Asin Journl of Agriculturl Sciences 3(1): 26-31, 2011 ISSN: 2041-3890 Mxwell Scientific Orgniztion, 2011 Received: October 05, 2010 Accepted: October 27, 2010 Published: Jnury 10, 2011 Differences in the Zinc Efficiency Among nd Within Mize Cultivrs in Clcreous Soil A. Chb, Gh. R. Svghebi nd B. Moteshrezdeh Deprtment of Soil Science, College of Agriculture nd Nturl Resources, University of Tehrn, Krj, Irn Abstrct: Low vilbility of Zn in clcreous soils is one of the widest rnging biotic stresses in world griculture. Greenhouse experiment were crried out with Four cultivrs of mize (301 Single Grss (A), 302 Single Grss (B), 307 Single Grss (C), 400 Single Grss (D), Ze mys L.) were used to study the influence of vried zinc (Zn) supply on Zn efficiency, shoot dry mtter production, Zn uptke, Chlorophyll content, Lef Are Index (LAI) nd Reltive Growth Rte (RGR). Plnts were grown in Zn-deficient clcreous soil under greenhouse conditions with (+Zn = 10 mg/ kg soil) nd without (-Zn) Zn supply. Plnts were hrvested fter 40 nd 80 dys. Zinc efficiency, expressed s the percentge of shoot dry weight produced under conditions of Zn deficiency compred to Zn supply, rnged between 62.3 nd 75.5% in first stge nd between 63.5 nd 81.2% in second stge. Appliction of Zinc cused increse in shoot dry weight in ll cultivrs. Zn uptke enhnced with ppliction of zinc nd rnged from 100.80 to 231.91 g/pot in first stge nd 458.01 to 858.83 g/pot mong cultivrs. Zinc ppliction incresed the Chlorophyll content, Lef Are Index nd Reltive Growth Rte. Zn efficiency hd high nd positive reltion with Shoot dry weight nd Zn uptke in different cultivrs. Key words: Mize, shoot dry weight, Zn efficiency, Zn uptke INTRODUCTION Zinc deficiency in soils nd plnts is globl micronutrient deficiency problem reported in mny countries (Allowy, 2004). Low vilbility of Zn in clcreous soils is one of the widest rnging biotic stresses in world griculture. The regions with Zndeficient soils re lso the regions where Zn deficiency in humn beings is widespred, for exmple in Indi, Pkistn, Chin, Irn nd Turkey (Ckmk et l., 1999; Allowy, 2004; Hotz nd Brown, 2004). Zinc deficiency is responsible for mny severe helth complictions, including impirments of physicl growth, immune system nd lerning bility, combined with incresed risk of infections, DNA dmge nd cncer development (Hotz nd Brown, 2004; Gibson, 2006; Prsd, 2007). Zinc is n importnt micronutrient. Plnt response to Zn deficiency occurs in terms of decrese in membrne integrity, susceptibility to het stress, decresed synthesis of crbohydrtes, cytochromes nucleotide uxin nd chlorophyll. Further, Zn-contining enzymes re lso inhibited, which include lcohol dehydrogense, crbonic nhydrse, Cu-Zn-superoxide dismutse, lkline phosphtse, phospholipse, crboxypeptidse, nd RNA polymerse (Mrschner, 1995). Mize, one of importnt food crops grown in most worlds' re, is sensitive to Zn deficiency. Stunted nd chlorotic plnts due to Zn deficiency re often observed on erly grown mize plnts in the field (Liu et l., 1993; Liu, 1996). Differentil cultivr responses grown under low soil Zn concentrtions hve been reported in mize, millet, sorghum, rice nd whet, mong others (Brown et l., 1972; Clrk, 1978; Ckmk et l., 1999; Fgeri, 2001). Zinc efficiency, defined herein s the bility of plnt to grow nd yield well under zincdeficient conditions, vries mong cerel species (Grhm et l., 1993; Erenoglu et l., 2000). Genotypic differences for zinc use efficiency hve been reported for severl crops species (Grhm et l., 1992; Ckmk et l., 1994; Wiren et l., 1994; Rengel et l., 1995). Physiologicl mechnism(s) conferring Zn efficiency nd their reltive significnce on low Zn soil/solution culture hve been investigted by severl workers (Erenoglu et l., 2000; Rengel et l., 2000; Gökhn et l., 2003). However, physiologicl nd biochemicl processes tht control Zn efficiency, in generl, nd Zn cquisition by the roots, in prticulr, is mong the less thoroughly studied spects of plnt Zn-nutrition. Grhm nd Rengel (1993) suggested tht more thn one mechnism could be responsible for estblishing Zn efficiency in genotype nd it is likely tht different genotypes subjected to Zn deficiency under different environmentl conditions will respond by one or more different efficiency mechnisms. Differences in Zn efficiency hve been demonstrted prticulrly for cerel species in both field nd greenhouse experiments Corresponding Author: A. Chb, Deprtment of Soil Science, College of Agriculture nd Nturl Resources, University of Tehrn, Krj, Irn 26
(Grhm et l., 1992; Klyci et l., 1999). In recent yers, reserch hs been crried out in severl different lbortories to elucidte the physiologicl mechnisms tht confer Zn efficiency; however, these mechnisms re still poorly understood. A number of different whet (Triticum estivum) cultivrs hve been screened for their response to low Zn in Zn-deficient clcreous soils nd significnt differences in Zn efficiency mong certin whet cultivrs hve been consistently found in both field nd growth chmber experiments (Ckmk et l., 1999; Klyci et l., 1999; Hcislihoglu et l., 2001). Cultivted cerel species, especilly whet, show lrge vrition in Zn efficiency, i.e., the bility of cultivr to grow nd yield better under Zn-deficient conditions in comprison with other cultivrs (Grhm et l., 1992; Ckmk et l., 1999). The im of this study ws to investigte the Zn efficiency nd growth indices of mize crop in Zn deficient soil. MATERIALS AND METHODS Mize seeds 301 Single Grss (A), 302 Single Grss (B), 307 Single Grss (C), nd 400 Single Grss (D), Ze mys L.) were grown in Zn-deficient clcreous soil under greenhouse conditions. The experiments were conducted during the norml winter-summer growing seson in greenhouse of university of Tehrn. The soil used in the experiments ws obtined from Zn-deficient re. Five seeds were sown in plstic pots contining 4 kg soil with (+Zn = 10 mg Zn. kg soil) nd without (-Zn) Zn supply. After emergence the seedlings were thinned to 2 seedlings per pot. The soil hd sndy lom texture, ph 8.3, contined 0.9% of orgnic mtter nd 6 % of CCO 3 s mesured by stndrd methods given in Jckson (1958). The concentrtion of plnt-vilble Zn ws low, t round 0.4 mg/kg DTPA-extrctble Zn, mesured by the method of Lindsy nd Norvell (1978). Zinc ws dded to soil in the form of ZnSO 4. A bsl tretment of 600 mg N kg soil s CO (NH 2 ) 2 nd 20 mg P kg soil s NH 4 H 2 PO 4 nd 500 mg K kg soil s K 2 SO 4 ws pplied to ll plnts. All nutrients were mixed homogeneously with soil before sowing. Zinc efficiency (%) ws determined by the rtio between shoot dry weights t -Zn to shoot dry weight t +Zn conditions (Peleg et l., 2007). To determine dry mtter yield nd Zn uptke, crops were hrvested fter 40 (stge 1) nd 80 dys (stge 2) nd dried t 75ºC. Dried crop smples were ground nd wet-shing nd Zn concentrtions ws determined with Shimdzu AA-660 Atomic Absorption Spectrophotometer (Jckson, 1958). Amount of Zn uptke per plnt cn be clculted s: Plnt dry weight (kg) Zn concentrtion (mg Zn per kg dry weight). Chlorophyll content (Chl) ws mesured by Konic Minolt (SPAD- 502) model (Fox et l., 1994). Lef Are Index (LAI) nd Reltive Growth Rte (RGR) were mesured by (1) nd (2) (Khn et l., 2008). LAI nd RGR were determined in two stges. StgeI (0-40 dys) nd stge II (40-80 dys). All smpling nd mesurements were crried out by using three replictions. All sttisticl nlyses were crried out using sttisticl pckge (SAS Institute, 2005). Lest Significnt Difference (LSD) ws used to compre the min tretment nd interction effects t p<0.05. RGR (mg/dy) = (Ln w 1 Ln w 2 ) / (T 2 T 1 ) (T: time w: dry weight) (1) LAI (m 2 ) = Lef re / Ground covered by plnt (2) RESULTS Zn efficiency of mize cultivrs: There ws differentil response of mize vrieties to Zn ppliction in both times of growth (Tble1 nd 2). The Zn efficiency of different mize vrieties ws clculted s the rtio of grin yield due to Zn control nd Zn ddition, multiplied by 100 (Peleg et l., 2007). This is lso clled tolernce index (%). The cultivrs exhibited vrition in Zn efficiency (62.3-75.5%) fter 40 dys nd (58.5-81.2%) fter 80 dys. in stge 1 cultivrs D nd B showed bove 70% Zn efficiency. In stge 2 cultivrs D nd A showed bove 70% Zn efficiency. According to Zn efficiency rtio (%), the cultivrs followed the order: D>B>C>A (40 dys) nd D>A>B>C. Such lrge vrition in Zn efficiency between whet cultivrs ws lso found in South Austrli (Grhm et l., 1992). Effect of Zn in shoot dry weight: Shoot dry weight of mize responded significntly to Zn ppliction. The Shoot dry weight incresed significntly with incresing Zn rtes, s observed in the two stges (Tble 1 nd 2). In efficient cultivr (D), high Shoot dry weight s obtined with two Zn rtes (0, 10 mg/kg) were 4.40-7.40 (in stge1) nd 13.9.-23.13 gr/pot (in stge 2), respectively. Most of the Zn-efficient cultivrs produced higher Shoot dry weight thn verge, while Shoot dry weight of most Zn-inefficient cultivrs were lower thn the verge, when Zn ws not pplied. In stge 2, cultivrs D nd A hd both, high Zn efficiency nd high Shoot dry weight under Zn-deficient conditions, nd the cultivr B, C hd the lowest Zn efficiency nd Shoot dry weight. There ws no significnt difference in Shoot dry weight between cultivrs when pply Zinc in both stges. Our results re in greement with the results obtined with whet (Grhm et l., 1992; Ckmk et l., 1997), chickpe (Khn et l., 1998) nd common ben (Hcislihoglu et l., 2004). Zn uptke: Zinc uptke of cultivrs is given in Tble 1 nd 2. There ws positive nd significnt difference in the Zn uptke between the efficient nd in-efficient cultivrs t Zn 0 nd Zn 10 in both stges. Under Zn-deficient 27
Tble 1: Effect of vried Zn supply in shoot dry weight (SDW) (g/plnt), Zn uptke ( g /pot) nd Zn Efficiency (%) in different cultivrs fter 40 dy SDW (g/pot) Zn uptke ( g/pot) ------------------------------------------ -------------------------------------------- Cultivr - Zn +Zn -Zn +Zn ZnEfficiency (%) A 3.63±0.9 d 7.3±0.2 39.04±12.9 f 188.40±11.9 b 62.3 B 4.16±0.5 c 6.73±0.6 b 76.75±7.5 e 160.21±22.5 c 73.1 C 3.73±0.3 d 7.06±0.2 56.29±13.7 f 165.32±5.2 c 65.1 D 4.40±0.2 c 7.40±0.5 100.80±4.6 d 231.91±17.6 75.5 : Vlues were compred using LSD multiple rnge test t the 5% level, Homogeneous groups re denoted with the sme letter, Shoot Dry Weight (SDW) Tble 2: Effect of vried Zn supply in shoot dry weight (SDW) (g/plnt), Zn uptke ( g /pot) nd Zn Efficiency (%) in different cultivrs fter 80 dy SDW (g/pot) Zn uptke ( g/pot) ------------------------------------------ -------------------------------------------- Cultivr - Zn +Zn -Zn +Zn ZnEfficiency (%) A 10.03±2.65 bc 23.67±2.8 254.40±83.4 d 803.46±6.3 71.5 B 8.00±1.7 cd 23.13±2.7 152.33±22 d 675.10±68.4 b 63.5 C 6.70±1.1 d 23.80±1.3 107.94±7.5 e 669.22±22.8 b 58.5 D 13.90±1.7 b 23.13±1.9 458.01±36.9 c 853.83±95.1 b 81.2 : Vlues were compred using LSD multiple rnge test t the 5% level, Homogeneous groups re denoted with the sme letter, Shoot Dry Weight (SDW) Fig. 1: Reltionship between Zn efficiency nd Shoot dry weight of different cultivrs fter 40 dy Fig. 3: Reltionship between Zn efficiency nd Zn uptke of different cultivrs fter 40 dy Fig. 2: Reltionship between Zn efficiency nd Shoot dry weight of different cultivrs fter 80 dy conditions, rnging from 100.80-231.91 (in stge 1) nd 458.01-858.83 g/pot (in stge 2). Zinc fertiliztion incresed Zn uptke of ll cultivrs by 130% in the first nd 87.5% in the second stge (Tble 1 nd 2). Efficient cultivrs such s D hd high mount of Zn uptke then inefficient cultivrs. Fig. 4: Reltionship between Zn efficiency nd Zn uptke of different cultivrs fter 80 dy Reltionship between Zn efficiency, shoot dry weight nd Zn uptke: As presented in Fig. 1 nd 2, for ll cultivrs Zn efficiency rtios ppered to be well relted to the Shoot dry weight. However, in the cse of Zn efficiency rtios higher thn 55% there ws high nd 28
Tble 3: Effect of vried Zn supply in chlorophyll content (Chl), Lef Are Index (LAI) nd Reltive Growth Rte (RGR) in different cultivrs fter 40 dy Cultivr CH1 LAI (cm 2 /cm 2 ) RGR I (mg/dy) ------------------------------------------ ---------------------------------- -------------------------------------- - Zn +Zn -Zn +Zn -Zn +Zn A 38.3±0.8 cd 39.9±1.2 c 0.18±0.02 d 0.33±0.02 b 136.6±4.6 d 152.7±0.9 b B 33.7±0.5 e 40.7±0.9 c 0.17±0.01 d 0.21±0 cd 139.7±2.5 cd 150.6±2.1 b C 34.1±0.9 de 36.8±0.8 d 0.26±0.2 c 0.3±0.02 b 137.5±1.7 d 151.9±0.7 b D 43.8±1.7 b 48±0.5 0.3±0.01 b 0.42±0.03 141±1.2 c 159.3±2.4 : Vlues were compred using LSD multiple rnge test t the 5% level. Homogeneous groups re denoted with the sme letter. Chlorophyll content (Chl), Lef Are Index (LAI) nd Reltive Growth Rte (RGR) Tble 4: Effect of vried Zn supply in chlorophyll content (Chl), Lef Are Index (LAI) nd Reltive Growth Rte (RGR) in different cultivrs fter 80 dy CH1 LAI (cm 2 /cm 2 ) RGR II (mg/dy) -------------------------------------- ------------------------------------ -------------------------------------- Cultivr - Zn +Zn -Zn +Zn -Zn +Zn A 40.7±2.5 c 45.5±0.8 b 0.44±0.02 c 0.68±0.02 42.3±2.6 bc 44.9±2.2 b B 45.2±0.7 b 50.1±1 0.36±0.04 cd 0.7±0.05 36.9±0.68 d 40.2±3 c C 41.9±3.4 c 46.9±2.1 b 0.33±0.02 d 0.51±0.008 b 36.8±2.02 d 39.6±0.9 c D 45.6±1.1 b 50.9±1.3 0.42±0.02 c 0.68±0.03 43.9±2.1 b 48.1±1.6 : Vlues were compred using LSD multiple rnge test t the 5% level, Homogeneous groups re denoted with the sme letter. Chlorophyll content (Chl), Lef Are Index (LAI) nd Reltive Growth Rte (RGR) positive reltion between Zn efficiency nd Shoot dry weight. The reltion between Zn efficiency nd Zn uptke under Zn-deficient conditions for both stges ws shown in Fig. 3, 4. Zn efficiency of cultivrs ws significntly correlted in both stges with Zn uptke per plnt (R 2 = 0.94 in first stge, R 2 = 0.99 in second stge). Incresing in Zn efficiency cused enhnce in Zn uptke. This result indictes tht not only enhnced Zn uptke but lso enhnced internl utiliztion of Zn plys n importnt role in expression of high Zn efficiency. Chlorophyll content, lef re index nd reltive growth rte: The nlysis of Chl, LAI nd RGR reveled tht significnt differences between tretments were estblished by 40 nd 80 dy post sowing with ech of the zinc pplictions leding to n increse in Chl, LAI nd RGR (Tble 3 nd 4). Ech vrible responded significntly to Zn ppliction. Under Zn-deficient condition efficient cultivrs such s D hd mximum chlorophyll content, Lef Are Index nd Reltive Growth Rte in two stges. In first stge, did not observe significnt differences between cultivrs in Reltive Growth Rte but there ws positive nd significnt difference between cultivrs of this viewpoint in second stge. DISCUSSION Zn nutrition of plnts is considered one of mjor problems in the rid nd semi-rid regions (Ekiz et l., 1998). Vrition in Zn efficiency ws found mong the cultivrs of mize. Decrese in shoot dry mtter production due to Zn deficiency ws most distinct in ll cultivrs of mize (Tble 1 nd 2). On verge, Zn efficiency rtio ws 66.9% for 301 Single Grss (A), 68.3% for 302 Single Grss (B), 61.8 for 307 Single Grss (C) nd 78.3% for 400 Single Grss. The cultivted forms of 307 Single Grss (C) possess s well the highest sensitivity to Zn deficiency compred to cultivted rye, triticle, brley, ot nd bred whet cultivrs (Ckmk et l., 1998; Ekiz et l., 1998). Under Zn deficiency, Zn uptke ws better relted to Zn efficiency (Fig. 1 nd 2), indicting tht Zn-efficient genotypes under Zn deficiency possibly hve greter Zn uptke cpcity. Enhncements in Zn uptke rte by roots nd Zn utiliztion t the cellulr level ws shown s importnt mechnisms ffecting expression of high Zn efficiency in whet (Rengel nd Whel, 1997; Ckmk et l., 1998). Efficient cultivrs such s D hd high mount of Zn uptke then in-efficient cultivrs. The importnce of Zn uptke to Zn efficiency grees with previous studies (Ckmk et l., 1998; Grhm nd Rengel, 1993). Multiple regression nlysis showed tht Zn uptke is the most importnt fctor sttisticlly explining vrition in Zn efficiency mong the considered rice genotypes (Hjibolnd nd Slehi, 2006). The higher Zn uptke cpcity of Zn efficient genotypes might be ttributble to greter mount of sulfhydryl groups in root-cell plsm membrnes, prticulrly in ion trnsport-relted proteins (Rengel et l., 1995; Rengel nd Whel, 1997). Zinc pplictions hd positive effect on plnt growth leding to incresed Chl, LAI nd RGR. The pprent mechnism for chieving these improvements ws the increse in lef re index, improved resource generting bse for the crop, Chlorophyll content nd Reltive Growth Rte. Other workers hve lso reported tht zinc ppliction improved Chl, LAI nd RGR (Judrth et l., 1977; Khn et l., 2008; Zhoori et l., 2009). It is becoming cler tht micronutrient deficiencies, including Zn deficiency, re significnt globl problem, ffecting more thn 2 billion people in the world, with serious implictions for humn helth (Grhm nd Welch, 1996; Welch et l., 1997). 29
High consumption of cerel-bsed foods, of low micronutrient content, hs been suggested s mjor reson for the widespred occurrence of micronutrient deficiency in humns, prticulrly in developing countries. Our study confirms tht tolernce to Zn deficiency is complex trit in which mny plnt chrcteristics re involved. We lso confirmed tht lrge set of genotypes needs to be considered in order to get complete view on crop tolernce to Zn deficiency. CONCLUSION The cultivrs exhibited vrition in Zn efficiency (62.3-75.5%) fter 40 dys nd (58.5-81.2%) fter 80 dys. According to Zn efficiency rtio (%), the cultivrs followed the order: D>B>C>A. In efficient cultivr (D), high Shoot dry weight s obtined with two Zn rtes (0, 10 mg/kg) were 4.40-7.40 (in stge 1) nd 13.90-23.13 gr/pot (in stge 2), respectively. Under Zn-deficient conditions, rnging from 100.80-231.91 (in stge 1) nd 458.01-858.83 g/pot (in stge 2). Incresing in Zn efficiency cused enhnce in Zn uptke. Under Zndeficient condition efficient cultivrs such s D hd mximum chlorophyll content, Lef Are Index nd Reltive Growth Rte in two stges. ACKNOWLEDGMENT The uthors grtefully cknowledge the scientific bord members of the Deprtment of Soil Science, Tehrn University for their vluble insights nd guidnce for crrying out this study. REFERENCES Allowy, B.J., 2004. Zinc in Soils nd Crop Nutrition. IZA Publictions, Interntionl Zinc Assocition, Brussels, pp: 1-116. Brown, J.C., J.E. Ambler, R.L. Chney nd C.D. Foy, 1972. Differentil responses of plnt genotypes to micronutrients. In: Mortvedt, J.J., P.M. Giordno nd W.L. Lindsy (Eds.), Micronutrients in Agriculture, Sss, Mdison, pp: 389-418. Ckmk, I., K.Y. Gulut, H. Mrschner nd R.D. Grhm, 1994. Effect of zinc nd iron deficiency on phytosiderophore relese in whet genotype differing in zinc efficiency. J. Plnt Nutr., 17: 1-17. Ckmk, I., H. Ekiz, A. Yilmz, B. Torun, N. Koleli, I. Gultekin, A. Alkn nd S. Eker, 1997. Differentil response of rye, triticle, bred nd durum whets to zinc deficiency in clcreous soils. Plnt Soil, 188: 1-10. Ckmk, I., B. Torun, B. Erenoglu, L. Ozturk, H. Mrschner, M. Klyci, H. Ekiz nd A. Yilmz, 1998. Morphologicl nd physiologicl differences in the response of cerels to zinc deficiency. Euphytic, 100: 349-357. Ckmk, I., M. Klyci, H. Ekiz, H. Brun nd A. Yilmz, 1999. Zinc deficiency s n ctul problem in plnt nd humn nutrition in Turkey: A NATO-Science for Stbility Project. Field Crop. Res., 60: 175-188. Clrk, R.B., 1978. Differentil Response of Mize Inbreds to Zn. Agron. J., pp: 1057-1060. Ekiz, H., S.A. Bgci, A.S. Krl, S. Eker, I. Gultekin, A. Alkn nd I. Ckmk, 1998. Effects of zinc fertiliztion nd irrigtion on grin yield nd zinc concentrtion of vrious cerels grown in zincdeficient clcreous soils. J. Plnt Nutr., 21: 2245-2256. Erenoglu, B., S. Eker, I. Ckmk, R. Derici nd V. Romheld, 2000. Effect of iron nd zinc deficiency on relese of phytosiderophores by brley cultivrs differing in zinc efficiency. J. Plnt Nutr., 23: 1645-1656. Fgeri, N.K., 2001. Screening method of lowlnd rice genotypes for zinc uptke efficiency. Sci. Agr., 58: 623-626. Fox, R.H., W.P. Piekielek nd K.M. Mcnel, 1994. Using chlorophyll meter to predict nitrogen fertilizer needs of winter whet. Commum. Soil Sci. Plnt Anl., 25: 171-181. Grhm, R.D., J.S. Ascher nd S.C. Hynes, 1992. Selecting zinc efficient cerel genotypes for soil of low zinc sttus. Plnt Soil, 146: 241-250. Grhm, R.D. nd Z. Rengel, 1993. Genotypic Vrition in Zn Uptke nd Utiliztion by Plnts. In: Robson, A.D. (Ed.), Zinc in Soils nd Plnts. Kluwer, Dordrecht, The Netherlnds, pp: 107-114. Grhm, R.D. nd R.M. Welch, 1996. Breeding for stple food crops with high micronutrient density. Agriculturl strtegies for Micronutrients. Working pper No. 3. IFPRI, Wshington D.C. Gökhn, H., J.J. Hrt, Y. Hong, I. Ckmk nd L. Kochin, 2003. Zinc efficiency is correlted with enhnced expression nd ctivity of zinc-requiring enzymes in whet. Plnt Physiol., 131: 595-602. Gibson, R.S., 2006. Zinc: the missing link in combting micronutrient mlnutrition in developing countries. Proc. Nutr. Soc., 65: 51-60. Hcislihoglu, G., J.J. Hrt nd L. Kochin, 2001. High nd low-ffinity zinc trnsport systems nd their possible role in zinc efficiency in bred whet. Plnt Physiol., 125: 456-463. Hcislihoglu, G., L. Ozturk, I. Ckmk, R.M. Welch nd L. Kochin, 2004. Genotypic vrition in common ben in response to zinc deficiency in clcreous soil. Plnt Soil, 259: 71-83. Hjibolnd, R. nd S.Y. Slehi, 2006. Chrcteriztion of zn efficiency in irnin rice genotypes I. uptke efficieny. Plnt Physiol., 32: 191-206. Hotz, C. nd K. Brown, 2004. Assessment of the risk of zinc deficiency in popultions nd options for its control. Food Nutr. Bull., 25: 94-204. 30
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