Grafting and Silicon Improve Photosynthesis and Nitrate Absorption in Melon (Cucumis melo L.) Plants

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1 J. Agr. Sci. Tech. (215) Vol. 17: Grfting nd Silicon Improve Photosynthesis nd Nitrte Asorption in Melon (Cucumis melo L.) Plnts Downloded from jst.modres.c.ir t 17:34 IRST on Fridy Octoer 5th 218 D. Neocleous 1 ABSTRACT Grfting of Cucuritcee species to some rootstocks seems to e especilly eneficil for the nitrogen nutrition of these plnts. Moreover, melons (Cucumis melo L.) hve een considered mong those plnts tht could enefit from the ddition of Silicon (Si) in the Nutrient Solution (NS). Thus, two experiments were crried out in the following order: (i) it ws investigted how grfting ffects nitrte sorption (following the disppernce of nitrtes from NS), lef wter reltions, lef gs exchnge, chlorophyll prmeters nd ntioxidnt ctivity, nd (ii) it ws lso ssyed which of the forementioned physiologicl fctors could e ssocited with Si supply in melon plnts t erly developmentl stge when metolism is intense. Results reveled tht grfting nd Si supply could improve photosynthesis, nitrte sorption, nd iomss production in melon plnts with respect to non-grfted or plnts not receiving extr Si. Grfting melon on Cucurit rootstock improved photosynthetic performnce ssocited with higher ntioxidnt ctivity in melon leves. Silicon supplementtion results lend support to n ctive role of Si in iochemicl processes t chloroplst level in melons. Incresed ssimiltion rtes in grfted nd Si treted plnts (2 to 35%), resulted in higher nitrte depletion from the medium (17 to 18%), which oosted shoot iomss production (23 to 26%) compred to the control plnts. Our results suggest tht grfting nd Si supply in melon plnts my led to etter crop performnce nd lower environmentl impct of greenhouse fertigtion effluents with respect to nitrte leching, in some instnces. Keywords: Antioxidnt ctivity, Biomss production, Gs exchnge, Hydroponic melons. INTRODUCTION Melons (Cucumis melo L.) re one of the most commercilly importnt crops in the Mediterrnen re nd production of Glitype melons in soilless systems could e n lterntive crop for greenhouse growers. Optimizing plnt growth while minimizing - the NO 3 trnsport to ground nd surfce wters remins mjor chllenge in greenhouse horticulture in these countries. Vegetle grfting is ecoming common prctise in Mediterrnen sin nd grfting of Cucuritcee to some rootstocks seems to e especilly eneficil for the nitrogen nutrition of these plnts (Sn Butist et l., 211). Svvs et l. (21) reveled tht certin Cucuritcee rootstocks enhnce not only the uptke of NO 3 nd trnsloction to the shoot ut lso its utiliztion y the plnt through more intensive ssimiltion into mino cids nd proteins. This notion ws lso supported y Ruiz nd Romero (1999) nd Coll et l. (21) studying N metolism in grfted melon plnts in hydroponics nd open field conditions. In this sense, other uthors (Slehi et l., 21) reported tht grfting chieves n increse in ion influx to the scion, resulting in the increse of light energy trnsformtion efficiency, CO 2 conductivity, drk rection ctivity, nd photosynthetic rte in the scion. However, few pulished dt re ville concerning which physiologicl nd iochemicl fctors 1 Agriculturl Reserch Institute, Ministry of Agriculture, Nturl Resources nd Environment, P. O. Box: 2216, 1516 Nicosi, Cyprus. e-mil: d.neocleous@rinet.ri.gov.cy 1815

2 Neocleous Downloded from jst.modres.c.ir t 17:34 IRST on Fridy Octoer 5th 218 could e ssocited with N efficiency in melon plnts prticulrly t erly developmentl stge when metolism is intense (Sn Butist et l., 211). Photosynthesis is core function nd its functionl sttus hs een considered n idel physiologicl ctivity to monitor plnt growth (Lrcher, 198). Since grfting cn influence photosynthesis nd, s consequence, the vilility of cron sed sustrtes (Coll et l., 21), is of prmount importnce to etter understnd photosynthetic responses of melon plnts to grfting. However, compring results from different studies re not lwys fesile since significnt differences my exist due to experimentl lyout (Boll et l., 29). Sn Butist et l. (211) reported tht grfting melon plnts did not ffect net photosynthetic vlues, wheres doule grfting incresed minerl nd wter sorption, light photosynthetic rection, nd iomss production. In this word context, Slehi et l. (21) reported tht grfting melon plnts did not ffect net CO 2 ssimiltion rte significntly, ut the grfted plnts hd more net CO 2 ssimiltion rte thn un-grfted ones. Despite the importnce of etter understnding of the photosynthetic metolism of grfted plnts, few studies re concerned out photosynthesis performnce nd protective ntioxidnt responses of grfted plnts (He et l., 29). It hs een reported tht Silicon (Si) exerts eneficil effects on soilless-grown plnts, nd melons hve een considered s one of the plnts tht could enefit from the ddition of Si in the nutrient solution (Adms, 22, Sonneveld nd Voogt, 29). Svvs et l. (27) reveled tht the stimultion of growth y Si my e either indirect, owing to the protective effects of Si ginst pthogens, or direct, originting from implictions of Si to oth morphologicl chnges nd physiologicl processes in plnts. Kmenidou et l. (29) lso reveled tht one of the most controversil Si enefits is its decrese of trnspirtion nd increse of photosynthesis ssocited with folir ccumultion of Si. In cucumer, one of the protective effects of Si in photosynthesis hs een considered to e ssocited with the ntioxidnt enzymes ctivity (Zhu et l., 24). Currently, lthough the inclusion of Si in the nutrition scheme in soilless culture of some plnt species is recommended (Sonneveld, 22; Svvs et l. 27), our knowledge regrding the hypothesized role for Si in plnt physiology is still insufficient. In view of the ove, the present two experiments imed to: (i) investigte how grfting ffects nitrte sorption, lef wter reltions, lef gs exchnge, chlorophyll prmeters nd ntioxidnt ctivity, nd (ii) ssy which of the forementioned prmeters could e ssocited with Si supply in the nutrient solution of melon plnts. MATERIALS AND METHODS Plnt Mteril Two experiments were conducted t Agriculturl Reserch Institute, Cyprus (34 44 N, E) during the period 25 April-15 June 213. A netted cultivr (cv. Dikti F 1, Rijk Zwn, De Lier, Netherlnds) of melon (Cucumis melo L.) plnts ws either Non-Grfted () or Grfted (R- GR) onto the Cucurit rootstock RS 841 (C. mxim C. moscht) in commercil nursery. The grfting comintion ws widely used y the locl growers. Seeds of oth melon nd sqush were sown on 2 Mrch 213 in trys filled with pet-sed sustrte. Grfting ws mde on 1 April 213 using the procedure of cleft grfting joining the melon scion nd the rootstock, using the tongue pproch, with clip nd cutting off the scion 15 dys lter just elow the grft union (Lee, 1994). The plnts were trnsplnted in mixture of pet (Shmrock moss pet) nd perlite (1:1, v:v) in 7 cm squre lck plstic pots nd used for Experiments 1 nd 2. Tp wter ws used for irrigtion. 1816

3 Responses of Melon to Grfting nd Silicon Downloded from jst.modres.c.ir t 17:34 IRST on Fridy Octoer 5th 218 Experiment 1 Rootstock-Grfted () nd Non- Grfted () melon plnts t the stge of two true leves (8-1 cm height) were trnsferred for hydroponic culture in floting system into culture room with 22±2ºC temperture, 55-65% reltive humidity, 16 hours photoperiod nd light intensity of 15 µmol m -2 s -1 from April 25 to My 15, 213. Floting system consisted of 12 individul polystyrene oxes (4 cm length 27 cm wide 17 cm deep) ech contining 16 L of erted nutrient solution. Six propgtion pots, ech contining one plnt, were floted on ech polystyrene ox. Ech ox ws considered s experimentl unit rrnged in Completely Rndomised Design (CRD) with six replictions. Plnts were hrvested three weeks fter trnsplnting (15 My 213). The NS initilly introduced into the system ws identicl in ll experimentl units, nd the composition ws s follows: 5.79 mm K +, 5.79 mm C 2+, 2.7 mm Mg 2+, 1.1 mm NH 4 +, mm NO 3 -,.8 mm H 2 PO 4 -, 2.97 mm SO 4 2-, 25 μm Fe, 5 μm Mn, 7 μm Zn, 1. μm Cu, 5 μm B, nd.5 μm Mo. Corresponding Electricl Conductivity (EC) vlue of NS ws 2.5 ds m -1 nd ph vlue ws djusted to Experiment 2 nd melon plnts were pruned to height of 12 cm (four true leves) nd trnsferred into culture room with 24±2 ºC temperture, 55-65% reltive humidity, 16 hours photoperiod nd light intensity of 15 µmol m -2 s -1 from My 23 to June 15, 213. Floting system consisted of 18 individul polystyrene oxes nd experimentl setup ws s in Experiment 1. nd plnts were supplemented with Si (N 2 SiO 3 ) t three rtes (,.5 nd 1 mmol L -1 ) in the NS. Ech ox ws considered s experimentl unit rrnged in Completely Rndomized Design (CRD) with three replictions. Plnts were hrvested three weeks fter trnsplnting (15 June 213). The NS initilly introduced into the system ws identicl in ll experimentl units, nd the sme s in Experiment 1. Hrvesting nd Hndling At finl hrvest, hlf of the shoots (eril prt of plnts) from ech plot ws frozen nd stored t 3 C for totl phenolics nd ntioxidnt ctivity nlysis nd the other hlf ws dried in forced-ir oven t 65 C to constnt weight for shoot iomss determintion. Mesurements To clculte nitrte (NO - 3 ) sorption, oth the input nd output of the NS were - determined nd the NO 3 sorption ws determined from the chnges in the solution volume nd nitrte concentrtions (disppernce of nitrtes from the solution). The chnges in wter volume corresponded to plnt wter uptke since wter losses from - the system were negligile. The NO 3 ion concentrtions in NS were mesured y UV/VIS spectroscopy t 22 nm (Eton, 25). Before finl hrvest, the lst functionl fully expnded leves on three melon plnts per plot were used etween 7: 9. m to mesure the following: (i) gs exchnge prmeters [i.e., net CO 2 ssimiltion (A), stomtl conductnce (g s ), intercellulr CO 2 concentrtion (Ci), nd rte of trnspirtion (E)] using LI-64 (LI-COR, Lincoln, NE, USA); nd (ii) Wter Use Efficiency (WUE) s A/E. LI-64 mesurements of photosynthesis nd trnspirtion re sed on differences in CO 2 nd H 2 O in n ir strem tht is flowing through lef chmer. The system ws clirted prior to mesurements. Susequently, leves were smpled nd used to mesure: (i) lef wter potentil (Ψ w ) nd osmotic potentil (Ψ π ) using SKPM 14 pressure chmer (Skye 1817

4 Neocleous Downloded from jst.modres.c.ir t 17:34 IRST on Fridy Octoer 5th 218 Instruments Ltd, Llndrindod, UK) nd HR- 33T microvoltometer (Wescor Inc., Logn, UT, USA), respectively; (ii) lef turgor pressure (Ψ p ) s Ψ w -Ψ π ; (iii) Reltive Wter Content (RWC) s descried y Lrcher (198); (iv) chlorophyll contents ccording to Lichtenthler (1987); (v) chlorophyll fluorescence (mximum efficiency of photosystem II; Fv/Fm rtio) using OS-3p fluorometer (Opti-Sciences, Hudson, NH, USA), nd (vi) Electron Trnsport Rte (ETR), following Bker (28). Totl phenolic content, Ferric-Reducing Antioxidnt Power (FRAP ssy) nd rdicl scvenging ctivity (2.2-DiPhenyl-1- PicrylHydrzyl; DPPH ssy) of shoots were mesured following Neocleous et l. (214). For silicon nlyses, ech tissue from ech Si tretment ws nlyzed in triplicte. Dry tissue ws microwve digested (MARS 24/5, CEM Microwve Corportion, NC, USA) nd Si content ws mesure y ICP- OES (Teledyne Leemns Ls, Prodigy Spec., NH, USA). Sttisticl Anlysis Anlysis of vrince ws evluted y SAS (Version 9.2; SAS Institute Inc., Cry, NC, USA). Mens were compred using Duncn s multiple rnge tests t P.5. Figures were drwn using GrphPd Prism (Version 5.; GrphPd Softwre; Sn Diego Cliforni, USA). RESULTS Experiment 1 Grfting incresed dry shoot iomss y 28% compred to non-grfted plnts s shown in Figure 1. Similr to iomss production, the net ssimiltion of CO 2 (A), stomtl conductnce (g s ), trnspirtion rte (E), nd Wter Use Efficiency (WUE) were significntly higher in rootstock-grfted plnts (Figure 1). However, internl CO 2 (Ci) remined unffected y tested tretments (Figure 1). Grfting hd no effect either on lef wter reltions, i.e. lef wter potentil (vg Mp), lef osmotic potentil (vg Mp), lef turgor pressure (vg..22 Mp) nd reltive wter content (vg. 93%) or chlorophyll prmeters, i.e. chlorophyll fluorescence in the form of Fv/Fm rtio (vg..8) nd chlorophyll content (vg mg g -1 FW). With respect to ntioxidnts, grfting incresed shoot phenolic content nd ntioxidnt ctivity s mesured y FRAP nd DPPH ssys (Figure 2). Finlly, plnts sored significntly higher levels of nitrte from the medium compred to plnts, s indicted y nitrte depletion from the nutrient solution (Figure 2). Experiment 2 As shown in Tle 1, grfting incresed dry shoot iomss, net ssimiltion of CO 2 (A), stomtl conductnce (g s ) nd trnspirtion rte (E) compred to nongrfted plnts. Plnts received extr Si t.5 mm showed the highest vlues with respect to iomss production nd A, wheres, plnts not receiving extr Si showed the lowest vlues nd the plnts tht received extr Si t 1. mm were in etween (Tle 1). Stomtl conductnce (g s ), E nd WUE remined unffected y Si supplementtion. However, Si supplemented plnts showed lower internl CO 2 (Ci) thn the other plnts (Tle 1). Neither grfting nor Si supply hd significnt effect on lef wter reltions, i.e. lef wter potentil (vg Mp), lef osmotic potentil (vg Mp), lef turgor pressure (vg..22 Mp) nd reltive wter content (vg. 88%) or chlorophyll prmeters, i.e. chlorophyll fluorescence Fv/Fm rtio vlue (vg..81) nd chlorophyll content (vg. 1.5 mg g -1 FW). With respect to ntioxidnts, grfting incresed shoot phenolic content nd ntioxidnt ctivity s mesured y FRAP nd DPPH ssys (Tle 1). However, this ws not the cse in Si supplemented plnts. Si supply decresed totl phenolics in 1818

5 Responses of Melon to Grfting nd Silicon A DW 1 1 Downloded from jst.modres.c.ir t 17:34 IRST on Fridy Octoer 5th 218 Net CO2 ssimiltion Stomtl conductnce (mmol H 2 O m -2 s -1 ) Trnspirtion rte (µmol CO 2 m -2 s -1 ) 15 1 (mmol H2O m -2 s -1 ) g s E Shoot dry weight (g plnt -1 ) Intercellulr CO 2 (µmol CO2 mol -1 ) Wter use efficiency (µmol CO2 mmol -1 H2O) Ci WUE Figure 1: Net CO 2 ssimiltion, shoot (eril prt) dry weight, stomtl conductnce (g s, intercellulr CO 2, trnspirtion rte nd wter use efficiency in hydroponiclly grown Rootstock-Grfted () nd Non-Grfted () melon plnts. Columns with different lower-cse letters for ech prmeter differ significntly t P.5 ccording to Duncn s MRT. SE rs re shown. shoots, while DPPH ssy detected reduction in ntioxidnt ctivity t high Si tretment. Either rootstock-grfted or Si supplemented melon plnts sored significntly higher levels of nitrtes from the medium thn the other plnts, s indicted y nitrte depletion from the medium (Tle 1). Finlly, grfting hd no effect on tissue Si ccumultion, wheres melon plnts tht received extr Si showed higher vlues compred to the plnts which did not receive extr Si (Tle 1). 1819

6 Neocleous Downloded from jst.modres.c.ir t 17:34 IRST on Fridy Octoer 5th 218 Nitrte sorption (mmol NO 3 - L -1) FRAP vlues (µmol AA g -1 FW) NO 3 - s FRAP DPPH (AEAC 1g -1 FW) Figure 2. Nitrte sorption, rdicl scvenging cpcity, ferric reducing ntioxidnt power nd totl phenolics in hydroponiclly grown nd melon plnts. Columns with different lower-cse letters for ech prmeter differ significntly t P.5 ccording to Duncn s MRT. SE rs re shown. DISCUSSION Grfting incresed net CO 2 ssimiltion (A), stomtl conductnce (g s ) nd trnspirtion rte (E), wheres internl CO 2 (Ci) remined unffected. This my suggest tht A ws not simply dependent on stomtl fctors. Given tht E ws enhnced while Ci ws not ltered, it could e suggested tht melon plnts modulted the width of stomtl pores to compromise wter losses nd CO 2 requirements (Medrno et l., 22; Neocleous nd Svvs, 213). Chlorophyll prmeters nd wter reltions cnnot ccount for this influence in photosynthetic chrcteristics, since they remined unffected y grfting. There is evidence tht internl O 2 concentrtions re high during photosynthesis nd chloroplsts re especilly prone to generte Activted Oxygen Species (ROS) (Prid nd Ds, Totl Phenolics (GAE g -1 FW) DPPH TP 25). Once produced, superoxide (O 2 ) will rpidly dismutte to yield hydrogen peroxide (H 2 O 2 ). In chloroplsts, H 2 O 2 cn inhiit photosynthesis cron ssimiltion y oxidizing enzymes of Clvin pthwy (Ashrf, 29). However, the production of ROS is uiquitous during metolism nd ll plnts cn cope with them. The question which rises is how efficiently melon plnts control the rte of ROS production nd ROS scvenging y producing different types of ntioxidnts. If grfting speeds up the production of ntioxidnts, it seems logicl to conclude tht more efficient protection of photosynthetic pprtus will e llowed (He t l., 29). Indeed, in the present study, showed incresed ntioxidnt ctivity s mesured y FRAP nd DPPH ssys, compred to plnts. In ddition, totl phenolic content, key-fctor in non-enzymtic H 2 O 2 scvenging in plnt cells (Blokhin et l., 23), ws lso enhnced y grfting. 182

7 Responses of Melon to Grfting nd Silicon Downloded from jst.modres.c.ir t 17:34 IRST on Fridy Octoer 5th 218 Plnt growth s iomss production is mesure of net photosynthesis (Prid nd Ds, 25). In the present experiment, dry shoot iomss ws enhnced in melon plnts ecuse of the incresed photosynthetic cpcity ssocited with iochemicl functions t chloroplst level. Higher yield hs een lso oserved in grfted cucumer plnts due to their ility to mintin higher net CO 2 ssimiltion (Coll et l., 21). Furthermore, grfted melon plnts hve een chrcterized y higher rtes of nitrte (NO 3 ) reduction nd higher demnd for this nutrient, incresing its uptke from the medium compred with non-grfted plnts (Ruiz nd Romero, 1999). In fct, Svvs et l. (21) reveled tht Cucuritcee rootstock enhnce not only the uptke of NO 3 nd its trnsloction to the shoot ut lso its utiliztion y the plnts through more intense ssimiltion into mino cids nd proteins. In view of the ove mentioned resons, it is suggested tht, in the current study, incresed photosynthetic rte incresed cron-sed ville sustrtes for nitrogen ssimiltion which entiled in higher shoot iomss production. It is stted in the literture tht grfting melon onto Cucurit rootstock directly ffects plnt yield y interction of some of the following processes: (i) increse of wter nd nutrient uptke s result of the vigorous root system, (ii) enhnced production of endogenous hormones, or (iii) enhncement of scion vigour (He et l., 29; Slehi et l., 21). The results of this study let us suppose tht the joint interction of photosynthesis nd ntioxidnt ctivity could explin the higher shoot iomss oserved in melon plnts grfted onto pumpkin rootstock. Since wter reltions nd chlorophyll prmeters remined unffected y grfting, iomss ccumultion in rootstock-grfted plnts ws minly the result of etter nitrogen nutrition ssocited with enhnced CO 2 ssimiltion rte nd ntioxidnt ctivity in leves. 1821

8 Neocleous Downloded from jst.modres.c.ir t 17:34 IRST on Fridy Octoer 5th 218 Plnts tht received extr Si in the medium showed higher vlues in shoot iomss production nd CO 2 ssimiltion rte (A), while the internl CO 2 (Ci) ws restricted with respect to the plnts not receiving extr Si. Tking into considertion tht stomtl conductnce (g s ) nd trnspirtion rte (E) remined unffected y tretment, lower Ci ws proly the result of either more intense RuBP-croxylse efficiency or morphologicl nd metolic modifiction in leves, ssocited with folir ccumultion of Si (Svvs et l., 27; Mttson nd Letherwood, 21). The results otined in the current study imply tht the stimultion of shoot iomss production possily originted from the involvement of Si in the physiologicl processes of melon plnts s indicted y dvnced photosynthetic cpcity. According to Adti nd Besford (1986), the ctivity of RuBp-croxylse ws 5% higher in the leves of cucumer grown in recirculting nutrient solution enriched with Si. Furthermore, Epstein (1999) reveled possile implictions of Si to iochemicl processes. These results coincide with the notion tht Si hs n ctive role in plnts physiology (Svvs et l., 27) nd lend support to the incorportion of Si in the nutrition schemes of melons in some instnces (Sonneveld, 22). Although our results lend support to the ctive role of Si in photosynthetic functions, they somehow do not support n enhnced ntioxidnt ctivity s indicted in other crops such s rley nd cucumer (Ling et l., 23; Zhu et l., 24). Moreover, Kmenidou et l. (29) cited some references on reserch results indicting decreses in the trnspirtion rte nd increses of photosynthesis in Si treted plnts, which ws not the cse in our study. It is possile tht n imposed stress would hve hd unoserved responses, which ws not studied in the present experiment. Lst ut not the lest, Si ppliction ltered folir Si ccumultion in melon plnts. Trce mounts of Si in the propgtion sustrte nd irrigtion wter my e used to explin the ccumultion of Si trces in plnts not receiving extr Si. However, plnts tht received extr Si in the nutrient solution incresed tissue Si concentrtion y 15 to 44% for the low nd high Si tretments, respectively, indicting tht melon plnts my enefit y supplementl Si (Mttson nd Letherwood, 21). CONCLUSIONS The results of the present study showed tht grfting nd Si supply could improve photosynthesis, nitrte sorption, nd iomss production in melon plnts t erly developmentl stges when metolism is intense compred with non-grfted or plnts not receiving extr Si. Grfting melon on Cucurit rootstock improved photosynthetic performnce ssocited with higher ntioxidnt ctivity in plnt tissue. Therefore, s result of this superiority, grfted melon plnts showed higher demnd for ville nitrtes in the medium, promoting iomss ccumultion. Silicon supplementtion results lend support to n ctive role of Si in melon plnts physiology. Incresed ssimiltion rtes in Si treted melon plnts, resulted in higher nitrte depletion from the medium s function of higher vilility of crohydrtes. As generl conclusion, grfting nd Si supply my led to etter crop performnce nd lower environmentl impct of greenhouse fertigtion effluents with respect to nitrte leching. Yet, there my e unoserved stress tolernce enefits from grfting or Si supplementtions which were not tested in this study, therefore, the economic impct of these prctices deserve further investigtion. REFERENCES 1. Adms, P. 22. Nutritionl Control in Hydroponics. In: Hydroponic Production of Vegetles nd Ornmentls, (Eds.): Svvs, D. nd Pssm, H. C. Emryo Pulictions, Athens, Greece, PP Adti, M. H. nd Besford, R. T The Effects of Silicon on Cucumer Plnts 1822

9 Responses of Melon to Grfting nd Silicon Downloded from jst.modres.c.ir t 17:34 IRST on Fridy Octoer 5th 218 Grown in Recirculting Nutrient Solution. Ann. Bot., 58: Ashrf, M. 29. Biotechnologicl Approch of Improving Plnt Slt Tolernce Using Antioxidnts s Mrkers. Biotechnol. Adv., 27: Bker, N. R. 28. Chlorophyll Fluorescence: A Proe of Photosynthesis In vivo. Annu. Rev. Plnt Biol., 59: Blokhin, O., Virolinen, E. nd Fgerstedt, K. 23. Antioxidnts, Oxidtive Dmge nd Oxygen Deprivtion Stress: A Review. Ann. Bot., 91: Boll, A., Koukourikou-Petridou, M., Voyitzis, D. nd Chimonidou, D. 29. Physiologicl Responses Associted to Sustrte Wter Avilility of Ros Eurored Plnts Grown in Soilless Greenhouse Conditions. Sci. Hort., 121: Coll, G., Suárez, C. M. C., Crdrelli, M. nd Rouphel, Y. 21. Improving Nitrogen Use Efficiency in Melon y Grfting. HortSci., 45(4): Eton, A. D. 25. Stndrd Methods for the Exmintion of Wter nd Wstewter. 21 st Edition, Am. Pulic Helth Assoc., Wshington, DC, USA. 9. Epstein, E Silicon. Ann. Rev. Plnt Physiol. Plnt Mol. Biol., 5: He, Y., Zhu, Z., Yng, J., Ni, X. nd Zhu, B. 29. Grfting Increses the Slt Tolernce of Tomto y Improvement of Photosynthesis nd Enhncement of Antioxidnt Enzymes Activity. Environ. Exp. Bot., 66: Kmenidou, S., Cvins, T. J. nd Mrek, S. 29. Evlution of Silicon s Nutritionl Supplement for Greenhouse Zinni Production. Sci. Hort., 119: Lrcher, W. 198: Physiologicl Plnt Ecology. 2 nd Totlly Revised Edition, Springer Verlg, Berlin, Heidelerg, New York. 13. Lee, J. M Cultivtion of Grfted Vegetles I. Current Sttus, Grfting Methods, nd Benefits. HortSci., 29: Ling, Y. C., Chen, Q., Liu, Q., Shng, W. H. nd Ding, R. X. 23. Exogenous Silicon (Si) Increses Antioxidnt Enzyme Activity nd Reduces Lipid Peroxidtion in Roots of Slt-Stressed Brley (Hordeum vulgre L.). J. Plnt Physiol., 16: Lichtenthler, H. K Chlorophylls nd Crotenoids: Pigments of Photosynthetic Biomemrnes. Meth. Enzymol., 148: Mttson, N. S. nd Letherwood, W. R. 21. Potssium Silicte Drenches Increse Lef Silicon Content nd Affect Morphologicl Trits of Severl Floriculture Crops Grown in Pet-sed Sustrte. HortSci., 45(1): Medrno, H., Esclon, J. M., Bot, J., Gulis, J. nd Flexs, J. 22. Regultion of C 3 Plnts in Response to Progressive Drought: Stomtl Conductnce s Reference Prmeter. Annl. Bot., 89: Neocleous, D., Koukounrs, A., Siomos, A. S. nd Vsilkkis, M Chnges on Photosynthesis, Yield nd Qulity of By Lettuce under Slinity Stress. J. Agr. Sci. Tech., 16: Neocleous, D., Svvs, D Response of Hydroponiclly-grown Strwerry (Frgri nnss Duch.) Plnts to Different K: C:Mg Rtios in the Nutrient Solution. J. Hort. Sci. Biotechn., 88 (3): Prid, K. A. nd Ds B. A. 25. Slt Tolernce nd Slinity Effects on Plnts: A Review. Ecotoxicol. Environ. Sf., 6: Ruiz, J. M. nd Romero, L Nitrogen Efficiency nd Metolism in Grfted Melon Plnts. Sci. Hort., 81: Slehi, R., Kshi, A., Lee, J-M., Blr, M., Delshd, M., Lee, S-G. nd Huh, Y-C. 21. Lef Gs Exchnge nd Minerl Ion Composition in Xylem Sp of Irnin Melon Affected y Rootstocks nd Trining Methods. HortSci., 45(5): Sn Butist, A., Cltyud, A., Neuer, S. G., Pscul, B., Mroto, J. V. nd López- Glrz, S Effects of Simple nd Doule Grfting Melon Plnts on Minerl Asorption, Photosynthesis, Biomss nd Yield. Sci. Hort., 13: Svvs, D., Coll, G., Rouphel, Y. nd Schwrz, D. 21. Ameliortion of Hevy Metl nd Nutrient Stress in Fruit Vegetles y Grfting. Sci. Hort., 127: Svvs, D., Gizs, G., Krrs, G., Lydkis- Simntiris, N., Slhs, G., Ppdimitriou, M. nd Tsouk, N. 27. Interctions etween Silicon nd NCl-slinity in 1823

10 Neocleous Downloded from jst.modres.c.ir t 17:34 IRST on Fridy Octoer 5th 218 Soilless Culture of Roses in Greenhouse. Europ. J. Hort. Sci., 72(2): Sonneveld, C. 22. Composition of Nutrient Dolution. In: Hydroponic Production of Vegetles nd Ornmentls, (Eds.): Svvs, D. nd Pssm, H. C.. Emryo Pulictions, Athens, Greece, PP (Cucumis melo L.) 27. Sonneveld, C. nd Voogt, W. 29. Plnt Nutrition of Greenhouse Crops. Springer Dordrecht Heidelerg, London, New York. 28. Zhu, Z., Wei, G., Li, J., Qin, Q. nd Yu, J. 24. Silicon Allevites Slt Stress nd Increses Antioxidnt Enzymes Activity in Leves of Slt-stressed Cucumer (Cucumis stivus L.). Plnt Sci., 167: (Cucumis melo L.).. (Si) ) (1 ): ( (2). Si Si. ( ). ( ). %35 %2 (%18 %17 ) Si. %26 %