Planta
Planta (1989) 178:143 146
9 Springer-Verlag 1989
Floral and growth responses in Chenopoch'um rubrum L. to an extract from flowering Nicotiana tabacum L. M. Kh. Chailakhyan 1, V. Lozhnikova 1, F. Seidlova 2 j. Krekule 2, N. Dudko x, and V. Negretzky 1 1 K.A. Timiryazev Institute of Plant Physiology, Academy of Sciences of the USSR, Botanicheskaya 35, 127276 Moscow, USSR 2 Institute of Experimental Botany, Czechoslovak Academy of Sciences, Ke dvoru 15, 166 30 Praha 6, Czechoslovakia
Abstract. Flowering of Chenopodium rubrum seedling plants was obtained in continuous light after application of fractions of a partially purified extract from leaves of flowering Maryland Mammoth tobacco (Nicotiana tabacum). The stage of flowal differentiation was dependent on the age of the Chenopodium plants used for the bioassay. Apices of plants treated with the extract at the age of four or seven days showed an advanced branching of the meristem or the beginning of formation of a terminal flower; treatment with the extract of plants 12 d old resulted in rapid formation of flower buds in all assay plants. Non-treated control plants kept in continuous light remained fully vegetative. The effects of the extract on flowering were associated with pronounced growth effects. Floral differentiation was preceeded by elongation of the shoot apex. Extension of all axial organs occurred, while growth of leaves, including leaf primordia, was inhibited. The pattern of growth after application of the flower-inducing substance(s) did not resemble the effects of the known phytohormones, but showed some similarities to growth changes resulting from photoperiodic induction of flowering.
from leaves of flowering Maryland M a m m o t h tobacco, a short-day plant, was demonstrated when tested on seedling plants of the short-day plant Chenopodium rubrum (Chailakhyan et al. 1977; for review see Zeevaart 1979). Application of the extract to such Chenopodium plants cultivated in continuous light resulted in transformation of a purely vegetative apex into a branched one, representing the first steps of inflorescence formation, while a similar extract from vegetative tobacco plants had no effect. Since that time the result has been reproduced many times. In earlier experiments with flower-inducing extracts from Xanthium tested on the same plant, only the first stages of floral transition, mainly apex enlargement, and only in few plants, were achieved in noninductive conditions (Lincoln et al. 1964; Hodson and Hamner 1970). The aim of this paper is to describe the morphogenetic changes accompanying floral differentiation that take place in Chenopodium rubrurn after application of extract from flowering tobacco plants, and to compare these changes with changes resulting from photoperiodic floral induction and from application of known phytohormones to Chenopodium rubrurn plants.
Key words: Chenopodium Florigen - Flowering - Nicotiana (flower-inducing extract) - Photoper-
Material and methods
iodic induction - Shoot apex
Introduction According to the hypothesis of a bicomponent florigen complex gibberellins and anthesins are necessary for flower formation (Chailakhyan 1958). The first results indicating the presence of anthesin in flowering plants were reported by Chailakhyan et al. in 1977. Flower-inducing activity in extracts
Lyophilized leaves of flowering Nicotiana tabacum L. cv. Maryland Mammoth plants were extracted with boiling ethanol. The extract was concentrated on a rotary evaporator. Lipids, chlorophyll and glycosides, were separated from the residue and the latter was fractionated on a silica-gel column that was eluted with a chloroform-methanol gradient. The active fractions were further purified by thin-layer chromatography (chloroformmethanol, 92:8, v/v) and by high-pressure liquid chromatography (Chailakhyan et al. 1983). The assay plants were treated with an aqueous solution of fractions of the extract, 1 ml of which contained the materials extracted from 1 g of lyophilized leaves of flowering tobacco plants. The experiments with Chenopodium rubrum, a strain maintained in the laboratory of J. Krekule, Institute of Experimental
144
M. Kh. Chailakhyan et al. : Floral and growth responses in Chenopodium
Fig. 1 a, b. Micrographs of shoot apices of ll-d-old plants of Chenopodium rubrum grown in continuous light, a Extract from flowering tobacco plants applied at the age of 4 to 6 d; b control apex. Bar = 50 gm Fig. 2a, b. Micrographs of shoot apices of 14-d-old plants of Chenopodium rubrum grown in continuous light, a Extract from flowering tobacco plants applied at the age of 4-6 d; b vegetative control apex. Bar = 50 gm Fig. 3a, b. Scanning electron micrographs of shoot apices of 14-d-old plants of Chenopodium rubrum grown in continuous light. a Extract from flowering tobacco plants applied at the age of 7-9 d; b vegetative control apex. Bar = 50 lam Fig. 4a, b. Scanning electron micrographs of floral apices of 19-d-old plants of Chenopodium rubrum grown in continuous light. a Extract from flowering tobacco plants applied at the age of 12 14 d (inflorescence with well-developed terminal flower bud and numerous axillary buds); h vegetative control apex. Bar= 100 gm
Botany Czechoslovak Academy of Sciences, Prague, were carried out in reach-in growth chambers at this institute. The Chenopodium plants were grown in perlite with a nutrient solution in continuous light (Ullmann et al. 1985a). Some of the plants were induced by one short day (SD) of 13 h of darkness at the age of 4, 7 or 12 d after sowing. Aqueous solution of the extract was applied with a microsyringe as a 3-gl droplet to the plumule of the assay plants on three consecutive days, starting at day 4, 7 or 12 after sowing. The timing of the treatments
corresponded to the first maximum, the minimum, and the second maximum of the floral response to one short day. In this way, experiments were performed with Chenopodium plants (i) at the stage of expanding cotyledons, (ii) at the stage of plumule growth, (iii) at the stage of two pairs of expanded leaves. In the last group the cotyledons were removed in order to prevent their presumed inhibitory effect. Evaluation of flowering and growth measurements were performed at the ages of 11, 13 or 14, or 19 d, according to
M. Kh. Chailakhyan et al. : Floral and growth responses in Chenopodium Table 1. Floral differentiation of Chenopodium rubrum in continuous light after application of extract from flowering tobacco plants, compared with non-treated control plants Age at start of treatment (days)
Treatmerit
Age at evaluation (d)
No. of plants": Vegetative
With branched apex
Flowering
4
Extract Control
11 or 14
0 15
6 0
1 0
7
Extract Control
14
0 10
6 0
1 0
12
Extract Control
19
0 10
0 0
8 0
" Apices with a round apical dome, a relatively large space between the youngest primordia, and bud initiation delayed by about four plastochrones were classified as vegetative apices. Branched apices exhibited bud formation close to the apical dome, both leaf and bud formation was enhanced, and the apical dome was reduced in size. Flowering apices showed distinct stamen and carpel formation
the different ages at the start of treatment. By that time the control plants of the first age group had two visible pairs of leaves of 4.3 and 1.7 m m average length; in those of the second age group the leaves were 9.3 and 3.9 m m long; and four visible pairs of leaves were present in plants of the third age group. The average hypocotyl length was about 5 m m in all groups. Shoot apices were dissected under a stereomicroscope. Drawings with the aid of a projection microscope and microphotographs were made. Some of the apical buds were fixed with glutaraldehyde 4%, postfixed with osmium tetroxide 1%, dehydrated, critical-point dried, coated with gold, and viewed ina scanning electronmicroscope (Tesla BS 300, Czechoslovakia).
145
Results and discussion
The first effect of the flower-inducing fractions of the extract from flowering Maryland Mammoth plants was elongation of the shoot apex of plants kept in continuous light as well as in plants induced by one SD (Fig. 1). The final effects were observed 7 d after the beginning of the treatments; by that time plants induced with two SD showed 100% flowering. The stage of floral differentiation depended on the age at the time of treatment (Table 1). In plants with extract application starting at the age of 4 d the pattern of branching in the uppermost part of the apical meristem closely approximated the formation of a terminal flower (Fig. 2). Application started at the age of 7 d elicited advanced branching in most of the apices (Fig. 3). In 12-d-old plants application of the extract resulted in rapid 100% flowering in continuous light, while the non-treated control plants remained fully vegetative under this condition (Fig. 4). Plants of Chenopodium rubrum treated with extract of Maryland Mammoth kept on long day, and hence vegetative, showed similar behaviour as control plants treated with water. The age dependence of the effects of the same amount of exogenously applied floral stimulus points to a developmental change in the sensitivity of the recipient tissue in the shoot apex. A similar age-dependence of the effectiveness of inductive photoperiodic treatment in Chenopodium rubrum was described by Ullmann et al. (1985 a).
Table 2, Growth effects in Chenopodiurn rubrum treated by extracts from flowering tobacco plants as compared with growth effects of photoperiodic induction (mean + SE) Photoperiod
Age (days)
Treatment
Hypocotyl length (ram)
Epicotyl length (ram)
Length of leaves (ram) of pair ...
extract water extract water
18.3 4- 0.33 a 5.0+_0.00 10.6+_0.42 a 4.8+-0.25
1.03 +_0.03 a 0.58+_0.04 1.81 _+0.13" 1.25+_0.05
1.77 +_0.09" 4.30+_0.34 5.57_+0.71 a 9.30+_0.70
0.80 +_0.06 a 1.68+_0.07 2.30_+0.30 b 3.88+_0.61
0.2 +0.00 ~ 0.54_+0.07 0.73 + 0.05 ~ 1.34+_0.11
extract water extract water
13.0+0.93 ~ 5.3+-0.25 10.6+-0.37" 5.5+-0.22
0.72_+0.05 0.60_+0.03 2.29+0.19 a 1.16+-0.06
1.63--+0.10 1.96+0.17 6.00_+0.38 6.50+-1.05
0.87_+0.09 1.04+-0.13 2.54_+0.11 2.35+-0.35
0.47_+0.10 0.29 + 0.02 0.80+_0.08 1.05+_0.16
At start of treatment
At evaluation
4
11
7
13
4
11
7
13
1 SD CL
11
no
6.1+_0.33 5.3+-0.20
-
4
11.1+0.60 ~ 14.4_+0.76
1 SD CL
7
14
no
5.0_+0.40 b 3.9_+0.22
3.7 4-_0.51b 2.2 -+0.24
-
Continuous light (CL) One short day (1 SD)
a Differences significant at 99% level b Differences significant at 95% level
1
2
3
4.7 +_0.46 b 6.2 _+0.31 14.6 _+1.12 14.4 +-1.10
5.2 +_0.70 5.0 4-0.45
146
M. Kh. Chailakhyan et al. : Floral and growth responses in Chenopodium
The results confirm our earlier observations which showed that full flowering of Chenopodium rubrum could be obtained under continuous light if the plants were treated with an extract from flowering tobacco plants (Chailakhyan et al. 1977). In the present experiments, the seedlings treated at the age of 12 d formed flower buds as early as at the age of 19 d. Such a rapid response is assumed to be the result of a higher purification of the extract fraction as well as to changed conditions of cultivation of the Chenopodium plants. All known phytohormones and growth regulators so far tested affected the flowering of Chenopodium rubrum only if combined with a short-day treatment (Seidlovfi 1985). Under continuous light, no floral differentiation took place in plants treated with auxin, cytokinin, gibberellin or abscisic acid, separately or in combinations (Lozhnikova et al. 1981 ; Ullmann et al. 1985b). The results presented in this paper as well as the previous findings of the initial steps of floral differentiation obtained in non-inductive photoperiod conditions after application of an extract from flowering tobacco plants indicate that substance(s) produced by the leaves of these flowering plants may act in triggering transition to flowering. The flower-inducing extract showed strong effects on the growth of the assay plants (Table 2). Increased elongation took place in the internodes and sometimes the axillary buds. In contrast, the leaves became shortener. The growth effects were stronger in continuous light than in plants given one SD. Photoperiodic induction without extract treatment resulted in less dramatic but analogous growth effects. The growth of leaves was particularly inhibited in induced young plants of Chenopodium rubrum (Table 2). Earlier experiments had shown growth effect of photoperiodic induction in Chenopodium rubruin (Opatrn/t et al. 1980). Both elongation of apical internodes and inhibition of the growth of leaf primordia were associated with the transformation of the apex from the vegetative to the reproductive state in Chenopodium rubrum (Seidlovfi and Sfidlikovfi 1983). This is in agreement with many findings which are indicative of a competitive role of leaf primordia in floral differentiation. The leaves themselves may serve as source of flower-inhibitory substances. The recent results obtained with flower-inducing fractions of extract from flowering tobacco plants are consistent with the idea of a florigen complex regulation flowering, and of anthesins as
a part of this complex. Further investigations should be directed at the chemical identification of the anthesin-like active substance(s) and at extending the plant species used as a source of anthesins and for bioassays. Detailed studies of organ formation in plants treated with the flower-induction substance(s) are equally needed. We thank Dr. Sterba and his coworkers at the Biological Centre of South Bohemia, (2esk~ Bud~jovice, Czechoslovakia, for preparation of the scanning electron micrographs.
References Chailakhyan, M. Kh. (1958) Hormonale Faktoren des Pflanzenblfihens. Biol. Zbl. 77, 641 662 Chailakhyan, M.Kh., Grigoreva, N.J., Lozhnikova, V.N. (1977) The effect of leaf extracts from flowering tobacco plants on flowering of seedlings and plants of Chenopodium rubrum L. (In Russ.). Dokl. Akad. Nauk SSSR 236, 773 776 Chailakhyan, M.Kh., Grigor~va, N.J., Lozhnikova, V.N. (1983) A method for extraction and purification of flower hormones from plants of short-day species. (Soy. Patent SU 1038343) (In Russ.) USSR State Committee on Matters of Inventions and Discoveries. Abstr. In Biull. Izobreteni~ - 0tkrytiya i Izobreteniya 32, 87, 30 Aug 83 Hodson, H.E., Hamner, K.C. (1970) Foral inducing extract from Xanthium. Science 167, 384-385 Lincoln, R.G., Cunningham, A., Hamner, K.C. (1964) Evidence for a florigenic acid. Nature 202, 559-561 Lozhnikova, V.N., Krekule, J., Seidlovfi, F., Bavrina, T.V., Chailakhyan, M.Kh. (1981) Promotive effect of abscisic acid in flowering of Chenopodium rubrum L. as the result of decreasing of apical dominance. Biol. Plant. (Prague) 25, 3640 Opatrn/t, J., Ullmann, J., Pavlovfi, L., Krekule, J. (1980) Changes in organ growth of Chenopodiurn rubrum due to suboptimal and multiple photoperiodic cycles with and without flowering effect. Biol. Plant. (Prague) 22, 454-464 Seidlovfi, F. (1985) Growth regulators in changing apical growth at transition to flowering. Biol. Plant. (Prague) 27, 350-359 Seidlovfi, F., Sfidlikov/t, H. (1983) Floral transition as a sequence of growth changes in different components of the shoot apical meristem of Chenopodium rubrum. Biol. Plant. (Prague) 25, 50-62 Ullmann, J., Seidlov~t, F., Krekule, J., Pavlova, L. (1985a) Chenopodium rubrum as a model plant for testing the flowering effects of PGRs. Biol. Plant. (Prague) 27, 367-372 Ullmann, J., Krekule, J., Pavlovfi, L., Josefusov/l, Z., Opatrnfi, J., Seidlovfi, F., Sou~kovfi, D. (1985b) Effect of two- or three-component PGR solution on the flowering of shortday plant Chenopodium rubrum. Biol. Plar~t. (Prague) 27, 398 401 Zeevaart, J.A.D. (1979) Perception, nature and complexite du signal transmis. In: La physiologie de la floraison (Coll. Int. du Centre National de la Recherche Scientifique N ~ 285), pp. 59 90. Editions du CNRS, Paris
Received 24 February; accepted 17 October 1988
Planta (1989) 178:143 146
9 Springer-Verlag 1989
Floral and growth responses in Chenopoch'um rubrum L. to an extract from flowering Nicotiana tabacum L. M. Kh. Chailakhyan 1, V. Lozhnikova 1, F. Seidlova 2 j. Krekule 2, N. Dudko x, and V. Negretzky 1 1 K.A. Timiryazev Institute of Plant Physiology, Academy of Sciences of the USSR, Botanicheskaya 35, 127276 Moscow, USSR 2 Institute of Experimental Botany, Czechoslovak Academy of Sciences, Ke dvoru 15, 166 30 Praha 6, Czechoslovakia
Abstract. Flowering of Chenopodium rubrum seedling plants was obtained in continuous light after application of fractions of a partially purified extract from leaves of flowering Maryland Mammoth tobacco (Nicotiana tabacum). The stage of flowal differentiation was dependent on the age of the Chenopodium plants used for the bioassay. Apices of plants treated with the extract at the age of four or seven days showed an advanced branching of the meristem or the beginning of formation of a terminal flower; treatment with the extract of plants 12 d old resulted in rapid formation of flower buds in all assay plants. Non-treated control plants kept in continuous light remained fully vegetative. The effects of the extract on flowering were associated with pronounced growth effects. Floral differentiation was preceeded by elongation of the shoot apex. Extension of all axial organs occurred, while growth of leaves, including leaf primordia, was inhibited. The pattern of growth after application of the flower-inducing substance(s) did not resemble the effects of the known phytohormones, but showed some similarities to growth changes resulting from photoperiodic induction of flowering.
from leaves of flowering Maryland M a m m o t h tobacco, a short-day plant, was demonstrated when tested on seedling plants of the short-day plant Chenopodium rubrum (Chailakhyan et al. 1977; for review see Zeevaart 1979). Application of the extract to such Chenopodium plants cultivated in continuous light resulted in transformation of a purely vegetative apex into a branched one, representing the first steps of inflorescence formation, while a similar extract from vegetative tobacco plants had no effect. Since that time the result has been reproduced many times. In earlier experiments with flower-inducing extracts from Xanthium tested on the same plant, only the first stages of floral transition, mainly apex enlargement, and only in few plants, were achieved in noninductive conditions (Lincoln et al. 1964; Hodson and Hamner 1970). The aim of this paper is to describe the morphogenetic changes accompanying floral differentiation that take place in Chenopodium rubrurn after application of extract from flowering tobacco plants, and to compare these changes with changes resulting from photoperiodic floral induction and from application of known phytohormones to Chenopodium rubrurn plants.
Key words: Chenopodium Florigen - Flowering - Nicotiana (flower-inducing extract) - Photoper-
Material and methods
iodic induction - Shoot apex
Introduction According to the hypothesis of a bicomponent florigen complex gibberellins and anthesins are necessary for flower formation (Chailakhyan 1958). The first results indicating the presence of anthesin in flowering plants were reported by Chailakhyan et al. in 1977. Flower-inducing activity in extracts
Lyophilized leaves of flowering Nicotiana tabacum L. cv. Maryland Mammoth plants were extracted with boiling ethanol. The extract was concentrated on a rotary evaporator. Lipids, chlorophyll and glycosides, were separated from the residue and the latter was fractionated on a silica-gel column that was eluted with a chloroform-methanol gradient. The active fractions were further purified by thin-layer chromatography (chloroformmethanol, 92:8, v/v) and by high-pressure liquid chromatography (Chailakhyan et al. 1983). The assay plants were treated with an aqueous solution of fractions of the extract, 1 ml of which contained the materials extracted from 1 g of lyophilized leaves of flowering tobacco plants. The experiments with Chenopodium rubrum, a strain maintained in the laboratory of J. Krekule, Institute of Experimental
144
M. Kh. Chailakhyan et al. : Floral and growth responses in Chenopodium
Fig. 1 a, b. Micrographs of shoot apices of ll-d-old plants of Chenopodium rubrum grown in continuous light, a Extract from flowering tobacco plants applied at the age of 4 to 6 d; b control apex. Bar = 50 gm Fig. 2a, b. Micrographs of shoot apices of 14-d-old plants of Chenopodium rubrum grown in continuous light, a Extract from flowering tobacco plants applied at the age of 4-6 d; b vegetative control apex. Bar = 50 gm Fig. 3a, b. Scanning electron micrographs of shoot apices of 14-d-old plants of Chenopodium rubrum grown in continuous light. a Extract from flowering tobacco plants applied at the age of 7-9 d; b vegetative control apex. Bar = 50 lam Fig. 4a, b. Scanning electron micrographs of floral apices of 19-d-old plants of Chenopodium rubrum grown in continuous light. a Extract from flowering tobacco plants applied at the age of 12 14 d (inflorescence with well-developed terminal flower bud and numerous axillary buds); h vegetative control apex. Bar= 100 gm
Botany Czechoslovak Academy of Sciences, Prague, were carried out in reach-in growth chambers at this institute. The Chenopodium plants were grown in perlite with a nutrient solution in continuous light (Ullmann et al. 1985a). Some of the plants were induced by one short day (SD) of 13 h of darkness at the age of 4, 7 or 12 d after sowing. Aqueous solution of the extract was applied with a microsyringe as a 3-gl droplet to the plumule of the assay plants on three consecutive days, starting at day 4, 7 or 12 after sowing. The timing of the treatments
corresponded to the first maximum, the minimum, and the second maximum of the floral response to one short day. In this way, experiments were performed with Chenopodium plants (i) at the stage of expanding cotyledons, (ii) at the stage of plumule growth, (iii) at the stage of two pairs of expanded leaves. In the last group the cotyledons were removed in order to prevent their presumed inhibitory effect. Evaluation of flowering and growth measurements were performed at the ages of 11, 13 or 14, or 19 d, according to
M. Kh. Chailakhyan et al. : Floral and growth responses in Chenopodium Table 1. Floral differentiation of Chenopodium rubrum in continuous light after application of extract from flowering tobacco plants, compared with non-treated control plants Age at start of treatment (days)
Treatmerit
Age at evaluation (d)
No. of plants": Vegetative
With branched apex
Flowering
4
Extract Control
11 or 14
0 15
6 0
1 0
7
Extract Control
14
0 10
6 0
1 0
12
Extract Control
19
0 10
0 0
8 0
" Apices with a round apical dome, a relatively large space between the youngest primordia, and bud initiation delayed by about four plastochrones were classified as vegetative apices. Branched apices exhibited bud formation close to the apical dome, both leaf and bud formation was enhanced, and the apical dome was reduced in size. Flowering apices showed distinct stamen and carpel formation
the different ages at the start of treatment. By that time the control plants of the first age group had two visible pairs of leaves of 4.3 and 1.7 m m average length; in those of the second age group the leaves were 9.3 and 3.9 m m long; and four visible pairs of leaves were present in plants of the third age group. The average hypocotyl length was about 5 m m in all groups. Shoot apices were dissected under a stereomicroscope. Drawings with the aid of a projection microscope and microphotographs were made. Some of the apical buds were fixed with glutaraldehyde 4%, postfixed with osmium tetroxide 1%, dehydrated, critical-point dried, coated with gold, and viewed ina scanning electronmicroscope (Tesla BS 300, Czechoslovakia).
145
Results and discussion
The first effect of the flower-inducing fractions of the extract from flowering Maryland Mammoth plants was elongation of the shoot apex of plants kept in continuous light as well as in plants induced by one SD (Fig. 1). The final effects were observed 7 d after the beginning of the treatments; by that time plants induced with two SD showed 100% flowering. The stage of floral differentiation depended on the age at the time of treatment (Table 1). In plants with extract application starting at the age of 4 d the pattern of branching in the uppermost part of the apical meristem closely approximated the formation of a terminal flower (Fig. 2). Application started at the age of 7 d elicited advanced branching in most of the apices (Fig. 3). In 12-d-old plants application of the extract resulted in rapid 100% flowering in continuous light, while the non-treated control plants remained fully vegetative under this condition (Fig. 4). Plants of Chenopodium rubrum treated with extract of Maryland Mammoth kept on long day, and hence vegetative, showed similar behaviour as control plants treated with water. The age dependence of the effects of the same amount of exogenously applied floral stimulus points to a developmental change in the sensitivity of the recipient tissue in the shoot apex. A similar age-dependence of the effectiveness of inductive photoperiodic treatment in Chenopodium rubrum was described by Ullmann et al. (1985 a).
Table 2, Growth effects in Chenopodiurn rubrum treated by extracts from flowering tobacco plants as compared with growth effects of photoperiodic induction (mean + SE) Photoperiod
Age (days)
Treatment
Hypocotyl length (ram)
Epicotyl length (ram)
Length of leaves (ram) of pair ...
extract water extract water
18.3 4- 0.33 a 5.0+_0.00 10.6+_0.42 a 4.8+-0.25
1.03 +_0.03 a 0.58+_0.04 1.81 _+0.13" 1.25+_0.05
1.77 +_0.09" 4.30+_0.34 5.57_+0.71 a 9.30+_0.70
0.80 +_0.06 a 1.68+_0.07 2.30_+0.30 b 3.88+_0.61
0.2 +0.00 ~ 0.54_+0.07 0.73 + 0.05 ~ 1.34+_0.11
extract water extract water
13.0+0.93 ~ 5.3+-0.25 10.6+-0.37" 5.5+-0.22
0.72_+0.05 0.60_+0.03 2.29+0.19 a 1.16+-0.06
1.63--+0.10 1.96+0.17 6.00_+0.38 6.50+-1.05
0.87_+0.09 1.04+-0.13 2.54_+0.11 2.35+-0.35
0.47_+0.10 0.29 + 0.02 0.80+_0.08 1.05+_0.16
At start of treatment
At evaluation
4
11
7
13
4
11
7
13
1 SD CL
11
no
6.1+_0.33 5.3+-0.20
-
4
11.1+0.60 ~ 14.4_+0.76
1 SD CL
7
14
no
5.0_+0.40 b 3.9_+0.22
3.7 4-_0.51b 2.2 -+0.24
-
Continuous light (CL) One short day (1 SD)
a Differences significant at 99% level b Differences significant at 95% level
1
2
3
4.7 +_0.46 b 6.2 _+0.31 14.6 _+1.12 14.4 +-1.10
5.2 +_0.70 5.0 4-0.45
146
M. Kh. Chailakhyan et al. : Floral and growth responses in Chenopodium
The results confirm our earlier observations which showed that full flowering of Chenopodium rubrum could be obtained under continuous light if the plants were treated with an extract from flowering tobacco plants (Chailakhyan et al. 1977). In the present experiments, the seedlings treated at the age of 12 d formed flower buds as early as at the age of 19 d. Such a rapid response is assumed to be the result of a higher purification of the extract fraction as well as to changed conditions of cultivation of the Chenopodium plants. All known phytohormones and growth regulators so far tested affected the flowering of Chenopodium rubrum only if combined with a short-day treatment (Seidlovfi 1985). Under continuous light, no floral differentiation took place in plants treated with auxin, cytokinin, gibberellin or abscisic acid, separately or in combinations (Lozhnikova et al. 1981 ; Ullmann et al. 1985b). The results presented in this paper as well as the previous findings of the initial steps of floral differentiation obtained in non-inductive photoperiod conditions after application of an extract from flowering tobacco plants indicate that substance(s) produced by the leaves of these flowering plants may act in triggering transition to flowering. The flower-inducing extract showed strong effects on the growth of the assay plants (Table 2). Increased elongation took place in the internodes and sometimes the axillary buds. In contrast, the leaves became shortener. The growth effects were stronger in continuous light than in plants given one SD. Photoperiodic induction without extract treatment resulted in less dramatic but analogous growth effects. The growth of leaves was particularly inhibited in induced young plants of Chenopodium rubrum (Table 2). Earlier experiments had shown growth effect of photoperiodic induction in Chenopodium rubruin (Opatrn/t et al. 1980). Both elongation of apical internodes and inhibition of the growth of leaf primordia were associated with the transformation of the apex from the vegetative to the reproductive state in Chenopodium rubrum (Seidlovfi and Sfidlikovfi 1983). This is in agreement with many findings which are indicative of a competitive role of leaf primordia in floral differentiation. The leaves themselves may serve as source of flower-inhibitory substances. The recent results obtained with flower-inducing fractions of extract from flowering tobacco plants are consistent with the idea of a florigen complex regulation flowering, and of anthesins as
a part of this complex. Further investigations should be directed at the chemical identification of the anthesin-like active substance(s) and at extending the plant species used as a source of anthesins and for bioassays. Detailed studies of organ formation in plants treated with the flower-induction substance(s) are equally needed. We thank Dr. Sterba and his coworkers at the Biological Centre of South Bohemia, (2esk~ Bud~jovice, Czechoslovakia, for preparation of the scanning electron micrographs.
References Chailakhyan, M. Kh. (1958) Hormonale Faktoren des Pflanzenblfihens. Biol. Zbl. 77, 641 662 Chailakhyan, M.Kh., Grigoreva, N.J., Lozhnikova, V.N. (1977) The effect of leaf extracts from flowering tobacco plants on flowering of seedlings and plants of Chenopodium rubrum L. (In Russ.). Dokl. Akad. Nauk SSSR 236, 773 776 Chailakhyan, M.Kh., Grigor~va, N.J., Lozhnikova, V.N. (1983) A method for extraction and purification of flower hormones from plants of short-day species. (Soy. Patent SU 1038343) (In Russ.) USSR State Committee on Matters of Inventions and Discoveries. Abstr. In Biull. Izobreteni~ - 0tkrytiya i Izobreteniya 32, 87, 30 Aug 83 Hodson, H.E., Hamner, K.C. (1970) Foral inducing extract from Xanthium. Science 167, 384-385 Lincoln, R.G., Cunningham, A., Hamner, K.C. (1964) Evidence for a florigenic acid. Nature 202, 559-561 Lozhnikova, V.N., Krekule, J., Seidlovfi, F., Bavrina, T.V., Chailakhyan, M.Kh. (1981) Promotive effect of abscisic acid in flowering of Chenopodium rubrum L. as the result of decreasing of apical dominance. Biol. Plant. (Prague) 25, 3640 Opatrn/t, J., Ullmann, J., Pavlovfi, L., Krekule, J. (1980) Changes in organ growth of Chenopodiurn rubrum due to suboptimal and multiple photoperiodic cycles with and without flowering effect. Biol. Plant. (Prague) 22, 454-464 Seidlovfi, F. (1985) Growth regulators in changing apical growth at transition to flowering. Biol. Plant. (Prague) 27, 350-359 Seidlovfi, F., Sfidlikov/t, H. (1983) Floral transition as a sequence of growth changes in different components of the shoot apical meristem of Chenopodium rubrum. Biol. Plant. (Prague) 25, 50-62 Ullmann, J., Seidlov~t, F., Krekule, J., Pavlova, L. (1985a) Chenopodium rubrum as a model plant for testing the flowering effects of PGRs. Biol. Plant. (Prague) 27, 367-372 Ullmann, J., Krekule, J., Pavlovfi, L., Josefusov/l, Z., Opatrnfi, J., Seidlovfi, F., Sou~kovfi, D. (1985b) Effect of two- or three-component PGR solution on the flowering of shortday plant Chenopodium rubrum. Biol. Plar~t. (Prague) 27, 398 401 Zeevaart, J.A.D. (1979) Perception, nature and complexite du signal transmis. In: La physiologie de la floraison (Coll. Int. du Centre National de la Recherche Scientifique N ~ 285), pp. 59 90. Editions du CNRS, Paris
Received 24 February; accepted 17 October 1988
