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Scientia Horticulturae 164 (2013) 155–159

Contents lists available at ScienceDirect

Scientia Horticulturae

journa l h om epage: www.elsev ier .com/ locate /sc ihor t i

ffect of water stress on dry matter accumulation and partitioning inot-grown olive trees (cv Leccino and Racioppella)

laudio Di Vaioa, Nadia Maralloa,∗, Giulia Marinob, Tiziano Carusob

Dipartimento di Agraria, Università degli Studi di Napoli Federico II, ItalyDipartimento Scienze Agrarie e Forestali, Università degli Studi di Palermo, Italy

r t i c l e i n f o

rticle history:eceived 16 July 2013eceived in revised form 3 September 2013ccepted 6 September 2013

a b s t r a c t

Three different water regimes were applied on young pot-grown olive trees of the cultivars Leccino andRacioppella, amounting to 100% (treatment T100), 50% (treatment T50) and 25% (treatment T25) of watertranspiration as determined by pot weight. During the two-year trial the following parameters were

eywords:liveater stress

ry matter partitioning

measured: midday stem water potential, shoots growth, total leaf area per tree, dry matter accumulationand partitioning in different parts of the plant (root, wood, leaves and fruits). Dry matter was affectedby the water regime and cultivar. The cv Leccino, for T100, displayed a greater accumulation of totaldry matter and fruit dry matter, while these two parameters were greatly reduced under the other waterregimes (T50 and T25). By contrast, the cv Racioppella always showed a lower accumulation of dry matterand a more balanced canopy/root ratio.

oot and canopy growth

. Introduction

The olive tree (Olea europaea L.) is an evergreen species widelyultivated in the arid and semiarid areas of the Mediterraneanasin characterized by prolonged water shortage during the sum-er months. In similar environmental conditions olive is capable

o survive and to produce and, for this reason, this species is wellnown for being very tolerant to drought (Turner, 1979; Bongi andalliotti, 1994; Fernandez and Moreno, 1999; Giorio et al., 1999;ognetti et al., 2004; Connor, 2005; Bacelar et al., 2006).

Different physiological, biochemical and morpho-anatomicalechanisms are involved in olive strategies of drought avoidance

nd/or drought tolerance (Levitt, 1980) that consist in maintaining,nder very drought conditions, the water status of tissues in a levelhat support the principal vital functions of the plants.

To achieve this, plants, subjected to water shortage, close theirtomata, reducing water losses but also transpiration and carbonssimilation (Giorio et al., 1999). Such a limited availability of pho-oassimilates causes, at whole plant level, a change in the patternf dry matter distribution: shoot growth is inhibited while a higheruantity of assimilates is transported and accumulated in the rootystem determining a higher root to shoot ratio in water stressed

lants (Xiloyannis et al., 1999).

Anyway, water stress is not the only parameter that affectsry matter distribution in the plant; in particular, many other

∗ Corresponding author.E-mail address: nadia.marallo@unina.it (N. Marallo).

304-4238/$ – see front matter © 2013 Elsevier B.V. All rights reserved.ttp://dx.doi.org/10.1016/j.scienta.2013.09.008

© 2013 Elsevier B.V. All rights reserved.

agronomic and genetic factors, such as rootstock, cultivar, trainingsystem, pruning and planting density have been shown to influencegrowth and to modify the distribution of biomass between rootsand canopy (canopy/roots ratio) and between the different plantorgans (Caruso et al., 1997, 2001, 2008; Zucconi, 1992; Xiloyanniset al., 2007; Di Vaio et al., 2012; Weibel and Reighard, 2012; Yanoet al., 2002).

Different cultivars respond differently to drought showing dif-ferences in terms of adaptation, dry matter distribution, productionand gas exchange responses to water shortage (Chartzoulakis et al.,1999; Bacelar et al., 2004, 2007; Tognetti et al., 2002).

We studied the effect of water stress on dry matter accumulationand partitioning between the different organs of young olive treeswith the aim to elucidate the different response of the two geno-types to drought stress and select a cultivar that is more suitablefor arid environments.

2. Materials and methods

In this work we tested the response of Raciopella, a low vigorcultivar native to the province of Benevento (Di Vaio et al., 2013)and Leccino, a vigorous and well productive cultivar from Tus-cany, but also grown widely elsewhere in Italy, to different waterregimes.

The observations were conducted for two years (2010/2011) on

two-year-old rooted plants of the cultivars Leccino and Racioppella.The plants were grown in 50-l pots containing a substrate formedby a mixture of peat, sand and soil (1:1:1 by volume) and regularlywatered by means of a drip irrigation system.

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56 C. Di Vaio et al. / Scientia H

The water regimes are 100 (treatment T100), 50 (T50) and 25%T25) of water transpired, determined every nine days by weighinghe pots. For T100, the losses of transpired water were replen-shed in full, while for T50 and T25 replenishment was 50% and5%, respectively, of the consumption of treatment T100. Irrigationas applied throughout the growing season from late March toovember. The pots were covered with a plastic film to avoid

nterference with rain and impede evaporation from the soil. Eachrrigation treatment was carried out on 12 plants per cultivar.

During the growing season stem water potential (� x) was mea-ured with a Scholander pressure chamber (Skye Instruments, UK,odel SKPM 1400) on one year in order to obtain water status of the

lants. The measurements were done at midday on the 28/6, 27/7nd 13/9 in 2010 and on the 10/7, 28/7, 20/8 and 13/9 in 2011; theeaves were covered at least 1 h before measurement with plasticnvelopes and aluminum reflective foils (Begg and Turner, 1970).

Vegetative activity of the trees was estimated by monitoring, at5 days intervals, the growth of three shoots per plant and deter-ining, at the end of each season, trunk cross section area (TCSA)

t 10 cm from the ground.At the end of each growth year, 18 randomly selected plants per

ultivar, six per water regime, were uprooted and broken down intooots, shoots, leaves, wood and fruits. The total leaf area per plantas measured with a Leaf Area Meter (Li-Cor 3100) and the amount

f dry matter in individual organs was determined; to do that, thergans were placed in a ventilated heater at a temperature of 80 ◦Cntil they reached constant weight. Canopy to root biomass ratioas calculated.

Statistical analysis was performed using the SPSS statisticalackage. All data were subjected to factorial analysis and the aver-ges separated by Tukey’s test at the 5% level.

. Results and discussion

.1. Year 2010

The different water regimes used in this experiment had a sig-ificant effect on the midday stem water potential (m� x): for bothultivars, from T100 to T50 and T25 the values of m� x significantlyecreased (from −2.1 to −2.6 and −2.9 MPa for Racioppella androm −1.9 to −2.3 and −2.7 MPa for Leccino) (Fig. 1).

Comparing the water status of the two cultivars, Racioppellahowed slightly lower values of m� x but differences were not sta-istically significant.

Shoots growth clearly differed in relation to the cultivar andater regime (Fig. 2). Leccino when fully irrigated (T100) showed,

t the end of the season, a greater length of shoots (31.12 cm) com-ared to cv Racioppella (14.37 cm). On the other hand, the relativeeduction in irrigation water influenced the vegetative activity ofhe plants differently in the two genotypes; final length of thehoots at the end of the growing season in Leccino cv decreased by6.9% in T50 and 45.6% in T25 with respect to T100 while for Raciop-ella the reduction was less marked (14.3 and 26.8%, respectively).onsequentially, in the less irrigated treatment (T25) the two culti-ars showed a similar length of the shoots at the end of the season8–10 cm).

In terms of accumulation and distribution of dry matter in theifferent plant organs, the two varieties behaved differently, both

n relation to one another and to water treatment (Table 1).A first aspect to highlight is the different vigor in the two

ultivars. On comparing the most irrigated treatments, total dry

atter production in the cv Leccino was significantly higher than

n Racioppella (1662.08 against 1190.92 g) (Table 1).However, Leccino was more sensitive to water deficit: from T100

o T50 there was a sharp drop in accumulated dry matter (51%),

turae 164 (2013) 155–159

especially the fraction of dry matter allocated into aerial parts (53%)and particularly to the fruits (79%) (Table 1).

These values diminished further in the least irrigated T25, suchthat, in this case, total biomass production was reduced by 61% andfruit production was practically zero.

The cv Racioppella showed a significantly lower decrease in totaldry matter accumulation (13% of reduction in T50 and 37% in T25)(Table 1), such that the values of the two treatments submittedto water deficit were even higher than those of cv Leccino. Theamount of dry matter allocated to the fruits of cv Racioppella wasmore constant despite the lower amount of water received (from78.95 g for T100, to 60.36 g for T50 and to 52.83 for T25 g), showinggreater rusticity and greater production efficiency in conditions ofwater shortage.

Such a different behavior of the two cultivars is likely to depend,at least in part, by the different vigor and canopy–root ratio of thetwo genotype (Table 2).

When fully irrigated the vigorous Leccino, thanks to a higherleaf area (1.28 m2), maximizes assimilation and hence total biomassand fruit production (Table 1); the higher canopy/roots ratio (5.8)helps this cultivar to show, in non-limiting conditions, higher per-formances with respect to the cv Racioppella.

On the other hand, under water deficit the reduced root systemof Leccino plants may limit water uptake and affect productivity;the strong reduction in canopy growth observed in Leccino plantsunder water deficit treatment is a defense strategy, common tomost species, that allows plants to minimize transpiration and, con-sequentially water losses, enabling plants to survive in condition ofdrought stress (Dichio et al., 2002).

Racioppella plants were characterized by a lower canopy–rootsratio (3.6), and hence a more balanced distribution of dry mat-ter between the two portions (Table 2) that allows the plants ofthis cultivar to maintain a good water status of the leaves understress, showing greater rusticity and greater production efficiencyin conditions of water shortage.

3.2. Year 2011

The m� x, observed in 2011, confirmed the same decreasingtrend described for the year 2010 although the stress level wasgenerally lower with respect to the previous year, probably as aconsequence of a more developed root system (Fig. 3).

Furthermore differences between the cultivars in this secondyear of observation became statistically significant, with lower val-ues of m� x measured in the cv Racioppella, especially for whatconcern T50 and T25 treatments.

As reported for the previous year, also in the year 2011, asdrought stress increased, total dry matter accumulation decreasedand the pattern of allocation of assimilates changed, resulting in adifferent response of the two cultivars to water stress (Table 3).

In particular, in the cv Leccino, the reduction in dry matter accu-mulation occurred only at the expense of the aerial part of the plant,and especially of the fruits, while dry matter allocated in the rootsystem remained almost unchanged for the three treatments.

Such a greater decrease in canopy growth compared to rootgrowth in water deficit conditions was observed also by Dichio et al.(2002) on Coratina olive cultivar; the same authors described thisresponse as a defense strategy which improves water availabilityper unit of leaf area, enabling plants to resist long water deficitperiods while keeping the leaves photosynthetically active.

Anyway, in this work, such behavior was observed only in theless arid-resistant cultivar Leccino, while in the rustic Racioppella,

as the irrigation volumes were reduced from T100 to T25, theaccumulated dry matter in the aerial part and in the root sys-tem decreased proportionally, determining a constant canopy toroot ratio among the different water treatments (Table 4); at the

C. Di Vaio et al. / Scientia Horticulturae 164 (2013) 155–159 157

Fig. 1. Year 2010: effect of water treatments (100%, 50% and 25% of transpiration water) on steam water potential in the cultivars Leccino and Racioppella (average ofmeasurements of 28/6, 27/7 and 13/9). Means with the different letters are significantly different using Tukey’s test (P < 0.05).

Fig. 2. Year 2010: effect of water treatments (100%, 50% and 25% of transpiration water) on the shoot growth of cultivars Racioppella and Leccino (mean ± SE). Means withthe different letters are significantly different using Tukey’s test (P < 0.05).

Table 1Year 2010: effect of different water regimes (100%, 50% and 25% of transpiration water) on dry matter accumulation and partitioning (roots, wood, leaves and fruits) in plantsof cv Racioppella and Leccino. Means with the different letters are significantly different using Tukey’s test (P < 0.05).

Cultivar Treatment Roots (g) >1 year old wood (g) 1 year old wood (g) Leaves (g) Fruits (g) Total (g)

Leccino T100 209.81 b 462.44 c 300.13 d 343.51 d 346.19 d 1662.08 cT50 139.53 a 242.16 ab 192.78 b 163.54 a 75.32 bc 813.33 abT25 154.42 a 193.17 a 157.64 a 145.12 a 0.00 a 650.35 a

Raccioppella T100 336.58 c 293.89 b 241.15 c 240.35 c 78.95 c 1190.92 bT50 312.65 c 261.76 b 202.91 b 200.82 b 60.36 bc 1038.50 abT25 219.60 b 196.10 a 142.40 a 140.40 a 52.83 b 751.33 a

Leccino Mean 167.92 a 299.26 b 216.85 b 217.39 b 210.76 b 1041.92 bRacioppella Mean 289.61 b 250.58 a 195.49 a 193.86 a 64.05 a 993.58 a

Table 2Year 2010: canopy/roots ratio, trunk cross-sectional area and plant leaf area for plant in the cultivars Leccino and Racioppella under three different water regimes (100%, 50%and 25% of transpiration water). Means with the different letters are significantly different using Tukey’s test (P < 0.05).

Cultivar Treatment Canopy/roots ratio Trunck cross sectional area (mm2) Plant leaf area (m2)

Leccino T100 5.8 a 420.1 a 1.28 aT50 4.3 b 265.2 b 0.75 bcT25 3.3 bcd 236.2 bc 0.60 cd

Racioppella T100 3.6 bc 253.5 b 0.91 bT50 2.5 cd 229.9 bc 0.74 bcT25 2.0 d 212.8 c 0.54 d

Leccino Mean 4.5 a 307.2 a 0.88 bRacioppella Mean 2.7 b 232.1 b 0.73 a

158 C. Di Vaio et al. / Scientia Horticulturae 164 (2013) 155–159

Fig. 3. Year 2011: effect of water treatments (100%, 50% and 25% of transpiration water) on steam water potential in the cultivars Leccino and Racioppella (average ofmeasurements of 10/7, 28/7, 20/8 and 13/9). Means with the different letters are significantly different using Tukey’s test (P < 0.05).

Table 3Year 2011: effect of different water regimes (100%, 50% and 25% of transpiration water) on dry matter accumulation and partitioning (roots, wood, leaves and fruits) in plantsof cv Racioppella and Leccino. Means with the different letters are significantly different using Tukey’s test (P < 0.05).

Cultivar Treatment Roots (g) >1 year old wood (g) 1 year old wood (g) Leaves (g) Fruits (g) Total (g)

Leccino T100 910.91 c 1439.21 e 400.22 d 547.51 e 376.37 e 3674.21 dT50 890.13 c 1214.74 d 383.01 c 431.57 d 41.80 b 2961.26 cT25 791.91 b 861.62 c 331.25 b 330.31 b 0.00 a 2315.09 b

Raccioppella T100 926.15 c 1047.66 cd 342.55 b 370.51 c 151.20 d 2838.07 cT50 718.15 b 649.39 b 335.97 b 341.28 bc 130.92 c 2175.71 bT25 455.56 a 247.91 a 308.48 a 253.90 a 123.53 c 1389.37 a

Leccino Mean 900.52 b 1171.86 b 371.49 b 436.46 b 209.08 b 2983.52 bRacioppella Mean 699.95 a 648.32 a 329.00 a 321.90 a 135.21 a 2134.38 a

Table 4Year 2011: canopy/roots ratio, trunk cross-sectional area and plant leaf area for plant in the cultivars Leccino and Racioppella under three different water regimes (100%, 50%and 25% of transpiration water). Means with the different letters are significantly different using Tukey’s test (P < 0.05).

Cultivar Treatment Canopy/roots ratio Trunck cross sectional area (mm2) Plant leaf area (m2)

Leccino T100 2.7 a 1306.3 a 2.58 aT50 2.6 a 1083.2 b 1.94 bT25 2.1 b 808.0 c 1.39 cd

Racioppella T100 1.9 c 711.9 cd 2.00 bcT50 1.8 c 630.5 de 1.82 bT25 1.8 c 492.4 e 1.21 d

Leccino Mean 2.5 a 1194.7 a 2.26 a

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Racioppella Mean 1.9 b

ame time the dry matter partitioned to fruits remained almostnchanged in the three treatments suggesting a higher water usefficiency of this cultivar under drought.

. Conclusions

In this work the results of young olive trees grown in pots con-rm the findings of other authors for different species (Steinbergt al., 1990; Buwalda and Lenz, 1992). Dry matter accumulationncreases in proportion to the amount of water administered withrrigation. In particular, the growth of shoots, the cross-section areaf the trunk, the leaf surface and total dry matter produced per plantre directly influenced by the water regime.

The parameters examined highlight significant changes

etween the cv Leccino and Racioppella in the allocation ofesources upon reduced water availability, showing a differentarietal behavior. Indeed, the response to the reduction in waterupplies was strongly dependent on the cultivar used, confirming

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what reported by Bacelar et al. (2007) that found intraspecificdifferences in term of growth, gas exchange xylem hydraulicproprieties and water use efficiency of three Portuguese cultivarsubjected to water stress.

The Racioppella cultivar, with the decrease in irrigationand reduction in total dry matter accumulation, maintained itscanopy/root ratio and yield almost unchanged. The other culti-var, Leccino, behaved differently: a suboptimal water supply ledto a considerable reduction in the aerial part and especially inproduction (2010 and 2011). In its early years of plant develop-ment, Leccino has a higher productive potential, with productionin the T100 treatment almost double that of Racioppella, duealso to higher dry matter accumulation. However, Leccino needsan optimal level of water availability to obtain such results. The

cv Racioppella, limited to the circumstances in which the trialwas held, proved more robust and showed a more balanced ratiobetween parts below and above ground, allowing a constant fruitproduction also under water stress.

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cknowledgement

The authors wish to thank Dr. Mark Walters for editing theanuscript.

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