EXPLORING THE POTENTIAL OF MORINGA (Moringa oleifera) LEAF EXTRACT AS NATURAL PLANT GROWTH ENHANCER

Transcription

1 EXPLORING THE POTENTIAL OF MORINGA (Moring oleifer) LEAF EXTRACT AS NATURAL PLANT GROWTH ENHANCER By AZRA YASMEEN DOCTOR OF PHILOSPHY IN AGRONOMY DEPARTMENT OF AGRONOMY FACULTY OF AGRICULTURE, UNIVERSITY OF AGRICULTURE, FAISALABAD, PAKISTAN. 2011

2 EXPLORING THE POTENTIAL OF MORINGA (Moring oleifer) LEAF EXTRACT AS NATURAL PLANT GROWTH ENHANCER By AZRA YASMEEN M.Sc. (Hons.) Agriculture 96-g-662 A thesis sumitted in prtil fulfillment of the requirements for the degree of DOCTOR OF PHILOSPHY IN AGRONOMY DEPARTMENT OF AGRONOMY FACULTY OF AGRICULTURE, UNIVERSITY OF AGRICULTURE, FAISALABAD, PAKISTAN. 2011

3 DEDICATED TO MY LOVING AND CARING, HUSBAND, MY SWEET SISTERS IN LAW, MY INNOCENT CHILDREN, MY RESPECTED MOTHER IN LAW, AND MY DEAR PARENTS, So much I hve ecome is ecuse of you nd I wnt to tell you Tht I pprecite you thnk you nd love you

4 ACKNOWLEDGEMENTS Sying of Prophet Muhmmd (PBUH) `A person who is not thnkful to his enefctor is not thnkful to ALLAH'. All nd every kind of prises is upon ALLAH ALMIGHTY, the strength of universe, who ever helps in drkness & difficulties. All nd every kind of respect to His Holy Prophet Muhmmd (PBUH) for unique comprehensive nd everlsting source of guidnce nd knowledge for humnity. I would like to extend my hertiest grtitude to Dr. Shhzd Mqsood Ahmd Bsr, Professor, Deprtment of Crop Pysiology, University of Agriculture, Fisld, under whose supervision, scholstic guidnce, consulting ehvior, this work ws plnned, executed nd completed. I pprecite nd thnk to memers of my supervisory committee, Dr. Rshid Ahmd, Professor, Deprtment of Crop Physiology, University of Agriculture, Fsisld for his helping ttitude nd Dr. Adul Whid, Professor nd Chirmn, Deprtment of Botny, University of Agriculture, Fisld, for their vlule nd continuous guidelines during the preprtion of this mnuscript nd kind herted ehvior throughout my doctorl studies. I m lso highly indeted to Higher Eduction Commission (HEC), Government of Pkistn for grnting me Indigenous fellowship throughout my doctorl study. Azr Ysmeen i

5 The Controller of Exmintion, University of Agriculture, Fisld, We, the supervisory committee, certify tht the contents nd form of thesis sumitted y Ms. Azr Ysmeen, Regd. No. 96-g-662 hve een found stisfctory nd recommend tht it e processed for evlution y the Externl Exminer (s) for wrd of Degree. SUPERVISORY COMMITTEE: CHAIRMAN : (Dr. Shhzd Mqsood Ahmd Bsr) MEMBER : (Dr. Rshid Ahmd) MEMBER : (Dr. Adul whid)

6 DECLARATION I herey declre tht contents of the thesis, Exploring the potentil of moring (Moring oleifer) lef extrct s nturl plnt growth enhncer re product of my own reserch nd no prt hs een copied from ny pulished source (except the references, stndrd mthemticl or genetic models/equtions/formulte/protocols etc.). I further declre tht this work hs not een sumitted for wrd of ny other diplom/degree. The university my tke ction if the informtion provided is found inccurte t ny stge. (In cse of ny defult, the scholr will e proceeded ginst s per HEC plgirism policy). Azr Ysmeen 96-g- 662 ii

7 TABLE OF CONTENTS Pge ACKNOWLEDGEMENTS... i DECLARATION. ii TABLE OF CONTENTS.. iii LIST OF TABLES.... x LIST OF FIGURES xvii ABBREVIATIONS.. xx ABSTRACT. xxii 1. Introduction Review of Literture Aiotic stresses High temperture stress Slinity stress Drought stress Mitigtion of iotic stresses Seed priming Folir ppliction Mterils nd Methods Source of moring leves Anlysis of moring leves Preprtion of MLE Plnt mteril Crop seson Experimentl sites Experiment I: Optimiztion of moring oleifer lef extrct (MLE) dilutions Experiment II: Evlution of MLE s priming gent Experiment III: Evluting the growth nd development of Tomto to exogenous ppliction of MLE (pot study) Experiment IV: Evluting the growth nd development of pe to ppliction of MLE (pot study) Experiment V: Evluting the response of lte sown whet to folir ppliction of MLE under field conditions Experiment VI: Mitigting effects of slinity stress in whet y MLE ppliction Experiment VII: Mitigting effects of drought stress in whet y MLE ppliction Sttisticl nlysis Results nd Discussion Experiment 1. Optimiztion of MLE dilution Experiment II: Evlution of MLE s priming gent Experiment III: Evluting the growth nd development of tomto to iii

8 exogenous ppliction of MLE (pot study) Experiment IV: Evluting the growth nd development of pe to exogenous ppliction of MLE (pot study) Experiment V: Response of lte sown whet to folir ppliction of MLE under field conditions Experiment VI:Response of whet to exogenous ppliction of MLE under sline stress conditions Experiment VII: Response of whet to exogenous ppliction of MLE under drought stress conditions Generl Discussion Summry LITERATURE CITED iv

9 LIST OF TABLES Tle 3.1. Bio-chemicl composition of Moring oleifere lef Anlysis report for soil filled in pots Dilutions of ovine serum lumin (BSA) Preprtion of gllic cid stndrds Dilutions for scoric cid stndrd solutions Men sum of squres of dt for germintion index (GI), men germintion time (MGT), nd time to 50% germintion (T 50 ) of whet grown in petri pltes treted with Moring oleifer lef extrct (MLE) Men sum of squres of dt for finl germintion percentge, shoot fresh weight nd shoot dry weight of whet seedling grown in petri pltes treted with MLE Men sum of squres of dt for shoot length, root fresh weight nd root dry weight of whet seedling grown in petri pltes treted with MLE Men sum of squres of dt for root length of whet seedling grown in petri pltes treted with MLE Men sum of squres of dt for emergence index (EI), men emergence time (MET), time to 50% emergence (E 50 ) of whet rised from seeds primed with different priming gents Men sum of squres of dt for shoot fresh weight, shoot dry weight nd shoot length of whet rised from seeds primed with different priming gents Men sum of squres of dt for root fresh weight, root dry weight nd root length of whet rised from seeds primed with different priming gents Men sum of squres of dt for lef re, lef chlorophyll nd chlorophyll contents of whet rised from seeds primed with different gents Men sum of squres of dt for numer of grins per spike, 100 grin weight nd grin yield per plnt of whet rised from seeds primed with different priming gents Men sum of squres of dt for totl solule protein nd enzymtic ntioxidnt i.e. superoxide dismutse (SOD) nd peroxidse (POD) of whet rised from seeds primed with different gents 64 Pge v

10 4.2.7 Men sum of squres of dt for enzymtic ntioxidnt ctlse (CAT) nd non-enzymtic ntioxidnts i.e. totl phenolic content nd scoric cid of whet rised from seeds primed with different gents Men sum of squres of dt for numer of vegettive rnches, numer of flowering rnches nd numer of flowers of tomto under exogenous ppliction of different plnt growth enhncers Men sum of squres of dt for numer of fruits, fruit yield plnt -1 nd lef chlorophyll of tomto under exogenous ppliction of different plnt growth enhncers Men sum of squres of dt for lef chlorophyll, plnt height nd lef totl solule protein of tomto under exogenous ppliction of different plnt growth enhncers Men sum of squres of dt for super oxide dismutse (SOD), peroxidse (POD) nd ctlse (CAT) of tomto lef under exogenous ppliction of different plnt growth enhncers Men sum of squres of dt for lef totl phenolic contents (TPC) nd fruit lycopene of tomto under exogenous ppliction of different plnt growth enhncers. Men sum of squres of dt for numer of vegettive rnches, numer of reproductive rnches nd numer of flowers of pe under exogenous ppliction of different plnt growth enhncers Men sum of squres of dt for numer of pods, pods weight plnt -1 nd lef chlorophyll of pe under exogenous ppliction of different plnt growth enhncers. Men sum of squres of dt for lef chlorophyll nd totl phenolic contents (TPC) of pe under exogenous ppliction of different plnt growth enhncers.... Men sum of squres of dt for LAI (50 DAS) LAI (57 DAS) nd LAI (75 DAS) of whet y exogenous ppliction of MLE under lte sown conditions Men sum of squres of dt for LAI (85 DAS), LAI (95 DAS) nd sesonl lef re durtion of whet y exogenous ppliction of MLE under lte sown conditions vi

11 Men sum of squres of dt for CGR (57 DAS), CGR (75 DAS) nd CGR (85 DAS) of whet y exogenous ppliction of MLE under lte sown conditions. Men sum of squres of dt for CGR (95 DAS), NAR (57 DAS) nd NAR (75 DAS) of whet y exogenous ppliction of MLE under lte sown conditions.. Men sum of squres of dt for NAR (85 DAS), NAR (95 DAS) nd numer of fertile tillers of whet y exogenous ppliction of MLE under lte sown conditions Men sum of squres of dt for numer of grins per spike, 1000 grin weight nd iologicl yield (m -2 ) of whet y exogenous ppliction of MLE under lte sown conditions.. 94 Men sum of squre summries of the dt for grin yield (m -2 ) nd hrvest index (%) of whet y exogenous ppliction of MLE under lte sown conditions. 95 Men sum of squres of the dt for shoot length, shoot fresh weight nd shoot dry weight of whet y exogenous ppliction of growth enhncers under sline conditions 105 Men sum of squres of dt for root length, root fresh weight nd root dry weight of whet y exogenous ppliction of growth enhncers under sline conditions. 105 Men sum of squres of the dt for lef re, lef chlorophyll nd chlorophyll of whet y exogenous ppliction of growth enhncers under sline conditions 106 Men sum of squres of the dt for totl solule protein, enzymtic ntioxidnts SOD nd POD of whet y exogenous ppliction of growth enhncers under sline conditions Men sum of squres of the dt for enzymtic ntioxidnts (Ctlse), nonenzymtic ntioxidnts i.e. totl phenolic contents nd scoric cid of whet y exogenous ppliction of growth enhncers under sline conditions Men sum of squres of the dt for N +, K + nd CI - contents of whet y exogenous ppliction of growth enhncers under sline conditions vii

12 Men sum of squres of the dt for numer of grins per spike nd 100 grin weight of whet y exogenous ppliction of growth enhncers under sline conditions Men sum of squres of dt for lef re, lef chlorophyll nd chlorophyll contents of whet y exogenous ppliction of growth enhncers under drought conditions Men sum of squres of dt for totl solule proteins, enzymtic ntioxidnts i.e. super oxide dismutse (SOD) nd peroxidse (POD) of whet y exogenous ppliction of growth enhncers under drought conditions Men sum of squres of dt for enzymtic ntioxidnt ctlse (CAT), nonenzymtic ntioxidnt scoric cid nd totl phenolics (TPC) of whet y exogenous ppliction of growth enhncers under drought conditions... Men sum of squres of dt for lef K + contents nd grin yield of whet y exogenous ppliction of growth enhncers under drought conditions viii

13 LIST OF FIGURES Figure Pge 3.1 Wether dt for Octoer 2008 to April Wether dt for Octoer 2009 to April Stndrd curve of protein estimtion Stndrd curve of Totl phenolic content estimtion Stndrd curve of scoric cid estimtion Effect of different dilutions of Moring oleifer lef extrct (MLE) on germintion index (), men germintion time (MGT) (), time to 50% germintion (T50) (c) nd finl germintion percentge of whet cv. Sehr under lortory conditions Effect of different dilutions of Moring oleifer lef extrct (MLE) on shoot fresh nd dry weight (), root fresh nd dry weight () nd shoot, root length (c) of whet cv. Sehr-2006 under lortory conditions Effect of seed priming on emergence index (EI) (), men emergence time (MET) () nd time to 50% emergence (E50) (c) of whet cv. Sehr (MLE10 =10 times diluted MLE, MLE30= 30 times diluted MLE, HP=Hydro priming, OFP= On-frm priming) Effect of seed priming on shoot fresh weight (), shoot dry weight (), shoot length (c), root fresh weight (d), root dry weight (e) nd root length (f) of whet cv. Sehr (MLE10= 10 times diluted MLE, MLE30= 30 times diluted MLE, HP=Hydro priming, OFP= On frm priming) Effect of seed priming on lef re (), chlorophyll () nd chlorophyll (c) of whet cv. Sehr (MLE10= 10 times diluted MLE, MLE30= 30 times diluted MLE, HP=Hydro priming, OFP= On frm priming) Effect of seed priming on numer of grins per spike (), 100 grin weight () nd grin yield per plnt (c) of whet cv. Sehr-2006 (MLE10= 10 times diluted MLE, MLE30= 30 times diluted MLE, HP=Hydro priming, OFP= On-frm priming) Effect of seed priming on lef totl solule protein (), enzymtic ntioxidnts (superoxide dismutse, peroxidse nd ctlse) (, d, c) nd non enzymtic ntioxidnts (scoric cid nd totl phenolic contents) (e, f) of whet cv. Sehr (MLE10= 10 times diluted MLE, MLE30= 30 times diluted MLE, HP=Hydro priming, OFP= On frm priming) Effect of exogenous ppliction of growth enhncer on numer of flowering rnches () nd numer of vegettive rnches () of tomto cv. Shil (MLE0, MLE10, MLE20, MLE30 =0, 10, 20, 30 times diluted MLE respectively, BAP= enzyl mino purine) 78 ix

14 4.3.2 Effect of exogenous ppliction of growth enhncer on numer of flowers plnt -1 (), numer of fruits () nd fruit weight (c) of tomto cv. Shil (MLE0, MLE10, MLE20, MLE30 = 0, 10, 20,30 times diluted MLE respectively, BAP= enzyl mino purine) Effect of exogenous ppliction of growth enhncer on totl solule protein (), SOD (), totl phenolics (c), POD (d), ctlse (e) of lef nd fruit lycopene (f) of tomto cv. Shil (MLE0, MLE10, MLE20, MLE30 = 0, 10, 20, 30 times diluted MLE respectively, BAP= enzyl mino purine) Effect of exogenous ppliction of growth enhncer on chlorophyll (), chlorophyll () nd plnt height (c) of tomto cv. Shil (MLE0, MLE10, MLE20, MLE30 = 0, 10, 20, 30 times diluted MLE respectively, BAP= enzyl mino purine) Effect of exogenous ppliction of different growth enhncers on numer of vegettive rnches (), reproductive rnches () nd numer of flowers per plnt (c) of pe cv. Climx. (MLE0, MLE10, MLE20, MLE30 = 0, 10, 20, 30 times diluted MLE respectively, BAP= enzyl mino purine) Effect of exogenous ppliction of different growth enhncers on numer of pods () nd pod yield plnt -1 () of pe cv. Climx. (MLE0, MLE10, MLE20, MLE30 = 0, 10, 20, 30 times diluted MLE respectively, BAP= enzyl mino purine) Effect of exogenous ppliction of different growth enhncers on chlorophyll (), () nd totl phenolics (c) of pe cv. Climx. (MLE0, MLE10, MLE20, MLE30 = 0, 10, 20, 30 times diluted MLE respectively, BAP= enzyl mino purine) Effect of exogenous ppliction of MLE on lef re index () nd sesonl lef re durtion () of whet cv. Sehr-2006 under lte sown conditions Effect of exogenous ppliction of MLE on crop growth rte () nd net ssimiltion rte () of whet cv. Sehr-2006 under lte sown conditions Effect of exogenous ppliction of MLE on numer of fertile tillers (), numer of grins per spike () nd 1000 grin weight (c) of whet cv. Sehr-2006 under lte sown conditions Effect of exogenous ppliction of MLE on iologicl yield (), grin yield () nd hrvest index of whet cv. Sehr-2006 under lte sown conditions Effect of exogenous ppliction of different plnt growth enhncer on shoot length (), shoot fresh weight (), shoot dry weight (c), root length (d), root fresh weight (e) nd root dry weight (f) of whet cv. Sehr-2006 under sline conditions x

15 4.6.2 Effect of exogenous ppliction of different plnt growth enhncers on lef re (), chlorophyll () nd chlorophyll (c) of whet cv. Sehr-2006 under sline conditions Effect of exogenous ppliction of different plnt growth enhncers on totl solule protein (), SOD (), scoric cid (c), ctlse (d), POD (e) nd totl phenolics (f) of whet cv. Sehr-2006 under sline conditions Effect of exogenous ppliction of different plnt growth enhncer on lef N + (), K + () nd Cl - (c) of whet cv. Sehr-2006 under sline conditions Effect of exogenous ppliction of different plnt growth enhncers on numer of grins () nd 100 grin weight () of whet cv. Sehr-2006 under sline conditions Effect of exogenous ppliction of different plnt growth enhncers on lef re (), chlorophyll () nd chlorophyll (c) of whet cv. Sehr-2006 under drought conditions Effect of exogenous ppliction of different plnt growth enhncer on totl solule protein (), super oxide dismutse (), scoric cid (c), ctlse (d), peroxidse (e) nd totl phenolic contents (f) of whet cv. Sehr-2006 crop under drought conditions Effect of exogenous ppliction of different plnt growth enhncer on lef K + contents () nd grin yield plnt -1 () of whet cv. Sehr-2006 under drought conditions xi

16 ABBREVIATIONS Arevition Full % percent AA Ascoric cid APX Ascorte peroxidse cm centimeter (s) CAT ctlse CGR Crop growth rte d dy (s) DAS dys fter sowing E 50 EI FC FEP g g m -2 GR h h -1 HI H 2 O 2 K kg kg h -1 LSD m m -2 MDAR MET MGT time to 50% emergence emergence index Field cpcity Finl emergence percentge grm (s) grm per squre meter Glutthione reductse hectre per hectre Hrvest index Hydrogen peroxide Potssium kilogrm kilogrm per hectre Lest Significnt Difference meter per squre meter Monodehydroscorte reductse men emergence time men germintion time xii

17 ml MLE mm mm MP N NAR NS O - 2 OH - P POD ROS RO Rs. SLAD SOD T 50 TPC milliliter Moring lef extrct millimeter milli Molr Meg Pscl Nitrogen Net ssimiltion rte non-significnt Superoxide rdicl Hydroxyl rdicl Phosphorus Peroxidse Rective oxygen species Alkoxy rdicl Rupees Sesonl lef re durtion Superoxide dismutse time to 50% germintion totl phenolic contents xiii

18 Astrct Among nturlly occurring plnt growth stimulnts, Moring oleifer hs ttined enormous ttention ecuse of hving cytokinin in ddition to other growth enhncing compounds like scortes, phenolics, other ntioxidnts long with mcro- micro nutrients in its leves. With these properties, exogenous ppliction of Moring lef extrct (MLE) ws done in whet, pe nd tomto to evlute its efficcy s crop growth enhncer The ojective ws to optimize dose, method of exogenous ppliction, enhncement of growth, yield nd ntioxidnt level under norml nd iotic stresses (lte sowing, slinity, nd drought). The results showed tht 30 times diluted MLE priming in whet under norml conditions ws found to e effective. MLE priming improved the seedling emergence rte, speed nd erly growth nd incresed level of ntioxidnts, lef totl solule protein nd chlorophyll contents s compred to MLE10, Hydro priming, On-frm priming nd CCl 2 priming. Lrge numer nd hevier grins were otined in plnts rised from MLE30 primed seed which resulted in highest grin yield per plnt. All the priming tretments gve more yield thn non primed control. Folir spry of MLE cused n increse of 10.73, 6.00, nd 4.00% in 1000 grin weight, iologicl yield, grin yield nd hrvest index respectively, with MLE spry t tillering + jointing + ooting + heding. MLE spry only t heding gve 6.84, 3.17, 6.80 nd 3.51% more 1000-grin weight, iologicl yield, grin yield, nd hrvest index respectively, s compred to control. MLE extended the sesonl lef re durtion (Sesonl LAD) y 9.22 nd 6.45 d over control when pplied t ll growth stges nd single spry t heding, respectively. MLE folir improved slinity tolernce in whet y improving whet seedlings vigour, more chlorophyll nd chlorophyll contents, exclusion of N + nd Cl - long with ccumultion of K + nd lrger contents of enzymtic ntioxidnts (ctlse, superoxide dismutse nd peroxidse) nd non enzymtic ntioxidnts (scoric cid nd totl phenolic contents) leding to more 100 grin weight s compred to enzylminpurine (BAP), hydrogen peroxide (H 2 O 2 ) nd control (wter spry) under slinity. The wter spryed plnts under highest slinity showed mximum ccumultion of N + nd Cl - while lrgest K + contents were oserved in cse of MLE spry under moderte slinity. MLE nd BAP ppliction improved lef totl solule protein nd superoxide dismutse (SOD). For non-enzymtic ntioxidnts (totl phenolics nd scoric cid), MLE ws rnked first under moderte slinity. BAP improved numer of grins spike -1 ut hevier grins were oserved under MLE ppliction in modertely sline conditions. These effects of MLE were more pprent under moderte slinity (8dS m -1 ) s compred to higher slinity (12dS m -1 ). The wter stress cused reduction in growth nd grin yield of whet due to decresed lef re nd reduced chlorophyll nd chlorophyll contents. However, folir ppliction of MLE nd BAP minimized these effects of drought. MLE ppliction produced more grin yield under moderte nd severe wter stress s compred to BAP, K + nd control. Moring leves eing rich source of β-crotene, protein, vitmin C, clcium nd potssium nd ct s good source of nturl ntioxidnts such s scoric cid, flvonoid, phenolics nd crotenoid, so the exogenous pplictions of MLE improve the ntioxidnt sttus nd yield of whet under drought stress. In cse of tomto crop folir ppliction of MLE30 exhiited lrge numer of flowers, more numer of fruits s well s heviest fruits. The folir ppliction of BAP produced sme numer of flowers ut lighter weight fruits s compred to MLE30. The minimum fruit weight ws recorded in cse of folir pplied MLE10, MLE0 nd control. The effectiveness of MLE s crop growth enhncer might e due to the presence of growth promoting sustnces. MLE proved potentil growth enhncer in mitigtion of iotic stresses. xiv

19 Chpter 1 Introduction Agriculture is fcing the dul chllenges of incresing crop production nd climte chnge. Rising temperture, drought, slinity, floods, desertifiction nd wether extreme re dversely ffecting griculture especilly in developing world (IPCC, 2007). Most of the predicted popultion growth to 2030 will e in developing countries (Popultion Reference Bureu, 2011) nd more thn hlf of the work force engged in griculture in the third world countries is prone to more dmge y climte chnge. Thus, there is need to improve crop productivity under chnged climte, iotic stresses nd to meet the needs of incresing world popultions. Of vrious iotic stresses, high temperture, slt stress nd drought lone or in comintion re mjor threts to crop productivity. Rising tempertures my led to ltered geogrphicl distriution nd growing seson of griculturl crops y llowing the threshold temperture for the strt of the seson nd erlier crop mturity (Porter, 2005). An extreme temperture shortens the growing period nd dversely effects ll phses of growth such s tillering, flowering nd grin filling in lte sown whet. The erly senescence of leves results in too low photosynthetic rte to contriute in fixing cron to rest of the plnt (Hensel et l., 1993; Shrm-Ntu et l., 2006) leding to poor quntity nd qulity of the hrvest (Hussin et l., 2008). A series of morphologicl, physiologicl, iochemicl nd moleculr chnges my reduce expression of full yield potentil of crop plnts under these climtic stress conditions (Wng et l., 2001). The decresed soil wter potentil cuses much reduction in lef expnsion s compred to root expnsion rte under drought or slinity (Kminek et l., 1997). The wter scrcity disturs plnt metolic ctivities y upsetting the memrne structure, ltered minerl uptke (Pospíšilová et l., 2000), reduction in the chlorophyll contents, reltive wter contents nd memrne stility index (Ts nd Ts, 2007). The limited vilility of wter not only reduces numer of grins per spike ut lso decreses the grin weight in whet (Li et l., 2000) nd qulity like low proteins (Grg et l., 2004). 1

20 The incresed ccumultion of N + nd Cl - under sline conditions leds to the reduced growth of vsculr plnts (Munns, 2002). Slt stress cuses less germintion nd poor seedlings estlishment in most of the crops such s whet (Afzl et l., 2006), mize, rley (El-Tye, 2005), sugr eet (Ghoulm et l., 2001), sunflower (Ashrf nd Tufil, 1995), cnol (Athr et l., 2009), cotton nd rice (Sttr et l., 2010). Reduction in growth nd yield under slinity is minly due to slt-induced osmotic stress nd specific ion toxities (Munns nd Tester, 2008). The depressed level of nturl osmoprotectnts nd endogenous hormones re oserved in severl plnts growing in sline soils (Deez et l., 2001). The comined effect of extreme temperture, drought nd slinity includes osmotic dmges (Xiong et l., 2002), oxidtive stress like incresed genertion of rective oxygen species (ROS) (Mittler, 2002, Gill nd Tutej, 2010) nd protein denturtion (Zhu, 2002). Biomolecules such s proteins, DNA nd lipids re dly injured y rective oxygen species (ROS) resulting in denturtion, muttion nd peroxidtion (Quiles nd Lopez, 2004). The peroxidtion of memrne lipids of plsmlemm nd other cellulr orgnelles (Cndn nd Trhn, 2003) leds to cell deth s consequence of ROS toxicity. It hs een identified tht plnts develop mny dpttions to cope with stress conditions i.e. osmotic djustment, comprtmentliztion of comptile solutes, ltertions in nutrients rtios specilly K + /N +, evpotrnspirtion modifictions y reducing lef size, chnges in photosynthetic pigments, stimultion of plnt hormones nd etter ntioxidnt scvengers (Sirm nd Tygi, 2004). The reeding progrmmes to develop crop plnts with forementioned trits re lorious nd time consuming (Jvid et l., 2011). The lterntive pproches re mngement prctices including exogenous ppliction of vrious ntioxidnts, minerl elements nd plnt growth regultors (PGRs). The ntioxidnts increse the scvenging cpcity ginst ROS (Mno, 2002). The ntioxidnts involved in detoxifiction of ROS exist in ll plnts under stress nd re ctegorized s enzymtic such s superoxide dismutse (SOD), ctlse (CAT), scorte peroxidse (APX), peroxidse (POD), glutthione reductse (GR) nd monodehydroscorte reductse (MDAR) nd nonenzymtic i.e. totl phenolics (TPC) nd scoric cid (AA) (Foyer, 2002). The degree to which the mount nd ctivities of ntioxidnt enzymes increse under iotic stress is extremely vrile mong severl plnt species nd even etween two cultivrs of the sme species (Chitny et l., 2002). The level of response depends on the species, the 2

21 development nd the metolic stte of the plnt, s well s the durtion nd intensity of the stress. Mny plnts produce significnt mount of ntioxidnts to prevent the oxidtive stress cused y photons nd oxygen, they represent potentil source of compounds with ntioxidnt ctivity such s scoric cid, totl phenols, nd vitmins in ddition to minerl elements K +, C 2+ nd PGRs. Ascoric cid is n importnt ntioxidnt, which rects not only with H 2 O 2 ut lso with O 2, OH nd lipid hydroperoxidses. In ddition to the well estlished scoric cid in nimls ginst wide rnge of ilments nd diseses it hs een implicted in severl types of iologicl ctivities in plnts such s n enzyme co-fctor, s n ntioxidnt nd s donor/ cceptor in electron trnsport t the plsm memrne or in the chloroplsts, ll of which re relted to oxidtive stress resistnce (Conklin, 2001). In chloroplsts scorte peroxidse uses scoric cid therey minimizes the risk of escpe nd rection of ROS with ech other ner PSI (Foyer nd Noctor, 2000). Ascorte lso protects or regenertes oxidized crotenoids or tocopherol (Imi et l., 1999). Plnt phenolic compounds re lso known for their function s ntioxidnts due to their free rdicl-scvenging cpilities (Wttenerg et l. 1980; Brcly et l. 1990; Fuconneu et l. 1997). In ddition to ntioxidnts plnts lso contin wide rnge of vitmins tht re essentil not only for humn metolism ut lso for plnts, ecuse of their redox chemistry nd role s cofctors, some of them lso hve strong ntioxidnt potentil. The ntioxidnt vitmins tht hve een the focus of most ttention in plnts re crotenoids (pro-vitmin A), scorte (vitmin C) nd tocochromnols (vitmin E, including oth tocopherol nd tocotrienols) (Demmig-Adms nd Adms, 2002; DellPenn nd Pogson, 2006; Linster nd Clrke, 2008; Foyer nd Noctor, 2009: Czzonelli nd Pogson, 2010; Flk nd Munne -Bosch 2010; Me`ne-Sffrne nd DellPenn, 2010). To comt iotic stresses nd enhnce crop yields, ppliction of minerl nutrients is widely used. Among minerl nutrients clcium is very importnt not only for cell wll nd memrne stilistion, ut hs lso een found to e involved in the regultion of specific plnt responses to environmentl stresses (Brm et l., 1996). Crmer et l. (1988) depicted 3

22 tht C 2+ hs lleviting effect on N + -induced root growth inhiition. Similrly, shortening of root growth zones ws prevented y C 2+ under sline condition (Bernstein et l., 1993). Perer et l. (1995) reported tht C 2+ incresed the stomtl conductnce nd restores the photosynthesis. Trnsport of wter in the root nd lef growing zones ws ffected with N + /C 2+ rtio (Crmer, 2002). Tyermn et l. (1997) showed tht slinity chnged the ionic content nd trnsport within the plnts. They concluded tht clcium hs mny regultory functions over memrne chrcteristics nd ionic trnsport in glycophytes nd hlophytes. For exmple, incresing the externl C 2+ concentrtion decresed the trnsport of N +, therey reducing N + influx in root cells. The cross tlk etween C 2+ nd ROS hs een studied during defense nd growth responses nd stomtl closure (Foremn et l., 2003; Hu et l., 2007; Mori nd Schroeder, 2004). Other studies lso implicted C 2+ function oth upstrem nd downstrem of ROS production (Jing nd Zhng, 2003; Hu et l., 2007). Potssium (K) is the most undnt ction in higher plnts. K + hs een the trget of some reserchers minly ecuse it is essentil for enzyme ctivtion, protein synthesis nd photosynthesis (Mrschner, 1995; Silv, 2004), nd it medites osmoregultion during cell expnsion, stomtl movements, tropisms, phloem solute trnsport nd the mintennce of ction: nion lnce in the cytosol s well s in the vcuole. K + supply from soil cn e rte limiting for griculturl production under conditions of osmotic nd ionic stress. Proper exogenous ppliction of PGRs long with certin nutrients, ntioxidnts, orgnic nd inorgnic chemicls hs een used to promote plnt growth nd development for inducing iotic nd iotic stress tolernce tht results in higher economic return (Ashrf nd Foold, 2007; Frooq et l., 2009). Exogenous use of cytokinins improves the crop growth nd yield under norml or stressful environments in numer of crop species (Zhir et l., 2001). Cytokinin retrds the lef senescence nd incresed the photosynthetic pigments (Gluszk et l., 2001). In field tril with the ppliction of commercil cytokinin contining product, cytogen, increse in yields of corn (26.3%), rice (45.8%), pepper (24.4%), cucumer (62.9%) nd cntloupe (36.8%) hs een reported (Myeux et l., 1983). Priming with cytokinins like kinetin or enzyl mino purine (BAP) induces physiologicl dpttion in whet y hormonl lnce under stress conditions (Iql nd Ashrf, 2006). BAP delyed the ROSinduced senescence of whet leves owing to incresed ctivities of ctlse nd scorte peroxidse in ddition to preventing chlorophyll degrdtion under oxidtive stress (Zvlet 4

23 et l., 2007). Under drought less reduction in totl solule protein, chlorophyll nd crotenoids contents were oserved y exogenous ppliction of cytokinin like products such s thidizurn, BAP, Krtolin 4 nd Krtolin 2 (Chernyd ev nd Monkhov, 2003). Ashrf nd Foold (2005; 2007) suggested tht exogenous ppliction of these compounds s seed priming or folir spry enhnced endogenous level nd iotic stress tolernce. These iologiclly ctive sustnces cn modulte plnt responses to stress fctors. But continuous use of synthetic chemicls nd use of commercilly ville plnt hormones s osmoprotectnts nd stimultors of ntioxidnts to quench ROS is usully not cost effective nd environmentlly friendly. Alterntively, toxicologicl effects of synthetic ntioxidnts nd consumer preference for nturl products hve resulted in incresed interest in the ppliction of nturl ntioxidnts (Cstenmiller et l., 2002; Kur nd Kpoor, 2001; Kolev et l., 2002; Pizzle et l., 2002). The serch for sfe nd effective nturlly occurring ntioxidnts is now focused on edile plnts, especilly spices nd hers (Nktni, 1997). A lrge numer of plnts hve een screened s vile source of nturl ntioxidnts including tocopherols, vitmin C, crotenoids nd phenolic compounds which re responsile for mintennce of helth nd protection from coronry hert diseses nd cncer (Cstenmiller et l., 2002; Kur nd Kpoor, 2001). Such s seweed extrct which is nturl products possess cytokinin nd uxin like properties nd cn stimulte endogenous cytokinin ctivities of plnts (Crouch et l., 1990). Another exmple is humic cid, which hs uxin-like ctivity, not only enhnces plnt growth nd nutrient uptke ut lso improves stress resistnce (Zhng nd Ervin, 2004). Among different nturl sources used to extrct PGRs nd ntioxidnts moring (Moring oleifer) is gining lot of ttention these dys (Foidle et l., 2001). Moring is one of the 13 species of genus Moring nd fmily Moringnnce. It is well known vegetle in Afric, Ari, Indi, Southest Asi, Americ nd Pkistn (Sengupt nd Gupt, 1970). Its roots, fruits, leves nd flowers een used s vegetles (Siddhurju nd Becker, 2003). Moring leves re potentil source of vitmin A nd C, iron, clcium, rioflvin, et-crotene nd phenolic cid (Nmir et l., 2005). Its leves nd oil re powerful nturl ntioxidnt (Njoku nd Adikwu, 1997). Siddhurju nd Becker (2003) oserved ntioxidnt properties in the solvent extrct of moring leves. On the sis of their results they reported tht, moring leves re potentil source of nturl ntioxidnts. 5

24 According to Arshhi et l. (2007) the extrcts from drumstick nd crrot hd higher ntioxidnt ctivity (83% nd 80%) thn α-tocopherol (72%). Jongrungrungchok et l. (2010) compred the composition nd minerl contents of moring lef otined from different regions of Thilnd nd reported , , nd percent of protein, ft, fier nd moisture. The potssium, clcium nd iron contents were in rnge of , nd mg / 100 g dry weight sis. Moreover, moring lef extrct (MLE) is enriched with zetin, purine denine derivtive of plnt hormone group cytokinin (Brciszweski et l., 2000) known for sty green nd stress tolernce cpilities. It is evident from erlier mentioned reports tht MLE possess ntioxidnts in considerle mounts ut very little pulished literture is ville tht explins MLE regulted metolic/physiologicl processes of whet nd other crops sujected to iotic stress. In view of ll these reports, it is hypothesized tht lef extrct from moring, hving numer of plnt growth promoters, minerl nutrients nd vitmins in nturlly lnced composition, my e eneficil for plnt growth nd development. This study ws conducted to evlute whether the dverse effects of stress on whet plnts could e mitigted y exogenous ppliction of osmoprotectnts i.e. K +, H 2 O 2, synthetic cytokinin enzyl mino purine (BAP) nd MLE especilly focusing the plnt ntioxidnt enzyme system. The ojectives of study were the optimiztion of MLE dose s nturl plnt growth enhncer in comprison to synthetic ones in different crops under norml nd iotic stresses. 6

25 Chpter 2 Review of Literture Plnt growth nd productivity is regulted y vriety of externl nd endogenous fctors. Optimum growth nd development is ensured when externl nd internl climtic fctors re within the optimum rnge. The externl fctors include different iotic nd iotic stresses. Among iotic stresses extreme tempertures (Ferris et l., 1998), drought (Bosch nd Alegre, 2004), slinity (Munns nd Tester, 2008), wterlogging (Olgun et l., 2008), low or high solr rdition (Alexiev et l., 2001), phototoxic compounds (Jml et l., 2006) nd indequte vilility of minerl nutrients in soil (Fgeri et l., 2010) re importnt. The endogenous fctors comprised of minerl nutrients (Azeem nd Ahmd, 2011), plnt growth regultors (Pospíšilová et l., 2000), ntioxidnts (Shoresh et l., 2011) nd plnt wter sttus (Athr nd Ashrf, 2005). It is elieved tht iotic nd iotic stresses cuse mjor reduction in crop yields (Athr nd Ashrf, 2009). Plnts responses to these stresses re not simple pthwys, ut re integrted complex circuits comprised of multiple pthwys nd specific cellulr comprtments, tissues, nd the interction of dditionl cofctors nd/or signling molecules to coordinte ginst n externl stress or stimuli to show specified response (Domrowski, 2003). Therefore rief review for externl stresses like extreme temperture, drought nd slinity long with endogenous fctors effecting plnt growth nd their mitigtion is mentioned elow: 2.1. Aiotic stresses High temperture stress In mny res of the world het stress induced y incresed temperture is one of mjor griculturl prolems. The economic yield reduced drsticlly s result of morpho physiologicl nd iochemicl chnges cused y trnsient or constnt high temperture which lso dly ffect plnt growth nd development Het stress Het stress is often defined s the rise in temperture eyond threshold level for period of time sufficient to cuse irreversile dmge in plnt growth nd development (Whid et l., 2007). In generl, trnsient elevtion in temperture, usully C ove mient, is 7

26 considered het shock or het stress. However, het stress is complex function of intensity (temperture in degrees), durtion nd rte of increse in temperture. The extent to which it occurs in specific climtic zones depends on the proility nd period of high tempertures occurring during the dy nd/or the night. The het stress s result of high mient tempertures is ecoming serious thret to crop production worldwide (Hll, 2001). A short exposure to very high tempertures, cused severe cellulr injury nd even cell deth within minutes (Sch offl et l., 1999) wheres modertely high temperture my tke long time to cuse injuries or cell deth. The denturtion nd ggregtion of protein with incresed fluidity of memrne lipids were direct injuries due to high tempertures. Indirect or slower het injuries were comprised of enzymes inctivtion in mitochondri nd chloroplst, retrdtion of protein synthesis, protein degrdtion nd loss of memrne integrity (Howrth, 2005). These injuries eventully led to strvtion, growth inhiition, reduced ion flux, genertion of toxic compounds nd rective oxygen species (ROS) (Sch offl et l., 1999; Howrth, 2005) Het stress threshold The threshold temperture is importnt in physiologicl reserch s well s for crop production. The vlue of dily men temperture t which detectle reduction in growth egins referred s threshold temperture. The knowledge of lower nd upper developmentl threshold tempertures elow nd ove which growth stops is necessry in physiologicl reserch s well s for crop production. For mny plnt species upper nd lower developmentl threshold tempertures hve een determined through experimenttion. The different plnt species hve different se or lower nd upper threshold tempertures ut 0 C is often predicted s est se temperture for cool seson crops (Miller et l., 2001). The determintion of consistent upper threshold temperture is difficult due to vrition in plnt ehvior depending on other environmentl conditions (Miller et l., 2001). The threshold temperture vlues for tropicl crops often higher thn temperte or cool seson crops. Threshold tempertures for whet is 26 C t post-nthesis (Stone nd Nicol s, 1994), rice 34 C t grin yield (Morit et l., 2005), perl millet 35 C t seedling (Ashrf nd Hfeez, 2004), corn 38 C t grin filling (Thompson, 1986), rssic 29 C t flowering (Morrison nd Stewrt, 2002), cotton 45 C t reproductive (Rehmn et l., 2004), tomto 30 C t emergence (Cmejo et l., 2005), cool seson pulses 25 C t flowering (Siddique et l., 8

27 1999), groundnut 34 C t pollen production (Vr et l., 2000), nd cowpe 41 C t flowering (Ptel nd Hll, 1990) Het stress sensitive growth stges The developmentl stge t which the plnt is exposed to the stress my determine the severity of possile dmges experienced y the crop. It is, however, unknown whether dmging effects of het episodes occurring t different developmentl stges re cumultive (Wollenweer et l., 2003). Vulnerility of species nd cultivrs to high tempertures my vry with the stge of plnt development, ut ll vegettive nd reproductive stges re ffected y het stress to some extent. During vegettive stge, for exmple, high dy temperture cn dmge lef gs exchnge properties. High temperture induced reduction in reltive growth rte nd net ssimiltion rte long with minimum effects on lef expnsion were oserved in sugr cne (Whid, 2007), perl millet nd mize (Ashrf nd Hfeez, 2004). Moreover, yield of crop species depends on mount of photosynthetic tissue, numer of leves, size of lef or totl lef re. For exmple, in whet, yield cn e forecsted upon lef re index (LAI) t flowering stge s well s crop growth rte (CGR) (Islm, 1992). The lef re index (LAI) nd crop growth rte (CGR) re determined y temperture previls during vegettive growth period (Zhng et l., 1999). While ssessing the effect of lte sowing on whet yield, Frooq et l. (2008) found tht previling high temperture reduced LAI nd CGR, which resulted in reduced yield. From these reports mentioned ove, it is suggested tht increse in mient temperture during erly or lte vegettive growth stge reduced yield indirectly y reducing growth. Of vrious plnt developmentl stges, reproductive stge is most sensitive to temperture stress. During reproductive stge, flowering, fertiliztion, nd post fertiliztion processes mrkedly ffected y high tempertures in most plnts, which resulted in reduced crop yield. For exmple, short period of het stress cn cuse significnt increses in florl uds nd opened flowers ortion (Guilioni et l., 1997; Young et l., 2004). Similrly, impirment of pollen nd nther development y elevted tempertures is nother importnt fctor contriuting to decresed fruit set in mny crops t moderte to high tempertures (Peet et l., 1998; Sto et l., 2006). Under high temperture conditions, erlier heding is dvntgeous in the retention of more green leves t nthesis, leding to smller reduction in yield (Tewolde et l., 2006). Het stress during nthesis induced sterility in mny plnt 9

28 species. It ws concluded from controlled conditions experiments tht dys fter flower visiility, 8-9 dys prior to nthesis nd fertiliztion were most sensitive for high temperture stress in vrious crop plnts (Foold, 2005). The het stress ssocited infertility nd yield decline hve een oserved in mny crops such s whet (Ferris et l., 1998) cotton, rice (Hll, 1992), pe (Guilioni et l., 1997) nd penut (Vr Prsd et l., 1999). At the mid-nthesis stge high temperture is lso injurious prticulrly for grin set nd grin fertiliztion ffecting numer of grins per spike nd grin weight, therey, leding to low yield (Ferris et l., 1998; Siddique et l., 1999). This is ecuse under such conditions plnts tend to divert resources to cope with the het stress nd thus limited photosynthtes would e ville for reproductive development (Pulsen, 1994; Gifford nd Thorne, 1984; Blum et l., 1994). The reduced fruit set t high temperture stress cn e explined in view of the rguments of Kinet nd Peet (1997) who suggested tht high temperture cused reduction in crohydrtes nd growth regultors iosynthesis nd their trnsloction in plnt sink tissues. In dwrf whet vriety, high temperture induced decrese in cytokinin content ws found to e responsile for reduced kernel filling nd its dry weight (Bnowetz et l., 1999). The improvement in grin yield y BA supply ws found with enhnced numer of grins (Trckov et l., 1992) wheres due to incresed grin weight rther thn grin numer (Wrrier et l., 1987; Gupt et l., 2003) under norml s well s lte sown conditions. The hevier grins reflected the more ccumultion nd prtitioning of dry mtter towrds sinks (grins) resulting in higher hrvest index under BA ppliction during high temperture stress in lte sown whet (Gupt et l., 2003). Thus, for successful crop production under high tempertures, it is importnt to know the threshold temperture, developmentl stges nd plnt processes tht re most sensitive to het stress Slinity stress Among iotic stresses, slinity stress is ecoming mjor limittion to crop productivity (Munns, 2011). According to estimtes, out 900 Mh lnd is ffected with slt stress (Flowers, 2004). The presence nd ccumultion of slts pproximtely ffected 30% of cultivted soils (Zhu et l., 1997). Excessive mounts of neutrl solule slts such s sodium chloride (NCl), sodium cronte (N 2 CO 3 ) nd prtilly clcium chloride (CCl 2 ) results in slty soils. 10

29 Adverse effects of slt stress on plnt growth nd yield Slt stress cuses dverse effects on plnt growth nd development y ltering physiologicl nd cellulr processes (Greenwy nd Munns, 1980; Ashrf, 1994; Munns, 2002; 2011; Munns nd Tester, 2008). The reduction of plnt growth nd dry mtter ccumultion under sline conditions hs een reported in severl importnt grin legumes (Tejer et l., 2006; Munns et l., 2006). It is elieved tht slt stress gretly reduced whet growth t ll developmentl growth stges, prticulrly t the germintion nd seedling stge (Munns et l., 2006). Slt stress cuses less germintion nd poor seedlings estlishment in most of the crops such s whet, rley, rice, lflf (Munns nd Tester, 2008) Bses of dverse effects of slinity The toxic effects of slinity cn e visulized from impirment of physiologicl nd iochemicl processes i.e. photosynthesis, protein synthesis nd lipid metolism therey reducing plnt growth. The slt induced growth reduction is generlly ttriutle to wter deficit or osmotic stress, specific ion toxicities, nutritionl imlnces nd oxidtive stress (Greenwy nd Munns, 1980; Munns, 1993; Afzl et l., 2006; Munns nd Tester, 2008) Osmotic stress Reduction in growth nd yield under slt stress is minly due to slt induced osmotic stress (Munns nd Tester, 2008). Excessive mount of solule slts in the root environment cuses osmotic stress, which my result in the disturnce of the plnt wter reltions in the uptke nd utiliztion of essentil nutrients nd lso in toxic ion ccumultion. As result of these chnges, the ctivities of vrious enzymes nd the plnt metolism re ffected (Munns, 2002; Lcerd et l., 2003). Reduction in the rte of lef nd root growth is proly due to fctors ssocited with wter stress rther thn slt specific effect (Munns, 2002). The reduced lef re oserved under highest slinity level my e due to reduction in wter uptke nd the nutritionl imlnce cusing toxicities or deficiencies of ions, so resulting in lef injuries (Munns nd Tester, 2008). The degree of growth inhiition due to osmotic stress depends on the time scle of the response, for the prticulr tissue nd species in question, nd whether the stress tretments re imposed ruptly or slowly (Ashrf, 1994; Munns et l., 2000). Mild osmotic stress leds rpidly to growth inhiition of leves nd stems, wheres roots my continue to grow nd elongte (Hsio nd Xu, 2000). 11

30 Specific ion toxicities Besides slt induced osmotic stress, ccumultion of toxic slts lso cuses growth suppression in plnts. Dominnt slts found in slt ffected soils re generlly N +, Cl - 2-, SO 4 nd HCO 3 which result in severe toxicity. However, the crops show vritions in their sensitivities to different toxic ions. It is generlly elieved tht excessive ccumultion of N + cuses nutrient imlnce, therey resulting in specific ion toxicity (Greenwy nd Munns, 1980; Grttn nd Grieve, 1999). In slt sensitive species or t higher slinity levels, plnt loose its ility to control N + trnsport s result slt induced ionic effect domintes the osmotic effect (Munns nd Tester, 2008). In most species, ccumultion of N + to toxic level ppers to occur more rpidly thn Cl -, therefore most studies focused on N + exclusion nd tht of N + trnsport control within the plnt (Munns nd Tester, 2008). For exmple, more ccumultion of N + nd Cl - ws oserved in ll prts of guv, especilly in the leves therey resulting in reduced growth (Ferreir et l., 2001). In ddition to N + eing toxic ion, Cl - is considered to e the more toxic ion in some species such s soyen, citrus, nd grpevine (Luchli, 1984; Grttn nd Grieve, 1999; Storey nd Wlker, 1999). Thus, the ccumultion of ny ction or nion in excessive mounts in growth medium cn cuse toxicity nd growth reduction depending upon species or cultivr Nutritionl imlnces The interctions of slts with minerl nutrients my result in considerle nutrient imlnces nd deficiencies (McCue nd Hnson, 1990). Ionic imlnce occurs in the cells due to excessive ccumultion of N + nd reduces uptke of other minerl nutrients such s K +, C 2+, nd Mn 2+ (Krimi et l., 2005). High sodium to potssium rtio due to ccumultion of high mounts of sodium ions inctivtes enzymes nd ffects metolic processes in plnts (Booth nd Berdll, 1991). Excess N + nd Cl - inhiits the uptke of K + nd leds to the ppernce of symptoms like those in K + deficiency. The deficiency of K + initilly leds to chlorosis nd then necrosis (Gopl nd Due, 2003). The role of K + is necessry for osmoregultion nd protein synthesis, mintining cell turgor nd stimulting photosynthesis (Freits et l., 2001). Both K + nd C 2+ re required to mintin the integrity nd functioning of cell memrnes (Wenxue et l., 2003). Mintennce of dequte K + in plnt tissue under slt stress seems to e dependent upon selective K + uptke nd selective cellulr K + nd N + comprtmenttion nd distriution in the shoots (Munns et l., 2000; 12

31 Crden et l., 2003). The mintennce of clcium cquisition nd trnsport under slt stress is n importnt determinnt of slinity tolernce (Soussi et l., 2001; Unno et l., 2002). Slt stress decreses the C 2+ /N + rtio in the root zone, which ffects memrne properties due to displcement of memrne ssocited C 2+ y N +, leding to dissolution of memrne integrity nd selectivity (Kinride, 1998). The incresed levels of N + inside the cells chnge enzyme ctivity resulting in cell metolic ltertion. Disturnce in K + uptke nd prtitioning in the cells nd throughout the plnt my even ffect stomtl opening thus diminishing the ility of the plnt to grow. Externlly supplied C 2+ hs een shown to meliorte the dverse effects of slinity on plnts, presumly y fcilitting higher K + /N + selectivity (Hsegw et l., 2000). Another key role ttriuted to supplementl C 2+ ddition is its help in osmotic djustment nd growth vi the enhncement of comptile orgnic solutes ccumultion (Girij et l., 2002). From ove discussion it is clerly evident tht reduced ccumultion of C 2+, K + nd Mg 2+ with incresed uptke nd ccumultion of N + gretly reduced crop growth nd yield under slt stress Oxidtive stress Slt stress cuses oxidtive stress in plnts i.e., the production of rective oxygen species (ROS) such s H 2 O 2 (hydrogen peroxide), 1 O 2 (singlet oxygen) nd OH - (hydroxyl rdicl). Mny iomolecules such s proteins, DNA nd lipids re dly injured y ROS resulting in cell deth (Apel nd Hirt, 2004). The decrese in the content nd the ctivity of vrious ntioxidnts in response to slt stress hs een reported in severl species (Shlt nd Neumnn, 2001; Al-Hkimi nd Hmd, 2001; Athr et l., 2008) nd is regrded s one of the mechnism explining, t lest in prt, the deleterious effects of slinity on crops. Plnts use two systems to defend ginst nd repir dmge cused y oxidizing gents. First, the enzymtic ntioxidnt system which is minly represented y superoxide dismutse (SOD), peroxidse (POD), ctlse (CAT) nd scorte peroxidse (ASPX) (Hrinsut et l., 1996), then, the non-enzymtic ntioxidnt system, consisting of molecules involved in ROS scvenging such s scoric cid (vitmin C), lph-tocopherol (vitmin B), β-crotene, glutthione (tripeptide) (Piotr nd Klous, 2005). Severl studies hve demonstrted the existence of close positive correltion etween the rte nd extent of the increse in ntioxidnt ctivity nd plnt slt tolernce (Sirm et l., 2005). The significnt decrese in cytokinin concentrtion ws oserved in roots nd shoots of rley cultivrs under slinity 13