SEASONAL VARIATION IN PRODUCTIVITY OF ATRIPLEX STOCKSII FROM A COASTAL MARSH ALONG THE ARABIAN SEA COAST

Transcription

1 Pk. J. Bot., 41(3): , 29. SEASONAL VARIATION IN PRODUCTIVITY OF ATRIPLEX STOCKSII FROM A COASTAL MARSH ALONG THE ARABIAN SEA COAST FARHAT AGHA 1, BILQUEES GUL 2 AND M. AJMAL KHAN 2* Deprtment of Botny, University of Krhi, Krhi-7527, Krhi, Pkistn 1 DHA College for Women, Defense Housing Authority, Krhi, Pkistn 2 Institute of Sustinle Hlophyte Utiliztion, University of Krhi, Krhi-7527, Pkistn. Astrt The produtivity of Atriplex stoksii popultion loted ner the ost (Gizri Creek) of Krhi, Pkistn ws studied for two yers. The net iomss prodution showed sesonl vrition nd produtivity ppered to e influened y rinfll during oth yers. Belowground nd ove ground iomss showed no hnge during the dry yer, however, onsiderle iomss ws produed fter the vilility of moisture. The ove ground ded iomss remined unhnged during ut it registered sustntil promotion during the wet seson. The ion onentrtion of root ws muh higher thn shoot. N + nd Cl - remined high however, the onentrtion of other ions did not hnge muh during oth sesons. Root fresh weight ws signifintly promoted t low slinity nd inrese in slinity inhiited root nd shoot growth. Fresh weight of shoots t low density ws not ffeted y low slinities, however, t higher slinity onentrtions there ws no effet of density. Root fresh nd dry weight were higher t low density nd low slinity, however under high slinity, density hd no effet. Suulene on dry weight sis ws lso higher t higher densities. However, suulene deresed sustntilly t high slinities on per plnt sis. Shoots of A. stoksii umulted lrge quntities of N + nd Cl - wheres other ions were found in lower mount. N + nd Cl - in root inresed ut were muh lower in omprison to shoot. Introdution Atriplex stoksii Boiss., is short, roust perennil shru distriuted in oth inlnd nd ostl mrshes nd deserts round Krhi, Pkistn. Costl speies reeive rre sewter inundtion, nd oth ostl nd inlnd popultions either tp underground wter soures or rely on monsoon rins tht ome during July nd August. Seeds germinte fter monsoon rins nd survivorship is high. Dormnt plnts eome tive nd produe vegettive prt immeditely, flowers nd fruits fter out 3 dys nd seeds fter 6 dys nd eome dormnt gin. The primry prodution of slt mrshes is ssoited with the hnges in soil slinity, nutrients, limte, mrsh physiognomy, sedimenttion proesses nd hnges in se level reltive to the lnd (Irlndi et l., 21; Msini et l., 21; Sntos & Esteves, 22; Tyler, 23; He et l., 27; Regn et l., 27). Slt mrshes re rnked mong the most produtive eosystems in the world nd rnge from out 2-2 g.m -2 yr -1 (Keenish, 1986). Net nnul primry produtivity (NAPP) estimtes for slt mrsh emergent s rnges pproximtely etween 1 nd 4 g dry weight m -2 yr -1 ut most reords of iomss re round 1-2 gm -2 yr -1 (Odum et l., 1984). The pttern of umultion of oveground iomss differs for eh mrsh nd is different every yer whih rnges from pproximtely 3 to 4 g.dw.m -2 yr -1 (Gllgher, 1978). Higher plnt densities hve higher prodution of lef iomss per unit re nd lower densities result in lower rnh dimeter nd n inresed proportion of lef produtivity in * Corresponding uthor: E-mil: mjmlk@uok.edu.pk; Phone: , Fx:

2 154 FARHAT AGHA ET AL., stnding iomss (Mittelh et l., 21). In hereous ommunities, elowground iomss n e 4% of the totl iomss nd in some ses where niml grzing is high, net produtivity (NP) n e underestimted when sed only on stnding rop-iomss (Pling & MCom, 2). Costl vegettion in nd round Krhi is dominted y shrus nd perennil grsses nd their distriution seems to e ontrolled y the degree nd frequeny of inundtion, rinfll nd soil type (Khn & Gul 22). Atriplex stoksii usully oupies the dunes nd those prts of the ostl vegettion whih re rrely inundted y sewter nd usully survive on the sewter seepge using n extensive rhizome system where ompetition ppers to ply little role in shping these hitts. Slt tolerne of the speies found in the re is highly vrile nd rnges from 25 ds.m -1 to 1 ds.m -1. Hlopyrum murontum ould tolerte up to 2 ds.m -1 NCl (Khn et l., 1999). Sporoolus ioldos nd Aeluropus lgopoides, ould survive in up to 5 ds.m -1 NCl (Gulzr & Khn, 25); Urohondr setulos, Arthronemum mrosthyum, Sued frutios, Hloxylon stoksii, Avienni mrin, Ceriops tgl nd Rhizophor muront ould survive t slinities (8-1 ds.m -1 ) higher thn sewter (55-6 ds m -1 ) (Aziz & Khn, 21; Gulzr et l., 23; Khn et l., 2, 25). Hlophytes vry in umultion of different ions (Khn et l., 25). Chenopds re known s slt umultors nd hve high N + nd Cl - ontents (Gul et l., 2; Khn et l., 2). N + inresed signifintly t slinities greter thn 3 mol.m -3 NCl (Nidoo & Rughunnn, 199; Nidoo & Kift, 26) nd is umulted in leves for osmoti djustment inreses suulene (Flowers & Yeo, 1986). Intr-speifi ompetition n influene survivl growth nd feundity of popultion (Ungr, 1991; Wng et l., 26). Morphologilly, the hlophytes my e plsti in their response to inresed plnt density ut mortlity ws not diretly relted with density dependent ftors (Riehl & Ungr, 1982). Survivl in popultion ppers to e diretly influened y level of slt stress nd is not diretly orrelted with initil plnt densities ourring in popultions from slt mrsh hitts (Riehl & Ungr, 1982, 1983; Jefferies et l., 1983; Wilkon-Mihlsk, 1985; Ellison, 1989). Little work hs een done on the produtivity nd growth of lol hlophytes round Krhi. The ojetives of this reserh were (1) to study the sesonl vrition in produtivity of Atriplex stoksii nd (2) to determine the role of vrious se slt onentrtions, plnting densities nd their intertions on its growth in green house onditions. Mterils nd Methods Study site: The produtivity of Atriplex stoksii ws studied for two yers from My 1997 to April The study site is loted t Gizri Creek, Krhi long the Arin Se ost. Experimentl design: Two plots with three qudrts (.5 m 2 ) were seleted rndomly every first week of the month for two yers. In plot # 1 plnt were lipped lose to the soil surfe nd divided into living nd ded prts. Litter remining on the surfe ws olleted seprtely in plsti gs. Soil ws olleted from the root zone in eh qudrt (pprox. 3 m). All elowground mteril (root) ws olleted y wshing the soil with wter over 2 mm sieve. In plot # 2 only ded shoot mteril ws removed nd stored, living shoot mteril ws tgged nd hrvested fter one month. The plnts were

3 VARIATION IN PRODUCTIVITY OF ATRIPLEX STOCKSII 155 hrvested nd growth prmeters i.e., fresh weight, dry weight, root length nd shoot length were reorded. Ded mteril ws seprted from the living nd ws weighed. Soil smples were olleted from -15 m nd 15-3 m depths. Fresh nd oven dried (8 C for 24 h) weight of soil smples ws mesured. Soil extrts (1:1) were mde y dissolving 5 g soil in 5 ml distilled wter nd filtered using Whtmn No 1 pper. Eletril ondutivity ws mesured y CDM 83 ondutivity meter (Rdiometer Copenhgen). Seeds of A. stoksii were olleted from popultion ner ost of Krhi. Seeds of A. stoksii were olleted in Jnury 21 nd stored t room temperture. Plsti pots of 36 m dimeter were filled with thoroughly wshed eh snd. Seeds were sown in June nd provided su-irrigtion y pling pots in plsti trys under nturl onditions. At the seond lef stge, seedlings were thinned y removing exess plnts from the pots to produe three density tretments (2, 5 nd 8 plnt pot -1 ) nd provided with 2, 4, 6, 8 nd 1 ds.m -1 seslt solutions fortified with nutrient solution (Popp & Polni, 1989) to supplement the mro- nd miro-nutrients required. Slinity onentrtions were grdully inresed y 2 ds.m -1 se slt solution t two dy intervls to reh the mximum slinity levels of 1 ds.m -1 fter 1 d. The slinity level of the ulture solution ws mintined in pots through dily su-irrigtion with tp wter nd solution ws repled t weekly intervls. Seedlings were grown for 6 dys fter mximum slinity onentrtion ws otined. The plnts were then hrvested nd fresh nd dry weight, root nd shoot length were noted. The dry weight ws reorded fter oven drying t 8 o C for 24 h. For ion nlysis hot wter extrt ws prepred..5 g dried plnt mteril ws oiled in 25 ml distilled wter for two hr t 1 o C in dry het th, ooled nd filtered. Cl, NO 3 nd SO 4 were mesured with DX-1 ion hromtogrph while N, K, C nd Mg were nlyzed using Perkin Elmer model 36 tomi sorption spetrophotometer. Dt were sttistilly nlyzed using ANOVA nd individul tretment mens were ompred y the post-ho Bonferroni test (SPSS, 1999). Results Produtivity of Atriplex stoksii ws studied for the two growing sesons in the ostl snd dunes ner Gizri Creek, Krhi. The preipittion dt for the yers of 1997, 1998 nd 1999 showed highly vrile pttern of rinfll (Fig. 1). There ws onsiderle rinfll during summer 1997, few spordi showers in 1998 nd lmost no rins in The higher net produtivity ws reorded from Novemer to My during oth seson, however, during growing seson net produtivity ws muh higher in omprison to the yer (Fig. 2). The months from June to Otoer hd lower produtivity. Aoveground iomss for the two sesons showed vried response (Fig. 3). During the yer oveground iomss prodution per unit re ws low throughout the sesons nd there ws little promotion during Septemer. However, during sesons there ws sustntil inrese in the oveground iomss in the month of Otoer nd it styed higher until Jnury 1999 (Fig. 3). Stnding rop iomss showed similr pttern in oth sesons little inrese from June to Septemer nd higher inrese from Otoer to My (Fig. 4). The oveground ded iomss remined unhnged during the yer ut it registered sustntil promotion during the seson from Deemer to April (Fig. 5).

4 156 FARHAT AGHA ET AL., Preipittion (mm) Jn Fe Mr Apr My Jun Jul Aug Sep Ot Nov De Month Month Fig. 1. Sesonl vrition in rinfll round ost t Mnor sttion, Krhi. Net produtivity (g m -2 d -1 ) M y Jun Jul Aug Sep Ot Nov De Jn Fe M r Apr Month Month Fig. 2. Sesonl vrition in net produtivity (g m -2 dy -1 ) of Atriplex stoksii during the suty. Soil ondutivity showed progressive derese from My to Septemer 1997 due to hevy monsoon rins. The soil ondutivity progressively inresed in My 1998 nd remined high for rest of the yer (Tle 1). N + nd Cl - ion onentrtions in shoot remined high during oth the sesons (Tle 2). The N + nd Cl - in Atriplex stoksii roots remined unhnged from My 1997 to Jnury 1998, inresed in Ferury 1998 nd deresed gin during Deemer 1998 (Tle 3). The ion onentrtion root ws muh higher thn roots. K + in shoots ws sustntilly higher s ompred to the roots. The K + in shoots nd roots deresed onsiderly during the months of low slinity (Tles 2 &.3). The onentrtion of other ions did not hnge muh during oth sesons.

5 VARIATION IN PRODUCTIVITY OF ATRIPLEX STOCKSII 157 Aoveground iomss (g m -2 ) M yjun Jul Aug Sep O tnovde Jn Fe M r Apr Month M o n th Fig. 3. Sesonl vrition in ove ground iomss (g m -2 ) of Atriplex stoksii during the stuty. Inrese in stnding rop iomss (g m -2 ) M y Jun Jul Aug Sep O t Nov De Jn Fe M r Apr Month M o n th Fig. 4. Sesonl vrition in stnding rop iomss (g m -2 ) of Atriplex stoksii. Fresh weight of shoots t low density (2 plnts pot -1 ) ws not ffeted y low slinities ( nd 2 ds.m -1 ) however; t higher slinity onentrtions there ws no effet of density (Fig. 6). The dry weight of shoot showed density effets t low slinities (Fig. 6). Root fresh weight ws signifintly promoted t low slinity nd inrese in slinity inhiited the root growth (Fig. 7). Both root fresh weight nd dry weight hd higher weight t low density under low slinity nd under high slinity effet of density ws sent (Fig. 7). Shoot nd root length hve shown density effets in non-sline medium nd inrese slinity hs diminished the effets of density (Fig. 8). Inrese in slinity deresed the shoot nd root length in ll tretments (Fig. 8). Root to shoot rtio sustntilly inresed with the density under non-sline onditions (Fig 9) nd fter the introdution of slinity the effet of density ws redued (Fig. 9).

6 158 FARHAT AGHA ET AL., Tle 1. Sesonl vrition in soil eletril ondutivity (ds m -1 ) t 15 m nd 3 m depth in Atriplex stoksii ommunity. Months m 3 m 15 m 3 m MAY 3.7 ± ± ± ±.2 JUN 1.4 ±.5.6 ± ± ± 1.7 JUL 1.9 ± ± ± ±.4 AUG 1.7 ± ± ± ±.7 SEP 2. ± ± ± ±.8 OCT 6.3 ± ± ± ±.3 NOV 4.4 ±.9 5. ± ± ±.3 DEC 4.5 ± ± ± ±.6 JAN 3.7 ± ± ±.9 5. ±.6 FEB 8.1 ± ±.1 3. ± ±.3 MAR 3.8 ± ± ± ±.1 APR 6.2 ± ± ± ±.2 Aoveground ded iomss (g m -2 ) My Jun Jul Aug Sep Ot NovDe Jn Fe Mr Apr Month Fig. 5. Sesonl vrition in ove ground ded iomss (g m -2 ) of Atriplex stoksii. Shoot tissue wter showed little effet in up to 6 ds m -1 seslt ut the suulene deresed with further inrese in slinity (Fig. 1). At high densities suulene ws higher. However, mount of wter per plnt deresed sustntilly t high slinities nd the effet of density ws highly signifint in deresing suulene in oth sline nd non-sline tretments (Fig. 1). Root suulene showed similr response (Fig. 11). Shoots of A. stoksii umulted high onentrtion of N + nd Cl - tht did not hnge muh with the inrese in slinity (Tle 4) wheres other ions were found in omprtively low mount. N + in root ws higher ut muh lower in omprison to shoot nd Cl - were present in the similr mount s tht of shoot (Tle 4).

7 VARIATION IN PRODUCTIVITY OF ATRIPLEX STOCKSII 159

8 16 FARHAT AGHA ET AL.,

9 VARIATION IN PRODUCTIVITY OF ATRIPLEX STOCKSII 161 Fresh weight (mg plnt -1 ) Dry weight (mg plnt -1 ) 1 2 Plnts 9 5 Plnts 8 Plnts Se slt (ds m -1 ) Fig. 6. Fresh nd dry weight (mg plnt -1 ) of Atriplex stoksii shoot rised t vrious se slt onentrtions nd plnt densities (2, 5 nd 8 plnts per pot). Br represents mens with stndrd error. Different letters ove r represents signifint differene (p>.5) etween slinity tretments within eh density. Disussion The produtivity of Atriplex sp. is highly vrile, depending on the eologil onditions of the soil nd limte (Osmond et l., 198). Over rod rnge of vegettion types, oveground net primry produtivity (ANPP) is strongly relted with preipittion, temperture (Lieth, 1972; Btes et l., 26) nd evpo-trspirtion (Rosenzweig, 1968). The net produtivity of A. stoksii reported in this study showed strong sesonl pttern. Monsoon rins, ssoited with redued mient temperture nd soil ondutivity, primrily determines the produtivity of A. stoksii dominted ommunities long the Arin Se ost. The mximum oveground iomss flutution ws oserved in with peks from Novemer to My while sustntilly deresing from June to Otoer. Low plnt iomss is ommonly relted to low rinfll in summer during while the greter (4-8 g.m -2 ) net produtivity, oveground iomss nd stnding rop iomss in is inditive of fvorle moisture onditions due to the 26 mm rinfll in Otoer, Soil slinities nd temperture were higher efore the rinfll nd my hve sustntilly redued in oveground iomss.

10 162 FARHAT AGHA ET AL., Fresh weight (mg plnt -1 ) Plnts 5 Plnts 8 Plnts d d 35 Dry weight (mg plnt -1 ) Seslt (ds m -1 ) Fig. 7. Fresh nd dry weight (mg plnt -1 ) of Atriplex stoksii roots rised t vrious se slt onentrtions nd plnt densities (2, 5 nd 8 plnts per pot). Br represents mens with stndrd error. Different letters ove r represents signifint differene (p>.5) etween slinity tretments within eh density. The oveground ded iomss did not show ny signifint differene during proly euse of low rinfll nd high temperture, while it vried during summer fter the rinfll nd remined unhnged for rest of the seson. This is in greement with the reports of Arthronemum mrosthyum nd Sprtin lterniflor in whih ded iomss ws higher during the entire summer (Gul & Khn, 1995). The rte of plnt deomposition ws ffeted y moisture, temperture, idity nd the nutrients sttus of eosystem, primrily nitrogen nd phosphorus-relted wter hemistry vriles (Szumiglski & Byley, 1996; Thormnn & Byley, 1997; Regn et l., 27). The elowground iomss of Atriplex stoksii showed similr pttern in oth sesons. The ourrene of sesonl flushes in elowground iomss ppers to vry with speies. Pek elowground iomss of Distihlis spit ws oserved in August (Gllgher & Plumley, 1979) nd in April nd Septemer were found for Sporoolus virginius.

11 VARIATION IN PRODUCTIVITY OF ATRIPLEX STOCKSII 163 Root length (m plnt -1 ) Shoot length (m plnt -1 ) Seslt (ds m -1 ) 2 Plnts 5 Plnts 8 Plnts Fig. 8. Root nd shoot length (m plnt -1 ) of Atriplex stoksii seedlings rised t vrious se slt onentrtions nd plnt densities (2, 5 nd 8 plnts per pot). Br represents mens with stndrd error. Different letters ove r represents signifint differene (p>.5) etween slinity tretments within eh density. Root : Shoot (dry wt) plnts 5 plnts 8 plnts d Seslt (ds m -1 ) Fig. 9. Root nd shoot dry weight rtio of Atriplex stoksii seedlings rised t vrious se slt onentrtions nd plnt densities (2, 5 nd 8 plnts per pot). Br represents mens with stndrd error. Different letters ove r represents signifint differene (p>.5) etween slinity tretments within eh density.

12 164 FARHAT AGHA ET AL., Tle 4. Element onentrtions in shoot nd root of Atriplex stoksii under vrious seslt tretments. Vlues for eletril ondutivity (EC) re in ds m -1 nd of ions in μmol g -1 dry wt. EC N + K + C 2+ Mg 2+ Cl - Shoot Root Shoot Root Shoot Root Shoot Root Shoot Root ±6.67 ±6.67 ±6.67 ±6.67 ± ± ±3.33 ± ± ± ±24.4 ± ± ±1.33 ±3.33 ± ± ±8.82 ± ± ±4 ±35.28 ± ±1.33 ± ±6.67 ±3.33 ±3.33 ± ± ±58.12 ±66.67 ±1.33 ± ± ±3.33 ± ±3.33 ± ± ±66.67 ±58.12 ±1.33 ±1.33 ± ± ±3.33 ±3.33 ± ± Suulene (mg g -1 dry wt) Plnts 5 Plnts 8 Plnts Suulene (mg plnt -1 ) EC (ds m -1 ) Fig. 1. Suulene of ove ground prts of Atriplex stoksii seedlings rised t vrious se slt onentrtions nd plnt densities (2, 5 nd 8 plnts per pot). Br represents mens with stndrd error. Different letters ove r represents signifint differene (p>.5) etween slinity tretments within eh density.

13 VARIATION IN PRODUCTIVITY OF ATRIPLEX STOCKSII 165 Suulene (mg plnt -1 ) Suulene (mg g -1 dry wt) EC (ds m -1 ) 2 Plnts 5 Plnts 8 Plnts d d Fig. 11. Suulene of elow ground prts of Atriplex stoksii seedlings rised t vrious se slt onentrtions nd plnt densities (2, 5 nd 8 plnts per pot). Br represents mens with stndrd error. Different letters ove r represents signifint differene (p>.5) etween slinity tretments within eh density. Atriplex stoksii, is slt tolernt hlophyte whih hs sh ontent of out 4% of dry weight (Khn et l., 2). N + nd Cl - re the min omponents of sline soils (Riehl & Ungr, 1983). Growth of Atriplex stoksii ws sustntilly promoted t low slinity (2-4 ds.m -1 ), ut deresed with further inrese in slinity (Khn et l., 2). Most hlophytes show optiml growth in the presene of slt (Nidoo & Rughunnn, 199; Rozem, 1991; Ayl & O Lery, 1995) however, growth of Atriplex spp. ws inhiited y high slt onentrtion (Ungr, 1991).

14 166 FARHAT AGHA ET AL., In the sene of slinity, density signifintly ffeted the growth prmeters, however, introdution of slinity redued the density effet nd t higher onentrtions, the effet of density ws ompletely diminished (Keiffer & Ungr, 1997; Wng et l., 25) however, the role of ompetition in perennil popultion ppers to e limited (Gul & Khn, 1998). Gul et l., (2) showed tht inresed ompetition used progressive redution in growth of A. oidentlis. High plnting density deresed growth even t low slinities. Intr-speifi ompetition my ffet the iomss prodution, reprodution, survivl, nd growth of hlophytes in sline hitts (Bdger & Ungr, 199; Ungr, 1991; Foderro & Ungr, 1997; Keiffer & Ungr, 1997; Wng et l., 25). Root nd shoot tissue wter showed little effet up to 6 ds.m -1 se slt ut suulene deresed with further inrese in slinity. However, mount of wter per plnt deresed sustntilly t higher slinities. Suulene is one of the mehnisms tht hlophytes utilize to del with the high internl ion onentrtions (Ahmed et l., 24). Suulene plys key role in the survivl nd mintenne of hlophytes under sline onditions y mintining positive turgor (Khn et l., 1999). Perennil grsses from Krhi lso mintined high wter nd osmoti potentil with progressively lower stomtl ondutne with the inrese in slinity (Gulzr & Khn, 25). At high slinity, wter ontent of plnts deresed nd plnt lost turgor using growth inhiition nd inrese in mortlity. Deleterious effets of slinity re thought to result from low wter potentils, ion toxiities, nutrient defiienies or omintion of these ftors. Nutrient defiienies n our in plnts when high onentrtions of N + in the soil redue the mounts of ville K +, Mg 2+ nd C 2+ (Epstein, 1972) or when N + disples memrne ound C 2+ (Crmer et l., 1985). Our results indited tht N + nd Cl - in shoots nd roots inresed with slinity. C 2+ nd Mg 2+ ontents were redued in shoots of A. stoksii plnts grown t high slinity similr to the results found for other hlophytes (Flowers, 1972; Nidoo & Rughunnn, 199; Ayl & O Lery, 1995). Ash ontent in leves of A. stoksii ws highest (39% of dry weight) t 36 mm NCl. These dt indite tht A. stoksii, n ion umultor should e onsidered for use in phyto-remedition of degrded sline lnds. This speies ould lso e rised s supplementry fodder for livestok using sline wter irrigtion. Atriplex stoksii is one of the ommon hlophytes distriuted in oth ostl nd inlnd sline flts nd dunes round Krhi. This speies is modertely slt tolernt nd ould hve higher produtivity if irrigted with rkish wter. Produtivity in highly ompetitive onditions mkes it etter ndidte for rehilittion of sline lnds nd the use of iomss s fodder. Referenes Ahmed, D., K. Ben Hmed, C. Grignon nd C. Adelly. 24. Slinity effets on germintion, growth, nd seed prodution of the hlophyte Ckile mritim. Plnt nd Soil, 262: Anderson, W.P., D.A. Wilkoks, nd B.J. Wright Eletrophysiologil mesurements on the root of Atriplex hstt. J. Exp. Bot., 28: Ayl, F. nd J.W. O Lery Growth nd physiology of Sliorni igelovii Torr. t su optiml slinity. Int. J. Plnt Si., 156: Aziz, I. nd M.A. Khn. 21. Effet of sewter on the growth, ion ontent nd wter potentil of Rhizophor muront Lm. J. Plnt Res., 114: Bdger, K.S. nd I.A. Ungr Effets of soil slinity on growth nd ion ontent of the inlnd hlophyte Hordum jutum. Bot. Gz., 151: Btes, J.D., T. Svejr, R.F. Miller nd R.A. Angell. 26. The effets of preipittion timing on sgerush steppe vegettion. J. Arid Environ., 64:

15 VARIATION IN PRODUCTIVITY OF ATRIPLEX STOCKSII 167 Crmer, G.R., A. Luhli nd V.S. Polito Displement of C 2+ y N + from the plsmlemm of root ells. Plnt Physiol., 79: Ellison, M.A Effets of ompetition, disturne nd herivory on Sliorni europe. Eology, 68: Flowers, T.J Slt tolerne in Sued mritim L. Dum.The effet of sodium hloride on growth, respirtion nd solule enzymes in omprtive study with Pisum stivum. J. Exp. Bot., 23: Flowers, T.J. nd A.R. Yeo Ion reltions of plnts under drought nd slinity. Aus. J. Plnt Physiol., 13: Foderro, M.A. nd I.A. Ungr Growth nd survivl of Polygonium viulre L. t rineontminted site in south estern Ohio. Am. Mid. Nt., 38: Gllgher, J.L Estimte ngiosperm: produtivity nd initil photosynthte dispersion in the eosystem. In: Esturine intertion, (Ed.): V.S. Kennedy, Ademi Press, New York. Gllgher, J.L. nd F.G. Plumely Underground iomss profiles nd produtivity in Atlnti ostl mrshes. Am. J. Bot., 66: Greenwy, H Growth stimultion y high hloride onentrtion in hlophytes. Isr. J. Bot., 17: Greenwy, H., A. Gunn nd D.A. Thoms Plnt response to sline sustrte VIII. Regultion of ion onentrtions I slt-sensitive nd hlophyti speies. Aust. J. Biol. Si., 19: Gul, B. nd M.A. Khn Produtivity of n Arthronemum indium dominted ostl slt mrsh t Krhi, Pkistn. In: Biology of Slt Tolernt Plnts. (Eds.): M.A. Khn nd I.A. Ungr, Deprtment of Botny, University of Krhi, Pkistn. Gul, B. nd M.A. Khn Popultion hrteristis of ostl hlophyte Arthronemum mrosthyum. Pk. J. Bot., 3: Gul, B., D.J. Weer nd M.A. Khn. 2. Effet of slinity nd plnting density on physiologil responses of Allenrolfe oidentlis. West.North Am. Nt., 6: Gulzr, S. nd M.A. Khn. 25. Comprtive slt tolerne of perennil grsses. In: Eophysiology of High Slinity Tolernt Plnts. (Eds.): M. A. Khn nd D.J. Weer, Springer Pulition, Netherlnds. Gulzr, S., M.A. Khn nd I.A. Ungr. 23. Slt tolerne of ostl slt mrsh grss. Comm.Soil Si. Plnt Anl., 34: He, M.Z., X. R. Zheng nd Y.L. Qin. 27. Environmentl ftors ffeting vegettion omposition in the Aln plteu, Chin. J. Arid Environ., 69: Irlndi, E., B. Orlnds, S. Mi, P. Bier, J. Thzy, L. Kufmn, D. Lirmn nd E.T. Ptterson. 21. The influene of freshwter runoff on iomss, morphometris nd prodution of Thlssi testudinum. Aqut. Bot., 72: Krimi, S.H. nd I.A. Ungr The effet of slinity on the ion ontent nd wter reltions of Atriplex tringulris. In: Proeeding of the symposium on the iology of Atriplex nd relted henopods. (Eds.): A.R. Tiedemnn, E.D. MArthur, H.C. Stutz, R. Stevens nd K.L. Jhonson, , Generl Tehnil Report Int-172USDA Forest Servie, Provo. Keenish, M.J Eology of Esturies. Vol. 1. Physil nd Chemil Aspets CRC Press In, Bo Rton, Florid. Keiffer, C.H. nd I.A. Ungr The effets of density nd slinity on shoot iomss nd ion umultion in five inlnd hlophyti speies. Cn. J. Bot., 75: Khn, M.A. nd B. Gul. 22. Slt tolernt plnts of ostl skhs of Pkistn. In: H. Brth, nd B. Boer. Skh Eosystems: Volume 1: The Arin Peninsul nd Adjent Countries. pp Kluwer Ademi Press, Netherlnds. Khn, M.A., I.A. Ungr nd A.M. Showlter The effet of slinity on growth, ion ontent nd osmoti reltions in Hlopyrum murontum (L.) Stpf. J. Plnt Nut., 22: Khn, M.A., I.A. Ungr nd A.M. Showlter. 2. Growth, wter, nd ion reltionships of lef suulent perennil hlophyte, Sued frutios (L.) Forssk. J. Arid Environ., 45:

16 168 FARHAT AGHA ET AL., Khn, M.A., I.A. Ungr nd A.M. Showlter. 2. Effets of sodium hloride tretments on growth nd ion umultion of the hlophyte Hloxylon reurvum. Comm. Soil Si. Plnt Anl., 31: Khn, M.A., I.A. Ungr nd A.M. Showlter. 2. Slt tolerne in the sutropil perennil hlophyte Atriplex griffthi Moq vr. stokii Boiss. Ann. Bot., 85: Khn, M.A., I.A. Ungr nd A.M. Showlter. 25. Slt stimultion nd tolerne in inter-tidl stem-suulent hlophyte. J. Plnt Nut., 28: Li, N., S. Chen, X. Zhou, C. Li, J. Sho, R. Wng, E. Fritz, A. Huttermnn nd A. Polle. 28. Effet of NCl on photosynthesis slt umultion nd ion omprtmenttion in two mngrove speies, Kndeli ndel nd Bruiguier gymnorrhiz. Aqut. Bot., 88: Msini, R.J., P.K. Anderson nd A.J. MCom. 21. A Hlodule-dominted ommunity in sutropil emyment physil environment, produtivity, iomss nd impt of dugong grzing. Aqut. Bot., 71: Mittelh, G.G., C.F. Steiner, S.M. Sheiner, K.L. Gross, H.L. Reynolds, R.B. Wide, M.R. Willig, S.I. Dodson nd L. Gough. 21. Wht is the oserved reltionship etween speies rihness nd produtivity. Eology, 82: Nidoo, G. nd J. Kift. 26. Responses of the sltmrsh rush Junus krussii to slinity nd wterlogging. Aqut. Bot., 84: Nidoo, G.R. nd R. Rughunnn Slt tolerne in the suulent hlophyte Sroorni ntlensis. J. Exp. Bot., 41: Odum, W.E., T.J. Smith III, J.K. Hoover nd C.C. Mlnvor The eology of fresh wter mrshes of the United Sttes est ost: ommunity profile. US. Fish Wildl. Serv. FWS/OBS-83/17: Osmond, C.B., O. Bjorkmn nd D.J. Andreson Physiologil Proess in Plnt Eology. Springer-Verlg, Berlin. Pling, E.I. nd A.J. MCom. 2. Autumn iomss, elowground produtivity, rhizome growth t ed edge nd nitrogen ontent in se grss from Western Austrli. Aqut. Bot., 67: Priee, A. nd H.J. Jegr Einfluss von NCl uf wshstum und ionengehieldlih sltztolertor Pflnzen. Ange. Bot., 52: Regn, E.C., M.S. Skeffingtor nd M.S. Gormlly. 27. Wetlnd plnt ommunities of turloughs in southest Glwylnorth Clre, Irelnd in reltion to environmentl ftors. Aqut. Bot., 87: Riehl, T.E. nd I.A. Ungr Growth potentil nd ion umultion in the inlnd hlophyte Atriplex tringulris under sline field onditions. At Oeol. Plnt, 4: Romo, J.T. nd M.R. HferKmp Effets of osmoti potentil potssium hloride nd sodium hloride on germintion of gresewood (Srotus vermiultus). Gret Bsin Nt., 47: Rosenzweig, M.L Net primry produtivity of terrestril ommunities: Predition from limtologil dt. Am. Nt., 12: Rozem, J Growth, wter nd ion reltionships of hlophyti monootyledone nd diotyledone: unified onept. Aqut. Bot., 39: Sntos, A.M. nd F.A. Esteves. 22. Primry prodution nd mortlity of Eleohris interstint in response to wter level flututions. Aqut. Bot., 74: SPSS SPSS: SPSS 9. for Windows updte. Chigo: SPSS In. Szumiglski, A.R. nd S.E. Byley Deomposition long og-fern grdient in Centrl Alert, Cnd. Cn. J. Bot., 74: Thormn, M.N. nd S.E. Byley Deomposition long moderte - rih fen- mrsh petlnd grdient in orel Alert, Cnd. Wetlnds, 17: Tyler, G. 23. Some eophysiologil nd historil pprohes to spp rihness nd liole/lifuge ehviour ontriution to dete. Foli Geoot., 38: Zhu, J.K. 21. Plnt slt tolerne. Tr. Plnt Si., 6: (Reeived for pulition 3 Jnury 29)