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The content of N-malonyl-D-tryptophan in wheat seedlings
Plant Science, 88 (1993) 121-124 Elsevier Scientific Publishers Ireland Ltd.
121
The content of N-malonyl-D-tryptophan in wheat seedlings K i m Z. G a m b u r g , Olga V. G l u z d o a n d N a t a l y a I. R e k o s l a v s k a y a Institute of Plant Physiology and Biochemistry, Siberian Branch of the Russian Academy of Sciences, 664033 lrkutsk (Russia) (Received March 23rd, 1992; revision received September 16th, 1992; accepted September 21st, 1992)
N-Malonyl-D-tryptophan (MTry) and L-tryptophan (L-Try) were not found in dry wheat seeds, but appeared and accumulated during their germination. Seedlings of Triticum aestivum L. (all varieties studied) and T. dicoccum L. contained MTry, whereas MTry was absent in seedlings of T. monococcum L. More than 90% of total MTry of the seedling located in the coleoptile and remaining amount was found in roots. Maximum contents of MTry in coleoptiles was observed at the 6th day after imbibition. The illumination of seedlings caused inhibition of growth of the coleoptiles and retardation of MTry accumulation. Growth of wheat seedlings from isolated embryos on the Norstog's medium was greatly reduced as compared with the growth of seedlings from intact seeds. MTry was not found in seedlings grown from isolated embryos. Addition of L-Try or o-Try into the medium resulted in the appearance of MTry in these seedlings, but their growth was not restored. It is assumed that MTry synthesis in wheat seedlings is regulated not only on the level of enzyme (racemase and N-malonyl-transferase) activity, but also on the level of substrate (L-Try) concentration.
Key words: wheat; germination; N-malonyl-D-tryptophan; tryptophan
Introduction
Many plants are capable of synthesizing D-Try and its accumulation in the form of MTry [1,2]. However, the physiological role of this phenomenon remains unknown. We have previously reported that seeds and seedlings of some plants contained MTry and that the content of MTry changed during the germination of tomato seeds and the growth of tomato seedlings [3]. Also, it was reported that MTry was absent in the seeds and appeared in the seedlings of wheat. Wheat is the most important crop in agriculture. Growth and productivity of crops depend to some extent on seed germination and initial growth of seedlings. Therefore, detection of the formation of m a l o n y l a t e d D - T r y accompanying germination of wheat seeds reported previously [3] needs further Correspondence to: K.Z. Gamburg, Institute of Plant Physiology and Biochemistry, Siberian Branch of the Russian Academy of Sciences, 664033 Irkutsk, P.O. Box 1243, Russia. Abbreviations: Try, tryptophan; MTry, N-malonyl-o-tryptophan.
investigation. In this work we report the changes in MTry and L-Try contents during germination of wheat seeds. Materials and Methods
The seeds of Triticum monococcum L. (line 13032, Yugoslavia), T. dicoccum L. (line A14035, Armenia), both from the collection of the Vavilov Institute of Plant Growing (St. Peterburg), T. aestivum L. (spring varieties from the collection of the Irkutsk Agricultural Institute and winter varieties from the collection of the Institute of Cytology and Genetics, Siberian Branch of the Russian Academy of Sciences, Novosibirsk) were used in the work. The seeds were imbibed for 1 h in running water and germinated on moistened filter paper at 25°C in darkness. Some seedlings were illuminated continuously with fluorescent tubes (10 W • m ) following 3-day germination in darkness. Embryos were isolated from dry seeds and treated for 20 min with a 4% solution of hydrogen peroxide for sterilization. Six embryos
0168-9452/93/$06.00 © 1993 Elsevier Scientific Publishers Ireland Ltd. Printed and Published in Ireland
122 Table I. The content of MTry in 5-day-old etiolated wheat seedlings Species
Lines and varieties
MTry (nmol/seedling)
T. monococcum L. T. dicoccum L. T. aestivum L.
13032 (Yugoslavia) A14035 (Armenia) Angara (spring) Tulunskaya (spring) Erythrospermum 172 (winter) Albidum 152 (winter) Skala (spring) Velutinum 158 (winter) Lutescens 198 (winter) Rannyaya 12 (spring) Skorospelaya 1 (spring)
0 1.42 + 5.89 + 5.58 + 5.01 +
0.10 0.18 0.20 0.33
4,70 4.54 3,85 3.54 3.23 2.97
0.31 1.02 0.25 0.24 0.29 0.35
+ + + + + +
were placed in each conical flask (100 ml) with 20 ml of the Norstog's medium [4] without amino acids. Germination was performed at 25°C in darkness. L-Try or D-Try were added in some flasks before autoclaving. MTry and L-Try were extracted and determined as described previously [3,51. In some experiments coleoptiles were dissected on three parts equal in length before the analysis. Each sample consisted of 200-300 seedlings. The experiments were repeated 2-3 times. The data presented in the tables are the means of the experiments with their statistical errors.
Table H.
Results
As shown in Table I, MTry was found in seedlings of T. dicoccum L. and T. aestivum L., but was not found in seedlings of T. monococcum L. MTry was observed in seedlings of all varieties of T. asetivum L. The maximum content of MTry (in seedlings of cv. Angara) was two times greater than the minimum content (in seedlings of cv. Skorospelaya 1). There were no reliable differences in MTry content between the spring and winter varieties. The data presented in Table II show that more than 90% of all MTry of the seedling was located in the coleoptile; the remaining amount was found in the roots. Transition area (scutellar node) and kernel contained only traces of MTry.The true leaves did not contain MTry. The content of MTry per 1 g fresh weight increased slightly from the apex to the base of the coleoptile. L-Try was found in all parts of wheat seedling and no significant differences in the L-Try content were observed between them. MTry was not found either in the coleoptiles (Table III) or in the roots during the first two days of germination. The amount of MTry in the coleoptiles increased during the following days and reached a maximum by the 6th day The growth of the coleoptile ceased by this time. Illumination of seedlings stopped the growth of coleoptiles and retarded the accumulation of MTry. The illumination did not affect L-Try accumulation in the coleoptiles.
Contents of MTry and L-Try in different parts of 5-day-old dark-grown wheat seedlings (cv. Skala).
Seedling parts
Fresh weight (rag)
Coleoptile Whole Upper part Middle part Lower part True leaves Roots
76 + 19 + 28 + 29 + 23 + 49 +
1 1 1 0 1 2
MTry
L-Try
nmol/g fresh wt.
nmol/seedling
nmol/g fresh wt.
nmol/seedling
101 + 76 + 103 + ! 16 + 0 15 +
7.73 + 1.49 + 2.88 + 3.36 + 0 0.72 +
417 + 288 + 464 + 462 + 366 + 336 +
32.0 + 1.8 5.6 + 0.4 13.0+0.1 13.4 + 0.4 8.4 + 1.2 16.5 + 2.9
12 5 11 2 4
0.92 0.10 0.31 0.06 0.20
24 20 4 13 53 60
123 Table m . Days
2 3 4 5 6 7
Time-course of growth, MTry and L-Try accumulation in coleoptiles of wheat seedlings (cv. Skala) Length (ram)
MTry (nmol/100 coleoptiles)
L-Try (nmol/100 coleoptiles)
Darkness
Light
Darkness
Light
Darkness
Light
5+ 1 35+ 1 67+ 2 77+ 5 81+ 9 83+11
--43+7 44+1 46+1 44+5
Traces 219+ 55 387+ 28 454+102 819+ 73 572+ 69
--216+ 38 235+ 35 478+138 469+ 19
Traces 343+ 39 1278+196 1008+ 56 935+185 1524+ 182
---1138+166 1480+ 47 641+100 1461+166
Fresh weight of isolated wheat seedling grown on the synthetic medium for 7 days was 35 mg, whereas that of the intact one was 158 rag. As shown in Table IV, additions of L-Try or D-Try in culture medium did not increase the growth of isolated seedlings, whereas IAA significantly reduced the fresh weight and coleoptile length of such seedlings. Growth abnormalities (twisted and swelled coleoptiles) and an additional number of roots were observed in seedlings grown in the presence of L-Try, D-Try or IAA. MTry was not found in isolated wheat seedlings grown for 14 days on the medium without Try. Inclusion of DTry into the medium led to accumulation of MTry (13.71+ 1.40 nmol/seedling, 4 0 2 + 4 0 nmol/g fresh wt.). It may be assumed that the isolated seedlings have the ability to malonylate D-Try. When such seedlings were grown in the presence of L-Try in the medium, MTry also appeared, but in less amount than in the presence of D-Try (5.78 + 0.58 nmol/seedling, 84 + 8 nmol/g fresh wt.). L-Try and D-Try did not restore the growth of isolated seedlings (Table IV). Table IV. Effects of L-Try (25 mg • din-l), o-Try (25 mg • dln -1) and IAA (1 mg . dm -l) on wheat (cv. Skala) seedlings grown from isolated embryos for 14 days Variants
Fresh weight (mg/seedling)
Length of coleoptile
Root no./ seedling
(m_m) Control L-T~ o-Try IAA
65+5 77+6 67+1 47+6
16+7 23+1 13+2 3+2
4.1+0.9 6.0+0.1 7.6+0.1 5.6+0.1
As shown in Table V, the content of endogenous
L-Try in the isolated seedlings was 3.5 times less than in intact seedlings, but greatly increased when isolated seedlings were grown on the medium with L-Try. The absence of MTry in isolated seedlings may be assumed to be caused by insufficient level of L-Try. Discussion
It may be concluded that regular changes in MTry content occured during germination of the wheat seed; this has been shown previously in tomato seedlings [3]. These data indicate a relationship between the MTry synthesis and the growth of coleoptiles (wheat) or hypocotyls (tomato). The simultaneous decrease of growth and MTry accumulation in these organs under the effect of illumination, which was observed both in tomato and in wheat, may be considered as further evidence of this relationship. It should be noted that the greatest amounts of MTry were found in the tomato hypocotyl and wheat coleoptile. In both cases they are nonphotosynthesizing organs with limited growth which is inhibited by the illumination. No prevailing localization of MTry in the upper part of the wheat coleoptile (where auxin synthesis proceeds) was observed. But the most MTry and IAA were found in the uppermost part of the tomato hypocotyl [3]. Thus, the relationship between the MTry synthesis and IAA synthesis seems to be problematic in the wheat coleoptiles. In addition, it may be noted that L-Try and D-Try exerted auxin-like effects on isolated wheat seedlings
124 Table V.
Contents of MTry and L-Tryin 5-day-old intact and 14-day isolated wheat seedlings (cv. Skala)
Variants
Isolated seedlings Isolated seedlings on the medium with L-Try (50 raM) Intact seedlings
MTry
L-Try
nmol/seedling
nmol/g fresh wt.
nmol/seedling
nmol/g fresh wt.
0 0.95 + 0.10
0 52 + 6
4.1 + 0.1 95 + 12
134 + 8 2930 + 360
5.27 + 0.62
38 + 5
69 + 9
(Table IV) and induce MTry accumulation in them, but did not restore their growth. MTry was found in the roots of wheat seedlings in contrast to tomato seedlings where MTry was absent in the roots [31. Elliott [6] also reported on the presence of MTry in the roots of wheat seedlings. MTry was not found in true leaves of the wheat seedling. Furthermore green leaves of adult wheat plants did not contain MTry, it appeared in them only during wilting [4]. As shown previously, L-Try is a precursor of MTry (with D-Try as an intermediate) in wilted tomato leaves [7] Experiments with isolated wheat seedlings showed that the formation of MTry was restored due to L-Try administration into the medium. These data support a possible role of LTry as the precursor of MTry synthesis. It may be assumed that the formation of MTry is regulated in some cases not only at the level of enzyme (racemase and N-malonyltransferase) activity, but also at the level of substrate (L-Try) concentration in plant tissues.
480 + 58
References 1 T. Robinson, ~Amino acids in higher plants. Life Sci., 19 (1976) 1097-1102. 2 K.Z. Gamburg and N.I. Rekoslavskaya, The formation and functions of N-malonyl-~-tryptophan in plants. Uspechi sovremennoi biologii (Moscow), 100 (1985) 44-50. 3 K.Z. Gamburg, O.V. Gluzdo and N.I. Rekoslavskaya, The content of N-malonyi-D-tryptophan in seeds and seedlings of plants. Plant Sci., 77 (1991) 149-153. 4 N.I. Rekoslavskaya, T.A. Markova and K.Z. Gamburg, Appearance of N-malonyI-D-tryptophan in plant leaves during wilting. I. The content of tryptophan and Nmalonyl-D-tryptophan as affected by water deficit. J. Plant Physiol., 132 (1988) 86-89. 5 K. Norstog, New synthetic medium for the culture of premature barley embryos. In Vitro, 8 (1973) 307-308. 6 M.C. Elliott, t~-N-Malonyl-D-tryptophan in seedling wheat roots. New Phytol., 70 (1971) 1005-1015. 7 T.A. Markova, N.I. Rekoslavskaya and K.Z. Gamburg, The induction of transformation of L-tryptophan to Dtryptophan due to wilting of tomato leaves. Fisiol. Rast., (Moscow) 37 (1990) 748-755.
121
The content of N-malonyl-D-tryptophan in wheat seedlings K i m Z. G a m b u r g , Olga V. G l u z d o a n d N a t a l y a I. R e k o s l a v s k a y a Institute of Plant Physiology and Biochemistry, Siberian Branch of the Russian Academy of Sciences, 664033 lrkutsk (Russia) (Received March 23rd, 1992; revision received September 16th, 1992; accepted September 21st, 1992)
N-Malonyl-D-tryptophan (MTry) and L-tryptophan (L-Try) were not found in dry wheat seeds, but appeared and accumulated during their germination. Seedlings of Triticum aestivum L. (all varieties studied) and T. dicoccum L. contained MTry, whereas MTry was absent in seedlings of T. monococcum L. More than 90% of total MTry of the seedling located in the coleoptile and remaining amount was found in roots. Maximum contents of MTry in coleoptiles was observed at the 6th day after imbibition. The illumination of seedlings caused inhibition of growth of the coleoptiles and retardation of MTry accumulation. Growth of wheat seedlings from isolated embryos on the Norstog's medium was greatly reduced as compared with the growth of seedlings from intact seeds. MTry was not found in seedlings grown from isolated embryos. Addition of L-Try or o-Try into the medium resulted in the appearance of MTry in these seedlings, but their growth was not restored. It is assumed that MTry synthesis in wheat seedlings is regulated not only on the level of enzyme (racemase and N-malonyl-transferase) activity, but also on the level of substrate (L-Try) concentration.
Key words: wheat; germination; N-malonyl-D-tryptophan; tryptophan
Introduction
Many plants are capable of synthesizing D-Try and its accumulation in the form of MTry [1,2]. However, the physiological role of this phenomenon remains unknown. We have previously reported that seeds and seedlings of some plants contained MTry and that the content of MTry changed during the germination of tomato seeds and the growth of tomato seedlings [3]. Also, it was reported that MTry was absent in the seeds and appeared in the seedlings of wheat. Wheat is the most important crop in agriculture. Growth and productivity of crops depend to some extent on seed germination and initial growth of seedlings. Therefore, detection of the formation of m a l o n y l a t e d D - T r y accompanying germination of wheat seeds reported previously [3] needs further Correspondence to: K.Z. Gamburg, Institute of Plant Physiology and Biochemistry, Siberian Branch of the Russian Academy of Sciences, 664033 Irkutsk, P.O. Box 1243, Russia. Abbreviations: Try, tryptophan; MTry, N-malonyl-o-tryptophan.
investigation. In this work we report the changes in MTry and L-Try contents during germination of wheat seeds. Materials and Methods
The seeds of Triticum monococcum L. (line 13032, Yugoslavia), T. dicoccum L. (line A14035, Armenia), both from the collection of the Vavilov Institute of Plant Growing (St. Peterburg), T. aestivum L. (spring varieties from the collection of the Irkutsk Agricultural Institute and winter varieties from the collection of the Institute of Cytology and Genetics, Siberian Branch of the Russian Academy of Sciences, Novosibirsk) were used in the work. The seeds were imbibed for 1 h in running water and germinated on moistened filter paper at 25°C in darkness. Some seedlings were illuminated continuously with fluorescent tubes (10 W • m ) following 3-day germination in darkness. Embryos were isolated from dry seeds and treated for 20 min with a 4% solution of hydrogen peroxide for sterilization. Six embryos
0168-9452/93/$06.00 © 1993 Elsevier Scientific Publishers Ireland Ltd. Printed and Published in Ireland
122 Table I. The content of MTry in 5-day-old etiolated wheat seedlings Species
Lines and varieties
MTry (nmol/seedling)
T. monococcum L. T. dicoccum L. T. aestivum L.
13032 (Yugoslavia) A14035 (Armenia) Angara (spring) Tulunskaya (spring) Erythrospermum 172 (winter) Albidum 152 (winter) Skala (spring) Velutinum 158 (winter) Lutescens 198 (winter) Rannyaya 12 (spring) Skorospelaya 1 (spring)
0 1.42 + 5.89 + 5.58 + 5.01 +
0.10 0.18 0.20 0.33
4,70 4.54 3,85 3.54 3.23 2.97
0.31 1.02 0.25 0.24 0.29 0.35
+ + + + + +
were placed in each conical flask (100 ml) with 20 ml of the Norstog's medium [4] without amino acids. Germination was performed at 25°C in darkness. L-Try or D-Try were added in some flasks before autoclaving. MTry and L-Try were extracted and determined as described previously [3,51. In some experiments coleoptiles were dissected on three parts equal in length before the analysis. Each sample consisted of 200-300 seedlings. The experiments were repeated 2-3 times. The data presented in the tables are the means of the experiments with their statistical errors.
Table H.
Results
As shown in Table I, MTry was found in seedlings of T. dicoccum L. and T. aestivum L., but was not found in seedlings of T. monococcum L. MTry was observed in seedlings of all varieties of T. asetivum L. The maximum content of MTry (in seedlings of cv. Angara) was two times greater than the minimum content (in seedlings of cv. Skorospelaya 1). There were no reliable differences in MTry content between the spring and winter varieties. The data presented in Table II show that more than 90% of all MTry of the seedling was located in the coleoptile; the remaining amount was found in the roots. Transition area (scutellar node) and kernel contained only traces of MTry.The true leaves did not contain MTry. The content of MTry per 1 g fresh weight increased slightly from the apex to the base of the coleoptile. L-Try was found in all parts of wheat seedling and no significant differences in the L-Try content were observed between them. MTry was not found either in the coleoptiles (Table III) or in the roots during the first two days of germination. The amount of MTry in the coleoptiles increased during the following days and reached a maximum by the 6th day The growth of the coleoptile ceased by this time. Illumination of seedlings stopped the growth of coleoptiles and retarded the accumulation of MTry. The illumination did not affect L-Try accumulation in the coleoptiles.
Contents of MTry and L-Try in different parts of 5-day-old dark-grown wheat seedlings (cv. Skala).
Seedling parts
Fresh weight (rag)
Coleoptile Whole Upper part Middle part Lower part True leaves Roots
76 + 19 + 28 + 29 + 23 + 49 +
1 1 1 0 1 2
MTry
L-Try
nmol/g fresh wt.
nmol/seedling
nmol/g fresh wt.
nmol/seedling
101 + 76 + 103 + ! 16 + 0 15 +
7.73 + 1.49 + 2.88 + 3.36 + 0 0.72 +
417 + 288 + 464 + 462 + 366 + 336 +
32.0 + 1.8 5.6 + 0.4 13.0+0.1 13.4 + 0.4 8.4 + 1.2 16.5 + 2.9
12 5 11 2 4
0.92 0.10 0.31 0.06 0.20
24 20 4 13 53 60
123 Table m . Days
2 3 4 5 6 7
Time-course of growth, MTry and L-Try accumulation in coleoptiles of wheat seedlings (cv. Skala) Length (ram)
MTry (nmol/100 coleoptiles)
L-Try (nmol/100 coleoptiles)
Darkness
Light
Darkness
Light
Darkness
Light
5+ 1 35+ 1 67+ 2 77+ 5 81+ 9 83+11
--43+7 44+1 46+1 44+5
Traces 219+ 55 387+ 28 454+102 819+ 73 572+ 69
--216+ 38 235+ 35 478+138 469+ 19
Traces 343+ 39 1278+196 1008+ 56 935+185 1524+ 182
---1138+166 1480+ 47 641+100 1461+166
Fresh weight of isolated wheat seedling grown on the synthetic medium for 7 days was 35 mg, whereas that of the intact one was 158 rag. As shown in Table IV, additions of L-Try or D-Try in culture medium did not increase the growth of isolated seedlings, whereas IAA significantly reduced the fresh weight and coleoptile length of such seedlings. Growth abnormalities (twisted and swelled coleoptiles) and an additional number of roots were observed in seedlings grown in the presence of L-Try, D-Try or IAA. MTry was not found in isolated wheat seedlings grown for 14 days on the medium without Try. Inclusion of DTry into the medium led to accumulation of MTry (13.71+ 1.40 nmol/seedling, 4 0 2 + 4 0 nmol/g fresh wt.). It may be assumed that the isolated seedlings have the ability to malonylate D-Try. When such seedlings were grown in the presence of L-Try in the medium, MTry also appeared, but in less amount than in the presence of D-Try (5.78 + 0.58 nmol/seedling, 84 + 8 nmol/g fresh wt.). L-Try and D-Try did not restore the growth of isolated seedlings (Table IV). Table IV. Effects of L-Try (25 mg • din-l), o-Try (25 mg • dln -1) and IAA (1 mg . dm -l) on wheat (cv. Skala) seedlings grown from isolated embryos for 14 days Variants
Fresh weight (mg/seedling)
Length of coleoptile
Root no./ seedling
(m_m) Control L-T~ o-Try IAA
65+5 77+6 67+1 47+6
16+7 23+1 13+2 3+2
4.1+0.9 6.0+0.1 7.6+0.1 5.6+0.1
As shown in Table V, the content of endogenous
L-Try in the isolated seedlings was 3.5 times less than in intact seedlings, but greatly increased when isolated seedlings were grown on the medium with L-Try. The absence of MTry in isolated seedlings may be assumed to be caused by insufficient level of L-Try. Discussion
It may be concluded that regular changes in MTry content occured during germination of the wheat seed; this has been shown previously in tomato seedlings [3]. These data indicate a relationship between the MTry synthesis and the growth of coleoptiles (wheat) or hypocotyls (tomato). The simultaneous decrease of growth and MTry accumulation in these organs under the effect of illumination, which was observed both in tomato and in wheat, may be considered as further evidence of this relationship. It should be noted that the greatest amounts of MTry were found in the tomato hypocotyl and wheat coleoptile. In both cases they are nonphotosynthesizing organs with limited growth which is inhibited by the illumination. No prevailing localization of MTry in the upper part of the wheat coleoptile (where auxin synthesis proceeds) was observed. But the most MTry and IAA were found in the uppermost part of the tomato hypocotyl [3]. Thus, the relationship between the MTry synthesis and IAA synthesis seems to be problematic in the wheat coleoptiles. In addition, it may be noted that L-Try and D-Try exerted auxin-like effects on isolated wheat seedlings
124 Table V.
Contents of MTry and L-Tryin 5-day-old intact and 14-day isolated wheat seedlings (cv. Skala)
Variants
Isolated seedlings Isolated seedlings on the medium with L-Try (50 raM) Intact seedlings
MTry
L-Try
nmol/seedling
nmol/g fresh wt.
nmol/seedling
nmol/g fresh wt.
0 0.95 + 0.10
0 52 + 6
4.1 + 0.1 95 + 12
134 + 8 2930 + 360
5.27 + 0.62
38 + 5
69 + 9
(Table IV) and induce MTry accumulation in them, but did not restore their growth. MTry was found in the roots of wheat seedlings in contrast to tomato seedlings where MTry was absent in the roots [31. Elliott [6] also reported on the presence of MTry in the roots of wheat seedlings. MTry was not found in true leaves of the wheat seedling. Furthermore green leaves of adult wheat plants did not contain MTry, it appeared in them only during wilting [4]. As shown previously, L-Try is a precursor of MTry (with D-Try as an intermediate) in wilted tomato leaves [7] Experiments with isolated wheat seedlings showed that the formation of MTry was restored due to L-Try administration into the medium. These data support a possible role of LTry as the precursor of MTry synthesis. It may be assumed that the formation of MTry is regulated in some cases not only at the level of enzyme (racemase and N-malonyltransferase) activity, but also at the level of substrate (L-Try) concentration in plant tissues.
480 + 58
References 1 T. Robinson, ~Amino acids in higher plants. Life Sci., 19 (1976) 1097-1102. 2 K.Z. Gamburg and N.I. Rekoslavskaya, The formation and functions of N-malonyl-~-tryptophan in plants. Uspechi sovremennoi biologii (Moscow), 100 (1985) 44-50. 3 K.Z. Gamburg, O.V. Gluzdo and N.I. Rekoslavskaya, The content of N-malonyi-D-tryptophan in seeds and seedlings of plants. Plant Sci., 77 (1991) 149-153. 4 N.I. Rekoslavskaya, T.A. Markova and K.Z. Gamburg, Appearance of N-malonyI-D-tryptophan in plant leaves during wilting. I. The content of tryptophan and Nmalonyl-D-tryptophan as affected by water deficit. J. Plant Physiol., 132 (1988) 86-89. 5 K. Norstog, New synthetic medium for the culture of premature barley embryos. In Vitro, 8 (1973) 307-308. 6 M.C. Elliott, t~-N-Malonyl-D-tryptophan in seedling wheat roots. New Phytol., 70 (1971) 1005-1015. 7 T.A. Markova, N.I. Rekoslavskaya and K.Z. Gamburg, The induction of transformation of L-tryptophan to Dtryptophan due to wilting of tomato leaves. Fisiol. Rast., (Moscow) 37 (1990) 748-755.