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Aluminium Induced Callose Synthesis in Roots of Soybean (Glycine max L.)
Short Communication
Aluminium Induced Callose Synthesis in Roots of Soybean (Glycine max L.) A. H. WISSEMEIER, F. KLOTZ, and W. J. HORST Institut fur Pflanzenernahrung, Universitat Hohenheim, Postfach 700562, D·7000 Stuttgart 70, Federal Republic of Germany Received December 2,1986· Accepted January 21,1987
Summary In solution culture root elongation of soybean (Glycine max L. cv. Maple Arrow) was inhibited by 93 JLM Al within one hour. Staining of root-tip sections with the fluorochrome Sirofluor showed (1,3)-iS-glucan (callose) formation in the cortex as early as after 30 minutes of Al treatment. Callose formation was confined to the 3 outer layers of cortical cells even after prolonged (28 h) Al treatment.
Key words: Glycine max, aluminium toxicity, {1,3}-iS-glucan, root growth.
Introduction Callose is a polysaccharide containing (1,3)-,B-glucan as the essential component. In higher plants, callose is a constituent of sieve plates, pit fields (Eschrich, 1975), and developing cell plates (Fulcher et al., 1976). The function of callose is thought to be that of a sealing system involved in the regulation of symplastic transport between cells. Also, a regulative role in water uptake has been proposed (Bhalla and Slattery, 1984). In addition to these structural functions callose formation seems to be a general response of plants to mechanical, chemical, and temperature stresses, and infections by fungi and viruses (Fincher and Stone, 1981). Up to date only limited attention has been paid to callose synthesis as a response to nutritional disorders. Increased callose deposition in sieve plates has been described in plants deficient in boron (Van de Venter and Currier, 1977) or treated with toxic concentrations of cobalt, nickel, or zinc (Peterson and Rauser, 1979). Excess boron supply led to callose deposition in discrete areas in bean leaves (McNairn and Currier, 1965). In cowpea leaves, callose formation is a sensitive indicator of manganese toxicity (Wissemeier and Horst, 1987). In the present paper callose formation is demonstrated in roots of soybean plants after short term treatment with aluminium. Materials and Methods Soybean (Glycine max L. cv. Maple Arrow) was grown in a growth chamber at 30 0 /25°C day/night temperatures, 16 h daylength, 150 W m - 2 light intensity and 70 % relative humidity. ]. Plant. Physiol. Vol. 129. pp. 487-492 {1987}
488
A. H. WISSEMEIER, F. KLOTZ, and W. J. HORST
Seeds were germinated for 2 days between filter paper soaked with 1 mM CaS04. The seedlings were then transfered to a constantly aerated nutrient solution (25 plants per 221 plastic pot) of the following composition (JLM): KN0 3 750; Mg(N0 3)2 325; CaS04 250; FeEDDHA 40; KH2P04 10; H 3B03 8; CUS04 0.2; ZnS04 0.2; MnS04 0.2; (NH4)6Mo7024 0.2. After preculture for 16 h at pH 5.5, the pH of the nutrient solution was adjusted to 4.2 with 0.1 N HCI and AI added to half of the pots as AICh to give a concentration of 93 JLM. During the experimental period the pH was kept constant at pH 4.2. The root elongation rate of primary roots was determined by marking the roots with a water resistant black marking pen behind the elongation zone before the onset of the treatments and measuring the distance of the root apex to this mark (accuracy ±0.5 mm) at intervals of 1 h. It was demonstrated that this procedure did not affect root growth. For the histochemical localization of callose the apical 3 cm of primary roots were excised and fixed in (v/v) 70 % ethanol containing 5 % formol and 5 % propionic acid at room temperature for at least 1 day. 5 mm segments were then embedded according to Hermanns and Schulz (1981). Sections, (5 JLm), were cut with a hard metal knife. To eliminate autofluorescence the sections were prestained with periodic acid - Schiff reagent (Smith and McCully, 1978). Callose was detected by fluorescence microscopy (Zeiss Standard, equipped with an epifluorescence unit, mercury vapor lamp, filter combination BP 400 - 440, FT 460, LP 470) on the basis of its Sirofluor fluorescence (Stone et aI., 1984) after incubation of sections with Sirofluor (Biosupplies Melbourne, Australia) 0.003 % (w/v) in 33 mM K3P0 4 (pH 12) for 30 minutes at room temperature.
Results Root elongation rate was a very senSItive indicator of Al tOXICIty in soybean (Fig. 1). As early as 1 h after the beginning of Al treatment there was a significant reduction in root elongation rate compared to the control ( - AI). At about the same Pr ima ry root elongation rate [ mm h - 1] O 4
- AI
D+A I
3
2
~
tI
t'
0 4-~~L,1~-C~'1~-C~,-~~~--~
o
1 Durat i on
of
2
3
4 [h]
A I- treatment
Fig. 1: Effect of AI (93 JLM as AICh) on the elongation rate of primary roots of soybean (cv. Maple Arrow) grown in solution culture (pH 4.2, 250 JLM Ca, 10 JLM P). Vertical bars represent standard deviation (n = 3).
J. Plant. Physiol. Vol.
129. pp. 487-492 {1987}
Aluminium induced callose synthesis in roots
489
5 j ..
.~
. )
c.:.r.": t\ .. . .... . '. ,, ~ -
\
\
/.lr ':.-'· ··· '~ . 'r~ .' , - ' ~.,'.. . ~. .
, ..
.
I
'
I
C'
.
\. .;,
25J.1rr;
' \
.,
Figs. 2-6: Fluorescence micrographs, stained with Sirofluor for (1,3)-J3-glucan (fluorescent material - callose), of longitudinal sections of soybean (cv. Maple Arrow) grown in solution culture without and with Al supply (93 p,M). Fig. 2: Control without Al supply. Fig. 3: 1 h Al supply. Fig. 4: 4 h Al supply. Fig. 5: Close-up of the junction between root cap and root, 21 h Al supply. Fig. 6: Close-up of the cortex 1 mm behind the apex, 4 h Al supply. Fig. 7: Bright field micrograph of Fig. 6.
J Plant. Physiol. Vol. 129. pp. 487-492 (1987)
490
A.
H. WISSEMEIER,
F.
KLOTZ,
and W. J.
HORST
time deposits of material which fluoresced with Sirofluor could be detected in the outer cortical cell layers of root tips treated with Al (Fig. 3), indicating formation of the (1,3)-,6-glucan callose. Fluorescent callose deposits in the cortex were absent in control roots without Al supply (Fig. 2). After 4 h of Al treatment (Fig. 4) callose formation was greater, but still restricted to the outer layers of cortical cells. Cell layers overlaying the cortex, probably derived from the root cap, did not stain for callose (Figs. 6 and 7). Callose deposits could also be found in the root cap and in cells between the root and root cap (Fig. 5). Callose deposits in response to Al treatment were also found in the cortex of differentiated parts of the roots. Again only the 2 to 3 outer cortical cell layers showed callose staining. Prolonged Al treatment up to 28 h did not change the intensity or location of callose deposition. Restriction of callose formation to the outer cortical cell layers was not due to the inability of inner cortical cells to synthesize callose: When root tips were split longitudinally with a razor blade, inner cells produced wound callose (not shown). The callose formation in the root cortex was specific for Al injury. Inhibition of root elongation by B, and Ca deficiencies, or Mn toxicity (1 mM Mn supply up to 28 h) did not induce callose synthesis (not shown). Discussion Induction of (1,3)-,6-glucan (callose) formation in the cortical cell layers of the root is a very sensitive response of soybean to Al supply (Figs. 3 -6). Callose formation might be an even more sensitive response than root elongation (Fig. 1), since first callose deposits could be detected as early as 30 minutes after the beginning of the Al treatment (not shown). (1,3)-,6-glucan synthase is located in the plasma membrane (Anderson and Ray, 1978). Its activity is stimulated by changes of membrane properties such as increased membrane permeability (leakage) following application of polycations (Kohle et aI., 1985), depolarization of transmembrane potential (Bacic and Delmer, 1981), or alterations of membrane architecture Gacob and Northcote, 1985). There is ample evidence that Al alters membrane properties. Viestra and Haug (1978) showed a dramatic decrease of membrane lipid fluidity by Al in Thermoplasma acidophilum. In plasma membrane vesicles of barley roots Al inhibited calmodulin dependent polarization of membrane potential (Siegel and Haug, 1983). Recently Suhayda and Haug (1986) demonstrated decreased M!f+-ATPase activity by Al in plasma membrane-enriched microsomal fractions of maize roots. The effect of Al on membrane function is also evident from studies on K + leakage which may increase (Woolhouse, 1969) or decrease (unpublished results). It is therefore possible that the described induction of callose formation was due to effects of Al on membrane properties. Kauss (1985), from work with soybean suspension cultures, concluded that (1,3)-,6-glucan synthesis is triggered by increased Ca2 + activities in the cytoplasm. If this holds true also for Al induced callose formation in roots, this would indicate that disfunction of the regulation of Ca2 + activity in the cytoplasm rather than the inhibition of Ca uptake is a primary cause of Al injury on roots. This would be compatible
J Plant. Physiol. Vol. 129. pp. 487-492 (1987)
Aluminium induced callose synthesis in roots
491
with results of Horst et ai. (1983), who observed short-term inhibition of root elongation by Al without apparent change in Ca status of cowpea root-tips. AI-induced callose formation was confined to the outer cortical cell layers. This might reflect Al distribution in the roots, as was shown in maize root tips (Bennet et aI., 1985). In contrast to this work with maize in our study with soybean, the root cap was affected later and less than the cortical cells (Figs. 3, 4). This could be due to protection of the root cap by mucilage (Horst et aI., 1982). However, it might also indicate, that in soybean injury of cortical root cells, rather than of root cap cells, was primarily responsible for the effect of Al on root elongation. The lack of callose formation in inner cortical cells even after prolonged exposure of the roots to Al does not necessarily exclude radial Al movement to the stele. Changes in Al speciation due to a higher pH (N supplied as N0 3 -) or the presence of organic complexing agents in the Free Space may have reduced the net charge on Al ions and hence reduced their effect on membrane properties (Kauss and Jeblick, 1985). Acknowledgements The authors are grateful to H. Kauss, Kaiserslautern, for the gift of the fluorochrome Sirofluor, R. Stosser, Stuttgart-Hohenheim, for providing technical support, and C. J. Asher, University of Queensland, Australia, for helpful suggestions concerning the manuscript. We thank the Commission of the European Communities for financial support.
References ANDERSON, R. L. and P. M. RAy: Plant Physio!. 61, 723-730 (1978). BACIC, A. and D. P. DELMER: Planta 152, 346-351 (1981). BENNET, R. J., c. M. BREEN, and M. Y. FEY: S. Afr. J. Plant Soil 2, 1-7 (1985). BHALLA, P. L. and H. D. SLATTERY: Ann. Bot. 53, 125-128 (1984). ESCHRICH, W.: In: ZIMMERMANN, M. H. andJ. A. MILBURN (eds.): Encyclopedia of plant physiology, New Series Vol I, 39-56, Springer-Verlag, Berlin (1975). FINCHER, G. B. and B. A. STONE: In: TANNER, W. and F. A. LOEwus (eds.): Encyclopedia of plant physiology, New Series VoiD B, 110-132, Springer-Verlag, Berlin (1981). FULCHER, R. G., M. E. MCCULLY, G. SETTERFIELD, and J. SUTHERLAND: Can. J. Bot. 54, 539-542 (1976). HERMANNS, W. and L. C. SCHULZ: In: DEICHER, H. and L. C. SCHULZ (eds.): Arthritis models and mechanisms, 137 -143, Springer-Verlag, Berlin (1981). HORST, W. J., A. WAGNER, and H. MARSCHNER: Z. Pflanzenphysio!. 105,435-444 (1982). - - - Z. Pflanzenphysio!. 109,95-103 (1983). JACOB, S. R. and D. H. NORTHCOTE: J. Cell Sci. Supp!. 2, 1-11 (1985). KAUSS, H.: J. Cell Sci. Supp!. 2, 89-103 (1985). KAUSS, H. and W. JEBLICK: FEBS Lett. 185, 226-230 (1985). KOHLE, H., W. JEBLICK, F. POTEN, W. BLASCHEK, and H. KAUSS: Plant Physio!. 77, 544-551 (1985). McNAIRN, R. B. and H. B. CURRIER: Phyton 22, 153 -158 (1965). PETERSON, C. A. and W. E. RAUSER: Plant Physio!. 63, 1170-1174 (1979). SIEGEL, N. and A. HAUG: Physio!. Plant. 59, 285-291 (1983). SMITH, M. M. and E. MCCULLY: Stain Techno!. 53, 79-85 (1978). SUHAYDA, C. G. and A. HAUG: Physio!. Plant. 68, 189-195 (1986). STONE, B. A., N. A. EVANS, I. BONIG, and A. E. CLARKE: Protoplasma 122, 191-195 (1984). VAN DE VENTER, H. A. and H. B. CURIUER: Am. J. Bot. 64, 861-865 (1977).
J Plant. Physiol. Vol. 129. pp. 487-492 (1987)
492
A. H. WISSEMEIER, F. KLOTZ, and W. ]. HORST
VIESTRA, R. and A. HAUG: Biochem. Biophys. Res. Comm. 84, 138-143 (1978). WISSEMEIER, A. H. and W.]. HORST: Plant and Soil, in press (1987). WOOLHOUSE, H. W.: In: RORISON, 1. H. (ed.): Ecological aspects of the mineral nutrition of plants, 357 -380, Blackwell Scientific Publications, Oxford (1969).
J Plant. P/rysiol. Vol. 129. pp. 487-492 (1987)
Aluminium Induced Callose Synthesis in Roots of Soybean (Glycine max L.) A. H. WISSEMEIER, F. KLOTZ, and W. J. HORST Institut fur Pflanzenernahrung, Universitat Hohenheim, Postfach 700562, D·7000 Stuttgart 70, Federal Republic of Germany Received December 2,1986· Accepted January 21,1987
Summary In solution culture root elongation of soybean (Glycine max L. cv. Maple Arrow) was inhibited by 93 JLM Al within one hour. Staining of root-tip sections with the fluorochrome Sirofluor showed (1,3)-iS-glucan (callose) formation in the cortex as early as after 30 minutes of Al treatment. Callose formation was confined to the 3 outer layers of cortical cells even after prolonged (28 h) Al treatment.
Key words: Glycine max, aluminium toxicity, {1,3}-iS-glucan, root growth.
Introduction Callose is a polysaccharide containing (1,3)-,B-glucan as the essential component. In higher plants, callose is a constituent of sieve plates, pit fields (Eschrich, 1975), and developing cell plates (Fulcher et al., 1976). The function of callose is thought to be that of a sealing system involved in the regulation of symplastic transport between cells. Also, a regulative role in water uptake has been proposed (Bhalla and Slattery, 1984). In addition to these structural functions callose formation seems to be a general response of plants to mechanical, chemical, and temperature stresses, and infections by fungi and viruses (Fincher and Stone, 1981). Up to date only limited attention has been paid to callose synthesis as a response to nutritional disorders. Increased callose deposition in sieve plates has been described in plants deficient in boron (Van de Venter and Currier, 1977) or treated with toxic concentrations of cobalt, nickel, or zinc (Peterson and Rauser, 1979). Excess boron supply led to callose deposition in discrete areas in bean leaves (McNairn and Currier, 1965). In cowpea leaves, callose formation is a sensitive indicator of manganese toxicity (Wissemeier and Horst, 1987). In the present paper callose formation is demonstrated in roots of soybean plants after short term treatment with aluminium. Materials and Methods Soybean (Glycine max L. cv. Maple Arrow) was grown in a growth chamber at 30 0 /25°C day/night temperatures, 16 h daylength, 150 W m - 2 light intensity and 70 % relative humidity. ]. Plant. Physiol. Vol. 129. pp. 487-492 {1987}
488
A. H. WISSEMEIER, F. KLOTZ, and W. J. HORST
Seeds were germinated for 2 days between filter paper soaked with 1 mM CaS04. The seedlings were then transfered to a constantly aerated nutrient solution (25 plants per 221 plastic pot) of the following composition (JLM): KN0 3 750; Mg(N0 3)2 325; CaS04 250; FeEDDHA 40; KH2P04 10; H 3B03 8; CUS04 0.2; ZnS04 0.2; MnS04 0.2; (NH4)6Mo7024 0.2. After preculture for 16 h at pH 5.5, the pH of the nutrient solution was adjusted to 4.2 with 0.1 N HCI and AI added to half of the pots as AICh to give a concentration of 93 JLM. During the experimental period the pH was kept constant at pH 4.2. The root elongation rate of primary roots was determined by marking the roots with a water resistant black marking pen behind the elongation zone before the onset of the treatments and measuring the distance of the root apex to this mark (accuracy ±0.5 mm) at intervals of 1 h. It was demonstrated that this procedure did not affect root growth. For the histochemical localization of callose the apical 3 cm of primary roots were excised and fixed in (v/v) 70 % ethanol containing 5 % formol and 5 % propionic acid at room temperature for at least 1 day. 5 mm segments were then embedded according to Hermanns and Schulz (1981). Sections, (5 JLm), were cut with a hard metal knife. To eliminate autofluorescence the sections were prestained with periodic acid - Schiff reagent (Smith and McCully, 1978). Callose was detected by fluorescence microscopy (Zeiss Standard, equipped with an epifluorescence unit, mercury vapor lamp, filter combination BP 400 - 440, FT 460, LP 470) on the basis of its Sirofluor fluorescence (Stone et aI., 1984) after incubation of sections with Sirofluor (Biosupplies Melbourne, Australia) 0.003 % (w/v) in 33 mM K3P0 4 (pH 12) for 30 minutes at room temperature.
Results Root elongation rate was a very senSItive indicator of Al tOXICIty in soybean (Fig. 1). As early as 1 h after the beginning of Al treatment there was a significant reduction in root elongation rate compared to the control ( - AI). At about the same Pr ima ry root elongation rate [ mm h - 1] O 4
- AI
D+A I
3
2
~
tI
t'
0 4-~~L,1~-C~'1~-C~,-~~~--~
o
1 Durat i on
of
2
3
4 [h]
A I- treatment
Fig. 1: Effect of AI (93 JLM as AICh) on the elongation rate of primary roots of soybean (cv. Maple Arrow) grown in solution culture (pH 4.2, 250 JLM Ca, 10 JLM P). Vertical bars represent standard deviation (n = 3).
J. Plant. Physiol. Vol.
129. pp. 487-492 {1987}
Aluminium induced callose synthesis in roots
489
5 j ..
.~
. )
c.:.r.": t\ .. . .... . '. ,, ~ -
\
\
/.lr ':.-'· ··· '~ . 'r~ .' , - ' ~.,'.. . ~. .
, ..
.
I
'
I
C'
.
\. .;,
25J.1rr;
' \
.,
Figs. 2-6: Fluorescence micrographs, stained with Sirofluor for (1,3)-J3-glucan (fluorescent material - callose), of longitudinal sections of soybean (cv. Maple Arrow) grown in solution culture without and with Al supply (93 p,M). Fig. 2: Control without Al supply. Fig. 3: 1 h Al supply. Fig. 4: 4 h Al supply. Fig. 5: Close-up of the junction between root cap and root, 21 h Al supply. Fig. 6: Close-up of the cortex 1 mm behind the apex, 4 h Al supply. Fig. 7: Bright field micrograph of Fig. 6.
J Plant. Physiol. Vol. 129. pp. 487-492 (1987)
490
A.
H. WISSEMEIER,
F.
KLOTZ,
and W. J.
HORST
time deposits of material which fluoresced with Sirofluor could be detected in the outer cortical cell layers of root tips treated with Al (Fig. 3), indicating formation of the (1,3)-,6-glucan callose. Fluorescent callose deposits in the cortex were absent in control roots without Al supply (Fig. 2). After 4 h of Al treatment (Fig. 4) callose formation was greater, but still restricted to the outer layers of cortical cells. Cell layers overlaying the cortex, probably derived from the root cap, did not stain for callose (Figs. 6 and 7). Callose deposits could also be found in the root cap and in cells between the root and root cap (Fig. 5). Callose deposits in response to Al treatment were also found in the cortex of differentiated parts of the roots. Again only the 2 to 3 outer cortical cell layers showed callose staining. Prolonged Al treatment up to 28 h did not change the intensity or location of callose deposition. Restriction of callose formation to the outer cortical cell layers was not due to the inability of inner cortical cells to synthesize callose: When root tips were split longitudinally with a razor blade, inner cells produced wound callose (not shown). The callose formation in the root cortex was specific for Al injury. Inhibition of root elongation by B, and Ca deficiencies, or Mn toxicity (1 mM Mn supply up to 28 h) did not induce callose synthesis (not shown). Discussion Induction of (1,3)-,6-glucan (callose) formation in the cortical cell layers of the root is a very sensitive response of soybean to Al supply (Figs. 3 -6). Callose formation might be an even more sensitive response than root elongation (Fig. 1), since first callose deposits could be detected as early as 30 minutes after the beginning of the Al treatment (not shown). (1,3)-,6-glucan synthase is located in the plasma membrane (Anderson and Ray, 1978). Its activity is stimulated by changes of membrane properties such as increased membrane permeability (leakage) following application of polycations (Kohle et aI., 1985), depolarization of transmembrane potential (Bacic and Delmer, 1981), or alterations of membrane architecture Gacob and Northcote, 1985). There is ample evidence that Al alters membrane properties. Viestra and Haug (1978) showed a dramatic decrease of membrane lipid fluidity by Al in Thermoplasma acidophilum. In plasma membrane vesicles of barley roots Al inhibited calmodulin dependent polarization of membrane potential (Siegel and Haug, 1983). Recently Suhayda and Haug (1986) demonstrated decreased M!f+-ATPase activity by Al in plasma membrane-enriched microsomal fractions of maize roots. The effect of Al on membrane function is also evident from studies on K + leakage which may increase (Woolhouse, 1969) or decrease (unpublished results). It is therefore possible that the described induction of callose formation was due to effects of Al on membrane properties. Kauss (1985), from work with soybean suspension cultures, concluded that (1,3)-,6-glucan synthesis is triggered by increased Ca2 + activities in the cytoplasm. If this holds true also for Al induced callose formation in roots, this would indicate that disfunction of the regulation of Ca2 + activity in the cytoplasm rather than the inhibition of Ca uptake is a primary cause of Al injury on roots. This would be compatible
J Plant. Physiol. Vol. 129. pp. 487-492 (1987)
Aluminium induced callose synthesis in roots
491
with results of Horst et ai. (1983), who observed short-term inhibition of root elongation by Al without apparent change in Ca status of cowpea root-tips. AI-induced callose formation was confined to the outer cortical cell layers. This might reflect Al distribution in the roots, as was shown in maize root tips (Bennet et aI., 1985). In contrast to this work with maize in our study with soybean, the root cap was affected later and less than the cortical cells (Figs. 3, 4). This could be due to protection of the root cap by mucilage (Horst et aI., 1982). However, it might also indicate, that in soybean injury of cortical root cells, rather than of root cap cells, was primarily responsible for the effect of Al on root elongation. The lack of callose formation in inner cortical cells even after prolonged exposure of the roots to Al does not necessarily exclude radial Al movement to the stele. Changes in Al speciation due to a higher pH (N supplied as N0 3 -) or the presence of organic complexing agents in the Free Space may have reduced the net charge on Al ions and hence reduced their effect on membrane properties (Kauss and Jeblick, 1985). Acknowledgements The authors are grateful to H. Kauss, Kaiserslautern, for the gift of the fluorochrome Sirofluor, R. Stosser, Stuttgart-Hohenheim, for providing technical support, and C. J. Asher, University of Queensland, Australia, for helpful suggestions concerning the manuscript. We thank the Commission of the European Communities for financial support.
References ANDERSON, R. L. and P. M. RAy: Plant Physio!. 61, 723-730 (1978). BACIC, A. and D. P. DELMER: Planta 152, 346-351 (1981). BENNET, R. J., c. M. BREEN, and M. Y. FEY: S. Afr. J. Plant Soil 2, 1-7 (1985). BHALLA, P. L. and H. D. SLATTERY: Ann. Bot. 53, 125-128 (1984). ESCHRICH, W.: In: ZIMMERMANN, M. H. andJ. A. MILBURN (eds.): Encyclopedia of plant physiology, New Series Vol I, 39-56, Springer-Verlag, Berlin (1975). FINCHER, G. B. and B. A. STONE: In: TANNER, W. and F. A. LOEwus (eds.): Encyclopedia of plant physiology, New Series VoiD B, 110-132, Springer-Verlag, Berlin (1981). FULCHER, R. G., M. E. MCCULLY, G. SETTERFIELD, and J. SUTHERLAND: Can. J. Bot. 54, 539-542 (1976). HERMANNS, W. and L. C. SCHULZ: In: DEICHER, H. and L. C. SCHULZ (eds.): Arthritis models and mechanisms, 137 -143, Springer-Verlag, Berlin (1981). HORST, W. J., A. WAGNER, and H. MARSCHNER: Z. Pflanzenphysio!. 105,435-444 (1982). - - - Z. Pflanzenphysio!. 109,95-103 (1983). JACOB, S. R. and D. H. NORTHCOTE: J. Cell Sci. Supp!. 2, 1-11 (1985). KAUSS, H.: J. Cell Sci. Supp!. 2, 89-103 (1985). KAUSS, H. and W. JEBLICK: FEBS Lett. 185, 226-230 (1985). KOHLE, H., W. JEBLICK, F. POTEN, W. BLASCHEK, and H. KAUSS: Plant Physio!. 77, 544-551 (1985). McNAIRN, R. B. and H. B. CURRIER: Phyton 22, 153 -158 (1965). PETERSON, C. A. and W. E. RAUSER: Plant Physio!. 63, 1170-1174 (1979). SIEGEL, N. and A. HAUG: Physio!. Plant. 59, 285-291 (1983). SMITH, M. M. and E. MCCULLY: Stain Techno!. 53, 79-85 (1978). SUHAYDA, C. G. and A. HAUG: Physio!. Plant. 68, 189-195 (1986). STONE, B. A., N. A. EVANS, I. BONIG, and A. E. CLARKE: Protoplasma 122, 191-195 (1984). VAN DE VENTER, H. A. and H. B. CURIUER: Am. J. Bot. 64, 861-865 (1977).
J Plant. Physiol. Vol. 129. pp. 487-492 (1987)
492
A. H. WISSEMEIER, F. KLOTZ, and W. ]. HORST
VIESTRA, R. and A. HAUG: Biochem. Biophys. Res. Comm. 84, 138-143 (1978). WISSEMEIER, A. H. and W.]. HORST: Plant and Soil, in press (1987). WOOLHOUSE, H. W.: In: RORISON, 1. H. (ed.): Ecological aspects of the mineral nutrition of plants, 357 -380, Blackwell Scientific Publications, Oxford (1969).
J Plant. P/rysiol. Vol. 129. pp. 487-492 (1987)