Ecophysiological Responses of Two Olive Tree Cultivars (Olea europaea L. CV Koroneiki and Chemlali) Under Three Water Treatments

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1 Europen Scientific Journl Jnury 2017 edition vol.13, No.3 ISSN: (Print) e - ISSN Ecophysiologicl Responses of Two Olive Tree Cultivrs (Ole europe L. CV Koroneiki nd Chemlli) Under Three Wter Tretments Mortdh Ben Hssine, PhD Higher Institute of Agriculturl Sciences of Chott Mriem, 4042 Chott Mriem, Sousse, Tunisi nd Olive tree Institute, Unit of Sousse, BP n 14 In Khldoun, 4061 Sousse, Tunisi Olf Boussdi Amni Bchir Ines Moul Mriem El Hfi Mohmed Brhm Olive Tree Institute, Unit of Sousse, BP n 14 In Khldoun, 4061 Sousse, Tunisi doi: /esj.2016.v13n3p327 URL: Astrct In this pper, our ojective is to ssess nd compre the effects of three levels of irrigtion ppliction on the ecophysiologicl ehvior nd plnt dry mtter ccumultion of two young olive tree cultivrs Koroneiki, promising greek cultivr, nd Chemlli, the est locl cultivr. According to this ssessment, we cn determine the most efficient wter tretment tht could e suitle for Mediterrnen environments sujected to wter shortge conditions. Mesurements were mde in the green house of the Tunisin Olive tree Institute under norml dy-light conditions from Mrch, 16 th to April, 21 st Three wter tretments were pplied which re T100% (control tretment: Dily irrigtion t 100% of Aville Wter Content (AWC)), T50% (Dily irrigtion t 50% of AWC) nd T0% (Without wtering). The results showed tht the two olive tree cultivrs possess importnt mechnisms to overtke limited wter resources. However, some striking vritions existed etween the two cultivrs studied. Indeed, s wter stress incresed (T0%), Chemlli mintined longer high middy lef wter potentil compred ( MP) to Koroneiki (- 5.8 MP). T50% tretment seems to e sufficient for oth cultivrs. Mesurements of totl Osmotic Adjustment (OA) showed tht olive trees use this mechnism to crete very negtive lef wter potentils in order to e 327

2 Europen Scientific Journl Jnury 2017 edition vol.13, No.3 ISSN: (Print) e - ISSN le to extrct wter from dry root environment. The root/shoot rtio of Chemlli plnts t T50% tretment ws the highest (1.08) comprtively with the other two tretments (0.70 nd 0.79 for T100% nd T0% AWC wter tretments, respectively). This result shows tht Chemlli plnts vlorize low quntities of wter (T50%) rther thn high quntities (T100%) nd Koroneiki plnts ehve etter when it is irrigted t 100% AWC. To conclude, Chemlli plnts irrigted t 50% AWC, compred to Koroneiki plnts, re the most suitle to tolerte wter restriction conditions. Keywords: Ole europe L., lef wter potentil, osmotic djustment, ecophysiologicl ehvior, plnt dry mtter ccumultion. Introduction Nowdys, 98% of the worldwide olive trees re cultivted within the Mediterrnen re. This region represents, from climtologicl point of view, trnsitionl re etween temperte nd tropicl climtes. In semirid Mediterrnen zone, like Tunisi, the climte is chrcterized y n irregulrity precipittions nd hot nd dry summers. In the long-term, this sitution could ecome more nd more excerted, considering the incresed risk of ridity cused y wrming climte. Olive trees grown in these regions re often exposed to long period of drought nd hrsh environmentl conditions, which ffects tree growth nd, hence, olive growing development. Much of the lnd, where olive trees re grown, is intrinsiclly incple of producing profitle crops under dry-frming conditions. In Tunisi, in order to increse productivity of olive trees, the intensifiction of this culture sector is necessity. The expnsion of irrigted olive frming nd the incresing concern for qulity of the hrvested products led to the introduction of cultivrs from the northern zone of the Mediterrnen in Tunisi. Koroneiki is the min olive cultivr grown for oil in Greece. This cultivr cn e plnted in highdensity orchrds, ut hs lso potentil for the more trditionl non-irrigted production sites. During the lst decde, effort hs een put in sustinle development of the olive orchrds in Tunisi pplying irrigtion nd fertilistion in order to improve the productivity nd qulity of olive oil. Till now, no study out the suitility of Koroneiki cultivr for more rid climte is ville, nor is it known how this cultivr compres with locl cultivrs under drought nd irrigtion conditions. Studying physiologicl responses to irrigtion supply my help to get fundmentl nd new insights into how this cultivr responds to wter demnd. Different cultivrs respond differently to wter tretment showing differences in terms of dpttion, dry mtter distriution, production nd 328

3 Europen Scientific Journl Jnury 2017 edition vol.13, No.3 ISSN: (Print) e - ISSN gs exchnge responses to wter shortge (Chrtzoulkis et l.,1999; Bcelr et l., 2004, 2007; Tognetti et l., 2002). In this context, the min im of this work ws to ssess the ehvior of two young olive tree cultivrs Koroneiki, which is promising Greek cultivr for oil production, nd Chemlli, the est locl cultivr for oil production, under three wter tretments. The comprison etween the two cultivrs ws sed on wter sttus, eco-physiologicl nd dry mtter ccumultion prmeters. This study is essentil to select the most suitle cultivr for Mediterrnen environments sujected to wter shortge conditions. Mteril nd methods Plnt mteril nd wter tretments One-yer-old olive trees (Koroneiki nd Chemlli) were grown in 4L plstic pots in greenhouse t the Tunisin Olive tree Institute (Tunisi, N, E) under norml dy-light conditions with n verge temperture of 25 C nd reltive humidity of 40%. Prior to the strt of the experiment, trees with height of out 1m were selected nd lifted from soil mix of orgnic mteril, snd nd cly. Roots were wshed nd plnts were trnsplnted into sustrte mixture of pet nd perlite (2/3 volume rtio). A full-strength efore strting, the plnts were wtered dily to 100% of Aville Wter Content (AWC) for period of 4 weeks with Hoglnd solution. Then, plnts were divided into two prts: the first one (control plnts) ws sujected to irrigtion to 100% of AWC nd the second one to drying until reching 50% of AWC. The experiment ws conducted from Mrch, 16 th to April, 21 st Three wter tretments were pplied: - T100%: Control tretment: Dily irrigtion t 100% of Aville Wter Content (AWC), - T50%: Dily irrigtion t 50% of AWC, - T0%: Without wtering. Control nd drought-stressed plnts were rrnged in complete rndomized design with eight replictions for ech cultivr. Wter tretments (three levels of wter ppliction) nd cultivrs (two) were considered s tretments. In totl, 48 olive plnts were used (8 plnts of ech cultivr/wter tretment). Lef wter sttus mesurements Plnt wter sttus ws determined y mesuring the totl lef wter potentil (Ψw) on fully expnded leves (tken from the mid-section of the shoots). 329

4 Europen Scientific Journl Jnury 2017 edition vol.13, No.3 ISSN: (Print) e - ISSN Three plnts per tretment were mesured t middy (12 m) with thermocouple psychrometer (smple chmers type C52; Wescor, Logn, Uth, USA) following the method descried y Chzen et l. (1995). For ech plnt nd t ech mesurement event, smple (surfce re of the lef disc = 0.25 cm 2 ) ws used to mesure Ψw. Osmotic djustment (OA) ws clculted for oth cultivrs y tking the difference etween middy Ψπ mesured t control (T100%) nd stressed (T50% nd T0%) plnts. Gs exchnge mesurements Fully expnded leves were used to mesure simultneously mximum net photosynthetic ssimiltion rte A (μmol CO 2 m -2 s -1 ) nd stomtl conductnce for wter vpour gs (mol H 2 O m -2 s -1 ) using portle gs exchnge system (LI-6400, LI-COR, Lincoln, NE, USA). The A/gs rtio ws clculted nd used s n estimte of the intrinsic wter use efficiency (WUE) ccording to Medivill et l. (2002). Mesurements were performed weekly in three replictes for ech tretment nd cultivr. Mesurements of A nd gs were performed t light sturtion (1500 μmol PAR m -2 s -1 ) etween 11 m nd 2 pm nd t fixed CO 2 concentrtion (C equl to 400 μmol mol -1 ), with lef temperture of 25 C nd reltive humidity of 50%. Plnt dry mtter ccumultion At the end of the wter stress ppliction (April, 21 st 2015), plnts destruction ws done in order to determine the dry weight ody (leves, root nd stem). Sttisticl nlysis The men dt were sttisticlly nlyzed using SPSS Significnt differences etween tretments were determined y one wy nlysis of vrince. Student Newmn Keuls s multiple rnge test ws used to compre the mens. Results nd discussion Effect of three wter tretments on lef wter sttus Effect of three wter tretments on lef wter potentil Figure 1 shows the effect of three wter tretments on the lef wter potentil (Ψw) of olive tree (Ole europe L. cv Koroneiki nd Chemlli). For oth cultivrs, T100% plnts show the highest lef wter potentil however T0% plnts show the lowest one throughout the experiment period. For Koroneiki plnts, fter 21 dys of pplying wter tretments, significnt difference ws oserved etween T0% nd the two other 330

5 Europen Scientific Journl Jnury 2017 edition vol.13, No.3 ISSN: (Print) e - ISSN tretments (T100% nd T50%). But, no significnt difference ws noticed etween Koroneiki T100% nd T50% plnts during the experiment period. The lef wter potentil of Koroneiki T0% plnts decreses to MP fter 35 dys of pplying wter tretments which represent 59.8% comprtively with the control plnts. For Chemlli plnts, 35 dys fter pplying wter tretments, no significnt difference ws oserved etween T100% nd T50%, while, the lef wter potentil of T0% plnts decreses to MP, which represent 35.93% comprtively with T100% plnts. It should e noted tht significnt difference etween Koroneiki nd Chemlli plnts ws recorded in T0%. According to these results, we cn deduce tht Chemlli plnts re more tolernt to wter restriction thn Koroneiki plnts. For oth cultivrs, Irrigtion t 50% AWC permits to mintin regulr lef wter potentil. Our results re similr with those otined y Giron et l. (2015) despite tht the experiment ws conducted in field conditions nd showed lower vlues minly in the middle of the wter stress period (from DOY 207 until 220), though vlues on the stress tretment tended to e lower throughout the wter stress period. According to Mrino et l. (2014), under severe drought, the lef wter potentil rnged etween ~ 4.5 MP (predwn) nd ~ 6.4 MP (middy). Wter potentil (Ψw; -MP) 6,8 6,4 6,0 5,6 5,2 4,8 4,4 4,0 3,6 3,2 2,8 T100% T50% T0% Koroneiki Dys fter pplying wter tretments Figure 1. Lef wter potentil (Ψw, - MP) of olive tree (Ole europe L. cv Koroneiki nd Chemlli) under three wter tretments during 35 dys fter pplying wter tretments. Ech vlue represents the men ± stndrd devition of three mesures. The verge of ech vlue followed y the sme letter do not differ sttisticlly etween tretment - SNK P <5%. T100% T50% T0% c Chemlli Dys fter pplying wter tretments 6,8 6,4 6,0 5,6 5,2 4,8 4,4 4,0 3,6 3,2 2,8 Wter potentil (Ψw; -MP) 331

6 Europen Scientific Journl Jnury 2017 edition vol.13, No.3 ISSN: (Print) e - ISSN Effect of three wter tretments on lef osmotic djustment Figure 2 indictes tht, for Koroneiki plnts, T50% plnts show very low osmotic djustment (0.16 MP) tht decreses throughout the experiment. However, for Koroneiki T0% plnts, the osmotic djustment did not exceed 0.5 MP fter 21 dys of pplying wter tretments. Then, it increses strongly y 85% nd reches 2.46 MP, fter 28 dys of pplying wter tretments. At the end of the experiment, the osmotic djustment of T50% nd T0% plnts reches 0.08 nd 2.02 MP respectively. Chemlli plnts show progressive increse of their osmotic djustment throughout the experiment, for oth wter tretments (50% AWC nd 0% AWC). At the lst dy of the experiment, the osmotic djustment of Chemlli T50% nd T0% plnts reches 1.25 nd 1.7 MP, respectively. Giron et l. (2015) showed tht the physiologicl response of the trees (osmotic djustment nd trunk dehydrtion) compensted the decrese in wter potentil. The ility of olive trees to rech such (extremely) negtive Ψw vlues is prtilly due to osmotic djustment. Osmotic djustment llows plnts to tolerte temporry or prolonged periods of wter shortge nd is one of the crucil processes involved in plnt dpttion to drought (Chves et l., 2003). According to Dichio et l. (2003), osmotic djustment is one of the erly mechnisms of trees in respond to wter stress (i.e. in olive trees). 3,0 3,0 T50% T0% T50% T0% 2,5 Chemlli 2,5 Koroneiki 2,0 2,0 1,5 1,5 1,0 1,0 0,5 0,5 0,0 0, Dys fter pplying wter Dys fter pplying wter tretments tretments Figure 2. Lef osmotic djustment (OA, MP) of olive tree (Ole europe L. cv Koroneiki nd Chemlli) under two wter tretments during 35 dys fter pplying wter tretments. Ech vlue represents the men ± stndrd devition of three mesures. The verge of ech vlue followed y the sme letter do not differ sttisticlly etween tretment - SNK P <5%. OA (MP) OA (MP) 332

7 Europen Scientific Journl Jnury 2017 edition vol.13, No.3 ISSN: (Print) e - ISSN Effect of three wter tretments on gs exchnge Effect of three wter tretments on stomtl conductnce Figure 3 shows the effect of three wter tretments on the lef stomtl conductnce (gs) of Koroneiki nd Chemlli cultivrs. For the oth cultivrs, t T100%, plnts show the highest stomtl conductnce, however T0% ones show the lowest vlue. We noted significnt difference etween Koroneiki T100% nd T50% plnts fter 14 dys of the strt of the experiment. The T0% plnts of the sme cultivr show low stomtl conductnce tht rnges etween nd mol H 2 O m -2 s -1. Chemlli plnts demonstrted significnt difference etween the three wter tretments fter 7 dys of pplying wter tretments. This difference ws mintined throughout the experimentl period. At the 35 th dy, no significnt difference ws oserved etween cultivrs for the three wter doses. As mechnism of dpttion to wter restriction, the stomtl conductnce limits the photosynthesis (A) rte y closing the stomt, so the photosynthesis decreses. The stomtl conductnce of Koroneiki plnts t T100% rnges etween 0.17 nd mol H 2 O m -2 s -1. However, Chemlli plnts for the sme tretment, stomtl conductnce rnges etween 0.16 nd mol H 2 O m -2 s -1. For Koroneiki plnts receiving 50% AWC, the stomtl conductnce rnges etween nd mol H 2 O m -2 s -1. Wheres, Chemlli plnts stomtl conductnce rnges etween nd mol H 2 O m -2 s -1. Stomtl closure, to mintin the lef s wter lnce, decreses A nd thus iomss production of plnts (Lwlor, 2002; Frineu nd Morot- Gudry, 2006). A controversy exists lredy for severl yers s to whether stomtl closure or iochemicl impirment limits most photosynthesis under drought stress. Cornic (2000) concluded tht the stomtl prt is the primry nd, therefore, proly the most importnt limiting fctor, ut the dete is up to tody still ongoing. Fernndez (2014) indicted tht the role of stomt is to regulte the entry of sufficient CO 2 for optiml photosynthesis while conserving wter inside the plnt. As in mny other plnts well dpted to dry res, stomtl closure in olive limits trnspirtion. In potted olive trees, Angelopoulos et l. (1996) nd Boussdi et l. (2008) determined tht stomtl conductnce (gs) ws limiting photosynthesis (A) in trees sujected to mild nd moderte wter stress. 333

8 Europen Scientific Journl Jnury 2017 edition vol.13, No.3 ISSN: (Print) e - ISSN gs (mol H 2 O m -2 s -1 ) 0,35 0,3 0,25 0,2 0,15 0,1 0,05 0 T100% T50% T0% Koroneiki c c c c T100% T50% T0% Chemlli c c c c ,35 0,3 0,25 0,2 0,15 0,1 0,05 0 gs (mol H 2 O m -2 s -1 ) Dys fter pplying wter tretments Dys fter pplying wter tretments Figure 3. Lef stomtl conductnce (gs, mol H 2 O m -2 s -1 ) of olive tree (Ole europe L. cv Koroneiki nd Chemlli) under three wter tretments during 35 dys fter pplying wter tretments. Ech vlue represents the men ± stndrd devition of three mesures. The verge of ech vlue followed y the sme letter do not differ sttisticlly etween tretments- SNK P <5%. Effect of three wter tretments on photosynthesis The effect of three wter tretments on the lef photosynthesis (A) of Koroneiki nd Chemlli olive plnts ws given in figure 4. For oth cultivrs, plnts t T100% show the highest photosynthesis rte wheres T0% plnts show the lowest one. For Koroneiki plnts, significnt difference ws noticed fter 14 dys of pplying wter tretments etween plnts treted t T100% nd T50%. Koroneiki T0% plnts show low photosynthetic rte tht decreses from 4.08 µmol CO 2 m -2 s -1, to 0.2 µmol CO 2 m -2 s -1, t the end of the experimentl period. For Chemlli plnts, significnt difference ws noticed etween T0% nd T100% plnts during the whole experiment. However, no significnt difference ws recorded t the end of the experimentl period etween T100% nd T50% plnts. As for Koroneiki T0% plnts, the photosynthesis rte of Chemlli plnts decreses from 8.46 µmol CO 2 m -2 s -1, to 1.29 µmol CO 2 m -2 s -1, 35 dys fter pplying wter tretments. The photosynthesis rte decreses strongly for Koroneiki T0% plnts thn Chemlli ones. So we cn deduce tht Chemlli plnts seem to present more plsticity to wter restriction thn Koroneiki plnts. Despite the decresing trend in A due to turgidity loss which compromises cell metolism nd, in prticulr, the photosynthetic system, the results confirm the cpcity of olive tissues to continue with 334

9 Europen Scientific Journl Jnury 2017 edition vol.13, No.3 ISSN: (Print) e - ISSN photosynthesis during prolonged wter restriction nd to lose tissue wter through trnspirtion ensuring some photosynthesis in cse of missing or insufficient irrigtion. Similr results were lso reported y Dichio et l., (2005) for Cortin olive trees. Petridis et l. (2012) determined tht photosynthetic rte ws reduced minly due to stomtl closure. Cultivrs hving high rtes of cron uptke, when conditions re fvorle, decrese rpidly upon instlling nd during the wter stress tretment. These cultivrs cn e ctegorized s opportunistic. Mximum reduction in A ws oserved fter 35 dys of wter stress: vlues reduced to 80% nd 56% compred to control vlues for Koroneiki nd Chemlli, respectively. Similr results hve een reported y Brhm (1997) nd Boussdi et l. (2008) for the sme cultivrs. Chrtzoulkis et l. (1999) noted tht the photosynthetic ctivity in two olive tree cultivrs Koroneiki nd Mstoid declined during the development of progressive wter restriction. Similr effects hve een reported y other reserchers (e.g. Giorio et l., 1999) noting tht the photosynthesis rtes of olive trees decresed y 50% when wter supply chnged from 66% to 33% ETP (evpotrnspirtion). 30 T100% T50% T100% T50% 30 T0% T0% 25 Koroneiki Chemlli c 5 c c c c 5 c Photosynthesis (A; µmol CO 2 m -2 s -1 ) Dys fter pplying wter tretments Dys fter pplying wter tretments Figure 4. Lef photosynthesis (A, µmol CO 2 m -2 s -1 ) of olive tree (Ole europe L. cv Koroneiki nd Chemlli) under three wter tretments during 35 dys fter pplying wter tretments. Ech vlue represents the men ± stndrd devition of three mesures. The verge of ech vlue followed y the sme letter do not differ sttisticlly etween tretments - SNK P <5%. Effect on intrinsic wter use efficiency The intrinsic WUE of Koroneiki, expressed s the rtio A/gs, shows no significnt difference etween T100% nd T50% plnts throughout the experiment (Figure 5). However, for Chemlli plnts, T50% presents etter Photosynthesis (A; µmol CO 2 m -2 s -1 ) 335

10 Europen Scientific Journl Jnury 2017 edition vol.13, No.3 ISSN: (Print) e - ISSN intrinsic WUE thn T100% plnts. A significnt difference is mintined etween T100% nd T50% during the experiment period. Koroneiki WUE rnged etween 83 to 98 μmol CO 2 m -2 s -1 compred to Chemlli WUE tht rnged etween 80 nd 135 μmol CO 2 m -2 s -1 for T50% tretment. This result indictes tht Chemlli plnts vlorizes etter low quntities of wter (T50%) rther thn high quntities (T100% plnts). A significnt difference etween Koroneiki nd Chemlli plnts for the two wter tretments ws shown, 35 dys fter pplying wter tretments. Intrinsic WUE (µmol CO 2 (mol H 2 O) -1 ) T100% T50% Koroneiki Dys fter pplying wter trtments T100% T50% Chemlli Figure 5. Intrinsic wter use efficiency (µmol CO 2 (mol H 2 O) -1 ) of olive tree (Ole europe L. cv Koroneiki nd Chemlli) under two wter tretments during 35 dys fter pplying wter tretments. Ech vlue represents the men ± stndrd devition of three mesures. The verge of ech vlue followed y the sme letter do not differ sttisticlly etween tretments - SNK P <5%. Effect of three wter tretments on plnt dry mtter ccumultion For oth cultivrs, root dry weight (DW) ws significntly ffected y the three wter tretments. Koroneiki plnts t T100% show the highest root DW. However, for Chemlli plnts, the highest one ws shown t T50% (Tle 1). At T100%, leves DW of Koroneiki cultivr show significnt difference with the other tretments (T50% nd T0%). For Chemlli t T50%, plnts show the highest leves DW ut no significnt difference is found, etween the three wter tretments. The highest Koroneiki stem DW ws otined in plnts treted t T100% nd T50% compred to T0%. Wheres, for Chemlli plnts, no significnt difference ws found etween the three wter tretments Dys fter pplying wter tretments Intrinsic WUE (µmpl CO 2 (mol H 2 O) - 1 ) 336

11 Europen Scientific Journl Jnury 2017 edition vol.13, No.3 ISSN: (Print) e - ISSN The root/shoot rtio of Chemlli plnts t T50% tretment ws the highest (1.08) comprtively with the other two tretments. This result shows tht Chemlli plnts vlorize low quntities of wter (T50%) rther thn high quntities (T100%). However, for Koroneiki t T100% tretment plnts show the est root/shoot rtio compred to T50% nd T0%. This result seems to indicte tht Koroneiki plnts ehve etter when it is irrigted t 100% AWC. To rech this ojective, plnts sujected to wter deficiency, close their stomt, reduce wter losses nd limit trnspirtion nd cron ssimiltion (Giorio et l., 1999). Such reduction of photossimiltes vilility cuses, t whole plnt level, chnge in the pttern of dry mtter distriution: shoot growth will e inhiited while higher quntity of ssimiltes will e trnsported nd ccumulted in the root system determining higher root/shoot rtio in wter stressed plnts (Xiloynnis et l., 1999). Di Vio et l. (2013) mentioned tht, under different wter regimes pplied on young pot-grown olive trees, the dry mtter ws ffected y the wter regime nd cultivr. Indeed, the cv Leccino, full irrigted, displyed greter ccumultion of totl dry mtter nd fruit dry mtter, while these two prmeters were gretly reduced under the other wter regimes (T50 nd T25). By contrst, the cv Rcioppell lwys showed lower ccumultion of dry mtter nd more lnced cnopy/root rtio. Nevertheless, wter stress is not the only prmeter tht ffects dry mtter distriution in the plnt; in prticulr, mny gronomic nd genetic fctors, such s rootstock, cultivr, trining system, pruning nd plnting density hve een shown to influence growth nd to modify the distriution of iomss etween roots nd cnopy (cnopy/roots rtio) nd etween the different plnt orgns (Cruso et l., 1997, 2001, 2008; Zucconi, 1992; Xiloynnis et l., 2007; Di Vio et l., 2012; Weiel nd Reighrd, 2012; Yno et l., 2002). Severl cultivrs respond differently to drought, showing differences in terms of dpttion, dry mtter distriution, production nd gs exchnge responses to wter shortge (Chrtzoulkis et l.,1999; Bcelr et l., 2004, 2007; Tognetti et l., 2002). 337

12 Europen Scientific Journl Jnury 2017 edition vol.13, No.3 ISSN: (Print) e - ISSN Tle 1. Root, leves nd stem dry weight (g/plnt) nd root/shoot rtio of olive tree (Ole europe L. cv Koroneiki nd Chemlli) under three wter tretments, 35 dys fter pplying wter tretments. Ech vlue represents the men ± stndrd devition of three mesures. The verge of ech vlue followed y the sme letter do not differ sttisticlly - SNK P <5%. The first letter is for the sttisticl nlysis within the cultivr nd the second is for the sttisticl nlysis within the wter tretment. Cultivr tretment Korone iki Chem lli -Wter Root Dry Weight (g/plnt) Leves Dry Weight (g/plnt) Stem Dry Weight (g/plnt) Root/shoot rtio T100% 45.96±2.32, 30.40±4.74, 32.76±2.62, 0.70±0.04, T50% 29.50±2.48, 18.96±3.28, 29.26±2.35, 0.61±0.02, T0% 16.51±0.62 c, 12.79±2.51, 17.73±3.43, 0.55±0.10, T100% 24.97±3.97, 16.85±4.31, 18.51±4.68, 0.70±0.07, T50% 33.80±5.37, 17.46±7.51, 16.07±5.62, 1.08±0.29, T0% 20.41±4.91, 11.10±1.52, 14.64±1.10, 0.79±0.13, Conclusion Our results showed tht, s wter stress increses (T0%), the cultivr Chemlli elong more resistnt to wter restriction thn Koroneiki y mintining longer high (less negtive) middy lef wter potentil. Mesurements of osmotic djustment showed tht olive trees use this mechnism to crete very negtive lef wter potentils in order to e le to extrct wter from dry root environment. Chemlli plnts showed progressive increse of their osmotic djustment throughout the experiment, for oth wter tretments (50% AWC nd 0% AWC). This Chemlli cultivr stress mngement strtegy ws confirmed y mesurements of stomtl conductnce showing significnt difference etween the three wter tretments from the first week fter pplying wter tretments. However, for Koroneiki cultivr, the stress mngement strtegy ws not s remrkle s Chemlli cultivr. As mechnism of dpttion to wter restriction, the stomtl conductnce limited the photosynthesis rte y closing the stomt, so the photosynthesis decreses nd thus the iomss production of plnts. Such reduction of photossimiltes vilility cuses, higher root/shoot rtio in wter stressed plnts (1.08 for Chemlli T50% plnts). In consequence, Chemlli T50% plnts showed the highest intrinsic wter use efficiency compred to Koroneiki plnts. In conclusion, the ssessment of the ehvior of two young olive tree cultivrs Koroneiki nd Chemlli under wter restriction conditions sed on wter sttus, eco-physiologicl nd dry mtter ccumultion prmeters showed tht olive tree (Ole europe L.) locl cultivr Chemlli irrigted t 50% AWC, compred to Koroneiki cultivr, is the most suitle cultivr to tolerte wter restriction conditions. 338

13 Europen Scientific Journl Jnury 2017 edition vol.13, No.3 ISSN: (Print) e - ISSN Acknowledgments The uthors cknowledge the Olive tree Institute (Unit of Sousse) technicl stff for the help nd support tht they gve us during the whole reliztion period of this reserch. References 1. Angelopoulos, K., Dichio, B., & Xiloynnis, C. (1996). Inhiition of photosynthesis in olive trees (Ole europe L.) during wter stress nd rewtering. Journl of Experimentl Botny, 47(8), Bcelr, E. A., Correi, C. M., Moutinho-Pereir, J. M., Gonçlves, B. C., Lopes, J. I., & Torres-Pereir, J. M. (2004). Sclerophylly nd lef ntomicl trits of five field-grown olive cultivrs growing under drought conditions. Tree physiology, 24(2), Bcelr, E. A., Moutinho-Pereir, J. M., Gonçlves, B. C., Ferreir, H. F., & Correi, C. M. (2007). Chnges in growth, gs exchnge, xylem hydrulic properties nd wter use efficiency of three olive cultivrs under contrsting wter vilility regimes. Environmentl nd Experimentl Botny, 60(2), Boussdi, O., Mriem, F. B., Mechri, B., Boussett, W., Brhm, M., & El Hdj, S. B. (2008). Response to drought of two olive tree cultivrs (cv Koroneki nd Meski). Scienti horticulture, 116(4), Brhm, M. (1997). Activité écophysiologique, étt nutritif et croissnce de l olivier (Ole europe L.) soumis à une contrinte hydrique, thèse d Étt, fculté des sciences gronomiques de Gnd, Belgique. 160 p. 6. Cruso, T., Inglese, P., Sidri, M., & Sottile, F. (1997). Rootstock influences sesonl drymtter nd crohydrte content nd prtitioning in ove-ground componentsof Flordprince pech trees. J. Am. Soc. Hortic. Sci. 122 (5), Cruso, T., Brone, E., & Di Vio, C. (2001). Fctors ffecting tree crop efficiency in youngpech trees: rootstock vigour nd trining system. Act Hortic. 557, Cruso, T., Motisi, A., Pernice, F., & Di Vio, C. (2008). Pech plnting systems in southernitly: ecophysiologicl spects nd technicl developments. Act Hortic. 772, Chrtzoulkis, K., Ptks, A., & Boslidis, A. M. (1999). Chnges in wter reltions, photosynthesis nd lef ntomy induced y intermittent drought in two olive cultivrs. Environmentl nd experimentl otny, 42(2),

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