Partitioning and mobilization of starch and N reserves in grapevine (Vitis vinifera L.)

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Partitioning and mobilization of starch and Nreserves in grapevine (Vitis vinifera L.)

Christophe Zapataa, Eliane Deleensb, Sylvain Chaillouc, Christian Magned,*

aLaboratoire de Biologie et Physiologie Vegetales, Universite de Reims Champagne-Ardenne, UFR Sciences,UPRES EA 2069, BP 1039, 51687 Reims Cedex 2, FrancebInstitut de Biotechnologie des Plantes, Universite de Paris-Sud, URA 1128, 91405 Orsay Cedex, FrancecLaboratoire de Physiologie Vegetale, Institut National Agronomique Paris Grignon, 16 rue Claude Bernard,75231 Paris Cedex 05, FrancedLaboratoire d’Ecophysiologie et Biotechnologie des Halophytes et des Algues Marines, Universite de BretagneOccidentale, IUEM, Technopole Brest Iroise, 29280 Plouzane, France

Received 22 May 2003; accepted 5 November 2003

This article is dedicated to the memory of Dr. Eliane Deleens, with whom working looked so simple and pleasant. After her recentdisappearance, we express here our gratitude and affection.

SummaryWe followed C and N reserves of grapevines grown in trenches under semi-controlledconditions over a 3-year period after planting. Temporal mobilization of stored C andN and subsequent distribution of reserve materials within the vines were described inparallel with 15N uptake, particularly during the third growing season. Storage C in theperennial tissues (roots, trunk, canes) was mainly made of starch, which accumulatedin the ray parenchyma of the wood. In the permanent tissues, starch and totalnitrogen contents were found to decrease early in the development (bleeding sap,budbreak) whereas, on a concentration basis, they decreased only after stage 7 (firstleaf fully expanded). Starch started to accumulate again in the perennial tissuesduring flowering. The same observation was made with total nitrogen, although Nlevels were much lower than those of starch. The 15N study showed that N uptake bythe roots started at budbreak and increased with vine development, becomingpredominant over reserve mobilization only after the onset of flowering. Takentogether, these results indicate that the spring growth period can be divided intothree main phases: In the first (dormancy to budbreak), significant losses of C and Nproceed mainly via root necrosis. In the second period (first leaf to the onset ofbloom), a strong mobilization of starch (and, to a lower extent, of N) occurred forsupporting vegetative and reproductive growth. At that point, most of the C and Nreserves used on the spring flush were those of the roots, rather than those of the old

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KEYWORDSGrapevine;Mobilization;Nitrogen uptake;Reserves;Starch;Vitis vinifera L

Abbreviations: AP, annual parts; PP, perennial parts*Corresponding author. Fax: þ33-(0)2-98-49-87-72.E-mail address: [email protected] (C. Magn !e).

0176-1617/$ - see front matter & 2004 Elsevier GmbH. All rights reserved.doi:10.1016/j.jplph.2003.11.009

Journal of Plant Physiology 161 (2004) 1031–1040

wood (trunk, canes). In the third period (bloom and early berry development), themobilization process became low and was relieved by N uptake (and CO2 assimilation)supplying nutrients to the sink structures.& 2004 Elsevier GmbH. All rights reserved.

Introduction

Woody plants are particularly reliant on reserves tosupport rapid seasonal growth phases (Zimmer-mann, 1971; Loescher et al., 1990; Mooney andGartner, 1991). Thus, reserve mobilization inperennial crop species is considered to be a majordeterminant of agricultural yield. In grapevine(Vitis vinifera L.), nitrogen uptake and carbonassimilation remain low for several weeks after budburst (Hale and Weaver, 1962; Kriedemann et al.,1970; Conradie, 1980; L .ohnertz, 1988). Therefore,spring growth flush is mainly sustained by theremobilization process (Scholefield et al., 1978;Conradie, 1980, 1986).

Carbon reserves in grapevine have long beenstudied. They consist mainly of starch (Bouard,1966), but significant amounts of soluble sugarsmay appear during winter depending on thetemperature. Seasonal dynamics of starch andsoluble carbohydrates have been described in thecanes of some varieties (Eifert et al., 1960; Bouard,1966). Accordingly, sugars accumulated in the trunkand roots are the first carbohydrates used byemerging shoots in the spring (Scholefield et al.,1978). On that point, it is assumed that sucrose isthe major transport form of carbohydrates ingrapevine, as in most higher plants (Kuhn et al.,1999). However, while starch fate in the aerialtissues is well documented, the process of starchmobilization in vine roots throughout the growingseason has received little attention.

Along with carbohydrates, nitrogen reserves playa crucial role in supporting early season growth ofwoody plants (Zimmermann, 1971; Conradie, 1980;Tromp, 1983). In grapevine, N reserves are locatedpredominantly in the roots and are made by aminoacids (mostly arginine) and proteins (Schaller et al.,1989; Kliewer, 1991). A fraction of these com-pounds may be lost by the vines through bleedingsap (Glad et al., 1992a) or by mobilization towardsthe growing upper structures (Conradie, 1991; Gladet al., 1992b). In addition, nitrogen uptake supple-ments N mobilization during the growing season.Although nitrogen uptake starts early in thedevelopment cycle (Conradie, 1980; L.ohnertz,1988), it generally remains low until flowering,even in cases of high nitrogen availability in the soil(Tromp and Ovaa, 1973; Conradie, 1980, 1986).

Accordingly, fine roots are most effective in mineraluptake (Murisier, 1996), but they start to differ-entiate and develop only several weeks after budburst (Zapata et al., 2001), root growth flushpeaking at or about anthesis (Roubelakis-Angelakisand Kliewer, 1992). Thus, nitrogen remobilizationupon spring growth might be the major processaccounting for N allocation to the growing tissues ofvines, at least until flowering. In that respect, theuse of 15N labelling has proved to be a potent toolto investigate N uptake, storage and mobilization incrop species (Deleens et al., 1994). Thus, it may beused to compare the relative contribution of Nreserves accumulated by grapevine during theprevious growing seasons to that of the currentyear N uptake.

Vegetative (including root) growth, dry matterpartitioning, and reproductive development ofgrapevines in trenches under semi-controlled con-ditions have been described recently (Zapata et al.,2001, 2003). This experimental design has beenfurther used to investigate starch- and total-Npartitioning as well as their translocation fromthe permanent to the annual upper organs. Wereport here the results of this study conducted on aPinot noir variety during a 3-year period afterplanting. Objectives of this study were: (1) todetermine at what point and to what extentgrapevine relies on stored reserves; (2) to describefurther the relative contribution of the rootreserves and those reserves located in the trunkor canes; and (3) to elucidate the fate andsignificance of N reserves accumulated 2 yearsearlier. The expected results should be of greatinterest to vine growers with regard to optimizingthe timing of nitrogen fertilization.

Material and methods

Plant culture

Cuttings of Pinot noir grapevine grafted onto SO4

(clone 5) rootstock were planted in trenches andgrown in a greenhouse under semi-controlledconditions during 3 years (Zapata et al., 2001).Plants were fed daily from the bleeding sap stage(mid March) until leaf fall (late October) with astandard nutrient solution (Co.ıc and Lesaint, 1971)

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1032 C. Zapata et al.

by means of a drip system. In those conditions, vinegrowth was very strong (Zapata et al., 2001) andreproductive characteristics in the third growingseason were similar to those of vineyard-grownplants (Zapata et al., 2003).

Labelling procedure

To study N uptake and distribution within the plant,one set of vines was fed standard nutrient solutioncontaining 1.39% stable 15N isotope (ca. four timesthe natural abundance) through the addition ofK15NO3. Forty-five plants were distributed inthree groups: the first and the second groups(15 vines in each) were supplied with 15N-enrichedsolution during years 1 and 2 after planting,respectively. The third set consisted of controlvines supplied with 15N-free solution during thewhole experiment.

Sampling

Three vines from each group were sampled atfive phenological stages: end of the first and thesecond years (dormant stage, in January), thenfirst leaf fully expanded, early bloom, and berriesat pea size during the third growing season. Thelast three stages corresponded respectively tostages 7, 19 and 31 as described by Eichhorn andLorenz (1977). All together, at the end of thesecond year, they determined three successiveperiods of about 65, 36 and 18 days in spring ofthe third year.

At each sampling date, vines were pulled outcarefully from the trenches, washed free of sandand, depending on the growth stage, divided intoroots, trunk, canes, shoots, leaves and bunches. Allsamples were frozen in liquid nitrogen and storedat �201C. For biomass analysis, samples werefreeze-dried and weighed. When indicated, rootswere considered together with trunk and canes asthe perennial parts (PP); shoots, leaves andbunches constituted the annual parts (AP).

Localization of starch

Starch localization in root and cane tissues wasexamined at each sampling date of the thirdgrowing season with light microscopy. Transversalsections (20 mm) of frozen tissues were made at�201C with a Cryostat 2800-Frigocut N microtome.Sections were stained using a 0.3% I2/1% KI Lugolsolution according to Johansen (1940), then exam-ined under a Zeiss light microscope and photo-graphed under visible light.

Starch determination

In order to assess starch mobilization during thethird growing season, starch was determined inthe perennial tissues at each sampling date in thethird growing season. Starch extraction from drysamples was performed with 90% DMSO at 1201C for1 h. In those conditions, starch was extractedexhaustively in a single step. After centrifugationfor 15min at 12 000g, starch content of the extractswas determined colorimetrically at 620 nm afterreaction with acidic iodine solution (0.06% KI and0.003% I2 in 0.05 N HCl).

Determination of N percentage and 15N

Total N (in %DW) and 15N contents were assayedaccording to a method described earlier (Deleenset al., 1994). Homogeneous aliquots of organpowders (three per sample) were put in stain boatsand introduced into a quantitative analyser (CarloErba, Fison), giving the total N percentage. Thenitrogen analyser was connected to a mass spectro-meter (Optima, Micromass) and the nitrogenisotope fraction (15N %) was obtained from the N2

coming from the analyser in the helium flux. Theatom excess was obtained by subtracting the 15Nconcentration found in the unlabelled control fromthat found in the labelled sample. N assimilatedduring the first or the second growing season wascalculated as follows:

N1st or 2nd year ¼ total N ðmgÞ

�atom % excess of tissue

atom % excess of applied solution:

Statistical analysis

Each measurement was repeated three times onnine different vines and standard errors werecalculated. Considering the distribution of Nassimilated in years 1, 2 and 3, means of threeplants were calculated.

Results

Carbon reserves

Starch localization in perennial tissuesTransverse sections of roots and canes allowedstarch localization in perennial tissues during thethird growing season (Fig. 1). At dormancy, a largestarch deposition was found in the ray storagetissues (parenchyma) of roots and canes (Figs. 1a

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Partitioning of C and N reserves in grapevine 1033

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Figure 1. Localization of starch in transverse sections of roots (a,c,e,g) and canes (b,d,f,h) of grapevine cv. Pinot noirduring the third growing season after planting. (a and b) End of year 2 (dormancy); (c and d) first leaf fully expanded; (eand f) first flower opened (early bloom); and (g and h) pea berry size. Scale bars ¼ 1mm. C, cortex; R, ray parenchyma;SP, secondary phloem; SX, secondary xylem; VC, vascular cambium.


and b). During the spring growth flush, starchstaining declined in both root (Figs. 1a,c,e,g) andcane (Figs. 1b,d,f,h) tissues. Starch located in thephloem rays of roots (Figs. 1c and e) and canes(Figs. 1d and f) was found to disappear more rapidlythan that of the xylem rays. Therefore, noticeableamounts of starch remained in xylem ray cells atthe pea-size stage (Figs. 1g and h). Meanwhile, newstarch material was found to accumulate uponfruit setting in the ray tissue of annual shoots (datanot shown). Furthermore, we found that cambiumactivity started at early bloom in the canes (Fig. 1f)and later in the roots (Fig. 1g).

Starch mobilization in year 3At the whole PP level, starch concentration washigh at dormancy and did not vary significantly untilstage 7 (Fig. 2). Thereafter, starch concentration

dropped markedly (�70%) until stage 19 (earlybloom). During the last period of our study, whichincluded flowering and fruit set, starch started toaccumulate again in the perennial tissues. Incontrast to starch concentration, starch contentin vine storage organs dropped by 40% uponbudbreak. At that point, changes in starch contentover the growing season followed similar trendsto those of starch concentration. Thus, half ofthe initial starch pool was lost by vine storageorgans during flower differentiation (first leaf-Fearly bloom). Thereafter, a new starch deposi-tion was found (þ16 g/vine by stage 31, whichcorresponded to a 20% recovery relative to theinitial starch pool).

Starch level was then tracked separately in roots,trunk, and canes of the vines (Fig. 3). In the roots,starch concentration at dormancy (# 29% DW) wasfour-times higher than in the other perennialtissues (Fig. 3a). It decreased upon spring growth,particularly during the first leaf–early bloomperiod. Thereafter, starch accumulated in the rootsduring flowering and berry setting. In the otherperennial structures, starch concentration in-creased transiently upon budbreak (by 72% and86% in the trunk and canes, respectively) andrecovered thereafter. Moreover, no significantdifference was found between the starch level ofthe trunk and that of the canes over the wholestudy period. When expressed in g/vine, starchcontent of the perennial tissues followed similarfluctuations to those of starch concentration(Fig. 3b). However, vine roots lost 40% of theirstarch pool before stage 7 (first leaf). Thecontribution of trunk and canes to the starchcontent of perennial tissues was very low atdormancy (4.2% and 1.1% for trunk and canes,respectively) and increased upon spring growth,

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Figure 2. Changes in starch concentration (B) andstarch content (O) in whole perennial tissues (rootsþtrunkþcanes) of grapevine cv. Pinot noir during the thirdgrowing season. Data are mean7SE of nine plants.

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Figure 3. Changes in starch concentration (a) and starch content (b) in the roots (B), trunk (&) and canes (n) ofgrapevine cv. Pinot noir during the third growing season. Data are mean7SE of nine plants.


peaking at the onset of bloom (12.5% and 2.5%,respectively).

Nitrogen reserves

Nitrogen level of vine plantsTotal nitrogen concentration of whole plants wasfound to be stable (#1.5% DW) throughout acomplete development cycle. Moreover, the nitro-gen pool was distributed quite equally betweenannual and PPs at the end of the development cycle(data not shown). Nitrogen concentration was highin the emerging annual tissues (almost 4% DW in thefirst leaf at stage 7), then declined markedly uponspring growth (�50% by stage 31) (Fig. 4a). In theperennial tissues, nitrogen concentration was muchlower than in the AP in the early growth phase (#1.5

DW). It decreased slowly throughout the springgrowth flush (�30% by stage 31).

Compared to nitrogen concentration, N contentfollowed different patterns. During the third grow-ing season, the nitrogen level of the annual organsincreased rapidly along with AP biomass (Fig. 4b).In parallel, a high amount of nitrogen was lost bythe perennial tissues before flower initiation (�3 g/vine, representing 54% of the initial N pool).Thereafter, the total nitrogen amount in the PPstarted to increase again.

Among the perennial tissues, total N concentra-tion was higher in the roots than in the trunks andcanes (Fig. 5a). Total root N level did not changesignificantly until early bloom, but then decreasedmarkedly upon flowering and berry setting. In theother perennial tissues, total N concentrationdecreased substantially over the first leaf–first

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Figure 4. Changes in total N concentration (B) and N content (J) of annual (a) and perennial (b) tissues of grapevinecv. Pinot noir during the third growing season. Data are mean7SE of nine plants.

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Figure 5. Changes in total N concentration (a), and N content (b) in the roots (B), trunk (&) and canes (n) ofgrapevine cv. Pinot noir during the third growing season. Data are mean7SE of nine plants.


flower period. On a g/plant basis, total N, was farmore abundant in the roots, decreased steadilyuntil early bloom, and then started to accumulateagain (Fig. 5b). In the trunks and canes, the amountof total N remained very low and did not vary muchover year 3.

Nitrogen mobilization in year 3Nitrogen reserves are defined here as the nitrogenfraction assimilated in years 1 or 2 after planting,and subsequently translocated to the growingaerial parts during year 3. In that respect, afraction of nitrogen reserves accumulated in year1 was translocated to the aerial annual organs andsubsequently lost by the plant through leaf fall orsuccessive prunings. Thus, the amount of year 1nitrogen in the perennial tissues at the end of year2 fell to 660mg/plant, representing only 12% of PPtotal nitrogen (Fig. 6). After budbreak in year 3,nitrogen in the PP consisted mainly of year 2nitrogen (about 92%). Then, a significant part wasrapidly translocated to the upper tissues (at least37% at early bloom, irrespective of the potentcycling of N between shoots and roots). In parallel,nitrogen uptake occurred and the resulting amountof year 3 N became predominant (over year 2 N)upon flowering. An equal distribution of year 2nitrogen between annual and perennial structuresseemed to be established by pea size.

The amount of AP nitrogen coming from thereserves increased less than that of AP total Nduring the third growing season (Table 1). At stages7 (first leaf fully expanded) and 19 (early bloom),the fraction of the AP nitrogen pool originating

from the reserves represented three-fourths andone-half, respectively. Then, at pea berry size, thisfraction dropped to one-fourth. Among each periodin year 3, a higher amount of mobilized nitrogenreserves was found between stage 7 and stage 19.

Nitrogen uptakeAside from reserve mobilization, nitrogen uptakewas investigated during the third growing season.On the basis of root biomass, nitrogen uptakeincreased throughout the spring growth flush(Table 2). It became particularly strong after theonset of bloom, reaching about 1mg N/g root/dayon average over flowering and berry setting (thirdperiod in our study).

Discussion

Analysis of the distribution of carbon reserves in P.noir perennial tissues at dormancy revealed thatstarch was mainly located in the roots, the mostabundant perennial tissues, and to a lower extentin the trunks and canes. Accordingly, roots con-tained more than 90% of the starch stored in thevines at the beginning of the season. These resultsconfirmed those previously reported for othergrape varieties (Eifert et al., 1960; Bouard, 1966;Bates et al., 2002) and for other woody species(Loescher et al., 1990). At that point, starch in thetrunk accounted for only 3% of PP starch. In theroots, starch concentration decreased upon springgrowth. Since this reduction was moderate com-pared to that of starch content, the root necrosisprocess reported previously (Zapata et al., 2001) islikely to be a major event accounting for thecarbohydrate loss in the early stages of the growingseason. In addition, bleeding sap should contribute

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N1 N2 N3

End year 2

1st leaf Early bloom Pea size

Year 3

Figure 6. Distribution of nitrogen assimilated in year 1(N1), year 2 (N2) and year 3 (N3) between annual (aboveabscissa axis) and perennial (below axis) tissues ofgrapevine cv. Pinot noir during the 3-year period. Dataare mean of three plants.

Table 2. Specific N uptake (in mg N/g root DW/day) byPinot noir/SO4 grapevines during the third growing season

First period Second period Third period

0.0270.00 0.3270.06 0.9370.17

Data are mean7SE of nine plants.

Table 1. Contribution (in % total N content) of nitrogenreserves to the N pool of the annual tissues of Pinot noircultivar during the third growing season

First leaf Early bloom Pea berry size

7378 5276 2475

Data are mean7SE of nine plants.


to the early decrease of root starch concentrationand content (Andersen and Brodbeck, 1989; Gladet al., 1992a; Campbell and Strother, 1996). As aconsequence, in our study, as much as 34 g of starchare lost by each vine through root necrosis andbleeding sap, representing 38% of total root starchor 11% of root biomass. Taking into account therelative abundance of starch in the perennialtissues, changes in starch level are the majorfactors contributing to the loss of PP dry massduring the spring growth flush.

Along with starch loss through root necrosis andbleeding sap, the study of starch mobilizationduring the growing season indicates that the rootcarbohydrates play a major role in supplying thegrowing tissues with nutrients, as compared to thestarch located in the trunks or canes. Accordingly,the marked drop off in root starch level during thespring growth flush was accompanied by a transientincrease of starch level in the trunk and old wood.Assuming that root necrosis is achieved at stage 7,as much as 49 g of PP starch are mobilized (86% ofwhich comes from the root system) during thesecond period (first leaf–early bloom). It represents57% of the dry matter loss by the PP. Thereafter, theconcomitant assimilation and mobilization processresulted in the net deposition of 17.3 g of starch inthe PP, representing 18.2% of the dry matter gain.

The concentration of nitrogenous compounds ingrapevine tissues generally depends on geneticfactors, environmental conditions, and culturalpractices (Araujo and Williams, 1988; L.ohnertz,1988; Schaller et al., 1989; Roubelakis-Angelakisand Kliewer, 1992). In our study, environmentalconditions as well as water and mineral nutritionwere optimal over the 3-year period after planting.As a consequence, N concentration of whole plantsremained rather constant at a high level (around1.5% DW), confirming previous experimental studiesperformed with potted (Conradie, 1980) and field-grown (Araujo and Williams, 1988) vines.

As found with starch, the roots were the majorstorage organ for nitrogen, accounting for 75% ofnitrogen stored in the dormant vines. However,storage nitrogen was far less represented thanstarch at dormancy (1.6% vs. 33% of root dryweight, respectively). Moreover, N was moreequally distributed among perennial tissues, withslightly higher concentrations in the roots (1.6%)than in the trunks (0.9%) and canes (0.65%). Theseresults confirmed those previously reported inother grapevine varieties (L .ohnertz, 1988; Schalleret al., 1989). Accordingly, trunks, although per-ennial organs, did not accumulate large amounts ofN reserves (less than 10% of PP total nitrogen) atthe end of a vegetation cycle.

Over the third growing season, tremendouschanges in nitrogen concentration of the APwere found. These changes, mostly due to theleaf fraction, are consistent with previous works(L .ohnertz, 1988; Schaller et al., 1989; Keller andKoblet, 1994). In the perennial organs, N concen-tration was high at dormancy and decreasedmoderately during spring growth (�20% by earlybloom). Although the 15N determination methodestimated total N but did not distinguish organicand inorganic nitrogen, our results confirmedprevious observations on soluble nitrogen (Schalleret al., 1989), in accordance with the predominanceof the soluble over insoluble N fraction in the vinetissues (Andersen and Brodbeck, 1989; Glad et al.,1992b). Considering the absence of root growthduring the study period (Zapata et al., 2001) andthe marked drop in starch level mentioned above,the limited decrease of total N until early bloomsuggests that storage N, unlike carbohydrates,contributes only slightly to the growth flush.Despite the slow decrease of nitrogen concentra-tion in the PP, grapevine roots lost rapidly a largeamount of nitrogen upon spring growth (30% by thefirst leaf stage, 60% by the onset of bloom).Moreover, the increase of N content in annualtissues was low upon budbreak and did notcorrespond to the N loss from the roots, indicatingthat another process would occur along withmobilization of root storage N towards AP. In thatrespect, it is likely that the previously reportedroot necrosis (Zapata et al., 2001), and to a lowerextent the bleeding sap process (Andersen andBrodbeck, 1989; Glad et al., 1992a; Campbell andStrother, 1996), was the major cause of nitrogenloss from vine roots. Moreover, due to the abun-dance of starch in vine perennial tissues, changes intotal N concentrations might be overestimatedrelative to those of starch. However, in ourexperiment, both starch and N levels followedsimilar patterns over the spring growth in year 3indicating that no interference was found betweenthe two processes.

The study of 15N uptake and distribution showedthat, although vines were fed with nutrients inexcess over the whole experiment, N uptakebecomes strong late in the season, namely afterthe onset of flowering. This result may be relatedto the delay in root development compared to thatof shoots, as evidenced by our histological study.

On the whole, the main events argued above canbe gathered in a table of balancing, showing therelative contribution of root necrosis, bleeding sap,reserve mobilization, and N uptake on solutepartitioning in grapevine tissues throughout thethird growing season (Fig. 7). During the first period

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(from dormancy to stage 7), vegetative growth waslow and only trace amounts of nitrogen weremobilized. However, significant amounts of starchand N disappeared from the roots, mainly due tothe process of root necrosis. During the secondperiod (from stage 7 to stage 19), vegetativegrowth was rapid and accompanied by a strongmobilization process but a low N uptake. As aconsequence, starch and nitrogen levels in theroots reached a minimum at early bloom. Duringthis period, a small loss of starch and nitrogenmaterials from the roots due to necrosis could notbe excluded. During the third period (from stage 19to stage 31), starch accumulation occurred in theroots and canes. This observation suggests thatcarbon assimilation in the leaves at the onset offlowering becomes strong enough to supportgrowth. In parallel, nitrogen uptake by the rootswas high, and thus capable of relieving nitrogenmobilization to provide the growing structures with

N compounds. Our results strongly suggest that theapplication of nitrogen fertilizer before the onsetof bloom in vineyards should be inefficient becauseN uptake is low, confirming previous works onpotted vines (Conradie, 1986). A similar observa-tion was made for late fertilization (Peacock et al.,1982, 1991), so that the optimal period for N supplyextends from early bloom to harvest time. Currentwork in our lab is more precisely addressing: (1) thespeciation of N and C reserve materials within thevine tissues over the whole growing season, and (2)the role of remobilization in supplying nutrients tothe growing inflorescences, and thus in berrysetting.

Acknowledgements

The authors are indebted to S.A. Mumm Perrier-Jou .et Vignobles et Recherches, Epernay (France)

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Dormancy First leaf Early bloom Pea size

93.05 60.11

ND ND

11.19

ND

28.46

PP PP

AP

PP

AP

PP

AP

StarchCO2

CO2CO2

Dormancy First leaf Early bloom Pea size

5.52 3.89

0.03 2.11

2.37

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2.79

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0.15 1.71 3.48

Total N

NO3-

NO3-

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1.15

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Figure 7. Contribution of the main nutrient flux during the third growing season to the partitioning of starch and total

N in perennial tissues of grapevine cv. Pinot noir. Loss through root necrosis; N uptake; reserve

mobilization; storage; CO2 assimilation; loss through bleeding sap.


for funding a Ph.D. grant (C.Z.) and to the inter-region VVS research network for financial support.

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Partitioning and mobilization of starch and N reserves in grapevine (Vitis vinifera L.)