Influence of Partial Soil Wetting on Water Relation Parameters of the Olive Tree

See discussions, s a s, and au ho p o iles o his publica ion a : h ps://www. esea chga e.ne /publica ion/248850251 Influence o pa ial soil we ing on wa e ela ion pa ame e s o he oli e ee A icleinAg onomie · No embe 2003 DOI: 10.1051/ag o:2003031 CITATIONS 45 READS 55 4 au ho s, including: Some o he au ho s o his publica ion a e also wo king on hese ela ed p ojec s: Ag oPHYS View p ojec Assessmen o ui g ow h esponse o wa e s ess in a supe -high-densi y oli e o cha d: moni o ing, physiological mechanisms and po en ial use o schedule i iga ion View p ojec M.J. Ma ín-Palomo Uni e sidad de Se illa 63 PUBLICATIONS1,151 CITATIONS SEE PROFILE An onio Diaz-Espejo Spanish Na ional Resea ch Council 108 PUBLICATIONS4,880 CITATIONS SEE PROFILE Ignacio Gi on Spanish Na ional Resea ch Council 65 PUBLICATIONS1,503 CITATIONS SEE PROFILE All con en ollowing his page was uploaded by M.J. Ma ín-Palomo on 02 Feb ua y 2015. The use has eques ed enhancemen o he downloaded ile. 545 Ag onomie 23 (2003) 545–552 © INRA, EDP Sciences, 2003 DOI: 10.1051/ag o:2003031 O iginal a icle In luence o pa ial soil we ing on wa e ela ion pa ame e s o he oli e ee José-En ique FERNÁNDEZ*, Ma ía-José PALOMO, An onio DÍAZ-ESPEJO, Ignacio-F ancisco GIRÓN Ins i u o de Recu sos Na u ales y Ag obiología (IRNAS, CSIC), A enida de Reina Me cedes 10, Apa ado 1052, 41080 Se illa, Spain (Recei ed 27 No embe 2001; accep ed 15 Janua y 2003) Abs ac – A d ip e sus pond i iga ion expe imen was ca ied ou wi h 30-yea -old ‘Manzanilla’ oli e ees plan ed a 7 m ´5 m in an o cha d in Sou hwes Spain. A he end o he d y season o 1998, we chose wo d y-land ees, D1 and D2, and wo d ip-i iga ed ees, I1 and I2. Du ing he expe imen s, he D1 and I1 ees we e pond-i iga ed, inc easing he soil wa e con en o a ound ield capaci y in he whole oo zone. The D2 and I2 ees we e d ip-i iga ed, emaining pa o he oo zone in d ying soil. The esul s showed ha he a io be ween he anspi a ion o he pond-i iga ed D1 ee and ha o he d ip-i iga ed D2 ee (D1/D2 Ep) inc eased om an a e age o 0.88 be o e i iga ion o 1.22 ou een days a e he i s wa e supply. Fo he I ees, I1/I2 Ep a ied om 0.76 o 1.02 nine days a e he I1 ee was pond-i iga ed o he i s ime. T anspi a ion, he e o e, was es ic ed when using a d ip i iga ion sys em which, despi e supplying enough wa e o co e he calcula ed c op demand, a ec ed a pa o he oo zone only. Du ing he d ip e sus pond i iga ion expe imen , he eco e y o lea wa e po en ial, s oma al conduc ance and pho osyn hesis a e was g ea e and quicke in he pond-i iga ed han in he d ip-i iga ed ees. oli e / i iga ion / wa e ela ion / pa ial we ing / ewa e ing / sap low Résumé – In luence de l’i iga ion pa ielle du sol su les pa amè es des ela ions hyd iques de l’oli ie . Une compa aison de l’i iga ion gou e à gou e a ec l’i iga ion en cu e e a é é condui e su oli ie s ‘Manzanilla’ âgés de 30 ans plan és à 7 m ´5 m dans un e ge du sud-oues de l’Espagne. À la in de la saison sèche de 1998, nous a ons choisi deux a b es su sol sec, D1 e D2, e deux a b es su sol i igué au gou e à gou e, I1 e I2. Du an les expé iences, les a b es D1 e I1 on é é i igués en cu e e, en augmen an la eneu en eau du sol jusqu’à la capaci é au champ dans ou e la zone acinai e. Les a b es D2 e I2 on é é i igués au gou e à gou e, laissan une pa ie de la zone acinai e dans un sol se desséchan . Les ésul a s on mon é que le quo ien en e la anspi a ion de l’a b e D1 i igué en cu e e e celle de l’a b e D2 i igué au gou e à gou e (D1/D2 Ep) a augmen é à pa i d’une moyenne de 0,88 a an i iga ion jusqu’à 1,22 qua o ze jou s ap ès le p emie appo d’eau. Pou les a b es I, I1/I2 Ep a a ié en e 0,76 e 1,02 neu jou s ap ès que l’a b e I1 ai é é i igué en cu e e pou la p emiè e ois. Pa conséquen , la anspi a ion é ai édui e quand on u ilisai un sys ème d’i iga ion au gou e à gou e qui, malg é l’appo d’eau su isan pou cou i les besoins po en iels des cul u es, a a ec é seulemen une pa ie de la zone acinai e. Du an ce e compa aison de l’i iga ion gou e à gou e e de l’i iga ion en cu e e, la écupé a ion de la eneu en eau des euilles, de la conduc ance s oma ique e du aux de pho osyn hèse é ai supé ieu e e plus apide pou les a b es i igués en cu e e que pou ceux i igués au gou e à gou e. oli ie / i iga ion / ela ion hyd ique / a osage pa iel / éhyd a a ion / lux de sè e 1. INTRODUCTION In mos Medi e anean a eas whe e oli e is cul i a ed he we season is ollowed by a long, d y and ho season. Many o he physiological p ocesses o he plan , including shoo and ui g ow h, ake place mainly in he d y mon hs. I iga ion is, he e o e, a compulso y p ac ice in oli e o cha ds whe e he maximum p oduc i i y is o be achie ed. D ip i iga ion is he mos popula sys em o applying wa e in oli e o cha ds, mainly due o he ac ha mos o cha ds a e in a id and semi- a id a eas whe e wa e o i iga ion is sca ce. The in luence o d ip i iga ion on he oo dynamics, oo dis ibu ion and oo ac i i y o he oli e ee was s udied by Fe nández e al. [13, 14]. La e , Mo eno e al. [26] used, o he i s ime in oli e, he compensa ion hea -pulse echnique, as desc ibed by G een and Clo hie [21], o s udy he wa e up ake beha iou o he oo s. Fu he s udies on oo wa e up ake we e published by Fe nández e al. [15]. In hese s udies, howe e , he in luence o he oo sys em on he lea con ol o anspi a ion was no conside ed. Bongi and Pallio i [3] ca ied ou a spli - oo expe imen wi h young ‘F an oio’ plan s in po s, and de ec ed s oma al closu e in he plan s wi h a small po ion o he oo * Co esponding au ho : je e @i nase.csic.es Communica ed by Gé a d Guyo (A ignon, F ance) 546 J.-E. Fe nández e al. sys em le in d y soil. To ou knowledge, his is he only pub- lished e e ence o a possible oo - o-lea signalling mechanism in oli e, and whe he his phenomenon occu s in ma u e oli e ees unde ield condi ions is unknown. In he ield, he oo sys em de elops in he whole oo zone du ing he g owing mon hs o he we season. Du ing he d y season, howe e , d ip and o he localised i iga ion sys ems a ec a pa o he oo zone only, he o he pa emaining in d ying soil. Unde hese condi ions s oma al closu e migh be induced by he oo s le in d y soil, leading o a educ ion in gas exchange be ween he lea es and he su ounding ai . This will in luence wa e up ake and, p obably, c op p oduc i i y. The e o e, any in o ma ion on his beha iou will be use ul o op imise i iga- ion p ac ices in oli e o cha ds. In ac , he oo - o-shoo sig- nalling p ocess is being exploi ed in ag icul u e o inc ease wa e use e iciency [7]. Ano he phenomenon ela ed o wa e use by he oli e ee is he eco e y o he ees a e a leng hy d ough pe iod. This is o in e es o designing de ici i iga- ion s a egies, widely used in oli e o cha ds [20]. The eco - e y o wa e s a us and gas exchange a e ewa e ing has been s udied o se e al oli e a ie ies [11, 16, 27] bu , o ou knowledge, he in luence o we ing he whole oo zone, o jus pa o i , on he eco e y, has no been s udied ye . The main objec i e o his wo k was o in es iga e whe he d ip i iga ion – as compa ed wi h pond i iga ion in which he whole oo zone is we ed - limi s wa e consump ion in ma u e ‘Manzanilla’ oli e ees unde ield condi ions. In addi ion, i was in es iga ed whe he he ype o i iga ion in luences he eco e y o lea wa e po en ial and gas exchange ollowing ewa e ing a e a long pe iod o d ough . 2. MATERIALS AND METHODS 2.1. Expe imen al o cha d The expe imen s we e conduc ed in an oli e o cha d o La Hampa, he expe imen al a m o he Ins i u o de Recu sos Na - u ales y Ag obiología (IRNAS, CSIC), close o Co ia del Río, Se ille (la i ude 37º17’ N, longi ude 6º3’ W, al i ude 30 m). The ees we e 30-yea -old ‘Manzanilla de Se illa’ ( e e ed o he e as ‘Manzanilla’) oli e ees (Olea eu opaea L.) a 7 m ´ 5 m spacing. The soil o he o cha d is a sandy loam (Xe o- ch ep ) o a iable dep h. A ha d limy sands one pan impedes he pene a ion o bo h oo s and wa e a a dep h which a ies wi hin he o cha d om abou 0.9 o 2.0 m. Soil ex u e is qui e homogeneous, bo h e ically and ho izon ally. F om he su - ace o he ha dpan, he a e age ex u al alues a e 14.8% clay, 7.0% sil , 4.7% ine sand and 73.5% coa se sand. The wa e able emains a below he maximum dep h o he oo sys em [18]. The olume ic soil wa e con en (q, m3·m–3) measu ed in he labo a o y was 0.33 m3·m–3 in sa u a ed soil samples and 0.10 m3·m–3 a a soil ma ic po en ial o –1.5 MPa. In he ield, he alues o measu ed close o he d ippe s a ew hou s a e i iga ion we e a ely g ea e han 0.20 m3·m–3. Nex o he expe imen al o cha d he e is an au oma ic wea he s a ion whe e hi y-minu e a e ages o wind speed and di ec ion, ain- all, ai empe a u e and humidi y, global sola adia ion and pho osyn he ically ac i e adia ion a e con inuously eco ded. The clima e o he a ea is ypically Medi e anean, being d y and ho om May o Oc obe and mild and ainy o he es o he yea . Fo he las 25 yea s, he a e age ain all and e e ence e apo anspi a ion (ETo) egis e ed in he o cha d ha e been 484 mm and 1442 mm, espec i ely. The c op managemen p ac ices ca ied ou in he o cha d a e simila o hose o ep- esen a i e comme cial o cha ds in he a ea. One pa o he o cha d has always been unde d y- a ming condi ions (D ees), whe eas he o he has always been d ip i iga ed du ing he d y seasons (I ees). In he las i e yea s a single d ip line pe ee ow has been used, placed on he soil su ace and wi h i e 3 L·h–1 d ippe s pe ee spaced 1 m apa . Daily i iga ion was applied o he I ees du ing he d y seasons, o eplace he c op wa e demand (ETc, mm). The i iga ion needs we e cal- cula ed e e y week, using he equa ion ETc = Kc K ETo.(1) The e e ence e apo anspi a ion was calcula ed by he FAO-Penman equa ion [9], which Man o ani e al. [23] ali- da ed as he mos app op ia e o he a ea. The alues o he c op (Kc) and educ ion (K ) coe icien s we e hose ecom- mended by Fe nández e al. [16] and Fe nández and Mo eno [12] o he o cha d condi ions. 2.2. I iga ion expe imen In 1998, he expe imen al yea , he d y season began in Ma ch. The I ees we e i iga ed daily om Ma ch 24 un il he end o Sep embe , when he i s au umn ains we e eco ded. Once he we ed bulbs – he soil olumes unde he d ippe s a ec ed by i iga ion – we e well es ablished, he diame e o he g ound su ace we ed by each d ippe was a ely g ea e han 1 m, which accoun s o a maximum we ed g ound su ace o abou 4 m2 pe ee. A ough es ima ion om soil sampling a ound he we ed bulbs allowed us o es ablish he a e age we ed soil olume pe ee as abou 7 m3, being a ely g ea e han 10 m3. This accoun s o 20 o 30% o he o al soil ol- ume o each ee. This, oge he wi h he da a on oo dis ibu- ion ob ained by Fe nández e al. [13] in he same o cha d, allows us o assume ha jus a pa o he oo sys em o he d ip-i iga ed I ees was a ec ed by i iga ion; he o he pa emained in d ying soil h oughou he d y season. In he non- i iga ed D ees, he whole oo sys em was in d ying soil h oughou he d y season. A he end o Augus 1998 we s a ed wha we will call he d ip e sus pond i iga ion expe imen . We chose wo d y- land ees, D1 and D2, and wo d ip-i iga ed ees, I1 and I2. All he ees we e simila in size, abou 4.5 m all and wi h a c own diame e o abou 5.0 m. They had a single unk o abou 0.2 m diame e wi h wo main b anches a abou 1.2– 1.6 m abo e g ound. The p e ious yea Palomo [28] had es i- ma ed ha he maximum lea a ea o he ees anged om abou 61 o 64 m2. An ea hen dyke o 13 m ´ 9 m was buil a ound he D1 and I1 ees, o pond i iga ion. Enough wa e was added o he D1 and I1 ees (Tab. I) o inc ease he soil wa e con en o a ound ield capaci y in he whole oo zone (Tab. II). The D2 ee was d ip i iga ed om Augus 25, by a d ip line wi h i e 6 L·h–1 emi e s spaced 1 m apa (Tab. I). The i iga ion doses applied o his ee we e mo e han double he equi ed amoun o wa e o eplace he ETc calcula ed wi h equa ion (1), which a e aged 73 L·d–1 o he pe iod be ween Augus 25 and Sep embe 11. Thus, in a sho pe iod o ime q Soil we ing and oli e 547 he we ed bulbs we e well es ablished in ha p e iously non- i iga ed D2 ee (Tab. II). The I2 ee was i iga ed om Ma ch 24, wi h daily d ip i iga ion o eplace ETc, as explained abo e. The e o e, a he beginning o Sep embe we had he D1 ee wi h he whole oo zone a ec ed by pond i i- ga ion and he D2 ee wi h jus pa o he oo zone a ec ed by d ip i iga ion. This pai o ees was p e iously unde d y- a ming condi ions. We also had a second pai o ees, he I1 ee wi h he whole oo zone a ec ed by pond i iga ion and he I2 ee wi h jus pa o he oo zone a ec ed by d ip i i- ga ion. This pai o ees was d ip i iga ed om he beginning o he d y season. 2.3. Sap low measu emen s We used he compensa ion hea -pulse me hod, as desc ibed by G een and Clo hie [21], o es ima ing sap lows in he ou expe imen al ees. De ails on he calib a ion and es ing o he echnique o he oli e ee, as well as on da a analysis, a e gi en in Fe nández e al. [17]. On Augus 20 h ee se s o hea -pulse p obes we e ins alled a h ee equal spacings a ound he azimu h o he D1 and D2 ee unks. On Augus 31 h ee se s o p obes we e also ins alled in he I1 and I2 ees, ollowing he same c i e ia as in he D ees. In all cases he p obes we e ins alled in places ee o gna led kno s and sca s. Each p obe measu ed he sap eloci y a 5, 12, 22 and 35 mm below he cambium. Measu emen s we e made e e y hal hou , o he en i e expe imen al pe iod. The da a we e col- lec ed by a Campbell CR10X da a logge (Campell Scien i ic Inc., USA). The anspi a ion o each ee (Ep, L·d–1) was es i- ma ed om he sap low eco ds, calcula ing he sap lux den- si ies (J, mm·h–1) as desc ibed by Fe nández e al. [17]. Despi e applying he desc ibed me hodology wi h igou and ca e, signi ican di e ences be ween he ac ual anspi a- ion alues and he calcula ed Ep alues migh no be a oided. This is due o he high a iabili y o he c oss-sec ional con- duc i e a ea in he unk o ma u e oli e ees, among o he ac o s desc ibed by Fe nández e al. [17]. In ha wo k, in ac , i is shown ha indi idual Ep da a om ma u e oli e ees a e in luenced by p obe loca ion. Consequen ly, and o he pu - pose o ou s udy, analysing he a io be ween he wo pai o ees (D1/D2 Ep and I1/I2 Ep) was mo e ad an ageous han conside ing indi idual Ep da a. This allowed us o de ec he in luence o we ing he whole oo zone, o jus pa o i , on anspi a ion, a he same ime as a oiding making mis akes caused by he men ioned a iabili y. Table I. Wa e supplied o he expe imen al ees a he end o he summe o 1998, in he d ip e sus pond i iga ion expe imen . The da es o he i iga ion e en s and he i iga ion ypes a e speci ied. P io o he i iga ion e en s de ailed in his able, he I1 and I2 ees we e i iga ed daily om he beginning o he d y season, on Ma ch 24, while he D1 and D2 ees we e unde d y- a ming condi ions. De ails a e gi en in he ex . DOY = day o yea . GMT = G eenwich Mean Time. T ee Da e DOY Wa e supplied I iga ion ype D1 Augus 25 " 27 " 31 Sep embe 4 " 7 237 239 243 247 250 142 mm(*) 62 " 78 " 87 " 72 " Pond " " " " D2 F om Augus 25 o Sep embe 11 237–254 190 L·d–1 (*) Daily d ip I1 Sep embe 3 " 7 246 250 151 mm(*) 78 " Pond " F om Augus 31 o Sep embe 6 243–249 82 L·d–1 Daily d ip F om Sep embe 7 o Sep embe 13 250–256 72 L·d–1 Daily d ip I2 F om Augus 31 o Sep embe 6 243–249 82 L·d–1 Daily d ip F om Sep embe 7 o Sep embe 13 250–256 72 L·d–1 Daily d ip (*) The i iga ion e en s o Augus 25 and Sep embe 3 began a abou 13.00 GMT. Table II. A e age olume ic soil wa e con en (q) measu ed a ound he expe imen al ees be o e and du ing he d ip e sus pond i iga ion expe imen . The shown da a co espond o he soil olumes a ec ed by i iga ion. The a e age q alues in he soil olumes non-a ec ed by i iga ion we e 0.11 m3·m–3 o he D ees and 0.12 m3·m–3 o he I ees, emaining abou cons an du ing he expe imen . De ails on he expe imen al ees and he measu emen s a e gi en in he ex . DOY = day o yea . q (m3·m–3) DOY D1 D2 I1 I2 237 238 239 240 243 245 246 250 254 0.14 0.18 0.18 0.20 0.19 0.19 0.19 0.19 0.10 0.12 0.13 0.14 0.15 0.16 0.17 0.17 0.18 0.20 0.19 0.19 0.20 0.21 0.20 0.20 548 J.-E. Fe nández e al. 2.4. Lea wa e s a us and gas exchange measu emen s Lea wa e po en ial (Yl, MPa) was measu ed in he D and in he I ees once pe mon h, om he beginning o he d y season o he beginning o he d ip e sus pond i iga ion expe imen . Measu emen s we e ca ied ou jus be o e dawn (Ypd) and a a ound 10.00 GMT (Y10) when he lea es showed he minimum daily alues o Yl [16]. One sunli and heal hy lea o he cu en yea was sampled pe ee, in six ees o bo h he D and I ea men s. We measu ed he xylem p essu e po en ial a he pe iole wi h a p essu e chambe (Soil- mois u e Equipmen Co p., San a Bá ba a, Cali o nia, USA), and assumed i o be equal o he lea wa e po en ial. Du ing he d ip e sus pond i iga ion expe imen , measu emen s o Ypd and Y10 we e made nea ly e e y day, in six lea es pe ee, in he ou expe imen al ees. Immedia ely a e measu - ing Y10, measu emen s o s oma al conduc ance o H2O (gs, mol·m–2·s–1) and he ne pho osyn hesis a e (PN, mmol·m–2·s–1) we e ca ied ou wi h a po able pho osyn hesis sys em (LI- 6400, LI-COR, Lincoln, Neb aska, USA). These wo a iables we e measu ed in 10 lea es pe ee o he same ype as desc ibed abo e, in each one o he ou expe imen al ees. The measu emen s we e made a a ound 10.30 GMT, when he daily maximum alues o gs we e egis e ed. 2.5. Soil wa e measu emen s Measu emen s o we e made e e y 15–20 d in h ee D and h ee I ees om he beginning o he d y season o he beginning o he d ip e sus pond i iga ion expe imen . We used a neu on p obe (T oxle 3300, Resea ch T iangle Pa k, No h Ca olina, USA) o measu ing q e e y 0.1 m, om 0.3 m down o he maximum dep h explo ed by he oo s. In he op soil laye s was measu ed by g a ime y. Du ing he d ip e sus pond i iga ion expe imen , measu emen s o q we e made nea ly e e y day. The access ubes o he neu on p obe we e ins alled 0.5, 1.5, 2.5 and 3.5 m away om he unks o he D1 and I1 ees, and 1.5 and 2.5 m away om he D2 and I2 ees. The access ubes wen o he dep h o he ha d- pan, 2 m in he D1 ee, 1.7 m in he D2 ee and 1 m in bo h he I1 and I2 ees. 3. RESULTS 3.1. Wa e s a us in he o cha d h oughou he d y season Figu e 1 shows he ime cou se o ETo, q, Ypd and Y10 eco ded om he beginning o he d y season o he beginning o he d ip e sus pond i iga ion expe imen , o bo h he D and I ees. The daily ETo (Fig. 1a) was o e 8 mm o en du - ing he season, eaching a maximum alue o 10 mm on Augus 3, day o yea (DOY) 215. This illus a es he high a mosphe ic demand no mally ound du ing he d y and ho summe mon hs in he a ea. Figu e 1b shows ha q emained a abou 0.19 m3·m–3 in he we ed bulbs o he d ip-i iga ed I ees. The ac ha q emained cons an and close o ield capac- i y h oughou he d y season indica es ha he wa e supplied o he I ees was enough o co e he c op wa e demand. As expec ed, q a ound he D ees dec eased h oughou he d y season, eaching a minimum a e age alue o 0.12 m3·m–3 on DOY 230. Signi ican di e ences in lea wa e s a us be ween he D and he I ees appea ed qui e la e in he season (Fig. 1c). Al hough da a on ela i e wa e con en and osmo ic po en ial a e also equi ed o assess he lea wa e s a us, da a on Yl (Fig. 1c) show clea di e ences be ween he D and I ees jus be o e he beginning o he d ip e sus pond i iga ion expe i- men (P< 0.001). Thus, on DOY 230, he las da e shown in Figu e 1c, he a e age Ypd was –0.35 MPa in he I ees and –0.57 MPa in he D ees. The a e age Y10 alues eco ded on ha day we e –2.08 MPa o he I ees and –2.64 MPa o he D ees. 3.2. T ee anspi a ion du ing he d ip e sus pond i iga ion expe imen The a io o Ep be ween he D1 and D2 ees (D1/D2 Ep) calcula ed om he sap low measu emen s be o e and du ing q q Figu e 1. Time cou se o e e ence e apo anspi a ion (ETo), olume ic soil wa e con en (q) and lea wa e po en ial (Yl) measu ed a p edawn (Ypd) and a abou 10.00 GMT (Y10), when he daily minimum alues we e eco ded. Measu emen s we e made h oughou he d y season o 1998, in he non-i iga ed (D) and d ip- i iga ed (I) ees o he expe imen al o cha d. I iga ion o he I ees began on Ma ch 24, DOY 83. Fo he D1 and I1 ees, each q poin ep esen s he a e age o he h ee soil wa e p o iles measu ed h ough he h ee access ubes closes o he unk. Fo he D2 and I2 ees he q poin s a e a e ages o he wo measu ed soil wa e p o iles. Fo Yl each poin ep esen s he a e age o six alues. Ve ical ba s indica e wice he s anda d e o . De ails on he measu emen s and on he i iga ion ea men s a e gi en in he ex . DOY = day o yea . GMT = G eenwich Mean Time. Soil we ing and oli e 549 he d ip e sus pond i iga ion expe imen a e shown in Figu e 2a. On he days be o e he beginning o he expe imen he daily D1/D2 Ep a e was qui e s able, wi h an a e age alue o 0.89. On DOY 238, jus one day a e he beginning o he expe imen , D1/D2 Ep was 0.96, inc easing quickly on he subsequen days o a maximum o 1.22 on DOY 251. Thus, wo weeks a e he beginning o he expe imen he inc ease in Ep was 37% g ea e on he pond-i iga ed D1 ee han on he d ip-i iga ed D2 ee. A simila end in ela i e anspi a- ion was obse ed in he I ees (Fig. 2b). In ac , p io o he beginning o he d ip e sus pond i iga ion expe imen he a e age I1/I2 Ep was 0.78, while a he end o he expe imen , on DOY 255, i was 1.02. This means ha he inc ease in Ep nine days a e he beginning o he expe imen was 31% g ea e o he pond-i iga ed I1 ee han o he d ip-i iga ed I2 ee. Figu es 2a and 2b also show he ETo alues calcula ed o he measu ing days. Table II shows sligh ly highe q alues on DOY 250 in he D1 ee han in he D2 ee. The di e ences, howe e , we e due o he wa e s o ed in deep soil laye s only. In ac , below 1 m dep h he a e age q alue measu ed on DOY 250 was 0.21 m3·m–3 in he D1 ee and 0.14 m3·m–3 in he D2 ee. In he laye o 0–1 m dep h, howe e , he a e age alue was 0.18 m3·m–3 o bo h ees, indica ing condi ions close o ield capaci y. Values o a ound hose o ield capaci y we e also eco ded in he we ed bulbs o he I ees (Tab. II). 3.3. Lea wa e s a us and gas exchange du ing he d ip e sus pond i iga ion expe imen The eco e y o Ypd a e i iga ion began ea lie in he D1 ee han in he D2 ee (Fig. 3a). Thus, on DOY 238, one day a e i iga ion, he alue o Ypd in he D1 ee was signi ican ly g ea e han on he p e ious day (P< 0.0001), while in he D2 Figu e 2. Rela i e o al daily anspi a ion be ween (a) he ees D1 and D2 (D1/D2 Ep) and (b) he ees I1 and I2 (I1/I2 Ep), calcula ed om sap low measu emen s in he unk o he ees be o e and du ing he d ip e sus pond i iga ion expe imen . The daily alues o e e ence e apo anspi a ion (ETo) a e also shown. The a ows ep esen he i iga ion e en s de ailed in Table I. The D1 and I1 ees we e pond i iga ed, while he D2 and I2 ees we e d ip i iga ed. Fu he de ails on bo h ea men s a e gi en in he ex . DOY = day o yea . q q Figu e 3. Lea wa e s a us and gas exchange measu emen s measu ed in cu en yea lea es o he D ees be o e and du ing he d ip e sus pond i iga ion expe imen . Figu e 3a shows he alues o lea wa e po en ial a p edawn (Ypd) and a 10.00 GMT (Y10); each poin ep esen s he a e age o six alues. Figu e 3b and 3c show he alues o s oma al conduc ance o H2O (gs) and ne pho osyn hesis (PN), espec i ely, measu ed a 10.30 GMT; each poin ep esen s he a e age o 10 alues. Ve ical ba s indica e wice he s anda d e o . The D1 ee was pond i iga ed, while he D2 ee was d ip i iga ed. Fu he de ails on bo h ea men s a e gi en in he ex . Figu e 3d shows he daily maximum alues o apou p essu e de ici o he ai (Da max) and pho on lux densi y (IP max) eco ded on he measu emen days. DOY = day o yea . GMT = G eenwich Mean Time. 550 J.-E. Fe nández e al. ee abou he same Ypd alue was eco ded on bo h days. The maximum Ypd alue, obse ed on DOY 240, was –0.32 MPa o he D1 ee and –0.49 MPa o he D2 ee. A he end o he expe imen al pe iod, on DOY 243, he eco ded alues we e –0.44 MPa o he D1 ee and –0.69 MPa o he D2 ee. The e o ba s shown in Figu e 3a indica e ha he di e - ences be ween ea men s a e ewa e ing we e signi ican on all he measu ing days. The Y10 alues shown in he same ig- u e, al hough mo e a iable due o he changing wea he con- di ions (Fig. 3d), show ha a he end o he expe imen , on DOY 243, he D1 ee was less s essed han he D2 ee. No signi ican di e ences, ei he in Ypd o in Y10, we e eco ded be ween he I1 and I2 ees du ing he d ip e sus pond i iga- ion expe imen (Fig. 4a). Figu e 3b shows ha be o e i iga ing on DOY 237, he a e age alue o gs measu ed a 10.30 GMT in he D1 ee (0.12 mol·m–2·s–1) was signi ican ly lowe (P<0.006) han ha o he D2 ee (0.17 mol·m–2·s–1). The alues o gs in bo h ees inc eased quickly du ing he d ip e sus pond i iga ion expe imen . In ac , he a e age alues o gs jus one day a e i iga ion we e 0.22 and 0.26 mol·m–2·s–1 o he D1 and D2 ees, espec i ely. A e DOY 238 no signi ican di e ences in gs be ween he D1 and D2 ees we e obse ed. Pe haps he high alues o gs eco ded a e ewa e ing we e no only due o he wa e supplied, bu also o he dec ease in he a mos- phe ic demand (Fig. 3d), which p obably educed s oma al closu e. The I2 ee showed abou he same gs alues h ough- ou he expe imen (Fig. 4b). This was expec ed, since he i i- ga ion p ac ice ca ied ou on his ee du ing he d ip e sus pond i iga ion expe imen was he same as ha applied since he beginning o he d y season, as explained in he “I iga ion expe imen s” sec ion. P io o pond i iga ing he I1 ee, he a e age gs alue measu ed in his ee (0.19 mol·m–2·s–1) was signi ican ly lowe (P< 0.002) han ha o he I2 ee (0.27 mol·m–2·s–1). No di e ences in gs be ween he I1 and I2 ees we e obse ed a he end o he expe imen al pe iod. As wi h gs, he di e ences in PN be ween he D1 and D2 ees (Fig. 3c), and also be ween he I1 and I2 ees (Fig. 4c), dec eased a e i iga ion, indica ing ha PN inc eased mo e in he pond-i iga ed han in he d ip-i iga ed ees. In he D ees, gs inc eased ma kedly om DOY 237 o DOY 238 (Fig. 3b), while PN dec eased (Fig. 3c). This appa en disc ep- ancy is explained by he wea he condi ions eco ded on bo h days. Day o yea 237 was a b igh day wi hou clouds and wi h a ela i ely high a mosphe ic demand. Day o yea 238, howe e , was pa ially cloudy, wi h a low a mosphe ic demand. A abou 10.30 GMT, when he alues o gs and PN we e measu ed, he a e age alues o inciden pho on lux densi y (IP) we e 1218 mmol·m–2·s–1 on DOY 237 and 345 mmol·m–2·s–1 on DOY 238. A ha ime o he day, he al- ues o apou p essu e de ici o he ai (Da) we e on a e age 2.8 kPa on DOY 237 and 0.8 kPa on DOY 238. Thus, on he one hand he low IP on DOY 238 was esponsible o he low alues o PN. Fo he ‘Manzanilla’ a ie y, Díaz-Espejo [8] ound ha ligh sa u a ion o PN occu s when IP³1600 mmol·m–2·s–1. On he o he hand, he low Da o DOY 238 allowed he plan o keep he s oma a open, which explains he high alues o gs eco ded on ha day. In p e ious expe imen s ca ied ou in a nea by o cha d wi h ees o simila cha ac e is ics o hose o ou expe imen al o cha d, Fe nández e al. [16] ound a p o- po ional dec ease in gs wi h inc easing Da, o Da alues o up o app oxima ely 3.5 kPa. 4. DISCUSSION We we e only able o ins umen wo pai s o D and I ees, due o ou limi ed numbe o senso s o eco ding sap lows. Despi e he lack o eplica ions, he same end on ela i e Ep was egis e ed in he wo pai s o expe imen al ees, which made us us he esul s. The ac ha he daily anspi a ion o he pond-i iga ed ees inc eased subs an ially mo e han ha o he d ip-i iga ed ees (Fig. 2) indica es ha he an- spi a ion o he ees in which jus a pa o he oo zone was a ec ed by i iga ion was cu ailed. The ime cou se o a mos- phe ic demand, illus a ed by he ETo alues shown in he igu e, does no seem o be esponsible o he changes in he ela i e Ep alues. The wa e con en s in he soil olumes a ec ed by Figu e 4. Lea wa e s a us and gas exchange measu emen s measu ed in cu en yea lea es o he I ees be o e and du ing he d ip e sus pond i iga ion expe imen . Figu e 4a shows he alues o lea wa e po en ial a p edawn (Ypd) and a 10.00 GMT (Y10); each poin ep esen s he a e age o six alues. Figu e 4b and 4c show he alues o s oma al conduc ance o H2O (gs) and ne pho osyn hesis (PN), espec i ely, measu ed a 10.30 GMT; each poin ep esen s he a e age o 10 alues. Ve ical ba s indica e wice he s anda d e o . The I1 ee was pond i iga ed, while he I2 ee was d ip i iga ed. Fu he de ails on bo h ea men s a e gi en in he ex . Figu e 4d shows he daily maximum alues o apou p essu e de ici o he ai (Da max) and pho on lux densi y (IP max) eco ded on he measu emen days. DOY = day o yea . GMT = G eenwich Mean Time. Soil we ing and oli e 551 i iga ion we e simila o all he expe imen al ees, and close o ield capaci y (Tab. II). We assume ha , e en in he case o he D1 and D2 ees whe e he g ea es di e ences in q we e obse ed, hey did no ha e any signi ican in luence on he ela i e Ep alues. Ac ually, q alues o bo h ees we e he same in he op me e o soil, whe e he g ea es pa o he oo sys em g ows [13]. The e o e, he di e ences in ela i e an- spi a ion be ween he pond-i iga ed and he d ip-i iga ed ee, o bo h pai s o ees, seem o be due o he amoun o he oo zone we ed by i iga ion. Bongi and Pallio i [3], in a spli - oo expe imen , di ided he oo sys em o young ‘F an oio’ oli e plan s in o wo pa s. The bigges pa was i iga ed a –0.2 MPa soil po en ial (Ysoil), while he smalles pa was main ained a –1.1 MPa. Lowe s oma al conduc ance and g ow h we e obse ed in hese plan s han in simila plan s wi h bo h spli oo s i iga ed a Ysoil = –0.2 MPa. The au ho s specula ed abou he idea o a signal o igina ed in he oo s, simila o wha Zhang and Da ies [34] obse ed in maize. Comp ehensi e e iews on he ole o abscisic acid (ABA), e hylene and o he molecules in he capaci y o he oo s o sensing soil condi ions and signalling hese o he shoo s ha e ecen ly been published [2, 24]. Ra he han he e ec o a sin- gle signal, he esul s ob ained by Bongi and Pallio i [3], and hose shown he e, may be due o a complex p ocess. As Ta - dieu and Da ies [32] s a ed, “S oma al conduc ance, lea and oo wa e po en ial, wa e lux, and xylem [ABA] ha e mul iple in e ela ions which canno be summa ised by a ela ionship be ween any o hese a iables”. Hyd aulic con ol o s oma a closu e had been epo ed mainly in woody species such as Douglas i [19] and Be ula occiden alis [29]. Howe e , i has ecen ly been epo ed in semi-woody species such as Hymen- oclea salsola [5], and in he he baceous bell peppe plan [33]. Fuchs and Li ings on [19] in e p e ed he di e ence in s o- ma al esponse o oo p essu isa ion be ween woody and he - baceous plan s on he basis ha he usually la ge woody plan s a e less elian on ela i ely slow-mo ing oo signals o sho - e m s oma al con ol. The hyd aulic signal is a sim- ple and apid o m o oo - o-shoo communica ion ha can ini ia e s oma al esponses o o he lea –le el changes. Schulze [30] sugges ed ha la ge woody species would lack a chemical oo signal, because he long anspo ime would make oo -signalling ine ec i e o sho - e m s oma al egu- la ion. Hubba d e al. [22] showed ha , unde con olled con- di ions whe e s eady-s a e low was p omo ed, gs and PN in ponde osa pine we e esponsi e o changes in he hyd aulic conduc ance o he soil o he lea pa hway. In hei s udy, hey oled ou any in ol emen o a oo signal in esponse o changes in he hyd aulic conduc ance; i s , because he plan s we e well-wa e ed h oughou he expe imen and, second, because he changes in he hyd aulic conduc ance we e induced dows eam om he oo s. We ha e no in es iga ed he na u e o any signal ac ing be ween he oo s and he shoo s, bu he esul s shown in Figu e 2 indica e ha when pa o he oo sys em o ma u e ‘Manzanilla’ oli e ees g owing unde ield condi ions is le in d ying soil he anspi- a ion o he ees is cu ailed. This can p obably be ex apo- la ed o o he ypes o localised i iga ion sys ems, apa om he d ip i iga ion used in ou o cha d. This does no necessa - ily mean ha localised i iga ion sys ems a e no app op ia e o i iga ing oli e o o he ui ee o cha ds. In ac , he plan s’ s ess signalling sys em is being cu en ly used in ag i- cul u e o inc ease he wa e use e iciency o some c ops. This is he case o he pa ial oo d ying app oach – PRD i iga ion – on g ape ine and oma o [6, 31]. We ha e o poin ou , how- e e , ha he condi ions o ou d ip e sus pond i iga ion expe imen di e om hose o he PRD app oach, since one o he key eac u es o PRD is ha he we ed and d ying sides o he i iga ion sys em mus be al e na ed on a 10–14 day cycle [7]. The ac ha he amoun o he oo zone we ed by i iga ion in luences wa e losses by anspi a ion should be aken in o accoun by he use s o equa ion (1), in he sense ha he soil olume a ec ed by i iga ion mus be conside ed be o e assuming han a Kc alue aken om he li e a u e is app op ia e o he o cha d. A e ewa e ing du ing he d ip e sus pond i iga ion expe imen , he eco e y o wa e s a us and gas exchange o he lea es was g ea e and quicke in he pond-i iga ed D1 ee han in he d ip-i iga ed D2 ee. This ag ees wi h he esul s on ela i e anspi a ion discussed abo e, suppo ing he hypo hesis ha a d ip i iga ion sys em which supplies wa e o only a pa o he oo sys em limi s wa e consump- ion o ‘Manzanilla’ oli e ees. Resul s om p e ious expe - imen s indica e ha bo h Ypd and Y10 in s essed oli e ees eco e quickly a e ewa e ing, and ha he alues o gs and PN eco e mo e slowly, he delay depending on he le el o wa e s ess p e iously eached [11, 16, 27]. Ou esul s show ha gs and PN inc eased quickly in he D ees a e ewa e - ing, eaching simila alues o hose o he I ees jus a couple o days a e applying wa e o he i s ime (Figs. 3 and 4). This quick eco e y was p obably due o he ac ha he deg ee o wa e s ess eached by he D ees be o e ewa e ing was no oo se e e (Fig. 3a). The unusually high ain all o he hyd ological yea 1997-98, 717.2 mm, led o a e age q alues on DOY 231 o 0.17 m3·m–3 in he 1–2 m deep soil laye , in bo h he D1 and D2 ees. These alues a e g ea e han hose eco ded in he o cha d a he end o he d y season on yea s o a e age ain all [25]. Maximum alues o Ypd we e eco ded on he D ees wo days a e ewa e ing. These alues emained below –0.3 MPa, while he Ypd alues eco ded in he I ees we e close o –0.2 MPa. E en so, he Ypd alues o he D ees a e ewa e ing we e well abo e –0.5 MPa, con- side ed as a h eshold o wa e de ici in oli e [16], as well as in o he species [4, 10]. In ac , Ypd is closely ela ed o he soil wa e con en , and i is gene ally accep ed ha Ypd can be used as an indica o o wa e s ess in ui ees. Al hough he e a e limi a ions o his assump ion [1], he wo k by Na ali e al. [27] and Fe nández e al. [16], among o he s, shows ha he alue o Ypd can be used as an indica o o he deg ee o wa e eco e y o he oli e ee a nigh . Al hough Y10 depends g ea ly on he a mosphe ic condi ions, he alues o Y10 eco ded in he D ees also eco e ed subs an ially a e ewa e ing. 5. CONCLUSIONS D ip i iga ion in which a pa o he oo sys em is le in d ying soil limi s anspi a ion in ‘Manzanilla’ oli e ees. This may apply o any o he ype o localised i iga ion sys em sup- plying wa e o a pa o he oo zone only. This may be due o s oma al closu e induced by oo s le in d y soil, al hough his 552 J.-E. Fe nández e al. poin has no been in es iga ed in his wo k. This does no nec- essa ily mean ha localised i iga ion sys ems a e no app o- p ia e o i iga ing oli e o o he ui ee o cha ds. On he one hand, a educ ion in anspi a ion could inc ease he wa e use e iciency in he o cha d. On he o he hand, any educ ion in anspi a ion could lead o a dec ease in c op pe o mance. This, and he na u e o he signal o signals in ol ed in he oli e’s s ess signalling sys em could be he opics o pionee - ing lines o esea ch. In uni iga ed oli e ees, he eco e y a e he d y season o bo h lea wa e po en ial and gas exchange was g ea e and quicke wi h pond i iga ion han wi h d ip i iga ion. Acknowledgemen s: The au ho s hank he Comisión In e minis e ial de Ciencia y Tecnología o he Spanish Minis y o Educa ion and Science o he inancial suppo o his p ojec . Thanks a e also due o B.E. Robinson and M.B. Ki kham, o hei aluable ad ice on he i s d a o his pape . The au ho s also exp ess hei app ecia ion o he s a o he expe imen al a m La Hampa o hei help wi h he expe imen al wo k. REFERENCES [1] Améglio T., A che P., Cohen M., Valancogne C., Daude F.A., Dayau S., C uizia P., Signi icance and limi s in he use o p edawn lea wa e po en ial o ee i iga ion, Plan and Soil 207 (1999) 155–167. [2] Bingham I.J., Soil- oo -canopy in e ac ions, Ann. Appl. Biol. 138 (2001) 243–251. [3] Bongi G., Pallio i A., Oli e, in: Scha e B., Ande sen P.C. (Eds.), Handbook o En i onmen al Physiology o F ui c ops. Volume I: Tempe a e C ops, CRC P ess, Inc., 1994, pp. 165–187. [4] B éda N., G anie A., Ba a aud F., Moyne C., Soil wa e dynamics in an oak s and, Plan and Soil 172 (1995) 17–27. [5] Coms ock J., Mencuccini M., Con ol o s oma al conduc ance by lea wa e po en ial in Hymenoclea salsola (T. & G.), a dese subshu b, Plan Cell En i on. 21 (1998) 1029–1038. [6] Da ies W.J., Bacon M.A., Thompson D.S., Sobeih W., González- Rod íguez L., Regula ion o lea and ui g ow h in plan s g owing in d ying soil: exploi a ion o he plan s’ chemical signalling sys em and hyd aulic a chi ec u e o inc ease he e iciency o wa e use in ag icul u e, J. Exp. Bo . 51 (2000) 1617– 1626. [7] Da ies W.J., Wilkinson S., Lo eys B., S oma al con ol by chemical signalling and he exploi a ion o his mechanism o inc ease wa e use e iciency in ag icul u e (Resea ch e iew), New Phy ol. 153 (2002) 449–460. [8] Díaz-Espejo A., Modelización del in e cambio gaseoso en el oli o: aplicación a la op imación del iego, Ph.D. Thesis, Depa men o Plan Biology and Ecology, Uni e si y o Se ille, 2000. [9] Doo enbos J., P ui W.O., Guidelines o p edic ing c op wa e equi emen s, FAO I iga ion and D ainage Pape No. 24, 2nd ed., FAO, Rome, 1977. [10] El ing D.C., Kau mann M.R., Hall A.E., In e p e ing lea wa e po en ial measu emen s wi h a model o he soil-plan -a mosphe e con inuum, Physiol. Plan . 27 (1972) 161–168. [11] Fe e es E., Ruz C., Cas o J., Gómez J.A., Pas o M., Recupe ación del oli o después de una sequía ex ema, P oceedings o he XIV Cong eso Nacional de Riegos, Aguadulce (Alme ía), 11–13 June, 1996, pp. 89–93. [12] Fe nández J.E., Mo eno F., Wa e use by he oli e ee, J. C op P od. 2 (1999) 101–162. [13] Fe nández J.E., Mo eno F., Cab e a F., A úe J.L., Ma ín-A anda J., D ip i iga ion, soil cha ac e is ics and he oo dis ibu ion and oo ac i i y o oli e ees, Plan and Soil 133 (1991) 239–251. [14] Fe nández J.E., Mo eno F., Ma ín-A anda J., Fe e es E., Oli e- ee oo dynamics unde di e en soil wa e egimes, Ag ic. Med- i e . 122 (1992) 225–235. [15] Fe nández J.E., Mo eno F., Clo hie B.E., G een S.R., Aplicación de la écnica de compensación de pulso de calo a la medida del lujo de sa ia en oli o, P oceedings o he XIV Cong eso Nacional de Riego. Aguadulce (Alme ía), 11–13 June, 1996, pp. 1–7. [16] Fe nández J.E., Mo eno F., Gi ón I.F., Blázquez O.M., S oma al con ol o wa e use in oli e ee lea es, Plan and Soil 190 (1997) 179–192. [17] Fe nández J.E., Palomo M.J., Díaz-Espejo A., Clo hie B.E., G een S.R., Gi ón I.F., Hea -pulse measu emen o sap low in oli es: es s, oo low and diagnos ics o wa e s ess, Ag ic. Wa e Manage. 51 (2001) 99–123. [18] Fe nández J.E., Mo eno F., Mu illo J.M., Cue as M.V., Kohle F., E alua ing he e ec i eness o a hyd ophobic polyme o con- se ing wa e and educing weed in ec ion in a sandy loam soil, Ag ic. Wa e Manage. 51 (2001) 29–51. [19] Fuchs E.E., Li ings on N.J., Hyd aulic con ol o s oma al con- duc ance in Douglas i [Pesudo suga menziesii (Mi b.) F anco] and alde [Alnus ub a (Bong)] seedlings, Plan Cell En i on. 19 (1996) 1091–1098. [20] Gi ona J., S a egia di de ici i iguo con olla o nell’oli o, Book o P oceedings o he Co so in e nazionale di aggio namen o ec- nico scien i ico “Ges ione dell’acqua e del e i o io pe un oli i- col u a sos enibile”, COI-SeSIRCA-ISPAIM, Napoli, 24–28 Sep embe (2001), pp. 138–148. [21] G een S.R., Clo hie B.E., Wa e use o kiwi ui ines and apple ees by he hea -pulse echnique, J. Exp. Bo . 39 (1988) 115–123. [22] Hubba d R.M., Ryan M.G., S ille V., Spe y J.S., S oma al con- duc ance and pho osyn hesis a y linea ly wi h plan hyd aulic conduc ance in ponde osa pine, Plan Cell En i on. 24 (2001) 113–121. [23] Man o ani C.E., Be engena J., Villalobos F.J., O gaz F., Fe e es E., Medidas y es imaciones de la e apo anspi ación eal del igo de egadío en Có doba, Ac as IX Jo nadas Técnicas de Riego, G a- nada, 1991. [24] Meinze F.C., Clea wa e M.J., Golds ein G., Wa e anspo in ees: cu en pe spec i es, new insigh s and some con o e sies, En i- on. Exp. Bo . 45 (2001) 239–262. [25] Mo eno F., Vachaud G., Ma ín-A anda J., Vauclin M., Fe nández J.E., Balance híd ico de un oli a con iego go a a go a. Resul ados de cua o años de expe iencias, Ag onomie 8 (1988) 521–537. [26] Mo eno F., Fe nández J.E., Clo hie B.E., G een S.R., T anspi a- ion and oo wa e up ake by oli e ees, Plan and Soil 184 (1996) 85–96. [27] Na ali S., Xiloyannis C., Angelini P., Wa e consump i e use o oli e ees (Olea eu opaea) and e ec o wa e s ess on lea wa e po en ial and di usi e esis ance, Ac a Ho ic. 171 (1985) 341–351. [28] Palomo M.J., Aplicación del mé odo de compensación de pulso de calo pa a medi lujo de sa ia en oli o, Ph.D. Thesis, Depa men o Ag onomy, Uni e si y o Có doba, Spain, 2000. [29] Saliend a N.Z., Spe y J.S., Coms ock J.P., In luence o lea wa e s a us on s oma al esponse o humidi y, hyd aulic conduc ance, and soil d ough in Be ula occiden alis, Plan a 196 (1995) 357– 366. [30] Schulze E.D., Wa e and nu ien in ac ions wi h plan wa e s ess, in: Mooney H.A., Winne W.E., Pell E.J. (Eds.), Response o plan s o mul iple s ess, Academic P ess, New Yo k, 1991, pp. 89–103. [31] S oll M., Lo eys B., D y P., Imp o ing wa e use e iciency o i i- ga ed ho icul u al c ops, J. Exp. Bo . 51 (2000) 1627–1634. [32] Ta dieu F., Da ies W.J., In eg a ion o hyd aulic and chemical sig- nalling in he con ol o s oma al conduc ance and wa e s a us o d ough ed plan s, Plan Cell En i on. 16 (1993) 341–349. [33] Yao C., Mo eshe S., Aloni B., Wa e ela ions and hyd aulic con- ol o s oma al beha iou in bell peppe plan in pa ial soil d ying, Plan Cell En i on. 24 (2001) 227–235. [34] Zhang J., Da ies W.J., Abscisic acid p oduced in dehyd a ing oo s may enable he plan o measu e he wa e s a us o he soil, Plan Cell En i on. 12 (1989) 73–81. View publica ion s a sView publica ion s a s