis of stomtl losur, ultivrs n iffrntit for thir slinity tolrn. Though stomtl siz n numr r lso fft y light intnsity n position of lf on th plnt, still lvs of iffrnt ultivrs grown unr similr onitions n us for this stuy. W oul not msur stomtl siz n frquny us thr ws grt vrition t iffrnt rs of vry lf in oth ultivrs whih ns sprt omprhnsiv stuy to sort out th most fftiv tim n r of th lf for tting slinity ffts. Conlusion On th sis of our rsults, w foun N + n K + ontnt, rs in lf r, s grmintion n sling growth s th st initors of slinity in otton for ultivr sltion. RLWC, plnt frsh wight, plnt ry wight, rltiv growth rt n stomtl hvior r goo prmtrs ut not goo nough to iffrntit ultivrs with nrrow gnotypi iffrns rgring slt tolrn. Prolin n hlorophyll onntrtion wr not usful for urt ssssmnt of slinity tolrn in otton ultivrs. Aknowlgmnts This work ws support y Ntionl Nturl Sin Fountion of Chin (Grnt No ) n th Ntionl Cotton Proution Th-support Progrm (Ministry of Agriultur, Chin). Rfrns Anonymous. 28. FAO. Arnon, D.T Coppr nzym in isolt hloroplsts, polyphnloxis in Bt vulgris. Plnt Physiol., 24: Ashrf, M. 22. Slt tolrn of otton: som nw vns. Crit. Rv. Plnt Si., 21: 1-32.

10 1694 M.F.H. MUNIS ET AL., Ashrf, M., n P.J.C. Hrris. 24. Potntil iohmil initors of slinity tolrn in plnts. Plnt Sin, 166: Bts, L.S., R.P. Wlrn n I.D. Tr Rpi trmintion of fr prolin for wtr strss stuis. Plnt Soil, 39: Chhr Q.I., A. Solngi n A. Vrhof. 28. Influn of soium hlori on s grmintion n sling root growth of otton (Gossypium hirsutum L.). Pk. J. Bot., 4: Chrtzoulkis, K., n G. Klpki. 2. Rspons of two grnhous pppr hyris to NCl slinity uring iffrnt growth stgs. Sinti Hort. 86: Evns, G.C Th quntittiv nlysis of plnt growth. Univrsity of Cliforni Prss, Brkly n Los Angls, Cliforni, pp Hogln, D.R. n D.I. Arnon Th wtr-ultur mtho for growing plnts without soil. Agriulturl Exprimnt Sttion Bulltin 347. Brkly, CA: Univrsity of Cliforni. Khn, M.A., S.N. Qurshi, S. Sh, J.N. Jnkins, C.L. Brukr n O.U.K. Ry. 26. Usfulnss of SSR riv from ttrploi Gossypium spp. for nlyss of iploi Gossypium spp. J. Crop Imp., 16: 1-2. Khn, M.A., M.U. Shirzi, M.A. Khn, S.M. Mujt, E. Islm, S. Mumtz, A. Shrn, R.U. Ansri n M.Y. Ashrf. 29. Rol of prolin, K/N rtio n hlorophyll ontnt in slt tolrn of wht (Tritium stivum l.). Pk. J. Bot., 41(2): Lutts, S., V. Mjrus n J.M. Kint NCl ffts on prolin mtolism in ri (Oryz stiv) slings. Physiol. Plntrum, 15: MConnll, J.S., P.B. Frnis, C.R. Strk n R.E. Glovr. 28. Plnt rsponss of ultr nrrow row otton to nitrogn frtiliztion. J. Plnt Nutr., 31: Mloni, D.A., M.A. Oliv, H.A. Ruiz n C.A. Mrtinz. 21. Contriution of prolin n inorgni soluts to osmoti justmnt in otton unr slt strss. J. Plnt Nutr., 24: Munis M.F.H., L. Tu, F. Dng, J. Tn, L. Xu, S. Xu, L. Long n X. Zhng. 21. A thumtin-lik protin gn involv in otton fir sonry ll wll vlopmnt nhns rsistn ginst Vrtiillium hli n othr strsss in trnsgni too. Biohm. Biophys. Rs. Commun. oi:1.116/j.r Munns, R. 25. Gns n slt tolrn: ringing thm togthr. Nw Phytol., 167: Munns, R., n M. Tstr. 28. Mhnisms of slinity tolrn. Annu. Rv. Plnt Biol., 59: Murshig, T., n F. Skoog A rvis mium for rpi growth n iossys with too tissu ulturs. Physiol. Plntrum, 15: Roinson, M.F., A-A. Vry, D. Snrs n T.A. Mnsfil How n stomt ontriut to slt tolrn? Ann. Bot., 8: Roriguz, H.G., J.K.M. Rorts, W.R. Jorn n M.C. Drw Growth, wtr rltions n umultion of orgni n inorgni soluts in roots of miz slings uring slt strss. Plnt Physiol., 113: Xu, C.X., Y.L. Liu, Q.S. Zhng n Z.P. Liu. 26. Silit improvs growth n ion sorption n istriution in Alo vr unr slt strss. J. Plnt Physiol. Mol. Biol., 32: Zhng, B.H., R. Fng, F. Liu n Q. Wng. 21. High frquny somti mryognsis n plnt rgnrtion of n lit Chins otton vrity. Botnil Bulltin of Ami Sini, 42: Zhu, J.K. 21. Plnt slt tolrn. Trns Plnt Si., 6: Zhu, J.K. 23. Rgultion of ion homostsis unr slt strss. Curr. Opin. Plnt Biol., 6: Zif, K., M. Amj, M.A. Prvz, Q. Iql, I.A. Rjwn n M. Ayu. 29. Evlution of iffrnt growth n physiologil trits s inis of slt tolrn in hot pppr (Cpsium nnuum L.). Pk. J. Bot., 41(4): (Riv for pulition 21 July 29)