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Effect of triacontanol on production and quality of flowers of Chrysanthemum morifolium Ramat
Scientia Horticulturae, 18 (1982/83) 87--92
87
Elsevier Scientific Publishing Company, Amsterdam -- Printed in The Netherlands
E F F E C T O F T R I A C O N T A N O L ON P R O D U C T I O N AND QUALITY OF FLOWERS O F C H R Y S A N T H E M U M MORIFOLIUM RAMAT
D. SKOGEN, A.B. ERIKSEN and S. NILSEN
The Phytotron, University of Oslo, Box 1066, Blindern, Oslo 3 (Norway) (Accepted for publication 3 December 1981)
ABSTRACT Skogen, D., Eriksen, A.B. and Nilsen, S., 1982. Effect of triacontanol on production and quality of flowers of Chrysanthemum morifolium Ramat. Scientia Hortic., 18: 87--92. Two cultivars of Chrysanthemum morifolium, 'Golden Horim' and 'Golden Miquel', were cultivated in nutrient solution containing the growth regulator triacontanol. The vegetative growth, production of inflorescences and quality of flowers were measured. The dry weight of the whole plant and the shoot from both cultivars increased. The number of inflorescences per plant and the number of flowers per inflorescence also increased in response to triacontanol treatment, which in turn enhanced the quality of flowers in accordance with the standards defined by sales-quality groups. The number of flowers of superior quality was more than doubled.
INTRODUCTION
When fertilizing t o m a t o and rice with chopped alfalfa, Ries et al. (1977a) observed increases in b o t h growth and yield which were larger than expected considering the a m o u n t of nitrogen supplied. Later, the active substance was isolated and identified as triacontanol, a saturated alcohol with 30 carbon atoms (Chibnall et al., 1933; Ries et al., 1977b). Triacontanol was found to be a natural constituent of the cuticular wax of many plant species (Kolker, 1978; Henry and Primo, 1979), b u t the most c o m m o n primary alcohols of the cuticular are hexacosanol (C-26) and octacosanol (C-28) (Kolattukudy, 1970). Jones et al. (1979)have tested these alcohols and other analogs of triacontanol (C-16 to C-32), b u t all failed to stimulate growth. Further studies on the effects o f triacontanol have revealed that triacontanol enhances the growth of vegetables and cereal crops when applied as a foliar spray or added to the root medium (Ries et al., 1978; Sagaral et al., 1978). The growth response seems to be quite rapid, since as early as 3--6 h after treatment an increase in fresh weight was observed (Ries and Wert, 1977; Bittenbender et al., 1978). This increase in fresh weight is not just due to an increase in water uptake, b u t is the result of an increase in dry matter production (Hangarter et al., 1978). 0304-4238/82/0000--0000/$02.75 © 1982 Elsevier Scientific Publishing Company
88
Our laboratory has confirmed that triacontanol causes an increase in the growth o f tomato, b u t not maize (Eriksen et al., 1981, 1982). We assume that triacontanol in some way regulates processes related to production, photosynthesis and photorespiration. Earlier papers have considered the effect of triacontanol on the production of vegetables and cereal crops. The present paper deals primarily with the effect of triacontanol on flower production. MATERIALS AND METHODS
Plant material and growth conditions. -- Cuttings of Chrysanthemum morifolium Ramat 'Golden Miquel' and 'Golden Horim' were treated with a root-
stimulating chemical, 2% Floramon (a-naphtyl-acetic-acid), before placing them into r o c k w o o l cubes. The cubes with the cuttings were placed in a tent made of transparent plastic inside a glasshouse. The relative humidity in the tent was kept close to 100% b y spraying the cuttings for 20 s each hour with water. In addition to natural daylight, the cuttings were illuminated with fluorescent tubes (Luma 65/80 W) with a photoperiod of 16 h light/8 h dark. The irradiance was 32 Wm -2, measured b y a light meter (Li-185, Lambda Instr. Corp., Lincoln, NE, U.S.A.). The temperature inside the tent was 23 +1°C during the light period and 19 + I ° C during the dark period. After 14 days, the plants were sprayed daffy with a standard nutrient solution of 0.2% (v/v) Hydroflor containing 0.05% (w/v) Ca(NO3)2 (Eriksen et al., 1981). Two experiments were performed, one in 1980 from January. to May and another in 1981 from December to May, which will be referred to as Experiments 1 and 2, respectively. After 21 clays in Experiment 1 and 39 days in Experiment 2, the plants were transferred to the glasshouse where the rockwool cubes were placed in 16 plastic gulleys, each 3 m in length, which were connected to a system that circulated nutrient solution (same as above) from a 560-1 reservoir through the gulleys. Control plants were grown in 8 gulleys with only nutrient solution and the treated plants grown in the other 8 gulleys with nutrient solution containing triacontanol (100 pg/1; 2.3 × 10 -7 M). These solutions were changed once a week. The triacontanol solution was prepared according to Eriksen et al. (1981). In Experiment 1 the control plants were grown in nutrient solution. However, in Experiment 2 t h e y were grown in nutrient solution containing the triacontanol solvents chloroform and Tween-20. The photoperiod during cultivation was 16 h light/8 h darkness for 43 days in Experiment 1 and 55 days in Experiment 2. Then the light period was reduced to 8 h/day in order to induce flower initiation. Additional light from Na-high pressure lamps (Gen. Elect. Lucalox 400/40), placed 135 cm from the gulleys, illuminated the plants at an irradiance of 200 Wm -2 when measured at a distance o f 125 cm below the lamps. The temperature of the nutrient solution was 20 + I°C. The glasshouse was kept at 17 + I ° C at night and not lower than 20°C during the day.
89 - - The flowers were ready for harvest after 52 days (Experiment 1) and 60 days (Experiment 2) after the short-day treatment began. All plants were removed and graded first for the quality of flowers. The inflorescences from all 48 plants in each group were divided into 4 quality groups: Superior: Inflorescences longer than 60 cm carrying 7 or more opened flowers. Grade 1 : Inflorescences longer than 60 cm carrying 5--6 opened flowers. Grade 2 : Four opened flowers. Length of inflorescence variable. Grade 3 : Three or less opened flowers. Length of inflorescence variable. Then 16 plants were used for fresh-weight and dry-weight measurements. The dry weight was determined after 48 h at 104 ° C. The rest of the plants were stored in a cold room (4 ° C) for 17--32 days. Plants were removed every third day and placed in a climate chamber at 20 ° C, light intensity 17 ~ Em-2s -~, 18 h light period, for approximately 35 days or until wilting occurred, to determine whether there were differences in the durability of the flowers.
Analysis.
RESULTS AND DISCUSSION
The effect of triacontanol on vegetative growth as shown by dry weight measurements is shown in Table I. An increase in dry weight was observed in both c h r y s a n t h e m u m cultivars and in both Experiments (Table I). The lower TABLE I The effect of triacontanol on the dry weight of different parts of chrysanthemum plants. The data are presented as % of control weights and represent the mean values of 16 plants Cultivar
Golden Miquel Golden Horim
Whole plant
Leavesand stems
Flowers
1980
1981
1980
1981
1980
1981
116 118
106 109
116 119
107 108
110 110
97 118
dry weight increase in 1981 might be due to the presence of the triacontanol solvents chloroform and Tween in the control group. The magnitude of the dry-weight increment in the treated plants was approximately the same as was observed by t o m a t o plants, which were given the same concentration of triacontanol as chrysanthemum, 31 and 17% increase, with and w i t h o u t triacontanol solvents, respectively (Eriksen et al., 1981). Other research with triacontanol showed that 100 pg/1 increased dry weight significantly when applied to several cereal crops (Ries et al., 1978). The number of inflorescences per plant was significantly higher in the triacontanol-treated plants (Table II). In 1980, there were 11--12% more inflorescences on the treated plants, while in 1981 there were 4--9% more. Again the difference may be due to the addition of triacontanol solvents to the nutrient solution of the control group in 1981.
90 T A B L E II R e s p o n s e o f f l o w e r i n g t o t r i a c o n t a n o l . E a c h g r o u p in 1 9 8 0 c o n s i s t e d o f 31 p l a n t s a n d in 1 9 8 1 o f 48 p l a n t s . S t a t i s t i c a l s i g n i f i c a n c e ( * ) 9 9 . 9 % Cultivar
Treatment
Inflorescences/plant 1980
1981
G o l d e n Miquel
Control Triacontanol
5.6 ± 0.5 6.2 ± 0 . 4 *
5.8 ± 0.4 6.3 ± 0 . 5 *
Golden Horim
Control Triacontanol
6.7 ± 0.4 7.4 ± 0.4*
9.8 ± 0.5 10.2 ± 0.6*
The most pronounced effect of triacontanol was on flower quality. The inflorescences were divided into the quality groups, defined sub "Methods". The number of inflorescences of superior quality more than doubled (Table III and Fig. 1). The most valuable inflorescences for sale are the quality groups Superior and Grade 1. Growth retardants have been used for some years to increase the quality of chrysanthemum. These chemicals reduce the height, induce sturdier stems and give darker and more luxurious foliage (Dicks, 1976; Menhenett, 1976). Triacontanol enhanced quality by increasing the number of flowers and infiorescences and producing sturdier plants without reducing height and dry weight The time of bud-breaking and flowering were noted in order to determine whether triacontanol affected the speed of plant development. Bud-breaking and flowering were about a week earlier in the triacontanol-treated group. However, there was no difference observed in flower durability. The increased number of inflorescences could have been caused by reduced apical dominance resulting from an internal reduction of the indole acetic acid level. Henry and Gordon {1980) have reported a higher peroxidase level and TABLEIII The effect o f t r i a c o n t a n o l o n quality d i s t r i b u t i o n o f inflorescences. The results represent the % o f the t o t a l inflorescences from 48 plants in e a c h group
Cultivar
Treatment
Inflorescences
Quality d i s t r i b u t i o n (%)
(total number) Superior Experiment 1 (1980) G o l d e n Miquel Control Triacontanol
Golden Horim
Control Triacontanol
Grade 1
Grade 2
Grade 3
302 321
2.3 4.8
11.3 34.3
45.4 30.1
41.1 30.8
331 355
4.5 18.9
23.3 33.0
38.1 26.8
32.0 21.4
Experiment 2 (1981) G o l d e n Miquel
Control Triacontanol
278 301
1.8 6.6
15.1 17.6
39.6 39.5
43.5 36.2
G o l d e n Horim
Control
470 491
1.5 6.3
21.2 16.5
49.6 45.4
27.7 32.0
Triacontanol
91 Golden Horim
Golden Mique[ 120 -
1980
1980
1981
1981
G,I u u
0
100 -
80-
C
60-
E
40-
Z
20-
r
Superior
Superior
Grade 1
Grade 1
Superror
Superior Grade 1
G rQde I
Quality distribution
Fig. 1. Distribution of Superior and Grade 1 inflorescences of control (clear bar) and triacontanol-treated (stippled bar) cultivars of chrysanthemum plants from experiments done in 1980 and 1981. auxin breakdown in triacontanol-treated Pisum sativum 'Little Marvel'. The main effects of triacontanol on chrysanthemum seem to be related to an increase in growth rate, which in turn may have resulted in a stronger plant with more and larger inflorescences carrying a higher n u m b e r of flowers. In previous studies using t o m a t o and maize, triacontanol seemed to change the balance between photorespiration and photosynthesis in favour of the latter (Eriksen et al., 1981). This m a y also be the explanation for the increased growth and flowering in chrysanthemum. At present, however, no specific hypothesis of triacontanol action has been proposed which can explain its various effects. Further experimentation both on the effect and the mechanism of action o f this growth regulator are needed. ACKNOWLEDGEMENTS The authors wish to t h a n k Dr. May K. Haugstad for valuable criticism and discussion of this paper. The cultivation of plants by Mr. P. Rudidalen and Mr. K. Haraldsen and the technical assistance of Mr. T. Lund are gratefully acknowledged. The 1980 experiment was financially supported by Norsk Hydro.
REFERENCES Bittenbender, H.C., Dilley, D.R., Wert, V. and Ries, S.K., 1978. Environmental parameters affecting dark response of rice seedlings (Oryza sativa L.) to triacontanol. Plant Physiol., 61: 851--854.
92 Chibnall, A.C., Williams, E.F., Latner, A.L. and Piper, S.H., 1933. The isolation of ntriacontanol from lucerne wax. Biochem. J., 27: 1885--1888. Dicks, J.W., 1976. Chemical restriction of stem growth in ornamentals, cereals and tobacco. Outlook Agric., 9(2): 69--75. Eriksen, A.B., Selld~n, G., Skogen, D. and Nilsen, S., 1981. Comparative analyses of the effect of triacontanol on photosynthesis, photorespiration and growth of t o m a t o (C 3plant) and maize (C 4-plant ). Planta, 152: 44--49. Eriksen, A.B., Haugstad, M.K. and Nilsen, S., 1982. Yield of t o m a t o and maize in response to foliar and r o o t applications of triacontanol. Plant Growth Regul., in press. Hangarter, R., Ries, S.K. and Carlson, P., 1978. Effect of triacontanol on plant cell cultures in vitro. Plant Physiol., 61: 855--858. Henry, E.W. and Gordon, C.J., 1980. The effect of triacontanol on peroxidase, IAA, and plant growth in I~'sum sativum 'Alaska' and 'Little Marvel'. J. Exp. Bot., 31: 1297--1303. Henry, E.W. and Primo, D.J., 1979. The effects of triacontanol on seedling growth and polyphenol oxidase. Activity in dark and light growth of lettuce. J. Plant Nutr., 1: 397--405. Jones, J., Wert, V. and Ries, S.K., 1979. Specificity of 1-triacontanol as a plant growth stimulator and inhibition of its effect b y other long-chain compounds. Planta, 144: 277--282. Kolattukudy, P.E., 1970. Cutin biosynthesis in Vicia faba leaves. Plant Physiol., 46: 759--760. Kolker, L.S., 1978. Analytical procedures for 1-triacontanol and its presence in plants and the environment. M.S. Thesis, Michigan State Univ., East Lansing. Menhenett, R., 1976. Plant hormones and the modification of growth and development. In: Chrysanthemums -- The Inside Story. National Chrysanthemum Society, London. Ries, S.K. and Wert, V., 1977. Growth responses o f rice seedlings to triacontanol in light and dark. Planta, 135: 77--82. Ries, S.K., Bittenbender, H., Hangarter, R., Kolker, L., Morris, G. and Wert, V., 1977a. Improved growth and yield of crops from organic supplements. In: Energy and Agriculture. W. Lockeretz (Editor), Academic Press, New York, pp. 377--384. Ries, S.K., Wert, V., Sweeley, C.C. and Leavitt, R.A., 1977b. Triacontanol: A new natural occurring plant growth regulator. Science, 195: 1339--1341. Ries, S.K., Richman, R.L. and Wert, V.F., 1978. Growth and yield of crops treated with triacontanol. J. Am. Soc. Hortic. Sci., 103: 361--364. Sagaral, E.G., Orcutt, D.M. and Foy, C.L., 1978. Influence of time and rate of triacontanol applications on the growth and yields of selected plants. Proc. 5th Am. Meet. Plant Growth Regulator Working Group, Blacksburg, June 25--29.
87
Elsevier Scientific Publishing Company, Amsterdam -- Printed in The Netherlands
E F F E C T O F T R I A C O N T A N O L ON P R O D U C T I O N AND QUALITY OF FLOWERS O F C H R Y S A N T H E M U M MORIFOLIUM RAMAT
D. SKOGEN, A.B. ERIKSEN and S. NILSEN
The Phytotron, University of Oslo, Box 1066, Blindern, Oslo 3 (Norway) (Accepted for publication 3 December 1981)
ABSTRACT Skogen, D., Eriksen, A.B. and Nilsen, S., 1982. Effect of triacontanol on production and quality of flowers of Chrysanthemum morifolium Ramat. Scientia Hortic., 18: 87--92. Two cultivars of Chrysanthemum morifolium, 'Golden Horim' and 'Golden Miquel', were cultivated in nutrient solution containing the growth regulator triacontanol. The vegetative growth, production of inflorescences and quality of flowers were measured. The dry weight of the whole plant and the shoot from both cultivars increased. The number of inflorescences per plant and the number of flowers per inflorescence also increased in response to triacontanol treatment, which in turn enhanced the quality of flowers in accordance with the standards defined by sales-quality groups. The number of flowers of superior quality was more than doubled.
INTRODUCTION
When fertilizing t o m a t o and rice with chopped alfalfa, Ries et al. (1977a) observed increases in b o t h growth and yield which were larger than expected considering the a m o u n t of nitrogen supplied. Later, the active substance was isolated and identified as triacontanol, a saturated alcohol with 30 carbon atoms (Chibnall et al., 1933; Ries et al., 1977b). Triacontanol was found to be a natural constituent of the cuticular wax of many plant species (Kolker, 1978; Henry and Primo, 1979), b u t the most c o m m o n primary alcohols of the cuticular are hexacosanol (C-26) and octacosanol (C-28) (Kolattukudy, 1970). Jones et al. (1979)have tested these alcohols and other analogs of triacontanol (C-16 to C-32), b u t all failed to stimulate growth. Further studies on the effects o f triacontanol have revealed that triacontanol enhances the growth of vegetables and cereal crops when applied as a foliar spray or added to the root medium (Ries et al., 1978; Sagaral et al., 1978). The growth response seems to be quite rapid, since as early as 3--6 h after treatment an increase in fresh weight was observed (Ries and Wert, 1977; Bittenbender et al., 1978). This increase in fresh weight is not just due to an increase in water uptake, b u t is the result of an increase in dry matter production (Hangarter et al., 1978). 0304-4238/82/0000--0000/$02.75 © 1982 Elsevier Scientific Publishing Company
88
Our laboratory has confirmed that triacontanol causes an increase in the growth o f tomato, b u t not maize (Eriksen et al., 1981, 1982). We assume that triacontanol in some way regulates processes related to production, photosynthesis and photorespiration. Earlier papers have considered the effect of triacontanol on the production of vegetables and cereal crops. The present paper deals primarily with the effect of triacontanol on flower production. MATERIALS AND METHODS
Plant material and growth conditions. -- Cuttings of Chrysanthemum morifolium Ramat 'Golden Miquel' and 'Golden Horim' were treated with a root-
stimulating chemical, 2% Floramon (a-naphtyl-acetic-acid), before placing them into r o c k w o o l cubes. The cubes with the cuttings were placed in a tent made of transparent plastic inside a glasshouse. The relative humidity in the tent was kept close to 100% b y spraying the cuttings for 20 s each hour with water. In addition to natural daylight, the cuttings were illuminated with fluorescent tubes (Luma 65/80 W) with a photoperiod of 16 h light/8 h dark. The irradiance was 32 Wm -2, measured b y a light meter (Li-185, Lambda Instr. Corp., Lincoln, NE, U.S.A.). The temperature inside the tent was 23 +1°C during the light period and 19 + I ° C during the dark period. After 14 days, the plants were sprayed daffy with a standard nutrient solution of 0.2% (v/v) Hydroflor containing 0.05% (w/v) Ca(NO3)2 (Eriksen et al., 1981). Two experiments were performed, one in 1980 from January. to May and another in 1981 from December to May, which will be referred to as Experiments 1 and 2, respectively. After 21 clays in Experiment 1 and 39 days in Experiment 2, the plants were transferred to the glasshouse where the rockwool cubes were placed in 16 plastic gulleys, each 3 m in length, which were connected to a system that circulated nutrient solution (same as above) from a 560-1 reservoir through the gulleys. Control plants were grown in 8 gulleys with only nutrient solution and the treated plants grown in the other 8 gulleys with nutrient solution containing triacontanol (100 pg/1; 2.3 × 10 -7 M). These solutions were changed once a week. The triacontanol solution was prepared according to Eriksen et al. (1981). In Experiment 1 the control plants were grown in nutrient solution. However, in Experiment 2 t h e y were grown in nutrient solution containing the triacontanol solvents chloroform and Tween-20. The photoperiod during cultivation was 16 h light/8 h darkness for 43 days in Experiment 1 and 55 days in Experiment 2. Then the light period was reduced to 8 h/day in order to induce flower initiation. Additional light from Na-high pressure lamps (Gen. Elect. Lucalox 400/40), placed 135 cm from the gulleys, illuminated the plants at an irradiance of 200 Wm -2 when measured at a distance o f 125 cm below the lamps. The temperature of the nutrient solution was 20 + I°C. The glasshouse was kept at 17 + I ° C at night and not lower than 20°C during the day.
89 - - The flowers were ready for harvest after 52 days (Experiment 1) and 60 days (Experiment 2) after the short-day treatment began. All plants were removed and graded first for the quality of flowers. The inflorescences from all 48 plants in each group were divided into 4 quality groups: Superior: Inflorescences longer than 60 cm carrying 7 or more opened flowers. Grade 1 : Inflorescences longer than 60 cm carrying 5--6 opened flowers. Grade 2 : Four opened flowers. Length of inflorescence variable. Grade 3 : Three or less opened flowers. Length of inflorescence variable. Then 16 plants were used for fresh-weight and dry-weight measurements. The dry weight was determined after 48 h at 104 ° C. The rest of the plants were stored in a cold room (4 ° C) for 17--32 days. Plants were removed every third day and placed in a climate chamber at 20 ° C, light intensity 17 ~ Em-2s -~, 18 h light period, for approximately 35 days or until wilting occurred, to determine whether there were differences in the durability of the flowers.
Analysis.
RESULTS AND DISCUSSION
The effect of triacontanol on vegetative growth as shown by dry weight measurements is shown in Table I. An increase in dry weight was observed in both c h r y s a n t h e m u m cultivars and in both Experiments (Table I). The lower TABLE I The effect of triacontanol on the dry weight of different parts of chrysanthemum plants. The data are presented as % of control weights and represent the mean values of 16 plants Cultivar
Golden Miquel Golden Horim
Whole plant
Leavesand stems
Flowers
1980
1981
1980
1981
1980
1981
116 118
106 109
116 119
107 108
110 110
97 118
dry weight increase in 1981 might be due to the presence of the triacontanol solvents chloroform and Tween in the control group. The magnitude of the dry-weight increment in the treated plants was approximately the same as was observed by t o m a t o plants, which were given the same concentration of triacontanol as chrysanthemum, 31 and 17% increase, with and w i t h o u t triacontanol solvents, respectively (Eriksen et al., 1981). Other research with triacontanol showed that 100 pg/1 increased dry weight significantly when applied to several cereal crops (Ries et al., 1978). The number of inflorescences per plant was significantly higher in the triacontanol-treated plants (Table II). In 1980, there were 11--12% more inflorescences on the treated plants, while in 1981 there were 4--9% more. Again the difference may be due to the addition of triacontanol solvents to the nutrient solution of the control group in 1981.
90 T A B L E II R e s p o n s e o f f l o w e r i n g t o t r i a c o n t a n o l . E a c h g r o u p in 1 9 8 0 c o n s i s t e d o f 31 p l a n t s a n d in 1 9 8 1 o f 48 p l a n t s . S t a t i s t i c a l s i g n i f i c a n c e ( * ) 9 9 . 9 % Cultivar
Treatment
Inflorescences/plant 1980
1981
G o l d e n Miquel
Control Triacontanol
5.6 ± 0.5 6.2 ± 0 . 4 *
5.8 ± 0.4 6.3 ± 0 . 5 *
Golden Horim
Control Triacontanol
6.7 ± 0.4 7.4 ± 0.4*
9.8 ± 0.5 10.2 ± 0.6*
The most pronounced effect of triacontanol was on flower quality. The inflorescences were divided into the quality groups, defined sub "Methods". The number of inflorescences of superior quality more than doubled (Table III and Fig. 1). The most valuable inflorescences for sale are the quality groups Superior and Grade 1. Growth retardants have been used for some years to increase the quality of chrysanthemum. These chemicals reduce the height, induce sturdier stems and give darker and more luxurious foliage (Dicks, 1976; Menhenett, 1976). Triacontanol enhanced quality by increasing the number of flowers and infiorescences and producing sturdier plants without reducing height and dry weight The time of bud-breaking and flowering were noted in order to determine whether triacontanol affected the speed of plant development. Bud-breaking and flowering were about a week earlier in the triacontanol-treated group. However, there was no difference observed in flower durability. The increased number of inflorescences could have been caused by reduced apical dominance resulting from an internal reduction of the indole acetic acid level. Henry and Gordon {1980) have reported a higher peroxidase level and TABLEIII The effect o f t r i a c o n t a n o l o n quality d i s t r i b u t i o n o f inflorescences. The results represent the % o f the t o t a l inflorescences from 48 plants in e a c h group
Cultivar
Treatment
Inflorescences
Quality d i s t r i b u t i o n (%)
(total number) Superior Experiment 1 (1980) G o l d e n Miquel Control Triacontanol
Golden Horim
Control Triacontanol
Grade 1
Grade 2
Grade 3
302 321
2.3 4.8
11.3 34.3
45.4 30.1
41.1 30.8
331 355
4.5 18.9
23.3 33.0
38.1 26.8
32.0 21.4
Experiment 2 (1981) G o l d e n Miquel
Control Triacontanol
278 301
1.8 6.6
15.1 17.6
39.6 39.5
43.5 36.2
G o l d e n Horim
Control
470 491
1.5 6.3
21.2 16.5
49.6 45.4
27.7 32.0
Triacontanol
91 Golden Horim
Golden Mique[ 120 -
1980
1980
1981
1981
G,I u u
0
100 -
80-
C
60-
E
40-
Z
20-
r
Superior
Superior
Grade 1
Grade 1
Superror
Superior Grade 1
G rQde I
Quality distribution
Fig. 1. Distribution of Superior and Grade 1 inflorescences of control (clear bar) and triacontanol-treated (stippled bar) cultivars of chrysanthemum plants from experiments done in 1980 and 1981. auxin breakdown in triacontanol-treated Pisum sativum 'Little Marvel'. The main effects of triacontanol on chrysanthemum seem to be related to an increase in growth rate, which in turn may have resulted in a stronger plant with more and larger inflorescences carrying a higher n u m b e r of flowers. In previous studies using t o m a t o and maize, triacontanol seemed to change the balance between photorespiration and photosynthesis in favour of the latter (Eriksen et al., 1981). This m a y also be the explanation for the increased growth and flowering in chrysanthemum. At present, however, no specific hypothesis of triacontanol action has been proposed which can explain its various effects. Further experimentation both on the effect and the mechanism of action o f this growth regulator are needed. ACKNOWLEDGEMENTS The authors wish to t h a n k Dr. May K. Haugstad for valuable criticism and discussion of this paper. The cultivation of plants by Mr. P. Rudidalen and Mr. K. Haraldsen and the technical assistance of Mr. T. Lund are gratefully acknowledged. The 1980 experiment was financially supported by Norsk Hydro.
REFERENCES Bittenbender, H.C., Dilley, D.R., Wert, V. and Ries, S.K., 1978. Environmental parameters affecting dark response of rice seedlings (Oryza sativa L.) to triacontanol. Plant Physiol., 61: 851--854.
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