The Chemical Composition of Xylem Sap Vitis vinifera ... fileIn xylem sap, nitrate was the major anion, followed by malate. Nitrate concentration was greatest in plants grown on Muschelkalk,

The Chemica l Compos i t ion of Xylem Sap in Vitis vinifera L. cv. Ries l ing Dur ing Vegetat ive Growth on Three Dif ferent

F r a n c o n i a n Vineyard Soils and as In f luenced by Ni trogen Fert i l izer

A N D R E A S D. P E U K E *

Cuttings of grapevine (Vitis vinifera L. cv. Riesling clone B 68) grafted on SO4 (Selection Oppenheim No. 4) rootstocks were grown in pots with three different soils from Franconian vineyards derived from different geological formations (namely, Loess, Muschelkalk (shell lime), or Keuper). Additionally, the influence of N- fertilizer treatment was investigated. From the midrib of leaves six to eight of the sole shoot, xylem sap was collected simultaneously by pressurizing the rhizosphere during the vegetative growth phase. The chemical composition of xylem sap was determined and compared with that of the aqueous soil extract. In Muschelkalk soil, carbon, nitrogen, and calcium were present in the greatest concentrations. Sulfur, boron, magnesium, sodium, and potassium were greatest in Keuper, and the concentrations in Loess soil were intermediate. Aqueous extraction of the soils resulted in a two-fold greater concentration of total solutes in Keuper extract compared with Muschelkalk, and more than threefold than in Loess. The apparent volume flow was greatest in the middle leaves along the shoot and in plants grown on Keuper; additionally there was a tendency for fertilizer treatment to increase flow. The concentrations of mineral ions in xylem sap were the same in all the leaves of a shoot of grapevine. An important exception was the supply to the leaves of amino acids, which increased in concentration along the transpiration stream and were greatest in the youngest leaves (particularly in non-fertilized plants). Potassium was the dominant cation in xylem sap and was greatest in plants grown on Keuper. Concentrations of sodium and calcium were increased in non-fertilized plants, but not significantly in vines grown on Muschelkalk. In xylem sap, nitrate was the major anion, followed by malate. Nitrate concentration was greatest in plants grown on Muschelkalk, while malate was greater in plants grown on Keuper. Chloride, sulfate, and phosphate concentration in sap were increased by fertilizer treatment. Abscisic acid was markedly increased in xylem sap of non-fertilized plants grown on Loess and Muschelkalk and was discussed as a signal for nutrient limitation. If Keuper was the substrate it was also increased by fertilizer treatment. Of the organic N-compounds, glutamine was the largest fraction. On the basis of the relation of nitrate to total N in xylem sap, it could be assumed that about 40% to 75% of nitrate reduction took place in the shoots. In general, soil type had only a moderate effect on the chemical composition of the xylem sap compared with the effect of N-fertilizer.

KEY WORDS: grapevine (Vitis vinifera L. cv. Riesling), cations, anions, abscisic acid, xylem sap, soil (geological formation)

Leaves and other shoot parts are supplied with mineral nutrients and organic products of root uptake and metabolism (organic forms of N, organic acids, phytohormones) via the xylem. One of the first steps in this process is the secretion/loading of ions into the xylem by the stellar parenchyma [32]. The composition of the soil solution has a marked influence on the composition of the xylem sap. For example, the relative concentrations of nitrate or ammonium generally have

*Julius-von-Sachs-lnstitut fQr Biowissenschaften, Lehrstuhl Botanik I, Julius-von-Sachs-Platz 2, D-97082 W0rzburg, Germany [e-mail: AD_Peuke @web.de].

Present address: Institut for Forstbotanik und Baumphysiologie, Professur for Baumphysiologie, Am Flughafen 17, D-79085 Freiburg im Breisgau.

Acknowledggements: This paper was supported by a grant of the Graduiertenkolleg "Pflanzen im Spannungsfeld zwischen N&hrstoffangebot, KlimastreB und Schadstoffbelastung" of the Deutsche Forschungsgemeinschaft and I thank the Bundesanstalt for Arbeit for personal finan- cial support. The vineyard soils were kindly provided by Mr M. Peternel and Dr. A. Schwab 'Bayerische Landesanstalt for Weinbau und Gartenbau'. I thank Mrs Elfriede Reisberg and Marion Reinhard for skilful technical assistance, Dr. W. Kaiser (W~rzburg) for anion chromatography, Dr. Hartung (W0rzburg) and Mrs Andrea BIo8 (Wassertr0dingen) for ABA-analysis, Dr. L. H. Wegner (W0rzburg), Dr. J. Hibberd (Cambridge), and Dr. M. Adams (Perth) for critical reading of the manuscript.

Manuscript submitted for publication 29 November 1999; revised 26 June 2000.

Copyright © 2000 by the American Society for Enology and Viticulture. All rights reserved.

large effects on the composition of the transport fluids in plants [1,4,5,22,23,29,30] as have concentrations of other ions such as K ÷, Mg +÷, and Ca ++.

Grapevine is an old agricultural plant and the quality of wine is the object of much debate [31]. While many factors including cultivar, climate, agriculture methods, etc. play roles in determining quality, soil type (including fertilizer) plays a major role [31]. The chemical and physical properties of soils influence the wine in numerous ways, but mostly indirectly since grapes are supplied largely by the phloem during rip- ening [15]. Recent studies have highlighted the circula- tory nature of xylem and phloem [8,10,12,13,22,25,26]. In general, the composition of xylem sap reflects both mineral and water uptake and also the general nutrition status of the plant. In addition, xylem sap is the major means of transport of abscisic acid (ABA), a major hormonal signal of drought and salinity, from roots to shoots [7]. Therefore, the xylem is not only responsible for solute exchange, but also for transport of root to shoot signals. ABA is considered to be an

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Am. J. Enol. Vitic., Vol. 51, No. 4, 2000

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indicator of nutri t ional conditions, particularly for nutr ient deficiency [7,26].

In the present study, xylem sap of t ranspir ing grapevines was collected from several leaves of a shoot simultaneously by applying pneumatic pressure to the rhizosphere. The chemical composition of the sap was determined and compared with the soil solutions. ABA was determined in the sap as a possible root to shoot signal of stress. The grapevines (Vitis vinifera L. cv. Riesling clone B 68 grafted on SO4 rootstocks) were grown in pots on three soils typical of Franconian vineyards. Additionally, the effects of N-fertilizer were tested. The aim is to demonstrate the influence of the chemical composition of different soils on the chemical composition of xylem sap and thus on the supply of grapevine shoots with mineral nutrients.

Materia ls and Methods Plant cultivation: One-year-old cuttings of grape-

vine (Vitis vinifera L. cv. Riesling clone B 68) grafted on SO4 rootstocks (Selection Oppenheim No. 4) were t ransferred to 1.5-L plastic pots containing one of three different soils from Franconian vineyards. Cuttings were obtained from Rebschule Steinmann, Sommer- hausen, Germany, where they were kept in a cold chamber during winter at 5°C. Soils derived from three geological formations in the vine cultivation region of F r a n k o n i a in N o r t h e r n Bavar i a , Germany . Muschelkalk (shell lime, chalky soil) was taken from the v ineya rd "Vei t shSchhe imer WSlflein", Loess (luvisol derived from loess) from the top of the hill of "Randersackerer Pfiilben", and Keuper (loamy clay) from "Abstwinder Altenberg". For each soil and fertilizer t rea tment three grapevines were grown. The characteristics of these soils were described in more detail by Mfiller [18]. The soils were kindly provided by Bayer i sche L a n d e s a n s t a l t fiir We inbau und Gartenbau.

Until budburst , the cuttings were grown in a green- house through the end of frost period to accelerate the early development. After budburst , for the rest of the vegetative period, the plants were grown in the botani- cal garden of the University of Wiirzburg. Only the main shoot was kept, other buds were removed so tha t only one shoot developed per rootstock. During the vegetative phase, plants were watered daily with rain water. Three pots from each t rea tment (soil) were supplied once after budburst with a commercial fertilizer diluted in water (6.5 g per plant (26% N, 12% S, and 0.2% B). This concentration was chosen to obtain a very high fertilization level [18]. These plants are indicated in the text, tables, and figures as fertilized in contrast to non-fertilized. Xylem sap was collected from the plants during the phase of vegetative growth.

Collecting of x y l e m sap: Xylem sap was collected using the technique of applying pneumatic pressure to the root sys tem described by Pass ioura [20] and Jeschke and Pate [10]. In brief, plastic pots were trans- ferred to a steel pressure vessel after they were watered and the excess water had been removed. Stems

were sealed with dental silicone impression material to ensure the vessel was gas-tight.

The midrib of leaves was cut in the middle of the laminae, and a rubber tube was fitted to the basal part of the dissected midrib. Since xylem sap could not be obtained from the oldest or youngest leaves of a shoot, the middle leaves were chosen for sampling. In non- fertilized grapevines the midribs of leaves 2 to 7 were cut, whereas in fertilized plants, due to better growth, leaves 2 to 9 were cut, although, more leaves developed (12 - 14). The leaf numbers were counted from the base of the shoot in order of emerging. The rhizosphere was pressurized to 6 × 105 Pa, sufficient to induce the flow of xylem sap from the roots to the cut midribs. Sap samples were collected from the fitted rubber tubes (after the first pL were discarded), weighed, and imme- diately frozen. Contamination of the xylem sap with phloem was avoided by this method, no sugars were found, and the pH of the sap was substantial ly less than 7. From each grapevine xylem sap was collected once. From each cut leaf, at least two samples were collected; from the leaves with greatest flow, four or more samples were collected. The applied pressure was chosen to obtain sufficient flow from all cut leaves simultaneously.

Chemical analysis: The chemical composition of dry soils was determined after d iges t ionwi th nitric acid under pressure for 10 hours at 170°C. Aqueous soil solutions were obtained by extracting dry soil over- night with water 1:1 (w:w) at room tempera ture for 16 hours with continuous shaking in a water bath. C and N in the dry soils were determined with a CHN analyzer (CHN-O-RAPID Heraeus, Hanau). The element composition of the soils and the aqueous soil extracts were analyzed using an ICP spectrometer (JY 70 plus, ISA, Ins t rument S.A. division Jobin-Yvon, France).

Sap was directly analyzed without further extraction. Cations (K ÷, Na ÷, Ca ++, Mg ÷÷) in the xylem sap were measured after dilution with an ionization buffer (CsC19.4 mM, Sr(NO3)2, 57.2 mM) by atomic absorption spectrometry (FMD 3, Carl Zeiss, Oberkochen). For anion determinations (inorganic and organic anions), xylem sap was boiled for 10 minutes, centrifuged, and the superna tan t was diluted with water before being analyzed by anion chromatography with suppressed conduct iv i ty de tec t ion (An ionenchrom-a tog raph , Biotronik Co., Maintal, Germany). Within this time less than 5% of malate degraded. Amino acids were determined using an amino acid analyzer (Biotronik Co., Maintal, Germany). The amino acids were sepa- rated in this HPLC-system by ion exchange and de- tected after post-column derivatization with ninhydrin at 570 nm. The C/N ratio of xylem sap was calculated from the elemental composition of component solutes (amino acids, organic acids, NO3- , NH4÷).

ABA analysis: Abscisic acid was analyzed immu- nologically using an ELISA with monoclonal antibodies as described by Mertens et al. [17]. Sap samples were taken up in TBS buffer (Tris buffered saline: 50 mM Tris, 1 mM MgC12, 150 mM NaC1; pH 7.8) without


SOIL AND XYLEM C O M P O S I T I O N IN G R A P E V I N E - 331

further purification and subjected to ELISA. For further details see Peuke et al. [26].

Statistics: In the text, figures, and tables means are given +_ SE or + SD. Three-way (leaf age, soil, and fertilizer t reatment) and two-way (soil and fertilizer t reatment) analysis of variances (ANOVA) were per- formed by the procedure GLM of SAS © release 6.12. Type III model sums of squares were used since the design was unbalanced. The adjustment of multiple comparison according to Tukey was chosen for the p- values and confidence limits for the differences of least squares means.

R e s u l t s

Composi t ion of soils and soil solutions: The chemical composit ion in the dry m a t t e r of th ree Franconian vineyard soils differed markedly due to the parent material. The elements determined by CHN and ICP analysis represented 14% to 23% of total dry mat te r of the soils. The greatest concentration of C and N was found in Muschelkalk, the lowest in Keuper (Table 1). On the other hand, the Keuper soil was rich in S, B, Mg, Na, and K. As was to be expected, Ca was most concentrated in Muschelkalk. The Loess soil was more or less similar to that of Muschelkalk, although containing consistently less C, N, S, B, Ca, and K. Due to fertilization, the amount of N/pot was approximately doubled (plus 70% - 170%). For S, the effects were different; while in Keuper the increase was only 20%, it was plus 150% in Muschelkalk and plus 270% in Loess.

The simple extraction of dried soils with water produced aqueous extracts tha t differed greatly among soils. Between 17% and 26% of total S content was extracted, about 7% of the N and 1% to 2% of the Na. Other elements were poorly recovered by water extraction. The spectra of elements in the soil solution were

Table 1. Chemical composition of the dry soil of three different Franconian vineyard soils derived from different geological formations, Loess, Muschelkalk (shell lime), and Keuper determined by CHN and

ICP analysis. Mean values + SD.

Loess Muschelkalk Keuper [ ppm ] (shell lime)

C 28897 + 175 48787 + 1124 25637 + 393

N 957 + 30 1667 + 113 650 + 40

S 203 + 4 371 + 18 2315 + 261

B 22 + 2 33 +1 96 + 2

Zn 76 + 0 54 + 2 124 + 4

P 530 + 28 579 + 3 705 + 44

Mn 695 + 13 677 + 34 664 + 9

Fe 22457 + 370 22267 + 609 34667 + 242

Mg 8297 + 141 8733 + 277 53913 + 292

Ca 68487 + 2135 104033 + 3686 53250 + 3288

AI 32087 + 515 39020 + 1071 57347 + 407

Na 293 + 6 382 + 31 737 + 13

K 7289 + 127 11457 + 405 22260 + 225

sum 170289 238058 252365

similar to those in the dry soil. Greatest concentrations for S, B, Mg, Ca, and K were found in the extract of Keuper soil, the concentrations of P, Mn, Fe, A1, and ni t rate were markedly greater in Muschelkalk extract. The Loess extract was intermediate. No amino acids and only traces of ammonium were found in the soil solutions. The greatest overall concentration of solutes was found in the Keuper extract (45.3 mM, Table 2); more than two-fold greater than tha t of Muschelkalk and threefold greater than Loess. Measured osmolality followed this t rend though was slightly greater than the sum of determined compounds, suggesting tha t some additional solutes were present. The pH of all soil solutions were moderately alkaline. For further char- acterization of the soils see Miiller [18].

Apparent vo lume flow and ion concentrat ion along the stem: The apparent sap flow from the midrib of leaves differed according to leaf age (Fig. 1). Flow was greatest in the middle leaves and least in old and young leaves. The greatest flows were observed in plants grown on Keuper. The fertilizer t rea tment had a positive effect on the volume flow, although this was only significantly higher in the xylem of vines grown on Loess.

In contrast to rates of flow, the ionic composition of xylem sap did not differ significantly with leaf age. The major cation (potassium, Fig. 2) and the major anion (nitrate, Fig. 3) are presented as examples. Since this

Table 2. Chemical composition of the aqueous soil extract of three different Franconian vineyard soils derived from different geological

formations, Loess, Muschelkalk (shell lime), and Keuper determined by CHN and ICP analysis. The soils were extracted with water over night. Mean values + SD.

Loess Muschelkalk Keuper [ ~MJ (shell lime) NO 3 4919 + 125 7002 + 428 3591 + 282

S 1314 + 17 1987 + 14 19086 + 187

B nd nd 15.68 + 0.59

Zn 0.080 + 0.032 0.097 + 0.040 0.030 + 0.011

P 20.24 + 1.05 50.89 + 0.95 5.11 + 1.59

Mn 2.83 + 0.33 8.44 + 0.56 1.40 + 0.04

Fe 6.24 + 0.82 11.14 + 2.75 3.40 + 0.69

Mg 284 + 2 337 + 5 2546+ 181

Ca 5385 + 42 7918 + 106 18552 + 209

AI 18.13 + 2.53 38.5 + 11.37 6.77 + 2.59

Na 282 + 9 293 + 9 254 + 18

K 89 + 1 157 + 3 1038 + 29

CI 423 + 16 347 + 5 171 + 12

[ mM] sum

solutes 12.74 + 0.15 18.15 + 0.45 45.27 + 0.87

sum positive charges 12.58 + 0.1 17.89 + 0.22 44.26 + 0.81

sum negative charges 8.00 + 0.13 11.39 + 0.40 41.94 + 0.66

difference of charges 4.58 + 0.12 6.50 + 0.42 2.32 + 0.25

pH 7.93 + 0.05 7.59 + 0.01 7.43 + 0.00

mosml/kg 15.67 + 0.33 24.33 + 0.33 50.67 + 0.33


~ 3 3 2 - - P E U K E

was also t rue for other ions, the da ta for all leaves were pooled. In contrast , the concentrat ion of total amino acids and amide N decreased with leaf age (Fig. 4). Additionally, the total N concentrat ion (organic nitrogen plus ni t ra te) in sap was grea tes t in the youngest leaves (data not shown).

Composi t ion of xylem sap: Comparison between different treatments: The dominant cation in xylem sap of grapevine was potassium. The general order of cation concentrat ions was : K ÷ (0.93 - 3.56 mM) > Ca ++ (0.6 - 2.03 mM) >> Mg ++ (0.24 - 0.33 mM) > Na ÷ ( 0 . 0 6 - 0.24 mM) (Table 3). Soil type had a significant effect only for the potass ium and calcium concentrations in xylem sap. The grea tes t concentrat ion of potas- s ium in the sap was observed in p lants grown on

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I I Non-ferti l ized ~ Fertilized

Fig. 1. Apparent volume flow to the leaves number 2-9 of the shoot of grapevine (Vitis v i n i f e r a L. cv. Riesling clone B 68) grown on three soils derived from different geological formations (Loess, Muschelkalk / shell lime, Keuper). The xylem sap was collected by pressurizing the rhizosphere to a level of 6 X 10 S Pa which caused flow of xylem sap from the roots to the cut midribs. Non-fertilized plants are shown by white columns and fertilized plants by hatched columns. Standard errors are indicated by bars, nm: not measured. The significance (***: p < 0.0001, **: 0.0001 < p < 0.001, *: 0.001 < p < 0.05, ns : not significant) of the main effects, soil type (S) and fertilizer treatment (F within each soil treatment) are also given. Differences in soil are indicated by letters in parentheses (only A: ns, A and B two groups, and A, B, and C all soils were significantly different).

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i Non-ferti l ized ~ Fertilized

Fig. 2. Potassium concentration in the xylem sap collected from the leaves number 2-9 of the shoot of grapevine (Vitis v i n i f e r a L. cv. Riesling clone B 68) grown on three soils derived from different geological formations. Standard errors are indicated by bars, nm: not measured. The significance (***: p _< 0.0001, **" 0.0001 < p < 0.001, *" 0.001 < p < 0.05, ns • not significant) of the main effects, soil type (S) and fertilizer treatment (F within each soil treatment) are also given. Differences in soil are indicated by letters in parentheses (only A: ns, A and B two groups, and A, B, and C all soils were significantly different).

Keuper, the least in p lants grown on Loess. Calcium concentrat ions in sap were s imilar in plants grown on Muschelka lk and Keuper, but significantly less in the sap of p lants grown on Loess. General ly, fert i l izer t r e a t m e n t decreased the concentrat ions of cations in sap. For magnes ium, no significant effects of soil or ferti l izer or interact ions were found.

The major anion in xylem sap of grapevine was ni t rate . The general order of anion concentrat ions was : n i t ra te (0.63 - 2.34 mM) > mala te (0.31 - 1.27 mM) > sulfate (0.11 - 0 . 3 1 mM) > phosphate (0.01 - 0 . 1 3 mM) > chloride (0.02 - 0.15 mM) (Table 3). The effects of soil type on the anion composition of xylem sap varied greatly. Ni t ra te and sulfate were grea tes t in sap of p lants grown on Muschelkalk; growth on Loess or Keuper resu l ted in s imi lar concentrat ions. Signifi- cantly lower concentrat ions of phosphate was found in the xylem sap of p lants grown on Loess, the two other


SOIL A N D X Y L E M C O M P O S I T I O N IN G R A P E V I N E - - 333

soils were similar. Malate concentrations in sap varied signif icantly with soil type and were greatest on Keuper and least on Muschelkalk. Fertilizer treatment always decreased malate concentrations in sap, while chloride concentrations were increased. There was also a significant effect of fertilizer on the other anions. Surprisingly, in plants grown on Musche lkalk or Keuper nitrate concentration in the sap was decreased by the addition of fertilizer.

The concentration of ABA was always greater in the xylem sap of non-fertilized grapevine (Fig. 5). In contrast to other treatments, the effect of fertilizer was not significant - the concentration of ABA in fertilized

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Fig. 3. Nitrate concentration in the xylem sap collected from the leaves number 2-9 of the shoot of grapevine (Vitis vinifera L. cv. Riesling clone B 68) grown on three soils derived from different geological formations. Standard errors are indicated by bars, nm: not measured. The significance (***: p< 0.0001, **: 0.0001 < p < 0.001, *: 0.001 < p < 0.05, ns: not significant) of the main effects, soil type (S) and fertilizer treatment (F within each soil treatment) are also given. Differences in soil are indicated by letters in parentheses (only A: ns, A and B two groups, and A, B, and C all soils were significantly different). Standard errors are indicated by bars, nm: not measured. The significance (***: p < 0.0001, **: 0.0001 < p< 0.001, *: 0.001 < p< 0.05, ns : not significant) of the main effects, soil type (S) and fertilizer treatment (F within each soil treatment) are also given. Differences in soil are indicated by letters in parentheses (only A: ns, A and B two groups, and A, B, and C all soils were significantly different).

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8TH 9TH Leaf number

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Fig. 4. Total amino acid and amide N concentration in the xylem sap collected from the leaves number 2-9 of the shoot of grapevine (Vitis vinifera L. cv. Riesling clone B 68) grown on three soils derived from different geological formations. Standard errors are indicated by bars, nm: not measured. The significance (***: p < 0.0001, **" 0.0001 < p < 0.001, *" 0.001 < p < 0.05, ns • not significant) of the main effects, soil type (S) and fertilizer treatment (F within each soil treatment) are also given. Differences in soil are indicated by letters in parentheses (only A: ns, A and B two groups, and A, B, and C all soils were significantly different).

vine was also relatively high and was significantly greater than on the two other soils.

The concentration of N-compounds in xylem sap from the basal leaves (2-4) are shown in Table 4. The major N-compounds in the xylem sap of grapevine were glutamine or nitrate in differing proportions. The proportion of ammonium was always much less than 10%, in fact mostly about 1% of total N. Additionally, glutamine-N was around 90% of amino acid N, and thus other amino acids played only minor roles in xylem transport . For p lants grown on Loess and Muschelkalk, there was a similar positive effect of N- fertilizer treatment on amino acid concentration and the proportion of reduced N to total N: both parameters increased due to fertilizer treatment as well as the total N concentration. For plants grown on Keuper as a substrate, this effect was reversed; amino acids and


~ 3 3 4 - - PEUKE

Table 3. Effect of soil and fertilizer treatment on concentrations [mM] of cations and anions in xylem sap. Means, standard errors (in parentheses) and the number of sap samples (n) for each soil and fertilizer treatment, are shown.

The significance (***: p < 0.0001, **: 0.0001 < p < 0.001, *: 0.001 < p < 0.05, ns : not significant) of the main effects, soil type (S) and fertilizer treatment (F) and their interaction (S'F) are also given. Differences in soil are indicated by letters

(only A: ns, A and B two groups, and A, B, and C all soils were significantly different). Type III model sums of squares were used since the design was unbalanced.

Ion

Potassium

Sodium

Magnesium

Calcium

Nitrate

Chloride

Sulfate

Phosphate

Malate

Loess Muschelkalk Keuper Significance

non-fert, fertilized non-fert, fertilized non-fert, fertilized S F S* n=13 n=21 n=10 n=16 n=14 n=33 F

A B C . . . . . . . . .

1.74 0.93 1.85 1.69 3.56 2.53 (0.19) (0.04) (0.13) (0.04) (0.12) (0.07)

A A A ns *** **

0.20 0.11 0.15 0.13 0.24 0.06 (0.02) (0.01) (0.03) (0.01) (0.06) (0.01)

A A A ns ns ns

0.27 0.28 0.33 0.32 0.33 0.24 (0.04) (0.01) (0.05) (0.02) (0.06) (0.01)

A B B . . . . . . . . .

0.96 0.72 1.57 1.12 2.03 0.60 (0.08) (0.03) (0.21) (0.08) (0.26) (0.03)

A B A . . . . . . . . 1.04 1.10 2.34 1.83 1.22 0.63

(0.08) (0.06) (0.13) (0.07) (0.10) (0.09) A A A ns *** ns

0.019 0.151 0.024 0.089 0.033 0.125 (0.006) (0.022) (0.010) (0.013) (0.009) (0.012)

A B A . . . . . . .

0.108 0.223 0.230 0.305 0.187 0.110 (0.012) (0.013) (0.053) (0.0155) (0.024) (0.098)

A B B . . . . . . . . .

0.023 0.014 0.073 0.095 0.033 0.125 (0.007) (0.005) (0.025) (0.011) (0.009) (0.007)

A B C . . . . . . . . . 0.714 0.325 0.313 0.289 1.271 0.923

(0.070) (0.029) (0.071 ) (0.013) (0.043) (0.027)

Table 4. Effect of soil and fertilizer treatment on nitrogen compounds in the xylem sap of grapevine (Vitis vinifera L. cv. Riesling clone B 68) grown on three soils derived from different geological formations (Loess, Muschelkalk / shell lime, Keuper).The significance

(***: p < 0.0001, **: 0.0001 p < 0.001, * : 0.001 < p < 0.05, ns: not significant) of the main effects, soil type (S) and fertilizer treatment (F) and their interaction (S'F) are also given. The xylem sap were collected from the basal leaves of the shoot

(leaves 2 - 4) by pressurising the rhizosphere to a level of 6"105 Pa. Mean values + SE.

Loess Muschelkalk Keuper Significance (shell lime)

non-fert, fert. non-fert, fert. non-fed, fert. S F S*F

glnN/AA-N [%] 79 92 91 91 84 63 * ns * +3 +1 +1 +1 +1 +14

Sum AA [m"] 0.29 0.71 0.37 0.58 0.47 0.33 ns . . . . +0.05 +0.05 +0.03 +0.13 +0.06 +0.12

NOJNto t[% ] 65 42 75 60 54 56 ns ns ** +4 +2 +3 +6 +2 +10

NH4÷/Ntot[%] 4 1 1 1 3 7 ns ns ns +1 +0 +0 +0 +0 +3

GInN/Nto t [%] 28 54 22 37 39 33 ns ns * +8 +3 +3 +7 +3 +13

Sum Ntot[ mM] 1.39 2.42 2.36 2.67 1.81 0.83 . . . . . . . . . +0.29 +0.15 +0.18 +0.36 +0.16 +0.26

Sum Ctot [mM ] 4.81 4.90 3.71 4.12 7.00 4.64 . . . . . . . . . +0.82 +0.36 +0.32 +0.84 +0.43 +0.53


SOIL A N D X Y L E M C O M P O S I T I O N IN G R A P E V I N E ~ 335

0.8 c~

E

x 0.6 .=_ t- .9

'- 0.4

c o

< to < 0.2

0.0

S ' A l F:***

S ' B l F:***

LOESS M.-KALK

._f_.

S'B F:n.s.

T

"////I

~'//Z,

"/////

KEUPER

i INon-fertilized t"/7"/-J Fertilized

Fig. 5. Abscisic acid concentration in the xylem sap collected from all leaves of the shoot of grapevine (Vitis vinifera L. cv. Riesling clone B 68) grown on three soils derived from different geological formations. Stan- dard errors are indicated by bars, nm: not measured. The significance (***: p < 0.0001, **: 0.0001 < p < 0.001, *: 0.001 < p < 0.05, ns : not significant) of the main effects, soil type (S) and fertilizer treatment (F within each soil treatment) are also given. Differences in soil are indicated by letters in parentheses (only A: ns, A and B two groups, and A, B, and C all soils were significantly different).

2000

1500

1000

5OO v ..{:

O E C

2000

x 1500 c

..£o 1000 4--.

E

"~ 500

O

2000 O. O_ <

1500

1000

500

Loess

i i i i i i I i

Muschelkalk

"T, ¢-

O E c

E

X c-

O 4.- C

~n O

c

c

c~

2000 l

Loess

b

1000 ,, ~

• • • • • •

2000

Muschelkalk

1000

2000

1000

]'; Keuper

l l ~ ~ l J J _ ~ [ . ~ L ~ " [ . ~ ~ ~n.m., , • • • • • • •


I I Non-fertilized f'-z"//3 Fertilized

Fig. 7. Apparent flows of total N to the leaves number 2-9 of the shoot of grapevine (Vitis vinifera L. cv. Riesling clone B 68) grown on three soils derived from different geological formations. Standard errors are indicated by bars, nm: not measured. The significance (***: p < 0.0001, **: 0.0001 < p < 0.001, *: 0.001 < p < 0.05, ns : not significant) of the main effects, soil type (S) and fertilizer treatment (F within each soil treatment) are also given. Differences in soil are indicated by letters in parentheses (only A: ns, A and B two groups, and A, B, and C all soils were significantly different).

K ii ] n n i i i i i i

i i i i i

2ND 3RD 4TH 5TH 6TH 7TH

I Non-fertilized ~ Fertilized

i i

Keuper

n . m .

I i

8TH 9TH

total N decreased in concentration with addition of fertilizer.

D i s c u s s i o n

Effects of leaf age on the c h e m i c a l compos i - t ion of x y l e m sap: The concentrations of all inorganic solutes in xylem sap were similar in all leaves along the axis of the shoot in grapevine. Thus, there was no specific 'resorption/unloading' of ions from the transpiration stream in the xylem of the stem. Hence, despite different solute requirements of leaves of different age (young developing leaves compared with mature full

Fig. 6 (left). Apparent flows of potassium to the leaves number 2-9 of the shoot of grapevine (Vitis vinifera L. cv. Riesling clone B 68) grown on three soils derived from different geological formations. Standard errors are indicated by bars, nm: not measured. The significance ( .... p < 0.0001, ** 0.0001 < p < 0.001, *" 0.001 < p < 0.05, ns • not significant) of the main effects, soil type (S) and fertilizer treatment (F within each soil treatment) are

Leaf number also given. Differences in soil are indicated by letters in parentheses (only A: ns, A and B two groups, and A, B, and C all soils were significantly different).


~ 3 3 6 - - PEUKE

Table 5. Relative selectivity (molar ion ratio xylem/soil solution) of grapevine xylem compared with soil solution. The xylem sap was collected from the cut midribs of the shoot of grapevine (Vitis vinifera L. cv. Riesling clone B 68) grown on

three soils derived from different geological formations (Loess, Muschelkalk / shell lime, Keuper) by pressurizing the rhizosphere to a level of 6 x 10 s Pa. The soil solutions were obtained by extracting the dry soils with water. In fertilized soils the input of N and S is not considered.

Non-fertilized Fertilizer mol / mol Loess Muschelkalk Keuper Loess Muschelkalk Keuper

(shell lime) (shell lime) Anions CI- 0.04 0.06 0.26 0.55 0.36 0.71

NO 3- 0.18 0.28 0.31 0.22 0.22 0.17 Phosphate 1.78 1.24 3.17 5.85 1.35 24.45

Sulfate 0.07 0.08 0.00 0.18 0.14 0.00 Cations K ÷ 15.96 10.19 2.84 13.75 12.82 2.45

Na ÷ 0.70 0.42 0.78 0.36 0.33 0.26

Mg ÷÷ 0.79 0.86 0.10 1.07 0.65 0.09

Ca +÷ 0.20 0.21 0.07 0.16 0.10 0.03

synthesizing leaves or old senescent leaves) the xylem stream delivered sap of more or less constant mineral composition. This result of the present study is in ac- cordance with those of previous studies in barley [33], or lupin [19], or Ric inus [12].

The concentration of the measured organic compounds, malate and ABA, in the xylem sap also did not vary among leaves. The only exception was the sum of the N-content of amino acids and amides. The concentrat ion of organic N increased along the shoot and was greatest in the youngest measured leaf (pronounced in non-fer t i l ized p lan t s grown on Keuper and on Muschelkalk, Fig. 4). In addition to amino acids derived from the root, amino acids from the older parts of the shoot are loaded into the xylem along the t ranspira- tion stream. This effect increases the supply of younger leaves with N (in addition to the supply via phloem). Jeschke and Pate [11] observed this effect in Ric inus and found that the xylem sap became more concen- t ra ted in N, and the ratio of NO3-N to reduced N decreased. They at t r ibuted this, in part, to the presence of t ransfer cells in the xylem of leaf traces exiting from nodal tissue.

Although the concentration of inorganic solutes in xylem sap did not differ with leaf age, the rate of supply to leaves differs due to the apparent ly different flows (see Fig. 1). The calculation of the apparent volume flow includes the effects of hydraulic architecture, since the whole mid rib of a leaf was cut. As a result, the middle leaves received the most minerals. As an example, the apparent potassium flow is shown (Fig. 6), although the same result was obtained for the other measured ions. In contrast, the apparent total nitrogen flow (Fig. 7) shifted in favor of the younger leaves owing to the acropetally increasing amino acid and amide N concentration along the stem. This effect was pronounced in non-fertilized grapevines. Jeschke and Pate [10] and Jeschke et al. [8]showed for Ric inus tha t the flow of water was greatest to those leaves tha t had the greatest assimilation and t ranspirat ion rates. Due to

this effect, the supply of leaves with inorganic ions is similar to the flow profile of water [12,13].

Ef fec t s of soil on the c h e m i c a l c o m p o s i t i o n in x y l e m sap: The soil had little impact on the composition of the xylem sap. The difference between two soils within a fertilizer t rea tment scarcely exceeded a factor of two. Only the greater potassium concentration in the xylem of grapevine grown on Keuper increased ni t rate in the case of Muschelkalk, and the low phosphate concentration in saps of vines grown on Loess were remarkable. Increased availability of potassium in the rhizosphere of plants growing on Keuper soil is clearly responsible for this observation. Rfihl [27] showed in four rootstock varieties of grapevine that the potassium concentration in xylem exudates increased with increasing supply of K ÷ (0.1, 1, 10 mM).

In the present study, an aqueous soil extract had been used to measure the available nutrients. This may underes t imate the available nutr ients because roots have the capacity to secrete organic substances and dissolve nutr ients from the soil. It is for this reason that, in soil chemistry, inorganic and organic solvents are used to extract nutr ients from the soil. For example, cations are measured only after displacing them from the soil using solvents such as ammonium chloride and bar ium chloride. Likewise other solvents are used to displace nutr ients such as iron, copper, manga- nese a luminium and zinc. However, it is not known whether these extraction methods provide an accurate est imate of available nutrients. It may be difficulty to compare the results of studies with different methods.

Nitrate concentrations (Fig. 8) as well as total N (Table 3) were greatest in the xylem sap of grapevine grown on Muschelkalk. In earlier investigations with soils from the same vineyards, the greatest mineral-N concentrations were found in Muschelkalk and the least in Keuper [18]; those results compare well to the present (Table 1 and 2). Hannachi et al. [6] showed for wheat tha t ni t rate flow to leaves, storage, and assimilation of ni t rate within leaves were greater in plants on


SOIL AND XYLEM COMPOSITION IN GRAPEVINE- 337

chalky than on loamy soils and concluded that nitrogen metabolism is strongly influenced by the soil type.

In the present investigation, nitrate was the major anion and potassium the prominent cation in the xylem sap, agreeing well with the results of Keller et al. [14] for grapevine. This seems to be a common phenomena, since it has been reported for other plants when nitrate is the major N-source and plants are not stressed by salt: e.g., in R i c i n u s [1,23,30], in beet and sorghum [4], in broccoli [29], and in maize [5]. The relative selectivity of the xylem for ions of the rhizosphere as calculated by the molar ratio of concentration in the xylem to those in the soil solution, shows that potassium was preferentially absorbed (Table 5). This ratio was least in the soil solution with the greatest potassium concentration (Keuper). Calcium was always least selected by plants despite its abundance in the soil solution. For anions, the greatest selectivity was found for phosphate; the anion present the least concentration in the soil extract. For the most abundant anion, nitrate, reduction and storage in the root must be taken into account.

ABA concentrations in the xylem sap of fertilized plants grown on Keuper were significantly greater than in vines grown on other soils. The greatest total solute concentration and osmolality was also found in the soil solution of Keuper. Since grapevine is known to be salt sensitive [16], it may be the effect of salt is responsible for the strong increase in ABA concentration [26 and li terature cited therein]. ABA is known to be an important hormonal long distance stress signal in plants under drought and salt stress [7].

Pate [21] introduced the ratio of NO3--N to reduced N as a simple estimate for the partitioning of ni trate reduction between root and shoot. This method is simple, but results agree well with other more complex and sophisticated techniques [24]. On this basis, 40% to 75% of the nitrate reduction occurred in the shoot, with the greatest ratio in plants grown on Muschelkalk (Table 3). Hence nitrate remains a major N-transport compound in the xylem. In contrast, Alleweldt and Merkt [3] suggested glutamine was the major t ransport form for N in xylem, and in the present experiments was the major amino acid. Nevertheless, the contribu- tion of shoot and root to nitrate reduction, and the composition of N compounds in the xylem sap, depends on several conditions, for example on N supply [21,24].

The effect of soil type on vine response was studied after transferring soil from vineyards into pots. Conse- quently, some physical characteristics of the soil such as bulk density and porosity of the soil would have changed. These physical characteristics affect root growth and the physiological activity of roots. There- fore, it must be pointed out that there is a limitation in making conclusions from results obtained in the pot trials for the situation in the field.

Effec t s o f N - f e r t i l i z e r t r e a t m e n t on t h e c h e m i - ca l c o m p o s i t i o n o f x y l e m sap: The effects of fertilizer t rea tment were greater than those of soil type with

respect to the observed ratios and the estimated significance (see Table 3). But, in parallel to soil type, the concentrations of anions were more affected than those of cations. In the xylem of fertilized grapevines, the concentration of chloride, sulfate (not on Keuper), phosphate (not on Muschelkalk) was increased and calcium and sodium decreased in comparison with non-fertilized plants. Keller et al. [14] found that N-fertilizer t rea tment had no effect on P, K, and Mg concentrations in xylem sap, in general agreement with the present results.

The concentration of ABA in xylem sap was always greater in non-fertilized grapevines. N-supply and N- status has previously been shown to affect ABA concentrations in xylem sap. Generally, the effect seems to be that ABA concentrations are reduced as nitrate concentrations increase owing to better nitrate supply [26 and li terature cited therein]. Increased ABA concentration may possibly be a root to shoot signal of lower nutr ient (N) supply in grapevine.

Surprisingly, the nitrate concentration in the xylem sap was greater in non-fertilized than fertilized vines grown on Muschelkalk and Keuper soil types. The low pH of extracts of these two soils suggests increased mobility of ammonium originating from fertilizer. Ammonium is a known inhibitor of nitrate uptake and may be the cause of our observation.

N-fertilizer had a marginal effect on the concentration of N in the xylem sap of grapevine [14]. In investigations with hydroponic systems or inert substrates like quartz sand, the nitrate concentration in xylem increased up to 12 mM in the rhizosphere [23 and li terature cited therein]. Natural soils with complex reactions will strongly buffer such effects. Addition of N-fertilizer to Loess and Muschelkalk soils increased the proportional reduction of ni trate in roots by about 15% to 20% (Table 4). In plants grown on Keuper, N- fertilizer t rea tment had no effect on this proportion. In contrast to the observed effect of N-fertilizer on grapevine, nitrate reduction typically shifts to the shoots after nitrate supply is increased [24] and li terature cited therein]. Nonetheless, in most of the cited experiments, nitrate supply was manipulated via hydroponic culture or in substrates without exchange properties. Plants grown on more complex substrates such as field soils and fertilized with NH4÷/NO3 -, clearly react differently. Additionally, if ammonium is taken up (although it is only present in traces in the soil solutions), almost all N-assimilation takes place in the root [22,24, and li terature cited therein]. Apart from the inhibitory effect of ammonium on nitrate uptake discussed above, the increased use of ammonium due to fertilizer treatment may have affected the site of N-assimilation, particularly since the amino acid concentration increased (Table 4). This effect largely explains, first, the increasing nitrate concentrations in xylem sap, and secondly the increased N-assimilation in the root due to fertilizer t reatment.

G e n e r a l r e m a r k s on m e t h o d o l o g y : Two methods have been previously used to sample xylem sap


~ 338 m PEUKE

from grapevines. Keller et al. [14] applied a nondestruc- tive vacuum extraction method to obtain samples of xylem sap from the t runk of grapevine. Alleweldt and Merkt [2,3] and Rfihl [27] used the decapitation technique -- severing the stem and relying on root pressure to force xylem sap to the top of the cut stump -- to obtain samples. An obvious limitation of the latter method is the interruption of recycling of solutes and supply of the roots with energy by the phloem.

In the present investigation, xylem sap from the midrib of leaves along the only developed shoot of grapevine were collected by pressurizing the rhizosphere [20]. The concentration of solutes and the volume flow depends on the applied pressure [28]. As chamber pressure is increased, volume flow increases, but the concentration of solutes decreases. Since xylem sap was collected from all leaves and under all conditions (soils and fertilizer) at the same pressure and physical conditions (particularly water availability), volume flows and concentrations of solutes are compa- rable. For volume flow, this method incorporates the hydraulic architecture for evaluating flow data. Com- pared with the collection of xylem exudates from de- capitated stems, a further advantage of the method used here (besides the chance to collect xylem sap from several leaves of a shoot simultaneously) is the fact that the composition of the xylem sap includes recycled ions from the shoot by the phloem due to the phloem- xylem transfer in the root. It has been shown that the concentrations of highly mobile ions in the phloem decrease strongly within 30 to 60 minutes in the xylem sap after excision of the shoot [9]. The apparent flows of ions in the xylem to the leaves should not be confused with the net supply of nutrients to the leaves, since the possible removal of compounds by the phloem is miss- ing. In young leaves (sink leaves), there is import of the phloem and in mature and old leaves, an export.

C o n c l u s i o n s The effects of the different soils on the chemical

composition of xylem sap in grapevines during vegetative growth was less than the effect of N-fertilizer treatment with respect to calculated significance and ratios of treatments to each other. There was a tendency for plants grown on Keuper soil to react differently from those grown on Loess or Muschelkalk with respect to a number of measured parameters. This was true also for differences in the chemical composition of soils; the Keuper type was noticeably different to the other types. The mineral composition of xylem sap did not differ along the axis of a shoot. The supply of leaves with mineral ions depended therefore, only on the volume flow to the leaves. In contrast, the concentration of total N increased acropetally, due to increasing amino acid concentrations. In general, the chemical composition of grapevine xylem sap was similar to other studied species. However, the effect of N-fertilizer on transport of N-compounds was more complex. This may be due to first to the nature of fertilizer which contained both inorganic N sources and second to the complex nature of field soils.

L i t e r a t u r e Ci ted 1. Allen, S., and J. A. C. Smith. Ammonium nutrition in Ricinus com-

munis: Its effect on plant growth and the chemical composition of the whole plant, xylem and phloem saps. J. Exp. Botany 37:1599-1610 (1986).

2. Alleweldt, G., and N. Merkt. Der Stickstoffexport der Wurzel und die Zusammensetzung des Xylemexsudats. Teil 1: Der Einflul3 einer zunehmenden StickstoffdQngung. Vitis 31:121-130 (1992).

3. Alleweldt, G., and N. Merkt The nitrogen output of the root and the nitrogenous compounds in the xylem exudate. Part 2: The influence of grafting. Vitic. Enol. Sci. 48:55-60 (1993).

4. Arnozis, P. A., and G. R. Findenegg. Electrical charge balance in the xylem sap of beet and Sorghum plants grown with either NO 3 or NH 4 nitrogen. J. Plant Physiol. 125:441-449 (1986).

5. Engels, C., and H. Marschner. Influence of the form of nitrogen supply on root uptake and translocation of cations in the xylem exudate of maize (Zea mays L.). J. Exp. Botany 44:1695-1701 (1993).

6. Hannachi, L., A. Bousser, and E. Deleens. Effect of soil type on nitrate uptake by wheat shoots characterized using lSN-labelled NH4NO3-fertilizer and in vitro leaf nitrate reductase activity. Austral. J. Plant Physiol. 25:465-474 (1998).

7. Hartung, W., A. D. Peuke, and W. J. Davies. Abscisic acid - a hormonal long distance stress signal in plants under drought and salt stress. In: Handbook of Plant and Crop Stress (2 nd ed). M. Pessarakli (Ed), pp 731-747. Marcel Dekker Inc., New York, Basel, Hong Kong (1999).

8. Jeschke, W. D., A. D. Peuke, et aL Effects of P deficiency on the uptake, flows and utilization of C, N and H20 within intact plants of Ricinus communis L.. J. Exp. Botany 47:1737-1754 (1996).

9. Jeschke, W. D., O. Wolf, and J. S. Pate. Solute exchange from xylem to phloem in the leaf and from phloem to xylem in the root. In: Recent Advances in Phloem Transport and Assimilate Compartimentation. J. L. Bonnemain et al. (Eds.) pp 96-104. Ouest Editions, Nantes (1991 ).

10. Jeschke, W. D., and J. S. Pate. Modelling of the uptake, flow and utilization of C, N and H20 within whole plants of Ricinus communis L. based on empirical data. J. Plant Physiol. 137:488-498 (1991a).

11. Jeschke, W. D., and J. S. Pate. Modelling of the partitioning, assimilation and storage of nitrate within root and shoot organs of castor bean (Ricinus communis L.). J. Exp. Botany 42:1091-1103 (1991b).

12. Jeschke, W. D., and J. S. Pate. Cation and chloride partitioning through xylem and phloem within the whole plant of Ricinus communis L. under conditions of salt stress. J. Exp. Botany 42:1105-1116 (1991).

13. Jeschke, W. D., E. A. Kirkby, et al. Effects of P deficiency on assimilation and transport of nitrate and phosphate in intact plants of castor bean (Ricinus communis L.). J. Exp. Botany 48:75-91 (1997).

14. Keller, M., B. Hess, et aL Carbon and nitrogen partitioning in Vitis vinifera L.: Responses to nitrogen supply and limiting irradiance. Vitis 34:19-26 (1995).

15. Lang, A., and H. D0ring. Partitioning control by water potential gradient: evidence for compartmentation breakdown in grape berries. J. Exp. Botany 42:1117-1122 (1991).

16. Mass, E. V., and G. J. Hoffman. Crop salt tolerance m current assessment. J. Irrig. Drain. Div. 103:115-134 (1977).

17. Mertens, R. J., B. Deus-Neumann, and E. W. Weiler. Monoclonal antibodies for the detection and quantitation of the endogenous plant growth regulator, abscisic acid. FEBS Letters 160:269-272 (1985).

18. MQller, K. Die Mineralisation des organisch gebundenen Stickstoffs in Weinbergsb6den. Teil I: Die Nm~n-Dynamik. Vitis 30:151-166 (1991).

19. Munns, R. Physiological processes limiting plant growth in saline soils: some dogmas and hypotheses. Plant Cell Environ. 16:15-24 (1993).

20. Passioura, J. B. The transport of water from soil to shoot in wheat seedlings. J. Exp. Botany 31:333-345 (1980).


SOIL AND XYLEM COMPOSIT ION IN GRAPEVINE m 339

21. Pate, J. S. Uptake, assimilation and transport of nitrogen compounds by plants. Soil Biology and Biochemistry 5:109-119 (1973).

22. Peuke, A. D., and W. D. Jeschke. The uptake and flow of C, N and ions between roots and shoots in Ricinus communis L. I. Grown with ammonium or nitrate as nitrogen source. J. Exp. Botany 44:1167-1176 (1993).

23. Peuke, A. D., and W. D. Jeschke. Effects of nitrogen source, nitrate concentration and salt stress on element and ion concentrations in transport fluids and on C and N flows in Ricinus communis L. In: Structure and Function of Roots. F. Baluska, M. Ciamporova, et aL (Eds.). pp 229-236. Kluwer Academic Pubishers, Dordrecht, Nether- lands (1995).

24. Peuke, A. D., J. Glaab, et aL The uptake and flow of C, N and ions between roots and shoots in Ricinus communis L. IV. Flow and metabolism of inorganic nitrogen and malate depending on nitrogen nutrition and salt treatment. J. Exp. Botany 47:377-385 (1996).

25. Peuke, A. D., W. Hartung, and W. D. Jeschke. The uptake and flow of C, N and ions between roots and shoots in Ricinus communis L. I1. Grown with low or high nitrate supply. J. Exp. Botany 45:733-740 (1994a).

26. Peuke, A. D., W. D. Jeschke, and W. Hartung. The uptake and flow of C, N and ions between roots and shoots in Ricinus communis L. II1. Long distance transport of abscisic acid depending on nitrogen nutrition and salt stress. J. Exp. Botany 45:741-747 (1994).

27. RC~hl, E. H. Effect of K ÷ supply on ion uptake and concentration in expressed root sap and xylem sap of several grapevine rootstock varieties. Viticulture Enol. Sci. 48:61-68 (1993).

28. Schurr, U., and E.-D. Schulze. The concentration of xylem sap constituents in root exudate, and in sap from intact, transpiring castor bean plants (Ricinus communis L.). Plant Cell Environ. 18:409-420 (1995).

29. Shelp, B.J. The composition of phloem exudate and xylem sap from broccoli (Brassica oleracea var. italica) supplied with NH4+, NO 3- or NH4NO 3. J. Exp. Botany 38:1619-1636 (1987).

30. van Beusichem, M. L., E. A. Kirkby, and R. Baas. Influence of nitrate and ammonium on the uptake, assimilation, and distribution of nutrients in Ricinus communis. Plant Physiol. 86:914-921 (1988).

31. Wahl, K., and W. Patzwahl. Beziehungen zwischen Boden und Wein. Rebe und Wein 9:304-309 (1997).

32. Wegner, L. H., and K. Raschke. Ion Channels in the xylem parenchyma of barley roots. A procedure to isolate protoplasts from this tissue and a patch-clamp exploration of salt passageways into xylem vessels. Plant Physiol. 105:799-813 (1994).

33. Wolf, O., R. Munns, et aL Concentrations and transport of solutes in xylem and phloem along the leaf axis of NaCI-treated Hordeum vulgare. J. Exp. Botany 41:1133-1141 (1990).


Documents

The Chemical Composition of Xylem Sap Vitis vinifera ... fileIn xylem sap, nitrate was the major anion, followed by malate. Nitrate concentration was greatest in plants grown on Muschelkalk,