Uptake and Translocation of [14C] -Monoethanolamine in Barley Plants

Biochem. Physiol. Pflanzen 183, 27-36 (1988) VEB Gustav Fischer Verlag J ena

Uptake and Translocation of [14C]-Monoethanolamine in Barley Plants HANS ECKERT, HANS BERGMANN and PETER REISSl\IANN Forschungszentrum fiir Bodenfruchtbarkeit Miineheberg der Akademie der Landwirtsehaftswissenschaften der DDR - Bereich Jena, Jena, DDR Key Te r m In d ex: ethanolamine, uptake, translocation; Hordeum vulgare

Summary Uptake and translocation of [14C]-monoethanolamine and its hydrochloride were investigated after application to an unwounded part of the fifth leaf from the main shoot of intact spring barley plants. After 48 and 72 h, respectively, the free EA-base was both absorbed rapidly and translocated out of the feeding leaf. The absorbed [14C] preferably migrated to the tillers, which resulted in an approximately uniform distribution of the radioactivity in the aboveground parts of the plant after the uptake phase (similar [14C]_ coneentrations in the main shoot and tillers), whereas only few radioactivity moved to the root~. On the other hand, the protonated EA (EA-HCl) exhibited both a reduced uptake and a restricted mobility. The bulk of radioactivity remained in the main shoot. As a eonsequence of the principally analogous metabolism of EA and its protonated form, the translocation differenees are compensated during ontogenesi". When the plants reached maturity, similar distribution patterns could be found in which the kernels rcpresrnted a considerable sink.

Introduction

The positive effect of mono ethanolamine (EA) on plants (KAMALYAN 1970; KAl\IALY AN et al. 1971; FUJII et al. 1972; LIN and KAUER 1985), and in particular the growthstimulating and stress-protecting effects on crop plants (hKER et al. 1976; BERGMANN ct al. 1983; HORVATH and VAN HASSELT 1985) suggest that the usc of the compound for crop plants seems to be promising. In this connection, the knowledge of uptake and transport characteristics as well as of information on the metabolism in plants is an essential prerequisite with regard to hygienic-toxicological requirements, to optimal application techniques and for understanding the mode of action. A preceding paper showed (ECKERT ct al. 1987) that the metabolism of both the free EA-base and its protonated form leads to lipid-soluble compounds on the one hand and to glycine betaine via choline on the other. In addition, the free base is also converted to volatile compounds to a great extent. However, uptake and translocation characteristics of EA have not yet been reported. Thus, in the following article, the uptake and mobility of labeled EA are to be investigated, with the following questions being in the centre of interest: a) To which extent is EA absorbed by unwounded leaves, and what is the influence of the molecular charge in this process? Abbreviations." EA, lllonodhanolamine; ce, tholine; GB. glycine betaine; PPO, 2,5-diphenyloxazole; POPOP, 2,2-p-phenylene-bis-(5-phenyloxazole); MeW, methanol-chloroform-water = 60 + 20 + 20 (v/v/v)

27

b) How rapid and via which transport paths (apoplastic or symplastic) is the compound translocated and arc there preferential accumulation sites? In order to achieve definite results on uptake and translocation characteristics, the [14C]-labeled compounds were applied to a particular section of the unwounded leaf of the main shoot. The uptake phase was limited within a given time by removing the feeding leaf. Material and Methods Radiochemicals [P4C]-Monoethanolamine-hydroehloride ([14C]-EAH+) was obtained from Isocommerz Dresden (G.D.R.). Purification and eonversion into the free base have been described by ECKEW[ et a1. (1987), except that spodfir radioadivities of the labeled componnds used in this work were in the range 5.23 to 23.67 MBq/mmol (for ddails see Table 1).

Plant 1Y1 alerial The spring barley (Hol'deum vulgare L.) eultivars used were Lada (in the vegetation period 1983) and Salome (in 1984). Methods for pot trials and mode of application to plants were as described previously (ECKERT et a1. 1987). For studies on uptake, one experiment with ('v. Lada was carried out in a growth chamber, morll'l KTLK 20000, for 16-h-d (for details see Table 1). Plants were harvested at different times after applieation (see Fig. 1). At eaeh harvest time, an analytieal sample comprised fOllr plants with six replicates divided into the following parts: cotton wool ring and uptah area (the seetion of fed blade contaminated outwardly); remainder of the fed leaf; blades and sheaths, intluding the stem of the main shoot above and below the fed leaf; tillers; roots and in addition at maturity, pars and kl'rnels of the tillers. The samples were frozen in liquid nitrogen and lyophilized.

Extraction and Detcrmination of Radioaciirit!f The freeze-dried samples were weighed, ground « 0.0 mm) and then extracted with the MCW procedure as described by ECKERT ct al. (19R7). Aliquots (1 to 3 ml) were taken for seintillation counting. Solutions eontaining ehlorophyll were bleaching with UV. Radioaetivity was measured in a scintillation ('Olmter, model LKI3 Wal!ae, using a dioxan ('o('ktail with the seintillators PPO and POPOP. Any quenehing was cOJ'J'Pcted for by an internal standard. All measurements were repeated three times with different aliqllots, and the obtained results were tested for significanee by means of t-test as well as Tukcy-tpst.

Results

Uptake Characteristics of [14C J-EA and [14C J-EAH+

In the following the term "uptake" is used to characterize the radioactivity taken up by the fed leaf and migrated out of it. Consequently, uptake is that radioactivity found in all plant parts with the exception of the [14C] retained in the fed leaf after the uptake phase had been stopped. After the application of the free base ([14C]-EA; pH 10), uptake rates were between 3.9 and 7.3 % of the applied radioactivity (Table 1 below). These rates are higher than those of different growth retardants determined with the same application technique (ECKERT 1973) and demonstrate the favourable uptake as well as translocation characteristics of the ullprotonated form. BeEides, the results have been shown to be affected by the preliminary treatment and to the uptake length. Plants cultivated under cold conditions exhibited only half of these uptake rates. The shortening of the uptake phase 28

RPP 183(988) 1

from 72 h (cv. Lada) to 48 h (cv. Salome) significantly reduced the uptake rate, too. Obviously, the cultivar plays an insignificant role because preliminary experiments showed that the lengthening of the uptake phase led to comparable rates of cv. Salome and cv. Lada. However, on the basis of the results represented here, one cannot decide whether the penetration into the feeding blade or the migration out of it was the limiting factor. This is true for both of the cultivars. Table 1. Uptake rates of [14Cl-EA alld [14Cj-EAH-' in sprilly barley. Appliration of approximately O.G mg EAjplant to a blade section of the unwounded fifth leaf of the main shoot at shooting phase. Uptake time and experimental dnration: 72 h (CY. Lacia), 48 h (CY. Salome). Pot trials; each analytical sample = 4 plants; six repli('ates pl'I treatmcnt. Compound Speeifir radioa(·tivity (lVmq/mmol) Cultivation tonditionsl) Cultivar Parametl'I Radioadivity applied (kll(] Pl'!' plant) [14 0J n'('oVl'red (kBq )2) [ 14 0] taken nfl (k Bq)3) reI. to the ['4C] applied

25.67

22.54

25.67

warm ('old La(ht Larla

norm. Lada

norm. Salome

norm. Lalla

norm. Salome

57.5 31.5 4.2 7.2

282.0 187.5 20.G 7.3

247.6 156.0 12.4 5.0

290.7 293.0 7.4 2.5

22G.4 225.6 3.6 1.6

5.23

57.5 23.1 2.3 ;3.9

22.64 LSD 5 %

0.8

1) ('old cultivation: ('ontinous reduetion of night temperatllrps until Fcekcs-stage 4/6 to -3 DC. warm ('ultiYation: minimulll tempcratnrcs at night: 5°C. normal (,Illtivation: during the day outdoors; at night greenhouse ~) the differeneps in the ease of free base (-14C]-EA) between radioactivity applied and recovered are explaincd by tIll' evaporation of EA from the ('otton wool rings 3) [14C I taken up = [14C] 1"('('ov8r('(\ in all plant parts with the cxeeption of that retaincd in the feeding leaf.

Table 2. Comparison between spray application (hair-Iae-sprayer) and application on a blade section of the fifth leaf of the main shoot viI! cot/all wool riny. Time of application: shooting stage; spray applieation: (i ml per pot (G.7 mg EA; 5.23 ;\IBqjmmol), pot surface covered with cotton wool; cotton wool ring application: 50 fll per plant (0.67 mg EA; 0.23 l\
cotton wool ring application (data per plant)

[HCJ-EA applied (mg and kBq)

0.67 = 57.6

Dry matter (ears) at maturity (g) P4C] reeovered in cars (kBq) [14Cjeolll'l'ntration (Bqjg cars) [l4Cj incorporation into cars in % to [14C] applied

spray application (data per pot) G.7

=

4.46 0.51 115

50.5 4.G1 91

0.89

0.80

575

BPP 183 (1988) 1

29

Parallel experiments carried out with the hydrochloride «(14C]-EAH+) only showed uptake rates between 1.6 to 2.5 % influenced by the length of the absorption phase (Table 1). These substantially decreased uptake rates can be explained, at least to some extent, by the reduced penetration of the protonated form. This was a result because the radioactivity found in the fed leaf only amounted to 40 % compared with the free base (not demonstrated in Table 1). On the other hand, EAH + as a salt exhibited no evaporation leading to considerable application losses in the case of the free base (Table 1; difference between [14C] applied and recovered). Thus, under conditions of practical application, the decreased uptake rates could be compensated for by the extended uptake phase. With regard to the low uptake rates of about 7 % of the applied radioactivity, the relationship between the application technique via a cotton wool ring and the spray application (sprinkling of the whole leaf canopy) was to be tested. Uptake rates after spray application, however, cannot be directly determined because uptake (absorption into the leaf) and contamination of the same are not separable from one another. Since, however, after [14C]-EA application a great deal of radioactivity is moved into the ears (Table 3), organs which are not contaminated by a spray application at the shooting stage, the recovered radioactivtiy in these parts at maturity can be a clue for the uptake rates after spray application. An experiment relating to this indicated that similar [14CJ-concentrations could be detected in the ears (0.8 to 0.9% of the applied [14C]) after the application via a cotton wool ring as well as after sprinkling the whole leaf canopy (Table 2). Despite the fact that in the case of spray application not all the applied radioactivity reached the plants because of drift-away, the uptake rates seems to be similar. Hence, it follows that the uptake rates per unit leaf area are much higher in the case of the application via cotton wool ring. This might be interpreted as concentration effect (MIDDLETON and SAUNDERS 1965), and be a result of the longer moistening phase. Translocation

The distribution of the radioactivity in the plant parts is summarized in Fig. 1. For better clarity, only [14C]-traJlslocation to the roots, tillers, main shoot, and ears are demonstrated. From the fed fifth leaf of the main shoot, the radioactivity from [14C]-EA is distributed to the rest of the plant very rapidly. As early as 3 d after application (end of the uptake phase) about 70 % of the radioactivity taken up had moved to the tillers in cv. Lada, whereas only little [14C] was found in the roots (Fig. 1; upper left). This led to a uniform distribution in the plant parts above ground (similar [14C]-concentrations in main shoot and tillers) and to the [14C] depletion in the roots (Fig. 1; data next to points). During the subsequent period of growth until maturity, the concentration of [HC] in the plant declined as a consequence of both the dilution by the growth and the conversion to volatile compounds. But the distribution of radioactivity in the plant parts only showed little modifications. Detailed studies, however, could demonstrate a mainly apical transport. The radioactivity found in the main stem and leaves below the application site as well as in the roots declined whereas the actively growing parts of the plant, particularly the ears, became a sizeable sink. Within the ears, the kernels contained about 90 % of the radioactivity recovered in the ears at maturity (Table 3). It seems noteworthy to mention that the radioactivity in the whole plant declined in

30

BPP 183 (1988) 1

the course of the experiment so that at maturity, only 36 % of that radioactivity could be found which was recovered after the uptake phase had finished (Fig. 1). It is likely that there was a conversion to volatile compounds. In this connection, the fact that the decline of [He] mainly concerned the tillers (Fig. 1) is particularly difficult to interpret.

11.2

20 18

16

41>2 .1 0.9 -:50.7

12

5

10

I

I

I

1.9

'---,-..=,=--.----,--,,-----'l-""'-- [ d 10

20

30

40

50

60

70

J

~~ 0.8V.~4

~]

'---,-~r=~,-~r-~

10

20

30

40

50

14 C-EA

14C-EkHCI

SALOME

SALOME

I'

I

60

70

:r

....

0,4

.--...- Plant ( totol)

-....- tillers -----<>-- main shoot (t cta I) - - - 0 - - ear of ma in shoot _ _ _ (lor$ of tillers

Fig. 1. Dislr£bution of [14 C] exported from th e fed leaf among plant parts of spring barley (cvs. Lada and Salome) after applicahon of [l4 G]-RA and [14G ]-EAli+, respectively. Ordina.tc: total [14C] reeovered in the plant parts ; abcsissa: harvest times (days after application). Numbers next to points on the curves are [14C] concentrations in the plant parts (kBq/g dry matter). Application: approximately 0.6 mg EA (as [14C]-EA and [14CJ-EAH +, respectively) in 50 f.LI water. Specific radioactivity: 25.67 MBq/mmol (cv. Lada); 22.54 MHq!mmol (ev. Salome). Application on a blade section of the unwounded fifth leaf of the main shoot at shooting stage. After application the cotton wool ring was moistened 72 h (cv. Lada); 48 h (ev. Salome) and subsequently removerl together with the fed blade. Each point is the mean of six replieates. The bars indicate the least significant difference at the 5 % level that is appropriate for comparing values vertically.

BPP 183 (1988) 1

31

Table 3. Distribution of radioactivity in the main shoot of spring barley (cv. Salome) at maturity after application of [14C J-EA and [ 14 eJ-EAH +. Pot trial; n = G; for details see legend under Fig. 1. Treatment Fraction

[14 C]-EA (Bq)

Main shoot (total)

1,G20

[14C]-EAH+ (Bq)

100

1,420 = 100

Plant parts below the appliultion site, without roots Plant parts above the app1i('ation site, without ears Ears

120 = 7.4

30 = 2.1

G70 = 41.-1

540 = 38.0

b30 = 51.2

850 = 59.9

Spindle and awns Kernels

GO = 7.2 770 = 92.8

40 = 4.7 810 = 95.3

=

But concerning studies on the metabolism of EA (ECKERT et al. 1987) it was shown that the EA: metabolite ratio in the tillers was much higher than in the main shoot. This means that, in contrast to the main shoot, the radioactivity found in the tillers could be mainly associated with EA. Hence, it follows that EA exhibited another mobility than its main metabolites (CC, GB) and, consequently, that the conversion to volatile compounds probably starts from EA. Contradictory results were obtained in the experiments with the protonated EA (Fig. 1; upper right). The decline of radioactivity in the whole plant was much smaller during the ontogenesis compared to the free base and can be explained by inevitable harvest losses. The protonated form also showed other translocation patterns. The level of radioactivity found after the uptake phase was much lower and the [14C] remained mostly in the main shoot, whereas the tillers only exhibited a low level of radioactivity. Only with increasing time more radioactivity moved into the tillers and, therefore, the distribution pattern at maturity was according to this of EA. The results presented here with cv. Lada arc not directly comparable with those of cv. Salome. Apart from the influence of the other cultivar, the distribution pattern might also have been influenced by the reduced uptake phase of only 48 h. Nevertheless, clear paralleles to the results with cv. Lada were observed concerning the small movement of [14C] to the roots and the rapid transport of radioactivity to the tillers. But the latter was not so obvious as in the case of cv. Lada, as shown by the data of [14C]-concentrations (Fig. 1). To some extent, this can be explained by the lower tiller development of cv. Salome. But clear differences between EA and its protonated form (EAH +) were recognizable in this cultivar as well. Discussion

The favourable uptake and translocation characteristics of the free EA-base and the different properties of its protonated form may be caused either by the pH dependent molecular charge of the compound or by uptake and translocation of metabolites. Particularly during long application periods, misinterpretations are possible if the compound in question undergoes rapid metabolic changes. Table 4 shows how far the latter 32

BPP 183 (1988) 1

Table 4. AIctabolite formation in the feeding solution and in the feeding leaf (without application site) after the end of the uptake phase. Pot trial with spring barley (cv. Salome); n = 3; for details of experimental data see Fig. 1, analytical methods according to ECKERT et al. (1987). Fraction

Treatm~nt

% of (14C]

[14C] total (kBq)

ER

CHCI 3

AN

NI

CC

GB

EA

100 100

0.;) 0.4

0.7 0.4

0.3 0.2

0.1 0.0

0.9 1.0

0.1 0.2

96.5 96.8

100 100

5.2 3.3

11.G

8.5 7.8

3.3 2.5

3.G 6.G*

0.5

O.G

68.5 76.7*

Feeding solution 2 )

EA EArll

33G.G 561.4

=

Fed blade 3 )

EA EAH+

23.7 12.2

=

=

=

Metabolites1 )

7.;)*

total

*

Significamc at LSD5 % for the comparison between EA and EAH + 1) ER = extraction residue; CHCl:) = ehloroform phase; AN = anionic compounds; NI ionie compounds (effluent); CC = eholinc; GD = glycine betaine; EA = monoethanolamine 2) radioactivity reeovcred on the cotton wool ring and applieation area. 3) without application area

=

non-

can explain the observed differences. After the end of the uptake phase, the feeding solution remaining on the cotton wool ring only contains EA. Since radioactive products made by microbes could not be detected, a metabolite uptake can be excluded. However, evidence of metabolites could be demonstrated in the feeding leaf at the end of the moistening phase whose translocation must be taken into consideration. But the low degradation makes a metabolic transport modifying the translocation parameters questionable. At least for the penetration into the feeding leaf, the differences can be explained by the molecular charge (degree of dissociation). Undissociated water-soluble molecules penetrate more readily than those which are dissociated (LIEN and ROGERS 1977; MORRISON and COHEN 1980). Consequently, an improved uptake efficiency for the protonated form might be a question of formulation (RICHARDSON 1977) and also be influenced by the counter anion. In the first experiments, it could be shown at least that the protonation of EA with organic acids enhanced the uptake rates to an extent which could not be sufficiently explained with the hydrolysis constant of the given compound. The decreased uptake by coldly adapted plants cannot be clearly interpreted, although temperature-induced uptake changes are a wellknown phenomenon (SHARMA and BORN 1978; SCHONHERR et al. 1979; STODDART and WILLIAMS 1980). It cannot be decided whether this is due to the decreased growth rate of the plants, changed cuticula properties, or to a changed penetration across the membranes because the uptake process is a very complex one. It is also still unclear whether the transport occurs in the phloem or in the xylem; a question which could have meaning for the mode of application. According to the ion trapping mechanism by JACOB (JACOB et al. 1973; JACOB and NEUMANN 1983; NEUMANN et al. 1985; GRIMM et al. 1985; JACOB 1985) only those compounds are phloem mobile which are less dissociated in the acid medium of the apoplast than in the alkaline medium of the sieve element-companion cell complex. EA as a base demonstrate the opposite and, like its protonated form, should be expected to be xylem mobile. However, the observed rapid migration out of the fed leaf, the preferential transport to the rapidly growing tillers in the meaning of a source-to-sink transport, and the autoradiographically not detectable accumulation of [14C] on the top of the fed leaf (Fig. 2) indicate, at least in the case of the free base a preferential phloem 3

BPP 183 (1988) 1

33

Fig. 2. Autoradiography of a plant of sprina IJltrley (cv. Lada) to which [l4 CJ-R,1 was applied. Harvest t ime: end of the uptake phasp. From left to right: top of the main shoot, upper part of the main shoot, tiller, root, feeding leaf (arrow marks the application site).

mobility. In addition, the remarkable translocation differences between EA and EAR + point to differences in their mobility, but an exclusive xylem mobility is to be excluded for EAR + as well because a basal transport could be demonstrated. For a better understanding of the mode of t ransport, the translocation quotient (Qtr) was determined b y means of the Sinapis test according to JACOB et a.l. (1973). Corresponding to this both EA forms proved to be ambimobile (Qtr EA = 0.79 ; Qtr EAH + = 0.88), but this explains neither the translocation differences nor the question why the basic EA is not protonated during the apoplast passage. Thus, the possibility of an active and carriermediated transport seems obvious. Some clues for that were found by RIFKIN and F AIRCAlVlB (1985). On the other hand, the approximation in the translocation characteristics of EA and EAR + leading to almost identical translocation patterns in the course of ontogenesis is clearly due to a metabolite transport. Apart from the fact that in the case of the free base a conversion to volatile compounds took place, the metabolism proceeded similarly in both EA forms and led to glycine betaine via choline (ECKERT et al. 1987) which exhibited a marked phloem mobility (LADYMAN et al. 1980). Acknowledgements We thank Prof. Dr. G. SE}IBDNEIt and Dr. C. BERGNER from the Institut fur Biochemic der Pflanzen der AdW der DDR for comments on the manuscript.

34

EPP 183 (1988) 1

References BERGMANN, H. , ECKERT, H., KWHEL, 1\. , nnd ROTH, D.: Der EinfluB von Ethanolamin auf den Kornertrag von Sommergerste bei untcrsthicdlicben klimatiscben Wasserbilanzen. Arcb. Acker- u. Pflanzenbau u. Bodenkd. 27, 127-134 (1983). ECKEHT, H.: D ntersll ebungen ii b er die Wirkung, das Verbaltcn and den Wirkungsmeebanislllus von Trimcthyl-(:2-eblordbyl)-ammoniumthlorid (CCC) nnd N, N-Dimethyl-N-(:2-brometbyl)-bydraziniumbromid (BMH) als Ilalmstabilisatorrn. Di8s., Halle 1973. ECKEHT, H., REISS}LI;>;;>;, P., and BEHGMANN, H.: Mdabolism of [14C]-Monoethanolamin8 in Hordeum vul:Jare. Biochem. PhyS101. Pflanzen 183, 15- :25 (1988). FUJII, K., KOBAYAS III, }I., and T.I K.IH .IsHf, E.: Effeds of organic acids and amines on growth of rice seed lings. VI. Alteration of soil microflora and their metabolism. Nippon Dojo Hiryogokll Zuss ki 43,211-217 (197:2). GHIM~f, E., "XEI:MANN , ST. , and JACOB , F.: Transport of xenobiotits in higb er plants. II. Absorption of Defenuron, Carboxyphen ylmethylurea an d maleic hydra.zidc by isolated conducting tissue of Cyclamen . Biothem. Physiol. Pflanzen ]80, 383-39:2 (1985). HORVATH, J., and nN H .ISSELT, P. R: Inhibition of chilling induced photooxidative dam agl' t() leaves of Cucumis slltiws L. by treatment with amino aleohols. Planta 164, 83- 88 (1985). lLKEH, R., WAlUNG, A. J., BREIDENBACH, R. W., and LYONS, J. M.: A light and electron mieroscopi c study of ehilling injury and its alleviation by ethanolamin e in tomato cotyledons. Plant Physiol. (SIlPpl.) 57,178 (1976). JA COB, F.: Die Allfnahme von Substanz en in das Phlocm-Transportsystem. Colloquia Pflanzellphysiologie del' Humboldt- 1:niversitat ZII Berlin Nr. S (1985). JA COB, F. , and N I·: UU NN , ST. : Quantitative determinat.ion of mobility of xenobiot.ics alld criteria of their phloem and xylem mobility. In: lUPAC Pesticide Cbemistry - Human Welfare and the E nviron ment. Eds. }fIY .\ ~1OTO, J . rt al.; Kyoto 198:2, Vol. 1, pp. 357-36:2, Pergamon Press, Oxford-New York- Toronto-Sydney-Paris-Frankfnrt 1983. JACOB, F., NEnLlxN, ST. , and STHOBEL, D.: Studies on mobility of exogen applied substances in. plants. In: Transniptions of the 3rd Symp. on Accumulation of Nutrients and Heg-ulators in Plant Organism. Warsaw. Procel'd. Res. lnst. Pomology Skierniewicc. Poland, Series E 5, pp. 315-330 (1973). KAMALYAN, G. V.: Wirkung von Ethanolamin und seiner Derivate auf Tiere und Pflanzen. (russ.) Mater Zakawkaz. Nallk. Konf. Vop. ShivotOllvod Ve.1970(PubI.1971), 431 - 4:34. KAMALYAN, G. V., D.IYTY.IX, L. V. , KAZAftYAN, R E. , und N.\TA SHVILI, N. N.: Mcchanismlls der Ethanola minwirkung a.\s Stimulator fiir Wachstum und Ertrag von Kultllrpflanzcn. (a.r men.) IZV Sel'shok Loz. :'lauk 14 (8),43- 50 (1971). L,\J)Y}LlN, J. A. R , HlTz, W. D., and H .IXSOX, A. D.: Translocation and metabolism of glycine b etai neby barley plants in relation to water stress. Planbt 1,)0, 191- 196 (1980). LI EN , R., and ROGEHs, S. K: Uptake of amino aeids by barley leaf slie-es. Physiol. Plant. Copenhagen. 41 , 175- 18il (1977). LIN, W. , and KIUEIl,.T. c.: Peptide alcohols as promotors of nitrate and ammonium uptake in plants .. Plant Physiol. 77, 40il-406 (1985). MIDDLETOX, L ..T., and S,\ U:-IDEHS, J.: The uptake of inorganic ions by plant It'aves. J. expo Bot. Hi, 197- :!1;J(1965). MORR ISON, J. ~., and COHEN, A. S.: Plant uptake, transport and metabolism. The H andbook of Environmental Chemistry. Vol. 2, Part A, 193-:219 (1980). ST, GHUHf, E., and JA con, F.: Transport of xenobiotirs in hi gher plants. I. Structural. prerequisites for translocation in t he plocm. Biochem. Physiol. Pflanzen 180, 257-268 (1985). RI CHARDSON, R G.: A review of foli ar absorption and translocation of 2,4-D and 2,4,5-T. Weed Research 17, 259-272 (1977). RIFKIN, M. R., and FAIRCAMIl, A. H. : Transport of ethanolamine and its incorporation into variant surface glycoprotein of bloodstream forms of Trypanosoma brucci. Mol. Biochcm. Parasitol. 15, 245- 256 (1985).

NEU ~I ANN ,

3*

BPP 183 (1988) 1

35

SCHONHERR, J., EARTH, K., and G]{ULER, H.: Water permeability of plant cuticules. The effect of temperature on diffusion of water. Planta 147, 21-26 (1979). SHAR~L\, 1.1. P., and BORN, W. H.: Penetration of [14C] asulam in wild oat and flax. Meeting of the Weed Seienee Society; Abstr. (1978). STODDA](T, 1. K., and WILLIAMS, P. D.: Interaction of [3H]-gibberellin Al with subcellular fraction from lettuce hypocotyls. Planta 148 485-490 (1980).

Received Sl'ptember 2;1, 198G; revised form accepted March 27,1987 Authors' address: Dr. HANS ECKERT, Dr. HANS BERGMANN and Dr. PETER REISSMANN, Forsehungszentrum fiir Hodenfruchtbarkeit Miinehebcrg der Akademie del' 1andwirtschaftswissenschaften der DDR, Naumburger StraUc 98a, Jena 9, DDR - 6909.

36

BPP 183 (1988) 1