NOTICE: this is the author s version of a work that was accepted for publication in Agricultural Water Management. Changes resulting from the

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1 NOTICE: this is the uthor s version of work tht ws ccepted for puliction in Agriculturl Wter Mngement. Chnges resulting from the pulishing process, such s peer review, editing, corrections, structurl formtting, nd other qulity control mechnisms my not e reflected in this document. Chnges my hve een mde to this work since it ws sumitted for puliction. A definitive version ws susequently pulished in Agriculturl Wter Mngement, Vol.146 (2014). DOI: /j.gwt

2 1 2 3 Uptke nd distriution of ions revel contrsting tolernce mechnisms for soil nd wter slinity in okr (Aelmoschus esculentus) nd tomtoes (Solnum esculentum) Jml Kmluldeen 1, Is A. M. Yunus 1,*, Aylsew Zerihun 2, Jeremy J. Bruhl 1, Pul Kristinsen 1 1 School of Environmentl & Rurl Sciences, University of New Englnd, Armidle, NSW 2351, Austrli 2 Deprtment of Environment nd Agriculture, Curtin University, Mrgret River Cmpus, Mrgret River, WA 6285, Austrli 9 *Corresponding uthor: is.yunus@une.edu.u; fx Running title: Slinity tolernce mechnisms in tomto nd okr Astrct Okr nd tomtoes re mjor vegetle crops commonly grown under irrigtion, nd understnding whether they respond to slinity y withstnding (tissue tolernce) or voiding (slt exclusion) ccumultion of slt in the shoots will ssist with mngement for optimising yield under declining soil nd wter resources. Both crops were grown in non-sline (0.0 ds/m) nd sline (3.0 ds/m) lomy snd nd drip irrigted with wter of 0.0, 1.2 or 2.4 ds/m. Differences in the growth nd yields of the two crops under sline conditions were ssocited with uptke nd distriution of ctions, especilly N. The tomto employed tissue tolernce mechnism in response to slinity nd produced fruits even when shoot/root N concentrtion ws >3.0; concentrtions of N in tomto tissues ws in the order shoots > roots fruits. Okr Slinity tolernce mechnisms in tomto nd okr Pge 1

3 ws sensitive to shoot N such tht shoot/root N concentrtion s low s 0.13 reduced yield y s much s 35%; this crop thus employed slt exclusion mechnism nd minimised shoot ccumultion of N, which ws distriuted in the order fruits > roots > shoots. Root nd shoot concentrtions of N, P nd S were correlted with flower ortion nd negtively correlted with yield nd yield components in oth crops. Fresh fruit produced on the sline soil were reduced y 19% in tomto compred with 59% in okr, reltive to yields on non-sline soil. Wter slinity reduced fresh fruit yields y s much s 36% with every unit (ds/m) rise in wter slinity compred with 27 % in okr. Soil slinity significntly reduced wter-use y 6% in tomtoes nd 29% in okr, ut hd no impct on wter use efficiency (WUE) tht verged 3.9 g of fresh fruits/l for tomtoes nd 1.75 g/l for okr. Every 1.0 ds/m rise in wter slinity reduced wter-use y 0.33 L in okr nd 3.31 L in tomtoes, nd reduced WUE y 2.61 g/l in tomtoes nd 0.53 g/l in okr. Soil slinity explined <5% of the vrince in yields in tomtoes nd 10 20% in okr, while wter slinity explined % of the vrince in tomtoes nd out 40% in okr. We conclude tht (1) wter slinity ws more injurious to yield in oth crops thn soil slinity, nd (2) yield losses due to slinity cn e minimised through frequent leching of soil slt under okr nd incresed irrigtion intervls in tomtoes. Keywords: flower ortion, fruit yield, root growth, shoot/root N, slinity, wter-use, wter-use efficiency Introduction Crop species differ in their responses to sline conditions s result of their reltive tolernce to ionic phytotoxicity. Two sic mechnisms tht define crop tolernce of slinity involve slt exclusion or tissue tolernce, ech of which is implemented to vrying degree y different Slinity tolernce mechnisms in tomto nd okr Pge 2

4 species with hlophytes eing dept lmost eqully t oth (Munns et l, 2006). Slt exclusion mechnism involves prevention of ions from getting into the trnspirtion strem y either minimising their uptke from the growth medi or if tken up expelling the ions into the thing/rooting medium, nd/or restrined rtes of root to shoot trnsfer. In tissue tolernce, on the other hnd, slts re sequestered in vcuoles of cells, especilly in root tissue, therey restricting their trnsport into the cytoplsm of shoot tissues tht re generlly more sensitive to slinity stress thn roots, nd where more physiologicl nd enzymtic processes occur (Rogers nd West, 1993; Ms nd Hoffmn, 1977). Either or oth of these mechnisms cn e overwhelmed resulting in phytoxicity nd deth under extreme slinity. Severity of impct of slinity on the plnt lso vries with the source of slinity, i.e. from wter or soil. Ms nd Hoffmn (1977) rgued tht plnt response is primrily determined y the slinity of the irrigtion wter rther thn of the soil. This is ecuse vilility nd uptke of slt is governed y the vilility of wter nd irrigtion nd/or rinfll reduces concentrtion of slts especilly in the top lyer of soil where most plnt roots reside; furthermore, the slts re not ville to the plnt when the topsoil dries. They explined how slinity of the topsoil will pproximte tht of the irrigtion wter, ut will e more severe t the ottom of the root zone (Ms nd Hoffmn, 1977). Such sitution should e prticulrly eneficil to plnts tht exclude slts s the predominnt mechnism for slinity tolernce. Severl ions hve een ssocited with cusing phytoxicity under sline conditions nd differ in their dverse impct on plnts (Shnnon nd Grieve, 1999). Amongst these, N nd Cl re the most commonly ssocited with sline injury in plnts, ecuse they re esily ccumulted in shoot where they interfere with enzymtic, developmentl nd physiologicl processes (Flowers, 2004; Ghnem et l., 2009; Munns et l. 2006; Shnnon nd Grieve, 1999). Stunted plnt growth Slinity tolernce mechnisms in tomto nd okr Pge 3

5 nd reduced yields hve often een ssocited with excessive N nd Cl concentrtions in the lef tht cuse scorching nd firing of leves (Shnnon nd Grieve, 1999) nd/or impirment of CO 2 ssimiltion nd photosynthetic cpcity (Yunus et l., 2009). Low yields, however, could lso result from lte onset of reproductive phse nd disruption of the processes involved. In tomtoes, poor flower viility ws ssocited with ccumultion of N t the expense of K in the flower tissues nd resulted in low fruit numers, i.e. low sink cpcity, nd consequently reductions in the overll fruit yield (Ghnem et l., 2009). Accumultion of N in the leves cn interfere with uptke of severl other ctions such s C, K nd Mg. This cn impir tolernce of slinity, which is generlly enhnced when plnts selectively ccumulte K reltive to other ctions especilly N (Ashrf, 2004; Mksimović et l., 2010). Tomto (Lycopersicon esculentum Mill.) nd okr (Aelmoschus esculentus (L.) Moench) re importnt vegetle crops commonly grown under irrigtion. Extensive ssessments of growth, physiologic nd iochemicl responses to slinity hve een undertken for tomtoes (e.g. Ghnem et l., 2009; Brgllo et l., 2012; del Amor et l., 2001; Perez-Alfoce et l., 2010), ut okr hs received limited investigtion in understnding its growth nd yield responses to ionic stress rising from medi nd/or wter slinity. In this study, we compred ionic uptke nd prtitioning, nd their influence on the growth nd yield of okr nd tomtoes grown on sline soil nd irrigted with wter of different slinities. The ims were to (1) quntify reltive tolernce to soil nd wter slinity, nd (2) identify which of the two mechnisms of slinity tolernce is dominnt in the two crops. 87 Slinity tolernce mechnisms in tomto nd okr Pge 4

6 Mterils nd Methods The Crops This study ws undertken in glsshouse t the School of Environmentl nd Rurl Sciences, the University of New Englnd, Armidle, Austrli, over 5-month period etween Mrch nd July in Tomto (Solnum esculentum 'Rouge de Mrmnde') nd okr (Aelmoschus esculentus 'Clemson's spineless') were rised from seeds otined from commercil supplier (Mr Fothergill's Seeds of Austrli ). The seeds were sown into vermiculite (0.0 ds/m) nd wtered with tp wter (EC of ds/m) nd they germinted within 6 dys. The seedlings were llowed to grow for 2 weeks (heights of 8 12 cm for okr nd cm for tomto), efore eing trnsplnted into potted soils hving different slinity. Three seedlings were trnsplnted per pot then thinned down to two fter 10 dys nd finlly to one fter 20 dys Slinity tretments A lomy snd soil (83% snd nd 10% cly) hving se slinity of ds/m, ph of 6.27, nd wter content t field cpcity of 22% ws collected from the nery university reserch frm (30 o 29' 16'' S, 151 o 38' 29'' E). Of this soil, 6 kg ws weighed into ech of 48 thick plstic gs. Ech g ws prepred to receive ny one of the six tretments rising from fctoril comintions of the following: 2 levels of soil slinity: Control (0.018 ds/m) nd sline (3.0 ds/m) 3 levels of wter slinity: ds/m (control), 1.2 ds/m (medium slinity) nd 2.4 ds/m (high slinity) Slinity tolernce mechnisms in tomto nd okr Pge 5

7 The soil slinity tretment of 3 ds/m ws generted y dding 1% (w/w) tle slt (NCl) to hlf the numer of the gged soil smples; the other hlf of the gged soil smples received no slt. The slinity nd ph of the soil were determined using ench top meter (Lchem- CP Benchtop Conductivity/TDS -ph/mv meter, TPS Pty Ltd., Brisne, Austrli). All 48 gs received dditionl 2 kg soil tht ws pre-mixed with 2.5 g compound (12.2% N, 5.1% P, 13.7% K, 4.5% C nd 1.1% Mg) fertiliser (Murite of Potsh, CSBP Ltd, Austrli). The gs were thoroughly shken to chieve homogeneous mixture. The gged soil ws then trnsferred into seprte, numered plstic pots ech hving dimeter of 25 cm t the top, 19 cm t the se nd depth of 24 cm. The three levels of irrigtion wter slinity (denoted s 0, 1.2 nd 2.4 ds/m) were otined using tp wter (EC, ds/m) nd dissolving 0, 88 or 225 g NCl/L, respectively. The tp wter ws considered s the control tretment. These solutions were then stored in seprte 220 L PVC tnks. 2.3 Experimentl lyout nd glsshouse wether The experimentl units (pots) were lid out on enches in glsshouse in rndomized design. There were 24 pots per species, mde up of two soil nd three wter slinity tretments in four replictes. The glsshouse ws mintined t diurnl temperture rnge of 24 28ºC nd reltive humidity of 30 50% Irrigtion nd nutrient mngement Ech pot ws supplied with dripper tht rn from hose from the respective tnk contining the three sline solutions tretments. Ech pot ws irrigted t rte of 100 ml for 5 min every dy, nd ws rought to field cpcity every week to void wter stress. Lechte ws collected seprtely from ech pot every week nd its volume determined. A 25 ml su-smple of Slinity tolernce mechnisms in tomto nd okr Pge 6

8 lechte ws stored in drk cool room nd lter nlysed for ph nd EC, nd the rest of the lechte returned to their respective pots to mintin prescried slinity for the pots. The slinity of the wter in the reservoirs ws checked weekly to ensure tht the prescried slinity ws mintined. All the pots were ech supplied with 200 ml nutrient solution (16 g/l of Aqusol Hortico contining NPK in 23:4:18) t 20 dys fter trnsplnting (DAT) nd repeted when the plnts in the control tretments (non-sline soil nd non-sline wter) showed symptoms of nutrient deficiency such s yellowing long the edges, curled leves or erly senescence of the older leves. Ten grms of dolomite (9% Mg nd 14.5% C) ws dded to ech pot to correct Mg deficiency for oth crops evident y drkening of the fruit t the se in the control plnts Mesurements Plnt growth The height nd lef numer for ech plnt ws ssessed every ten dys, while lef re ws determined on the lst thinned plnt t 20 DAT. Lef re ws mesured with scnning device (CID Portle Lef Are Meter CI-202, CID Bioscience Inc., Cms, WA, USA). The reltive chlorophyll concentrtion in the leves ws determined t 95 nd 117 DAT using n opticl device (SPAD 502 Plus Chlorophyll Meter, Minolt, Jpn); the SPAD redings were converted to chlorophyll content ccording to Coste et l. (2010). Dtes of ppernce of first flower nd fruit were recorded, while numers of flowers nd fruits were counted dily. Flower ortion ws tken s the totl numer of fruits y the plnt divided y the totl numer of flowers counted for the sme plnt during its lifetime. Slinity tolernce mechnisms in tomto nd okr Pge 7

9 Fruit yield nd qulity The fruits were crefully picked s they mtured nd weighed fresh. Weight of fruits hrvested from individul plnts were collted nd summed fter picking the lst fruit to determine totl yield. Sugr content of tomto fruit ws determined on 1.0 ml squeezed juice using hnd-held device (Cors Accutrend Plus instrument, Roche Ltd, Schweiz, Switzerlnd). The fruits long with the shoots were dried t 60 o C for 72 h to determined dry weights. The roots were recovered from the pots, thoroughly wshed nd lso dried t 60 o C for 72 h. Totl dry weight per plnt ws determined s the sum of dry weights of fruits, roots nd shoots Wter use Amounts of wter supplied to, nd drined from, ech pot ws recorded nd wter-use ws otined s: wter-use (WU) = wter pplied (L) - wter drined (L). The weekly vlues for WU were summed t the end of the tril to otin totl mount of wter used y the plnt in ech pot. Wter-use efficiency (WUE) ws determined s: totl weight of fresh fruit (kg)/wu (L) Elementl uptke nd distriution Dried smples of the fruit, root nd shoot tissues were ground seprtely using mortr nd pestle to pss 2 mm screen. Susmples of the ground tissues ( 0.5 g) were digested in concentrted HNO 3 (70%) nd H 2 O 2 (30%) in microwve digester. The digests were rought to finl volumes of 100 ml with doule-deionized wter, nd the elementl contents determined using ICP-MS (ICP-MS Agilent 7500CE, Agilent Technologies, Inc. Snt Clr, USA) Sttisticl nlyses All dt collected were sujected to nlysis of vrince (ANOVA) using SPSS Sttistics for Slinity tolernce mechnisms in tomto nd okr Pge 8

10 Windows v17.0 (SPSS Inc., Chicgo, USA). The dt were first tested for normlity; Levene s test ws used to determine equlity of vrinces mong the tretment groups. Sttisticl significnce ws determined when p Tukey s highest significnt difference (HSD) ws used for men seprtion when tretment effect ws significnt; dt presented here re mens of t lest four replictes. One im of this work ws to exmine inter-reltionships etween plnt growth nd yield vriles, root nd shoot nutrient concentrtions vis-à-vis the slinity tretments. The numer of vriles, however, ws lrge (>30), therefore principl component nlysis (PCA) ws used to reduce the dimensionlity of the dt y extrcting nd summrising most of the vrince in the multivrite dt into few dimensions. The vriles nlysed here hd different units (mss, re, numer, etc.), so the PCA nlyses used correltion mtrix s input Results Growing conditions The temperture in the glsshouse fluctuted within 15% of their set vlues during the course of the study. There ws spike in temperture in mid-july tht cused the humidity to devite y up to 25% from the set rnge of 30 50%, otherwise the humidity remined within 10% of the desired rnge throughout the study period. The photosyntheticlly ctive rdition (PAR) within the glsshouse rnged etween 260 nd 900 µmol m -2 s -1 during dylight hours. 3.2 Plnt growth chrcteristics Responses of vegettive nd reproductive growth trits to slinity re summrised in Tle 1. Lef production, lef re nd height of tomto plnts were reduced on the sline soil nd y sline irrigtion. On the sline soil, tomto plnts were 12% shorter, hd 25% fewer leves tht Slinity tolernce mechnisms in tomto nd okr Pge 9

11 hd 73% smller totl re, compred with those on the non-sline soil. Reltive chlorophyll concentrtion, flower numers nd flower ortion in the tomto were insensitive to soil slinity. Irrigtion wter slinity significntly reduced lef re, numers of leves nd flowers nd plnt height, ut incresed reltive chlorophyll concentrtion nd flower ortion in this crop All growth vriles in okr were reduced on the sline soil nd y sline irrigtion, while flower ortion incresed in response to the slinity tretments (Tle 1). In okr, flower ortion incresed under slinity tretments, nd more so thn in tomto. Of ll the trits exmined in oth species, lef re ws the most sensitive to slinity irrespective of its source. Only wek interctions were oserved etween soil nd wter slinity in their effects on the mesured vriles in oth crops, ut were strong on chlorophyll concentrtions in tomto Fruit yield nd qulity Sline irrigtion severely reduced the yield nd yield components of tomto (Tle 2). When compred with the control, the 2.4 ds/m wter slinity, reduced fruit yield y 88%, fruit numer y 77% nd fruit size y 54%. Soil slinity lso negtively ffected tomto yield nd yield components, except the verge fruit size. Wter nd soil slinity, however, incresed sugr concentrtion in tomto fruits, nd for plnts on the non-sline soil, irrigtion with sline wter incresed fruit sugr concentrtion y up to 34%, wheres on the sline soil, the increse ws 74% (Tle 2). The yield nd yield components of okr were significntly reduced y wter nd soil slinity; the exception ws fruit size (Tle 2). Irrespective of soil slinity, incresing wter slinity from 0.0 to 2.4 ds/m reduced fruit yield nd numer y more thn 50%, ut fruit size ws comprtively less sensitive. Okr lost more fruits on sline soil (19%) thn the tomto (7%). Totl fruit weight Slinity tolernce mechnisms in tomto nd okr Pge 10

12 per plnt ws the most responsive yield vrile to oth wter nd soil slinity in okr s in the tomto. The yield response to irrigtion wter slinity ws driven primrily vi fruit numer wheres the response to soil slinity ws lmost eqully driven oth yield components Totl iomss production nd its prtitioning The dry weight of tomto plnts fell significntly with wter slinity on oth sline nd nonsline soils (Tle3). The weights of the plnt components (roots, shoots nd fruits) followed similr trend in their response to wter slinity. On oth soils, wter slinity reduced root/shoot nd fruit/shoot (puttive hrvest index). In contrst to wter slinity, soil slinity hd no significnt effect on plnt dry weight or on its prtitioning in the tomto. The severity of dverse impct of slinity on plnt dry weight nd its components (roots, shoots nd fruits) in okr incresed with wter slinity, especilly on the sline soil. Wter slinity lso reduced root/shoot rtio ut fruit/shoot rtios were unffected. Soil slinity ffected okr totl iomss, its components nd prtitioning (Tle 3) Wter use nd wter-use efficiency Wter used y tomto ws reduced on sline soil nd y slinity of the irrigtion wter (Tle 4), nd more so with wter slinity (~17%) thn soil slinity (6%). While wter-use efficiency (WUE) or the mount of fresh fruits produced for tomto per unit volume of wter ws not ffected y soil slinity, it fell with ech increse in the slinity of irrigtion wter. The deteriortion in WUE with incresing slinity of the irrigtion wter ws more severe on sline soil thn on non-sline soil. There were significnt correltions etween either the wter-use or WUE with wter slinity: Wter-use: y = -3.31x , r 2 = 0.81, n = 24 1 Slinity tolernce mechnisms in tomto nd okr Pge 11

13 WUE: y = -2.61x r 2 = 0.59, n = 24 1 Wter use for okr ws reduced y wter nd soil slinity (Tle 4). On the non-sline soil, wter-use ws only reduced when wter slinity ws rised to 2.4 ds/m, ut on the sline soil wter-use ws reduced with every increse in wter slinity. On verge, okr used out 11 L of wter less when grown on sline soil thn on non-sline soil. The WUE for okr fell with every increse in wter slinity on the non-sline soil, dropping y 52% t the highest wter slinity tretment, while it declined y 43% with sline irrigtion on the sline soil. There ws, however, no significnt difference etween the two soils in their men WUE. The wter-use nd WUE were relted with wter slinity s: Wter-use: y = x , r 2 = 0.45, n= 23 2 WUE: y = -0.53x , r 2 = 0.33, n = Elementl uptke nd distriution Soil slinity did not lter nutrient concentrtions in tomto tissues, ut in the okr it incresed concentrtions of N nd P in the roots nd fruits, in ddition to S in the roots (Fig. 1). Concentrtion of nutrients in the root of tomtoes ws in the order N > C Mg > K > S > P, while in the shoot the order ws N > K > C > Mg > P S. Elementl concentrtions in the fruit ws dominted y N on oth sline nd non-sline soils. Soil slinity significntly incresing concentrtions of N, P nd S in the root, P in the shoot nd N nd P in fruit in okr; N ws the dominnt nutrient in oth root nd fruit, while C nd K dominted in the shoot (Fig. 1). Concentrtions of N nd K in the roots, nd of C, K nd Mg in the shoots, were higher for okr thn found in tomtoes. Sline irrigtion incresed concentrtions of N in ll the three tissues of the plnt, in ddition to those of S in the root nd Slinity tolernce mechnisms in tomto nd okr Pge 12

14 fruit, nd of K, P nd S in the shoot, in the tomto (Fig. 2 c). Sline irrigtion reduced concentrtion of C, ut incresed tht of K, in the shoot. In okr, sline irrigtion incresed concentrtions of N in ll the plnt prts, nd reduced those of C nd K in the shoots (Fig. 2d f). Shoot concentrtions of N in okr ws not more thn third tht found in the tomto, while those of C, K nd Mg in okr were twice those in the tomto. In oth crops, soil nd wter slinity generlly incresed shoot/root N concentrtions, more so in the tomto in which the rtio ws in sline conditions compred with in okr (Tle 3) Reltionships etween ionic concentrtions nd plnt growth nd yield vriles Inter-reltionships etween root nd shoot minerl nutrient concentrtions, plnt growth nd yield vriles for ech species re displyed long the first two orthogonl dimensions from PCA for the two crops (Fig. 3). For tomto, the inter-reltionships etween the nutritionl sttus nd plnt trits re shown long the first two PCA dimensions, which jointly extrcted out 60% of the totl vrince (Fig 3). The first dimension (40% of the vrince) reflects impct of wter slinity nd shows tht there were positive ssocitions mong the shoot P, K, S, N, Cu, Zn, Mn, root N concentrtions, nd floret ortion (ll with moderte to high positive lodings), nd ll these were negtively correlted with fruit yield, wter-use, WUE, fruit numer per plnt s well s shoot C level (ll with high negtive lodings). The second dimension (20% vrince) reveled the impct of soil slinity. It contrsted root nutrient sttus (positive lodings) with lef numer nd re, plnt height nd floret ortion (ll with negtive lodings) to show generlly inverse ssocition etween the two sets of vriles. The impcts of the three wter slinity levels were distinctly seprted, with hrdly ny overlps mongst the symols, long the first principl dimension (Fig. 3). The influences of the soil slinity tretments were pprent long the second dimension leit less distinctly, with some overlps etween lue nd red symols, Slinity tolernce mechnisms in tomto nd okr Pge 13

15 thn oserved with wter slinity tretments. For okr, the first dimension extrcted 45% of the totl vrince s mesure of the impct of wter slinity on tissue nutrient concentrtions, yield nd growth vriles (Fig. 3c). This dimension revels negtive correltion etween root nd shoot N nd P sttus (high negtive lodings nd closely ssocited), on the one hnd, nd the plnt growth nd yield vriles s well s shoot concentrtions of Mn, Mg, C, S nd K sttus (high positive lodings), on the other. There ws thus dichotomous ssocition mongst these vriles. In one group were N nd P either in root or shoot tht hd negtive ssocitions with WU, WUE, fruit yield nd growth vriles (chlorophyll on the 26th, lef numer nd re, fruit numer, nd plnt height). In the other group were shoot concentrtions of C, Mg, Mn, S, nd K nd root concentrtion of K, ll which hd positive ssocitions with the physiologicl, growth nd yield vriles. The second dimension of portrying impct of soil slinity ccounted for out further 17% of the vrince; this hd high lodings on root concentrtions of C, Cu, Mg, Mn nd Zn (Fig. 3c). The vrition represented y the second dimension ws however only wekly ssocited with the plnt growth nd yield vriles. Overll impcts of soil nd wter slinity re clerly displyed in figure 3c. It shows tht the control nd high (2.4 ds/m) irrigtion were well seprted, with those of medium slinity overlpping with the other two, long dimension 1; there were significnt overlps in the responses etween the two soil slinity levels, especilly with sline irrigtion, long dimension 2. As would e expected, there were lso strong ssocitions mong the physiologicl, plnt growth nd yield vriles. For exmple, the mount of wter used per plnt ws closely relted with the numer of leves per plnt, lef re nd functionl stte s indicted y the lte seson chlorophyll concentrtions. Similrly, tight clustering ws evident mong fruit numer nd Slinity tolernce mechnisms in tomto nd okr Pge 14

16 yield per plnt, plnt height nd wter use efficiency. Differentil impcts of wter- nd soilslinity were further illustrted in terms of their reltive contriutions to totl vrince, e.g., in yield nd yield components for oth crops (Fig. 4). Overll, not more thn 5% of the vrince in fruit yield nd the min yield components for tomtoes were due to soil slinity compred to 10 28% in okr. In contrst, wter slinity ccounted for t lest 50% of the vrince in yield nd ssocited components in tomtoes, much higher thn mximum of 40% vrince ccounted for in okr Discussion Both crops were dversely impcted y slinity, ut they differed in their reltive sensitivity to the source of slinity. Soil slinity ws less injurious to tomto, which experienced yield reduction of just 13% compred with 48% in okr on the sline soil reltive to non-sline soil (Tle 2). The two crops lso differed in their ttriutes tht were more sensitive to soil slinity. Vegettive ttriutes (height, lef numer nd re) were dversely ffected, while the physiologicl nd reproductive ttriutes (chlorophyll contents nd numer of flowers produced nd their survivl) remined unffected in the tomto on sline soil. This ws contrry to reductions in ll the three ctegories of plnt ttriutes in okr grown on the sline soil (Tle 1). The two crops, however, were ffected y wter slinity with oth crops experiencing significnt reductions in yield with every step increse in slinity on oth soils. Regression nlyses (dt not presented) using pooled dt for ll tretments showed tht fruit yield in tomto fell y lmost 124 g/plnt (36% of yield under non-sline conditions) with every unit increse in wter slinity. Every unit increse in wter slinity reduced yield in okr reltive to non-sline irrigtion y g/plnt with n verge of 28% fll. Thus, tomto ws more sensitive to sline irrigtion. Slinity tolernce mechnisms in tomto nd okr Pge 15

17 The tomto showed lrge tolernce to shoot concentrtion of N. An increse in shoot/root N to 1.05 cused loss of only 14% in fruit yield, on sline soil (Tle 3). It ws likely tht the N in the shoot ws sequestered in the vcuoles nd wy from the cytoplsm of the lef, where most iochemicl processes occur, consistent with tissue tolernce mechnism of slinity (Munns et l., 2006). Sline irrigtion, however, incresed tissue concentrtions of N throughout the tomto plnt, with shoot concentrtion douling with every step up in the wter slinity tretment (Fig. 2) nd rising shoot/root N to s high s 3.06 (Tle 3). It ws prole tht such high N lod would hve overwhelmed the vcuolr cpcity to sequester N which must hve then leked into the cytoplsm of the lef to impir growth processes. This ppered to hve occurred in the current study when shoot/root N concentrtion exceeded the men vlue of 0.8 found on non-sline soil. The tissue tolernce in tomto could e ssocited with its lrge cpcity for osmotic djustment tht mintined osmotic potentil of the lef constnt ove -1.0 MP even with sline irrigtion of up to 7.4 ds/m (Psternk et l., 1986). In contrst to tomto, okr ws more sensitive to shoot N nd so minimised prtitioning this nutrient to the shoot. The shoot/root N concentrtion in okr did not exceed 0.35 in plnts on sline soil irrigted with sline irrigtion, which ws desirle since even the low shoot/root N concentrtion of 0.16 with 1.2 ds/m irrigtion on non-sline soil reduced fresh fruit yields y 36%. Minimising the trnsfer of N to the shoot (minly leves) y the okr ws consistent with slt exclusion mechnism for tolerting sline conditions. In this crop the fruits ecome N sink lmost s lrge s the roots when the crop ws exposed to sline environments (Fig. 1 nd 2). The other fctor in slinity responses in oth crops is the role of other ctions in either eing detrimentl to yield or uffering the phytotoxic effects of N. For instnce, P concentrtion in Slinity tolernce mechnisms in tomto nd okr Pge 16

18 either shoot or roots ws negtively, while C nd Mg were positively correlted with fruit yields nd severl other yield ttriutes in oth crops (Fig. 3). Excessive tissue concentrtion of P in okr ws reported to induce deficiency of severl micronutrients such s Zn nd Mn (Lonergn et l., 1981) tht ply key roles in enzyme systems nd chlorophyll synthesis. Shoot P concentrtion of 0.25% (2500 mg/kg) fr exceeded the upper limits of 40 mg/kg found in severl studies (Aknde et l., 2006). Preferentil ccumultion of K over N in the shoot (mostly leves) is nother mechnism commonly ssocited with slinity tolernce in plnts (Gorhm et l., 1990). The iplots of our dt show the shoot concentrtion of K nd yields for okr eing on the sme side of the reference line on dimension one in the plot of vector lodings (Fig. 3). The shoot K/N vlues found here were much lrger thn K/N vlues pulished for okr of not more thn 2.0 even under non-sline conditions (Sleem et l., 2011), possily result of high nutrient mngement in the current study. Tissue K nd yield nd growth vriles for the tomto were on the opposite sides of the reference line on the first dimension suggesting n inverse reltionship. It ws possile tht K might hve een ntgonistic to uptke of other ctions such s C nd Mg in the tomto since oth ions hd low shoot concentrtions tht were just frctions of those found in okr (Fig. 2 nd 3), or even when compred to 4% reported in severl vegetle crops (Mksimović nd Ilin, 2012). Increses in shoot N in the two crops dversely ffected growth nd yield vriles, including developing flowers nd fruits. Incresed incident of flower ortion under sline conditions hs een widely reported for mny plnt species, including crops s vried s tomtoes (Ghnem et l., 2009), chickpe (Krishnmurthy et l., 2011), sunflower (Frncois, 1995) nd jojo (Benzioni et l., 1992). The mechnism of flower ortion due to slinity is not fully understood, Slinity tolernce mechnisms in tomto nd okr Pge 17

19 ut the results presented here revel it could e the result of high concentrtions of mcro (K, P nd S) nd micro-nutrients (N, Cu nd Zn) in the shoot of tomto (Fig. 3). Reductions in growth nd ssocited processes due to slinity (Tle 3), including wter-use nd wter-use efficiency (Tle 4), re consistent with mny previous studies on tomtoes (Brgllo et l. 2012) nd okr (Adewoye et l., 2010; ul-hq et l., 2012). Reductions in root growth re often ssocited with low wter nd osmotic potentil in the rhizosphere tht then impedes uptke of nutrient nd wter (Munns nd Tester, 2008), therey restricting root nd shoot growth tht would hve constrined wter-use in oth crops (Tle 4). Soil nd wter slinity oth incresed glucose content of tomto fruit s found in severl erlier studies nd ws ssocited with incresed K concentrtion in the fruits (Mchdo et l., 2003; Yurtseven et l., 2005) s we present here. For oth crops, the impct of soil slinity ws much smller thn of sline irrigtion, especilly for tomto. Under field conditions, preferentil ion uptke from the less sline topsoil hs een invoked to explin differentil plnt growth responses to soil vs wter slinity (Ms nd Hoffmn, 1977). The extent to which such preferentil wter extrction explined the lower phytoxicity of the soil slinity in the current study is not cler since the roots proliferted the whole of the 24 cm deep soil. Although it ws possile tht the frequent irrigtion from the top could hve creted concentrtion grdient in the soil profile over time, it ws more likely tht the dissolved slt in the irrigtion wter ws more redily ville since its ddition coincided with irrigtion tht incresed wter vilility, which promoted sorption of dissolved slt y the plnt (Mksimović et l., 2010) in preference to the slt sourced from the soil. These results suggest tht contrsting irrigtion strtegies re needed to optimise productivity for the two crops under sline conditions. The high sensitivity of tomto to irrigtion slinity Slinity tolernce mechnisms in tomto nd okr Pge 18

20 suggests tht reducing irrigtion events, i.e. longer irrigtion intervls, would minimise the potentil for the uptke nd ccumultion of slts dissolved in the irrigtion wter y plnts. For okr, frequent nd regulr over irrigtion will lech out the slt nd prevent its ccumultion in the root zone. Frequent irrigtion with sline wter of up to 4.9 ds/m, twice the mximum used in the current study, mintined the mtric potentil in the root zone of silty cly ove the threshold of -30 kp to mintin crop wter-use (Wn et l., 2007) Summry nd conclusions Tomto nd okr differed in their responses to soil or wter slinity. The tomto due to its pprent inility to divert N wy from the shoot (minly leves), showed tissue tolernce in mintining resonle yields even s shoot/root N concentrtion rose to 0.8. This crop must hve sequestered the N in the vcuoles of lef tissues llowing mintennce of growth processes, ut the storge cpcity of vcuoles would hve een overwhelmed with incresed slt lod due to wter slinity. Okr ws quite sensitive to shoot N with yield significntly reduced with shoot/root N s low s In okr, we found most tissue N in fruits nd little in leves, functioning s slt exclusion mechnism. The yield penlty due to sline irrigtion ws therefore more severe in the tomto tht lost out 85% of its fresh fruits thn in the okr tht lost n verge of 64% of its fresh fruits. Sline irrigtion ws more injurious to plnts thn wter slinity in oth crops, ccounting for the overwhelming mjority of vrince, proly due to greter vilility to the plnts of dissolved slt in irrigtion wter thn in the soil. These results suggest tht contrsting irrigtion strtegies re needed to optimise productivity for the two crops under sline conditions. The high sensitivity of tomto to irrigtion slinity cn e mnged y extending irrigtion intervls to minimise opportunities for slt uptke nd ccumultion. By contrst, frequent nd regulr over irrigtion will lech out the slt nd Slinity tolernce mechnisms in tomto nd okr Pge 19

21 prevents its ccumultion in, the root zone to ensure high yields in okr. Acknowledgements The uthors Michel Fint for the enormous technicl ssistnce he provided in undertking the experiment. The ssistnce of Ms Lenne Leslie with chemicl nlyses, Ms Jn Cruthers with smple processing, nd Ms Chrissie Prychid with plnt mesurements is pprecited. The uthors lso cknowledge the nonymous reviewers whose comments improved this pper. The first uthor thnks the Irqi Government for postgrdute scholrship. 428 Slinity tolernce mechnisms in tomto nd okr Pge 20

22 References Adewoye, A.O., Okunde, D.A. nd Adeklu, K.O. (2010). Assessing the yields nd nutrient uptke of okr (Aelmoschus esculentus) using diluted stilised wstewter for irrigtion in south-western Nigeri. Journl of Wste Wter Tretment nd Anlysis, 1: 104. doi: / Aknde, M.O., Oluwtoyino, F.I., Kyode, C.O. nd Olowokere, F.A. (2006). Response of mize (Ze mys) nd okr (Aelmoschus esculentus) intercrop relyed with cowpe (vign unguicult) to different levels of cow dung mended phosphte rock. World Journl of Agriculturl Science 2: Ashrf, M. (2004). Some importnt physiologicl criteri for slt tolernce in plnts. Flor 199: Brgllo, R.N., Silvestro, D. nd Ptné, C. (2012). Yield, physicochemicl trits, ntioxidnt pttern, polyphenol oxidse ctivity nd totl visul qulity of field-grown processing tomto cv. Brigde s ffected y wter stress in Mediterrnen climte. Journl of the Science of Food nd Agriculture 93: Benzioni, A, Nerd, A, Rosenärtner, Y nd Mills D. (1992). Effect of NCl Slinity on Growth nd Development of Jojo Clones: I. Young Plnts. Journl of Plnt Physiology 139: Coste, S, Brloto, C, Leroy, C, Mrcon, E, Renud, A, Richrdson, A.D., Roggy, J-C., Schimnn, H., Uddling, J., Hérult, B. (2010). Assessing folir chlorophyll contents with the SPAD-502 chlorophyll meter: clirtion test with thirteen tree species of tropicl rinforest in French Guin. Annls of Forest Science 67: 607 (5pp). Slinity tolernce mechnisms in tomto nd okr Pge 21

23 del Amor, F. M., Mrtinez, V. nd Cerd, A. (2001). Slt tolernce of tomto plnts s ffected y stge of plnt development. HortScience 36: Flowers, T. J. (2004). Improving crop slt tolernce. Journl of Experimentl Botny 55: Frncois, L (1995). Slinity effects on four sunflower hyrids. Agronomy Journl 88: Gorhm, J, Bristol A, Young EM, Wyn Jones RG, Kshour G (1990). Slt tolernce in the Triticee: K/N discrimintion in rley. Journl of Experimentl Botny 41: Ghnem, M.E., vn Elteren, J., Alcete, A., Quinet, M., Mrtínez-Andújr, C., Kinet, J-M., Pérez-Alfoce, F., Lutts, S. (2009). Impct of slinity on erly reproductive physiology of tomto (Solnum lycopersicum) in reltion to heterogeneous distriution of toxic ions in flower orgns. Functionl Plnt Biology 36: ul-hq, I., Khn, A.A., Khn, I.A., Azmt, M.A. (2012). Comprehensive screening nd selection of okr (Aelmoschus esculentus) germplsm for slinity tolernce t theseedling stge nd during plnt ontogeny. Journl of Zhejing Univ-Sci B (Biomed & Biotechnol) 13: Krishnmurthy, L., Turner, N.C., Gur, P.M., Updhyy, H.D., Vrshney, R.K., Siddique, K.H.M., Vdez, V. (2011). Consistent vrition cross soil types in slinity resistnce of diverse rnge of chickpe (Cicer rietinum L.) genotypes. Journl of Agronomy nd Crop Science 197: Lonergn, J.F., Grunes, D.L., Welch, R.M., Aduyi, E.A., Tengh, A., Lzr, V.A., Cry, E.E., (1981). Phosphorus Accumultion nd toxicity in leves in reltion to zinc supply. Soil Science Society of Americ Journl 46: Slinity tolernce mechnisms in tomto nd okr Pge 22

24 Ms, E.V., Hoffmn, G.J. (1977). Crop slt tolernce-current ssessment. Journl of Irrigtion nd Dringe, Div. Civ. Eng., 103: Mchdo, R.M.A., Rosri, M., Oliveir, G. nd Ports, C.A.M. (2003). Tomto root distriution, yield nd fruit qulity under susurfce drip irrigtion. Plnt nd Soil 255: Mksimović, I. nd Ilin, Ž. (2012). Effects of slinity on vegetle growth nd nutrients uptke. Irrigtion systems nd prctices in chllenging environments. < intechopen. com/ooks/irrigtion-systems-nd-prctices-in-chllenging-environments/effects-ofslinity-on-vegetle-growth-nd-nutrients-uptke, 180. (ccessed: Decemer 18, 2013). Mksimović, I., Putnik-Delić, M., Gni, I., Mrić, J. nd Ilin, Ž. (2010). Growth, ion composition, nd stomtl conductnce of pes exposed to slinity. Centrl Europen Journl of Biology 5: Munns, R., Jmes, R.A., Läuchli, A. (2006). Approches to incresing the slt tolernce of whet nd other cerels. Journl of Experimentl Botny 57: Munns, R., Tester, M. (2008). Mechnisms of slinity tolernce. Annul Reviews of Plnt Biology 59: Psternk, D., De Mlch, Y. nd Borovic, I. (1986). Irrigtion with rckish wter under desert conditions. VII. Effect of time of ppliction of rckish wter on production of processing tomtoes (Lycopersicon esculentum Mill.). Agriculturl Wter Mngement 12: Perez-Alfoce, F., Alcete, A., Ghnem, M. nd Dodd, I.C. (2010). Hormonl regultion of source-sink reltions to mintin crop productivity under slinity: cse study of root to shoot signlling in tomto. Functionl Plnt Biology 37: Slinity tolernce mechnisms in tomto nd okr Pge 23

25 Rogers, M.E., West, D.W. (1993). The effects of rootzone slinity nd hypoxi on shoot nd root growth in trifolium species. Annls of Botny 72: Sleem, A., Ashrf, M., Akrm nd N.A. (2011). Slt (NCl)-induced modultion in some key physio-iochemicl ttriutes in okr (Aelmoschus esculentus L.). Journl of Agronomy nd Crop Science 197: Shnnon, M. C., Grieve, C. M., Lesch, S. M. nd Drper, J. H. (2000). Anlysis of slt tolernce in nine lefy vegetles irrigted with sline dringe wter. Journl of the Americn Society for Horticulturl Science 125: Wn, S., Kng, Y., Wng, D., Liu, S. P. nd Feng, L. P. (2007). Effect of drip irrigtion with sline wter on tomto (Lycopersicon esculentum Mill) yield nd wter use in semi-humid re. Agriculturl Wter Mngement 90: Yunus, I.A.M., Burchett, M.D., Mnohrn, V., DeSilv, D.L., Emus, D., Skileck, G.C. (2009). Photosynthetic pigment concentrtion, gs exchnge nd vegettive growth of selected monocots nd dicots treted with contrsting col fly shes. Journl of Environmentl Qulity 38: Yurtseven, E. Kesmez, G.D. nd Unlukr, A. (2005). The effects of wter slinity nd potssium levels on yield, fruit qulity nd wter consumption of ntive centre Antolin tomto species. Agriculturl Wter Mngement 78: Slinity tolernce mechnisms in tomto nd okr Pge 24

26 513 Tle 1. Impct of soil nd wter slinity on plnt growth vriles for glsshouse grown tomtoes nd okr Soil slinity (ds/m) Wter slinity (ds/m) Lef re/ plnt (cm 2 ) Leves/ plnt 1 Finl plnt height (cm) Chlorophyll content (µg/cm 2 ) t 95 DAT 117 DAT Flowers/ Plnt 2 Flower ortion (%) Tomto c c c 67.3c 133.0c 86.4c 47.3c 40.8c 93.8 Men 343.0A 73.8A 138.6A 72.3A 39.0A 42.8A 82.8A c c c c 92.9 Men 93.0B 55.8B 123.3B 62.4A 43.8A 41.7A 81.9A Okr c c c 10.0 c 76.8c 53.0c 52.7c Men 92.3A 11.9A 97.9A 62.0A 61.4A 8.3A 15.2A c c 5.3c 31.3c 41.9c 42.5c 6.0c 45.6 Men 5.3B 8.9B 52.8B 49.2B 47.6B 7.8B 32.6B 1 mesured t 20 dys fter trnsplnting (DAT); for ech crop, mens in the sme columns followed with the sme letter(s) for given soil slinity re sttisticlly similr t p 0.05; the lowercse letters compre mens for wter slinity levels, nd uppercse letters compre mens for soil slinity 516 Slinity tolernce mechnisms in tomto nd okr Pge 25

27 517 Tle 2. Impcts of soil nd wter slinities on fresh fruit yields nd yield components for glsshouse grown tomto nd okr. Soil slinity Wter slinity Fruits/plnt Totl fruit Weight/fruit Glucose content in (ds/m) (ds/m) yield/plnt (g) (g) tomto fruit (mmol/l) Tomto c 49.9c 14.4c 56.9c Men 7.4A 201.7A 23.9A 50.8A c 38.1c 13.2c 88.0c Men 6.9B 174.6B 20.7A 70.1B nd Okr nd c 45.5c 9.0 nd Men 6.4A 74.4A 10.4A nd nd nd c 8.9 nd Men 5.2B 38.5B 8.7A nd nd, not determined; for ech crop, mens in the sme columns followed with the sme letter(s) for given soil slinity re sttisticlly similr t p 0.05; the lowercse letters compre mens for wter slinity levels, nd uppercse letters compre mens for soil slinity. Slinity tolernce mechnisms in tomto nd okr Pge 26

28 Tle 3: Impcts of soil slinity nd wter slinity on the dry weights of plnt tissues, nd shoot/root rtio in N concentrtions for glsshouse grown tomto nd okr. Soil slinity (ds/m) Wter slinity (ds/m) Root (g) Shoot (g) Fruit (g) Totl 1 (g) Root/shoot Fruit/shoot Shoot/root N Tomtoes c 49.6c 0.7 c 53.7c c 1.21 Men 6.8A 59.1A 1.0A 67.0A 0.10A 0.017A 0.71B c 39.8c 0.6c 43.0c 0.06 c c 3.06 Men 3.5A 52.7A 1.0A 57.3A 0.06A 0.018A 1.54A Okr c 8.6c 0.8c 11.3c Men 3.1A 12.8A 1.1A 17.0A 0.22A 0.08A 0.12B c 4.2c 0.5c 5.5c Men 1.4B 7.2B 0.8B 9.5B 0.13B 0.1B 0.24A 1 sums of root, shoot nd fruit t hrvest; for ech crop, mens in the sme columns followed with the sme letter(s) t given soil slinity re sttisticlly similr t p 0.05; the lowercse letters compre mens for wter slinity levels, nd uppercse letters compre mens for soil slinity. Slinity tolernce mechnisms in tomto nd okr Pge 27

29 Tle 4: Impcts of soil slinity nd wter slinity on wter-use nd wter use efficiency for fruit yield (WUE) for glsshouse grown tomtoes nd okr Soil slinity (ds/m) Wter slinity (ds/m) Wter use (L/plnt) Tomto W UE (g/l) c 1.0c Men 43.3A 4.2A c 0.8c Men 40.7B 3.6A Okr c 1.4c Men 35.3A 2.0A c 1.2 Men 25.0B 1.5A For ech crop, mens in the sme columns followed with the sme letter(s) t given soil slinity re sttisticlly similr t p 0.05; the lowercse letters compre mens for wter slinity levels, nd uppercse letters compre mens for soil slinity Slinity tolernce mechnisms in tomto nd okr Pge 28

30 Concentrtion (w/w%) () Control soil Sline soil (d) C K Mg N P S C K Mg N P S () (e) 4.0 Concentrtion (w/w%) C K Mg N P S (c) C K Mg N P S (f) Concentrtion (w/w%) C K Mg N P S Nutrients C K Mg N P S Nutrients Figure 1. Impct of soil slinity on nutrient concentrtions in the root (, d), shoot (, e) nd fruit (c, f) t hrvest for tomto ( c) nd okr (d f). Where tretment mens re significntly different (p < 0.05) re indicted y different letters. 537 Slinity tolernce mechnisms in tomto nd okr Pge 29

31 3.0 () (d) 3.0 Concentrtion (w/w%) ds/m 1.2 ds/m 2.4 ds/m C K Mg N P S c c C K Mg N P S Concentrtion (w/w%) () c c C K Mg N P S (c) c c c (e) c C K Mg N P S (f) Concentrtion (w/w%) C K Mg N P S c C K Mg N P S Nutrients Nutrients Figure 2. Impct of sline irrigtion on nutrient concentrtions in the root (, d), shoot (, e) nd fruit (c, f) t hrvest for tomto ( c) nd okr (d f). Where tretment mens re significntly different (p < 0.05) re indicted y different letters. 542 Slinity tolernce mechnisms in tomto nd okr Pge 30

32 c d Figure 3. Interreltionships mongst plnt response vriles generted y principl component nlyses (PCA) showing vector lodings (, c) nd iplots for slinity tretments (, d) for tomtoes (, ) nd okr (c, d). Codes in nd d re: C (control, 0 ds/m, circles) M (medium, 1.2 ds/m, squres) nd H (high, 2.4 ds/m, tringles) irrigtion wter slinity, nd C (control, 0 ds/m, lue) nd 3 ds/m (red) soil slinity. The vriles plotted re wter-use (WU), lef re (LA), lef numer (lefno), chlorophyll concentrtions (ch) on two dtes, flower numer (FlwrNo) nd flower ortion (FlArt), plnt height (PlntHt), fruit yield (FrtYld) nd fruit numer (FrtNo), nd ionic concentrtions in the shoot (_s) or root (_r). Slinity tolernce mechnisms in tomto nd okr Pge 31

33 Fig. 4. Reltive impcts of soil slinity nd wter slinity on selected yield vriles for okr nd tomto: () proportions of vrince due to the respective slinity source, nd () plnt response vriles normlized over control vlues Slinity tolernce mechnisms in tomto nd okr Pge 32