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Effects of ethrel and gibberellin on impatiens plants
Scientia Horticulturae 76 (1998) 29±35
Effects of ethrel and gibberellin on impatiens plants Guy Tamari, Lamprini Pappa, Tamar Zered, Amihud Borochov* The Kennedy-Leigh Centre for Horticultural Research, Faculty of Agriculture, The Hebrew University of Jerusalem, P.O. Box 12, Rehovot 76100, Israel Accepted 7 April 1998
Abstract Impatiens (Impatiens balsamina L.) is a qualitative short-day plant that flowers, in Israel, all year round. This lowers the quality of impatiens stock plants. The goal of this work was to examine treatments that will eliminate flowering in stock plants without reducing other qualities of the cutting crop. Impatiens plants (cv. Tempo Pink (Sultanii) and Aruba (New-Guinea)) were sprayed with ethrel alone or in combination with gibberellin. Ethrel treatment caused a transient increase in ethylene production and inhibited vegetative growth. A bi-weekly ethrel application, at 400 ppm and above, resulted in a complete elimination of flowering. Ethrel treatments led to an increase in cutting crop with a better rooting, but a shorter cutting length due to growth inhibition. Gibberellin, when applied in combination with ethrel, restored vegetative growth to control levels without affecting flowering. # 1998 Elsevier Science B.V. All rights reserved Keywords: Cuttings; Ethrel; Ethylene; Flowering; Gibberellin; Impatiens balsamina; Rooting
1. Introduction Several commercial farms in Israel produce large quantities of impatiens (Impatiens balsamina L.) cuttings, for both the local market and export. In general, the overall quality of stock plants is dependent on the number of cuttings produced, their length and rooting capacity. In addition, cuttings should not have flowers, as flowering cuttings were regarded as having lower rooting ability, as found in other plants (for example in Coleonema, Heller et al., 1994). * Corresponding author. Fax: +972 8 9468263. 0304-4238/98/$19.00 # 1998 Elsevier Science B.V. All rights reserved PII S 0 3 0 4 - 4 2 3 8 ( 9 8 ) 0 0 1 2 8 - 9
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G. Tamari et al. / Scientia Horticulturae 76 (1998) 29±35
Though impatiens are qualitative short-day plants (Sharma et al., 1978), most cultivars in Israel produce flowers all year round. Maintaining stock plant quality for cutting production requires techniques to inhibit flowering without adverse effects on number, length and rooting capacity. In several plants, ethylene inhibits floral development at a rather early stage (Reid and Wu, 1991). Impatiens exposure to ppm levels of ethylene for few hours lead to significant flowers abscission (Dostal et al., 1991). In chrysanthemums, the effects of gibberellin in combination with ethrel has recently been tested in order to counteract the growth inhibition caused by ethrel alone (Strefeler et al., 1996). However, enhanced flowering of impatiens following gibberellin treatments has been reported (Sharma et al., 1978). The goal of the present study was to examine the possibility that a combined treatments of ethrel and gibberellin could improve the cutting quality of impatiens stock plants. 2. Materials and methods 2.1. Plant material and growth conditions Impatiens (Impatiens balsamina L.) plants of Sultanii (cv. `Tempo Pink') and New-Guinea (cv. `Aruba') cultivars were grown from cuttings, supplied by Dan nurseries (Mishmar Hashivaa, Israel), each plant in a 1.5 l pot containing peat:volcanic gravel (1:1, v:v) and Osmocote granules (NPK 14:14:14, 0.03%) and watered twice a day. The plants were held in a glass-house, at 27/178C (day/ night) under natural day length. The experiments were conducted twice, during winter (January±April) and spring (March±June), with similar results. The results presented are from the winter experiments. In one experiment, ten plants were treated with different concentrations of ethrel, while in an another experiment, where the effects of combinations of gibberellin and ethrel were tested, 13 plants per treatment were held under similar conditions. 2.2. Chemical treatments Treatments were applied as whole canopy sprays, ca. 30 ml per plant, in the afternoons. Ethrel (Agan, Israel) was applied at various concentrations (200± 800 ppm) and gibberellin (Berelex, ICI, UK) at 25 ppm. 2.3. Measurements Production of ethylene by cuttings were measured within 1 h following harvest. For each measurement, four cuttings were weighed and then enclosed, separately,
G. Tamari et al. / Scientia Horticulturae 76 (1998) 29±35
31
each in a 30 ml syringe for 1 h at 228C. Subsequently, 1 ml air samples were withdrawn from each syringe, and ethylene concentration measured by gas chromatography as described previously (Porat et al., 1995). Growth and flowering of the plants were measured weekly; the height of the plant canopy was measured from the pot level. Chlorophyll content of the leaves was measured following extraction with dimethylformamide (Lichtenthaler, 1987). Cuttings that included three internodes each were harvested, measured and counted at the end of the experiment. One hour after harvest, ten cuttings from each treatment were treated with Homoril T3 hormone powder (0.3% IBA, Assia Reisel, Israel) and transferred to rooting trays containing a peat:granular polystyrene mix (3:1, v:v) for rooting. During the rooting process, the cuttings were watered for 20 s at 30 min intervals. After 2 weeks, the quality of the developed root system was evaluated as follows: (0) no roots; (1) several thin and short roots that did not hold any of the rooting mixture; (2) several long roots that did not hold any of the rooting mixture; (3) thick cluster of short roots and; (4) thick cluster of fully developed roots. Rooting quality of one (and above), was considered as acceptable.
2.4. Statistics Means and standard errors (SE) were calculated for each of the experimental groups of plants.
3. Results and discussion 3.1. Ethylene production A day after the Aruba plants were sprayed with 400 ppm ethrel, the level of ethylene produced by the harvested cuttings increased significantly (Fig. 1), peaking after an additional day to a level that was ca. four times that of control cuttings. The rate of ethylene production declined during the subsequent 3 days to the control level, and increased again following the next application of ethrel. The response to other ethrel concentrations (200, 600 and 800 ppm) was similar, and the levels were concentration-dependent (data not shown), as shown for other plants (for example, liatris tubers, Keren-Paz et al., 1989). A single treatment, therefore, was insufficient to affect the plants for a period of time that was long enough, and repeated ethrel treatments in subsequent experiments which were needed every other week.
32
G. Tamari et al. / Scientia Horticulturae 76 (1998) 29±35
Fig. 1. Effect of ethrel treatments on production of ethylene by impatiens cuttings. Aruba plants were sprayed with water (~) or 400 ppm ethrel (^) when indicated by arrows; cuttings were harvested at various times and their ethylene production was measured.
Table 1 Effects of ethrel treatments on height and flowering of plants of Aruba and Tempo Pink Ethrel concentration (ppm)
0 200 400 800
Aruba
Tempo Pink
Plant height (cm)
Flowers/plant
Plant height (cm)
Flowers/plant
33.82.5 28.31.2 27.10.7 19.71.0
24.03.0 2.00.1 0.00.0 0.00.0
68.94.0 70.22.0 65.22.0 46.83.0
69.03.0 5.01.2 0.00.0 0.00.0
Plants were sprayed with ethrel at various concentrations every 2 weeks. Values of flowering are presented as the number of flowers at anthesis at the time of measurement. The results presented are means taken after 9 weeksSE (n4).
3.2. Plant growth and flowering At the beginning of the experiment, both Tempo Pink and Aruba plants were about 10 cm tall. The plants exhibited different growth rates, with Tempo Pink having double the growth rate of Aruba. During the 9-week experiment, Tempo Pink plants grew up to ca. 7 fold and Aruba plants up to 3 fold (Tables 1 and 2). In all cases, ethrel treatments retarded the growth with a dose-related effect. The growth-inhibition effect of the ethrel treatments was apparent within 4 weeks from treatment. The highest ethrel concentration (800 ppm) gave the strongest growth inhibition (30±40%) (Table 1). Similar effects of growth inhibition by ethrel had been reported for other species (Rounkova, 1989).
G. Tamari et al. / Scientia Horticulturae 76 (1998) 29±35
33
Table 2 Effects of ethrel (400 ppm) and gibberellin (25 ppm) treatments on the performance of Aruba and Tempo Pink stock plants Treatment
Water (control) Ethrel Gibberellin Ethrelgibberellin
Aruba
Tempo Pink
Plant height (cm)
Flowers/plant
Plant height (cm)
Flowers/plant
22.00.7 13.90.4 25.61.1 19.40.6
9.00.5 0.00.0 8.11.3 0.00.0
36.03.4 21.11.8 46.23.7 32.12.0
9.00.5 0.00.0 8.11.3 0.00.0
Plants were sprayed with chemicals every 2 weeks. Measurements were conducted after 8 weeks. The results presented are meansSE (n13).
Morphological properties were also affected by the ethrel treatments; leaves of control Tempo Pink plants were light green in color and had a lower chlorophyll content compared with the Aruba controls (data not presented). Ethrel had almost no effect on the chlorophyll content of Tempo Pink leaves. In contrast, Aruba leaves, treated with ethrel, had lower chlorophyll content. As a result, the leaves of plants of the two cultivars had similar chlorophyll contents when treated with 800 ppm ethrel (data not shown). Tempo Pink plants bloomed in a shorter time than Aruba plants, with control plants reaching anthesis in 3 (Tempo Pink) or 6 weeks (Aruba). There were double the number of flowers in Tempo Pink at the end of the experiment (Table 1). Ethrel treatments significantly reduced the number of flowers in both cultivars; plants that had been treated with 200 ppm ethrel had 10% or less flowers compared to the control, and plants treated with higher concentrations of ethrel had no flowers at all (Table 1). The lack of flowers, in impatiens, resulted from bud abscission, and not from inhibition of flower development as in chrysanthemums (Strefeler et al., 1996). 3.3. Cuttings Plants of Tempo Pink had ca. 50% more cuttings than Aruba (Fig. 2(A). In both cultivars, ethrel treatments increased the number of cuttings in a concentrationrelated manner, resulting in a two-fold crop at the highest ethrel concentration (800 ppm). It is probable that the increase in the number of cutting was due to the effect of ethrel on lateral branching, associated with a reduced apical dominance (Raskin, 1991). Cuttings of all treated plants rooted within 2 weeks. In general, ethrel treatments applied to the stock plants improved the quality of the root system (Fig. 2(B)). Similar effects of ethrel on rooting had been reported for chrysanthemums (Soffer et al., 1989).
34
G. Tamari et al. / Scientia Horticulturae 76 (1998) 29±35
Fig. 2. Effect of ethrel treatments, applied to the stock plants, on: (A) number of cuttings in Tempo Pink (*) and Aruba (&) plants. (B) rooting quality of Tempo Pink (*) and Aruba (&) cuttings. (C) length of cuttings in Tempo Pink (*) and Aruba (&) plants. Bars represent a 2SE (n10).
Though cutting yield increased following ethrel treatments, these cuttings were generally shorter (Fig. 2(C)). This phenomenon was probably due to the inhibitory effects of ethrel on plant growth (Table 1), and was more pronounced in Aruba. Treating impatiens stock plants with ethrel resulted in an increase in ethylene production and smaller plants with no flowers. More cuttings were harvested from treated plants and their rooting was satisfactory. However, cuttings from ethrel-treated plants were shorter than those produced from untreated plants. In
G. Tamari et al. / Scientia Horticulturae 76 (1998) 29±35
35
both cultivars gibberellin, in combination with ethrel, produced taller plants than the ethrel treated plants. The same results were found for the length of the harvested cuttings (data not shown). In all treatments, gibberellin had no effect on the number of flowers. The treatments applies to both cultivars had no significant effect on the number of cuttings per plant or on the extent or quality of the rooting. In summary, the results of this work show that bi-weekly treatments of ethrel combined with gibberellin produce impatiens stock plants of a good quality that do not have flowers. Cuttings should not be harvested in the 3 days immediately following the treatments, since at that period the cuttings produce large amounts of ethylene (Fig. 1) that might be harmful for the post-harvest keepability of the cuttings. References Dostal, D.L., Howard Agnew, N., Gladon, R.J., Weigle, J.L., 1991. Ethylene, simulated shipping, STS, and AOA affect corolla abscission of New-Guinea Impatiens. Hort. Science 26(1), 47±49. Heller, A., Borochov, A., Halevy, A.H., 1994. Factors affecting rooting ability of Coleonema aspalathoides. Scientia Horticulturae 58(4), 335±341. Keren-Paz, V., Borochov, A., Mayak, S., 1989. The involvement of ethylene in liatris corm dormancy. Plant Growth Regulation 8(1), 11±20. Lichtenthaler, H.K., 1987. Chlorophylls and carotenoides: Pigments of photosynthetic biomembranes. Methods of Enzymology 148, 350±382. Porat, R., Halevy, A.H., Serek, M., Borochov, A., 1995. An increase in ethylene sensitivity following pollination is the initial event triggering an increase in ethylene production and enhanced senescence of phalaenopsis orchid flowers. Physiologia Plantarum 93(4), 778±784. Raskin, I., 1991. Ethylene in vegetative growth. In: Mattoo, A.K., Suttle, J.C. (Eds), The Plant Hormone Ethylene. CRC Press, Boca Raton, FL, pp. 183±192. Reid, M.S., Wu, M-J., 1991. Ethylene in flower development and senescence. In: Mattoo, A.K., Suttle, J.C. (Eds), The Plant Hormone Ethylene. CRC Press, Boca Raton, FL, pp. 215±234. Rounkova, L.V., 1989. Effect of ethylene producing substances and cultar on some ornamental plants. Acta Horticulturae 251, 281±288. Sharma, R., Kumar, S., Nanda, K.K., 1978. The effect of gibberellic acid and guanosine monophosphates on extension growth, leaf production and flowering of Impatiens balsamina. Physiologia Plantarum 44(4), 359±364. Soffer, H., Mayak, S., Burger, D.W., Reid, M.S., 1989. The role of ethylene in the inhibition of rooting under low oxygen tensions. Plant Physiology 89(1), 165±168. Strefeler, S.M., Anderson, N.O., Ascher, P.D., 1996. EthyleneGA3 sprays for delaying flower bud initiation in chrysanthemum (Dendranthema grandiflora Tzvelv.) stock plants. Hort Technology 6(3), 251±253.
Effects of ethrel and gibberellin on impatiens plants Guy Tamari, Lamprini Pappa, Tamar Zered, Amihud Borochov* The Kennedy-Leigh Centre for Horticultural Research, Faculty of Agriculture, The Hebrew University of Jerusalem, P.O. Box 12, Rehovot 76100, Israel Accepted 7 April 1998
Abstract Impatiens (Impatiens balsamina L.) is a qualitative short-day plant that flowers, in Israel, all year round. This lowers the quality of impatiens stock plants. The goal of this work was to examine treatments that will eliminate flowering in stock plants without reducing other qualities of the cutting crop. Impatiens plants (cv. Tempo Pink (Sultanii) and Aruba (New-Guinea)) were sprayed with ethrel alone or in combination with gibberellin. Ethrel treatment caused a transient increase in ethylene production and inhibited vegetative growth. A bi-weekly ethrel application, at 400 ppm and above, resulted in a complete elimination of flowering. Ethrel treatments led to an increase in cutting crop with a better rooting, but a shorter cutting length due to growth inhibition. Gibberellin, when applied in combination with ethrel, restored vegetative growth to control levels without affecting flowering. # 1998 Elsevier Science B.V. All rights reserved Keywords: Cuttings; Ethrel; Ethylene; Flowering; Gibberellin; Impatiens balsamina; Rooting
1. Introduction Several commercial farms in Israel produce large quantities of impatiens (Impatiens balsamina L.) cuttings, for both the local market and export. In general, the overall quality of stock plants is dependent on the number of cuttings produced, their length and rooting capacity. In addition, cuttings should not have flowers, as flowering cuttings were regarded as having lower rooting ability, as found in other plants (for example in Coleonema, Heller et al., 1994). * Corresponding author. Fax: +972 8 9468263. 0304-4238/98/$19.00 # 1998 Elsevier Science B.V. All rights reserved PII S 0 3 0 4 - 4 2 3 8 ( 9 8 ) 0 0 1 2 8 - 9
30
G. Tamari et al. / Scientia Horticulturae 76 (1998) 29±35
Though impatiens are qualitative short-day plants (Sharma et al., 1978), most cultivars in Israel produce flowers all year round. Maintaining stock plant quality for cutting production requires techniques to inhibit flowering without adverse effects on number, length and rooting capacity. In several plants, ethylene inhibits floral development at a rather early stage (Reid and Wu, 1991). Impatiens exposure to ppm levels of ethylene for few hours lead to significant flowers abscission (Dostal et al., 1991). In chrysanthemums, the effects of gibberellin in combination with ethrel has recently been tested in order to counteract the growth inhibition caused by ethrel alone (Strefeler et al., 1996). However, enhanced flowering of impatiens following gibberellin treatments has been reported (Sharma et al., 1978). The goal of the present study was to examine the possibility that a combined treatments of ethrel and gibberellin could improve the cutting quality of impatiens stock plants. 2. Materials and methods 2.1. Plant material and growth conditions Impatiens (Impatiens balsamina L.) plants of Sultanii (cv. `Tempo Pink') and New-Guinea (cv. `Aruba') cultivars were grown from cuttings, supplied by Dan nurseries (Mishmar Hashivaa, Israel), each plant in a 1.5 l pot containing peat:volcanic gravel (1:1, v:v) and Osmocote granules (NPK 14:14:14, 0.03%) and watered twice a day. The plants were held in a glass-house, at 27/178C (day/ night) under natural day length. The experiments were conducted twice, during winter (January±April) and spring (March±June), with similar results. The results presented are from the winter experiments. In one experiment, ten plants were treated with different concentrations of ethrel, while in an another experiment, where the effects of combinations of gibberellin and ethrel were tested, 13 plants per treatment were held under similar conditions. 2.2. Chemical treatments Treatments were applied as whole canopy sprays, ca. 30 ml per plant, in the afternoons. Ethrel (Agan, Israel) was applied at various concentrations (200± 800 ppm) and gibberellin (Berelex, ICI, UK) at 25 ppm. 2.3. Measurements Production of ethylene by cuttings were measured within 1 h following harvest. For each measurement, four cuttings were weighed and then enclosed, separately,
G. Tamari et al. / Scientia Horticulturae 76 (1998) 29±35
31
each in a 30 ml syringe for 1 h at 228C. Subsequently, 1 ml air samples were withdrawn from each syringe, and ethylene concentration measured by gas chromatography as described previously (Porat et al., 1995). Growth and flowering of the plants were measured weekly; the height of the plant canopy was measured from the pot level. Chlorophyll content of the leaves was measured following extraction with dimethylformamide (Lichtenthaler, 1987). Cuttings that included three internodes each were harvested, measured and counted at the end of the experiment. One hour after harvest, ten cuttings from each treatment were treated with Homoril T3 hormone powder (0.3% IBA, Assia Reisel, Israel) and transferred to rooting trays containing a peat:granular polystyrene mix (3:1, v:v) for rooting. During the rooting process, the cuttings were watered for 20 s at 30 min intervals. After 2 weeks, the quality of the developed root system was evaluated as follows: (0) no roots; (1) several thin and short roots that did not hold any of the rooting mixture; (2) several long roots that did not hold any of the rooting mixture; (3) thick cluster of short roots and; (4) thick cluster of fully developed roots. Rooting quality of one (and above), was considered as acceptable.
2.4. Statistics Means and standard errors (SE) were calculated for each of the experimental groups of plants.
3. Results and discussion 3.1. Ethylene production A day after the Aruba plants were sprayed with 400 ppm ethrel, the level of ethylene produced by the harvested cuttings increased significantly (Fig. 1), peaking after an additional day to a level that was ca. four times that of control cuttings. The rate of ethylene production declined during the subsequent 3 days to the control level, and increased again following the next application of ethrel. The response to other ethrel concentrations (200, 600 and 800 ppm) was similar, and the levels were concentration-dependent (data not shown), as shown for other plants (for example, liatris tubers, Keren-Paz et al., 1989). A single treatment, therefore, was insufficient to affect the plants for a period of time that was long enough, and repeated ethrel treatments in subsequent experiments which were needed every other week.
32
G. Tamari et al. / Scientia Horticulturae 76 (1998) 29±35
Fig. 1. Effect of ethrel treatments on production of ethylene by impatiens cuttings. Aruba plants were sprayed with water (~) or 400 ppm ethrel (^) when indicated by arrows; cuttings were harvested at various times and their ethylene production was measured.
Table 1 Effects of ethrel treatments on height and flowering of plants of Aruba and Tempo Pink Ethrel concentration (ppm)
0 200 400 800
Aruba
Tempo Pink
Plant height (cm)
Flowers/plant
Plant height (cm)
Flowers/plant
33.82.5 28.31.2 27.10.7 19.71.0
24.03.0 2.00.1 0.00.0 0.00.0
68.94.0 70.22.0 65.22.0 46.83.0
69.03.0 5.01.2 0.00.0 0.00.0
Plants were sprayed with ethrel at various concentrations every 2 weeks. Values of flowering are presented as the number of flowers at anthesis at the time of measurement. The results presented are means taken after 9 weeksSE (n4).
3.2. Plant growth and flowering At the beginning of the experiment, both Tempo Pink and Aruba plants were about 10 cm tall. The plants exhibited different growth rates, with Tempo Pink having double the growth rate of Aruba. During the 9-week experiment, Tempo Pink plants grew up to ca. 7 fold and Aruba plants up to 3 fold (Tables 1 and 2). In all cases, ethrel treatments retarded the growth with a dose-related effect. The growth-inhibition effect of the ethrel treatments was apparent within 4 weeks from treatment. The highest ethrel concentration (800 ppm) gave the strongest growth inhibition (30±40%) (Table 1). Similar effects of growth inhibition by ethrel had been reported for other species (Rounkova, 1989).
G. Tamari et al. / Scientia Horticulturae 76 (1998) 29±35
33
Table 2 Effects of ethrel (400 ppm) and gibberellin (25 ppm) treatments on the performance of Aruba and Tempo Pink stock plants Treatment
Water (control) Ethrel Gibberellin Ethrelgibberellin
Aruba
Tempo Pink
Plant height (cm)
Flowers/plant
Plant height (cm)
Flowers/plant
22.00.7 13.90.4 25.61.1 19.40.6
9.00.5 0.00.0 8.11.3 0.00.0
36.03.4 21.11.8 46.23.7 32.12.0
9.00.5 0.00.0 8.11.3 0.00.0
Plants were sprayed with chemicals every 2 weeks. Measurements were conducted after 8 weeks. The results presented are meansSE (n13).
Morphological properties were also affected by the ethrel treatments; leaves of control Tempo Pink plants were light green in color and had a lower chlorophyll content compared with the Aruba controls (data not presented). Ethrel had almost no effect on the chlorophyll content of Tempo Pink leaves. In contrast, Aruba leaves, treated with ethrel, had lower chlorophyll content. As a result, the leaves of plants of the two cultivars had similar chlorophyll contents when treated with 800 ppm ethrel (data not shown). Tempo Pink plants bloomed in a shorter time than Aruba plants, with control plants reaching anthesis in 3 (Tempo Pink) or 6 weeks (Aruba). There were double the number of flowers in Tempo Pink at the end of the experiment (Table 1). Ethrel treatments significantly reduced the number of flowers in both cultivars; plants that had been treated with 200 ppm ethrel had 10% or less flowers compared to the control, and plants treated with higher concentrations of ethrel had no flowers at all (Table 1). The lack of flowers, in impatiens, resulted from bud abscission, and not from inhibition of flower development as in chrysanthemums (Strefeler et al., 1996). 3.3. Cuttings Plants of Tempo Pink had ca. 50% more cuttings than Aruba (Fig. 2(A). In both cultivars, ethrel treatments increased the number of cuttings in a concentrationrelated manner, resulting in a two-fold crop at the highest ethrel concentration (800 ppm). It is probable that the increase in the number of cutting was due to the effect of ethrel on lateral branching, associated with a reduced apical dominance (Raskin, 1991). Cuttings of all treated plants rooted within 2 weeks. In general, ethrel treatments applied to the stock plants improved the quality of the root system (Fig. 2(B)). Similar effects of ethrel on rooting had been reported for chrysanthemums (Soffer et al., 1989).
34
G. Tamari et al. / Scientia Horticulturae 76 (1998) 29±35
Fig. 2. Effect of ethrel treatments, applied to the stock plants, on: (A) number of cuttings in Tempo Pink (*) and Aruba (&) plants. (B) rooting quality of Tempo Pink (*) and Aruba (&) cuttings. (C) length of cuttings in Tempo Pink (*) and Aruba (&) plants. Bars represent a 2SE (n10).
Though cutting yield increased following ethrel treatments, these cuttings were generally shorter (Fig. 2(C)). This phenomenon was probably due to the inhibitory effects of ethrel on plant growth (Table 1), and was more pronounced in Aruba. Treating impatiens stock plants with ethrel resulted in an increase in ethylene production and smaller plants with no flowers. More cuttings were harvested from treated plants and their rooting was satisfactory. However, cuttings from ethrel-treated plants were shorter than those produced from untreated plants. In
G. Tamari et al. / Scientia Horticulturae 76 (1998) 29±35
35
both cultivars gibberellin, in combination with ethrel, produced taller plants than the ethrel treated plants. The same results were found for the length of the harvested cuttings (data not shown). In all treatments, gibberellin had no effect on the number of flowers. The treatments applies to both cultivars had no significant effect on the number of cuttings per plant or on the extent or quality of the rooting. In summary, the results of this work show that bi-weekly treatments of ethrel combined with gibberellin produce impatiens stock plants of a good quality that do not have flowers. Cuttings should not be harvested in the 3 days immediately following the treatments, since at that period the cuttings produce large amounts of ethylene (Fig. 1) that might be harmful for the post-harvest keepability of the cuttings. References Dostal, D.L., Howard Agnew, N., Gladon, R.J., Weigle, J.L., 1991. Ethylene, simulated shipping, STS, and AOA affect corolla abscission of New-Guinea Impatiens. Hort. Science 26(1), 47±49. Heller, A., Borochov, A., Halevy, A.H., 1994. Factors affecting rooting ability of Coleonema aspalathoides. Scientia Horticulturae 58(4), 335±341. Keren-Paz, V., Borochov, A., Mayak, S., 1989. The involvement of ethylene in liatris corm dormancy. Plant Growth Regulation 8(1), 11±20. Lichtenthaler, H.K., 1987. Chlorophylls and carotenoides: Pigments of photosynthetic biomembranes. Methods of Enzymology 148, 350±382. Porat, R., Halevy, A.H., Serek, M., Borochov, A., 1995. An increase in ethylene sensitivity following pollination is the initial event triggering an increase in ethylene production and enhanced senescence of phalaenopsis orchid flowers. Physiologia Plantarum 93(4), 778±784. Raskin, I., 1991. Ethylene in vegetative growth. In: Mattoo, A.K., Suttle, J.C. (Eds), The Plant Hormone Ethylene. CRC Press, Boca Raton, FL, pp. 183±192. Reid, M.S., Wu, M-J., 1991. Ethylene in flower development and senescence. In: Mattoo, A.K., Suttle, J.C. (Eds), The Plant Hormone Ethylene. CRC Press, Boca Raton, FL, pp. 215±234. Rounkova, L.V., 1989. Effect of ethylene producing substances and cultar on some ornamental plants. Acta Horticulturae 251, 281±288. Sharma, R., Kumar, S., Nanda, K.K., 1978. The effect of gibberellic acid and guanosine monophosphates on extension growth, leaf production and flowering of Impatiens balsamina. Physiologia Plantarum 44(4), 359±364. Soffer, H., Mayak, S., Burger, D.W., Reid, M.S., 1989. The role of ethylene in the inhibition of rooting under low oxygen tensions. Plant Physiology 89(1), 165±168. Strefeler, S.M., Anderson, N.O., Ascher, P.D., 1996. EthyleneGA3 sprays for delaying flower bud initiation in chrysanthemum (Dendranthema grandiflora Tzvelv.) stock plants. Hort Technology 6(3), 251±253.