- Email: [email protected]
Rooting and initial establishment of stem cuttings of oregano, peppermint and balm
Scientia Horticulturae, 13 (1980) 53--59 Elsevier Scientific Publishing Company, Amsterdam -- Printed in The Netherlands
53
ROOTING AND INITIAL ESTABLISHMENT OF STEM CUTTINGS OF OREGANO, PEPPERMINT AND BALM 1
2
A. KURIS , A. ALTMAN and E. PUTIEVSKY 1
1
Division of Medicinal and Spice Crops, Agricultural Research Organization, Newe Ya 'ar ~egional Experiment Station (Israel) Department of Horticulture, The Hebrew University of Jerusalem, Rehovot (Israel) (Accepted for publication 17 December 1979)
ABSTRACT
Kuris, A., Altman, A. and Putievsky, E., 1980. Rooting and initial establishment of stem cuttings of oregano, peppermint and balm. Scientia Hortic., 13: 53--59. Stem cuttings of 3 Labiatae spices, oregano (Origanum vulgare L.), peppermint (Mentha piperita L.) and balm (Melissa offlnicalis L.) were analyzed for their rooting-patterns and initial establishment under controlled conditions. Approximately 100% of cuttings from all 3 species rooted, but the number of roots per cutting varied in the order: oregano ~ balm ~ peppermint. Treatment of cuttings with IBA, IAA and Hormex increased both the number of roots per cutting and the rate of root formation in all 3 species. This effect was, however, dependent on their natural capacity for root formation, with the greatest effect on the slowest root producer, balm, where root number increased 3-fold. Enhanced root formation was reflected in increased fresh-weight accumulation by both root and shoot systems. Hormone treatment also increased shoot length of peppermint. All the above mentioned effects were concentration-dependent. Thus, hormonal treatment of cuttings of these 3 Labiatae spices clearly aided early establishment, and especially so in cuttings which were initially less vigorous.
INTRODUCTION O r e g a n o (Origanum vulgare L.), p e p p e r m i n t (Mentha piperita L. vat. ' M i c h a m ' ) a n d b a l m (Melissa officinalis L.), 3 i m p o r t a n t L a b i a t a e spices, usually g r o w wild a n d v e r y little is k n o w n o n h o r t i c u l t u r a l p r a c t i c e s concerning t h e i r g r o w t h a n d d e v e l o p m e n t (Parry, 1 9 6 2 ; R o s e n g a r t e n , 1 9 6 9 ; P u t i e v s k y a n d Barker, 1 9 7 7 ; P u t i e v s k y et al., 1977). T h e s e spices are u s u a l l y p r o p a g a t e d v e g e t a t i v e l y since seed p r o p a g a t i o n is difficult: p e p p e r m i n t d o e s n o t p r o d u c e seeds d u e t o a n h e x a p l o i d s t a t e ( M u r r a y et al., 1 9 7 1 ) , o r e g a n o seeds are v e r y small a n d , thus, d i f f i c u l t t o handle, a n d seed p r o d u c t i o n a n d g e r m i n a t i o n in b a l m are p o o r . In a d d i t i o n , p r o p a g a t i o n o f t h e s e spices f r o m seeds m a y result in a c o n s i d e r a b l e d e l a y in yield p r o d u c t i o n . A l t h o u g h m o s t o f t h e L a b i a t a e species are easily p r o p a g a t e d
54
vegetatively through cuttings or stolons, some problems occur in commercial cultivation with lack of r o o t formation and delayed establishment of cuttings (Putievsky et al., 1977). Thus, the rooting-behavior and early establishment of stem cuttings of the above-mentioned species were investigated in relation to hormonal treatment. M A T ER I ALS AND METHODS
Apical stem cuttings, 12 cm in length, were removed in December from one-year-old plants, which were grown in a dark brown vertisol soil under Mediterranean conditions (Newe Ya'ar Regional Experiment Station). Leaves were removed from the lower half of the cuttings. In the case of balm, the remaining leaves were trimmed to a b o u t half-size in order to prevent excessive transpiration by the relatively large leaves. The basal 4 cm of all cuttings were dipped for 4 s in solutions of 500--4000 mg 1 -' IBA (~-indole butyric acid), or 500--2000 mg 1-1 IAA (~-indole acetic acid), as specified in the figures and tables. In addition, Hormex, a commercial rooting-powder containing 0.1% IBA, was applied to the basal cut surface of the cuttings. Two types of stems were observed on oregano, those with visible r o o t primordia on the surface ( " r o o t initials"), and those without visible primordia; cuttings were prepared from the second t y p e only. After treatment, the cuttings were planted in propagation beds in a rootingmedium composed o f horticultural grade peat: perlite (1:1), and maintained in a heated greenhouse. Each experimental treatment consisted of 5 randomized replicates, 8 cuttings in each replicate. After 69 days, all cuttings were removed from the propagatingmedium, rinsed in tap water, and the number of roots per cutting was recorded. Shoot fresh weight, which included the original cutting and the new growth (and in the case of peppermint the stolons also), r o o t fresh weight and length of the longest branch were measured. At various time intervals during the rooting-period, 2 cuttings from each replicate (total 10 cuttings for each treatment) were csxefully removed from the medium and their roots were counted, after which they were inserted back into the propagation beds. In the case of peppermint and balm, root counting was discontinued after 27 and 31 days, respectively. Standard errors of the means of all treatments for the entire period were calculated. RESULTS
Oregano. -- All cuttings rooted. However, treatment with IAA and IBA, at various concentrations, resulted in a slight increase in the number of roots during the first 3 weeks, but the final number of roots after 69 days was similar in each treatment (Fig. 1). There was a slight reduction in the number of roots per cutting during certain dates, and this is related to the samplingm e t h o d (see Materials and Methods).
55
I
I
I
l
I
I
I
40--
~.j-
30-
Z F-
D.
2o
O 0 rr
10
/ 10
1
I
I
I
1
20
3O
40 DAYS
50
60
I 70
Fig. 1. R o o t formation in oregano cuttings in response to hormonal treatments. Cuttings were treated with various concentrations of I B A or IAA, or with Hormex. Root n u m b e r was recorded over a period of 69 days, and data represent average root n u m b e r per cutting. I B A series: 1=500 m g l-I ; 2 = 1 0 0 0 m g 1-1 ; 3 = 2 0 0 0 m g l-I ; 4 = 4 0 0 0 m g l-I . I A A series: 5=500 m g I-I;6 = 2 0 0 0 m g l-I. H o r m e x : 7.
While only a slight effect of hormonal treatment on r o o t formation was found, it markedly affected the initial establishment of cuttings, as judged by the fresh weight of the r o o t and the shoot systems (Table I). IBA, IAA, and especially Hormex increased r o o t fresh weight. The effect of IAA on increasing shoot weight was, however, greater than that of IBA which is clearly reflected in the s h o o t - - r o o t ratio. Final stem length was not affected by hormonal treatment o f cuttings. Peppermint. - - While almost 100% of untreated peppermint stem cuttings formed adventitious roots after 27 days in the rooting-medium, the number of roots per cutting was increased b y hormonal treatment (Fig. 2). This effect was, however, dependent on the t y p e and concentration of the growth substance. IAA at 2000 mg 1-1 (Treatment 6) doubled the number of roots per cutting as compared with control. For reasons that will be discussed later,
56 TABLE I The effect o f h o r m o n a l t r e a t m e n t of oregano cuttings on their initial growth and establishment. Cuttings were u p r o o t e d 69 days after h o r m o n a l t r e a t m e n t , and the fresh weight o f the roots and shoot, as well as s t e m length, were determined. S h o o t / r o o t ratio was calculated f r o m fresh weight data
Control mg mg mg mg
Fresh weight (g) Roots Shoot
Shoot/root ratio
Stem length (cm)
10.1
24.5
2.42
19.9
IBA,
500 1000 2000 4000
1-1 1-1 1-1 1-1
11.9 14.9 13.1 16.2
29.4 26.4 26.9 31.2
2.47 1.77 2.05 1.92
18.7 16.0 22.2 18.7
IAA,
500 mg 1-1 2000 mg 1-1
16.1 14.9
35.3 33.6
2.19 2.25
18.6 21.6
20.2
28.1
1.40
19.3
Hormex
,sI I
I
/D61
SE
z° 10 I.I...-
•
/
#a
(.J ¢,.. I.U Q. I-
o
~
~_.~
I
10 Fig. 2. R o o t f o r m a t i o n in were treated with various see legend to Fig. 1. R o o t sent average r o o t n u m b e r
~
I
20 DAYS
CONTROL
I
30
p e p p e r m i n t cuttings in response to h o r m o n a l t r e a t m e n t . Cuttings c o n c e n t r a t i o n s of I B A or IAA, or with H o r m e x . F o r treatments n u m b e r was r e c o r d e d over a period of 27 days, and data repreper cutting.
57
the major effect of the growth substances was evident from the 19th day on, following an arrest of root development in the preceding week. The reduction in the number of roots per cutting in that week is related to the samplingmethod. Although other morphological observations were made until 69 days, counting of roots was discontinued after 31 days because of massive formation of stolons in addition to regular root initiation. Both root and shoot growth were dependent on initial treatment of cuttings (Table II). Stem length increased by more than, or almost 100% in response to IBA, IAA, and Hormex at the higher concentrations. In addition, the number of axillary branches T A B L E II The e f f e c t o f h o r m o n a l t r e a t m e n t o f p e p p e r m i n t c u t t i n g s o n t h e i r initial g r o w t h a n d e s t a b l i s h m e n t . Cuttings were uprooted 69 days after hormonal treatment and the fresh weight of the roots and shoot, as well as s t e m l e n g t h a n d n u m b e r o f n e w l y - f o r m e d a x l l l a r y b r a n c h e s a n d s t o l o n s , w e r e d e t e r m i n e d . Shoot/roo+. ratio was calculated from fresh weight data F r e s h w e i g h t (g)
Control mg mg mg mg
Shoot/root ratio
Stem length (cm)
No. of branches
No. of stolons
Roots
Shoot
3.4
14.0
4,12
5.0
0,4
0.3
IBA,
500 1000 2000 4000
I-Ii I I II- I
4.7 2.8 2.1 6.5
24.5 16.7 7.3 31.7
5,21 5,96 3.48 4,88
7.2 6.3 4.0 11.3
1.5 0.9 0.6 2.1
0.7 0.3 0.2 0.6
IAA,
500 mgl -I 2 0 0 0 m g ]-I
3.1 4.0
14.1 23.4
4,55 5.85
4.6 II.I
1.0 1.5
0.4 0.6
3.6
26.2
7.27
9.0
1.3
0.7
Hormex
TABLE III The effect of hormonal treatment of balm cuttings on their initial growth and establishment. Cuttings were uprooted 69 days after hormonal treatment, and the fresh weight of the roots and shoot, as well as stem length, were determined. S h o o t / r o o t ratio was calculated from fresh weight data
Fresh weight (g) Roots Shoot Control
Stem length (cm)
6.3
27.0
4.3
8.3
IBA,
500 1000 2000 4000
1-1 1-1 1-1 1-1
12.5 11.1 6.2 9.4
39.1 45.2 18.1 32.6
3.13 4.07 2.92 3.46
9.4 9.5 8.8 9.1
IAA,
500 mg 1-1 2000 mg 1-1
7.8 8.8
32.0 34.9
4.10 3.96
9.5 8.9
11.8
44.1
3.74
10.4
Hormex
mg mg mg mg
Shoot/root ratio
58
and of newly formed stolons increased in response to hormonal treatment. Balm. - - R o o t formation in balm-stem cuttings increased with time and was p r o m o t e d by the application of growth substances (Fig. 3). Thus, a 3-fold increase in the number of roots was found in cuttings pre-treated with 1000 mg 1-' IBA or Hormex, while other concentrations were less effective. R o o t and shoot fresh weights were increased by 500 mg 1-1 IBA and by Hormex (Table III) b u t the response to various concentrations of IBA and IAA was inconsistent. No significant differences in s h o o t / r o o t ratio and stem length were found.
30
I
I
I
SE
~ /
o20 I-I,-
/
I.)
2
4
,
/
rr" LI,J
7
,76
o
o~0
t"
I 0
10
20
30
DAYS
Fig. 3. R o o t f o r m a t i o n in b a l m c u t t i n g s in r e s p o n s e t o h o r m o n a l t r e a t m e n t . C u t t i n g s were t r e a t e d w i t h various c o n c e n t r a t i o n s o f I B A or I A A , o r w i t h H o r m e x . F o r t r e a t m e n t s see legend t o Fig. 1. R o o t n u m b e r was r e c o r d e d over a p e r i o d o f 31 days, a n d d a t a r e p r e s e n t average r o o t n u m b e r p e r c u t t i n g .
DISCUSSION
The need for vegetative propagation of oregano, peppermint and balm brings a b o u t several practical problems with regard to early establishment and growth under field conditions. This is especially so in the above mentioned spices since, in contrast with most other vegetatively propagated plants, their commercial cultivation has many similarities with that of forage plants which are produced from seeds (Putievsky et al., 1977). Early establishment and vigorous growth of the cuttings are especially important in view of: (a) the need
59
for frequent irrigation of rootless cuttings; (b) the attainment of a well-rooted plant before the start of an early new vegetative growth in order to get more than one harvest during the spring; (c) the need for fast ground-covering to avoid weed establishment. All the cuttings of the 3 species that were studied rooted relatively easily, which is characteristic of the Labiatae (Rosengarten, 1969). However, significant differences in the rate of root formation, final number of roots and shoot growth were found in response to hormonal treatment of cuttings. These differences are related to the specific growth habits of the plants, as may indeed be expected in view of the numerous physiological and morphological traits which affect r o o t formation in cuttings (Girouard, 1967; Altman, 1972; Haissig, 1974; Hartmann and Kester, 1975). Thus, the increase in root formation in oregano, due to hormonal treatment, is reflected in a decreased s h o o t / r o o t ratio which seems to be advantageous for initial cutting establishment. The same holds true with s h o o t / r o o t ratio of balm cuttings, though to a lesser degree due to the extensive shoot development which is a characteristic of this species. In the case of peppermint, the marked increase in s h o o t / r o o t ratio in most treatments resulted from the effect of hormones on shoot develo p m e n t via extensive stolon development. The differences in rooting-patterns of the 3 species, evincing various periods of an accelerated r o o t formation (Figs. 1--3), are probably also related to inherent differences in growth characteristics, and this is especially evident in the case of peppermint. Thus, the 2 distinct waves of root formation during a 27-day period reflect competitive growth of roots and of the shoot and stolons. The observed decrease in the number of roots in certain cases is due to the sampling-method, and was evident mainly during the period of initial and slow r o o t formation. The reason for the inconsistent response to different concentrations of IBA in certain cases was not investigated.
REFERENCES Altman, A., 1972. The role of auxin in root initiation in cuttings. Proc. Int. Plant Propag. Soc., 22: 280--294. Girouard, R.M., 1967. A n a t o m y of adventitious root formation in stem cuttings. Proc. Int. Plant Propag. Soc., 17: 289--302. Haissig, B.E., 1974. Influence of auxin and auxin synergistics on adventitious root primordium initiation and development. N . Z . J . For. Sci., 4: 311--323. Hartmann, H.T. and Kester, D.E., 1975. Plant Propagation, Principles and Practices. Prentice Hall, New Jersey. Murray, J.M., Marble, M.P. and Lincoln, D.E., 1971. Inter-sub-generic hybrids in the genus Mentha. J. Hered., 62: 363--366. Parry, J.W., 1962. Spices, their Morphology, Histology and Chemistry. Chemical Publishing Co., New York. Putievsky, E. and Barker, D., 1977. Experimental cultivation of marjoram, oregano and basil. J. Hortic. Sci., 52: 181--188. Putievsky, E., Kuris, A. and Barker, D., 1977. (Research on spice crops, 1973--1976.) Special Publication No. 87, Volcani Center, Bet Dagan, Israel (in Hebrew). Rosengarten, F., 1969. The Book o f Spices. Livingstone, Philadelphia, PA.
53
ROOTING AND INITIAL ESTABLISHMENT OF STEM CUTTINGS OF OREGANO, PEPPERMINT AND BALM 1
2
A. KURIS , A. ALTMAN and E. PUTIEVSKY 1
1
Division of Medicinal and Spice Crops, Agricultural Research Organization, Newe Ya 'ar ~egional Experiment Station (Israel) Department of Horticulture, The Hebrew University of Jerusalem, Rehovot (Israel) (Accepted for publication 17 December 1979)
ABSTRACT
Kuris, A., Altman, A. and Putievsky, E., 1980. Rooting and initial establishment of stem cuttings of oregano, peppermint and balm. Scientia Hortic., 13: 53--59. Stem cuttings of 3 Labiatae spices, oregano (Origanum vulgare L.), peppermint (Mentha piperita L.) and balm (Melissa offlnicalis L.) were analyzed for their rooting-patterns and initial establishment under controlled conditions. Approximately 100% of cuttings from all 3 species rooted, but the number of roots per cutting varied in the order: oregano ~ balm ~ peppermint. Treatment of cuttings with IBA, IAA and Hormex increased both the number of roots per cutting and the rate of root formation in all 3 species. This effect was, however, dependent on their natural capacity for root formation, with the greatest effect on the slowest root producer, balm, where root number increased 3-fold. Enhanced root formation was reflected in increased fresh-weight accumulation by both root and shoot systems. Hormone treatment also increased shoot length of peppermint. All the above mentioned effects were concentration-dependent. Thus, hormonal treatment of cuttings of these 3 Labiatae spices clearly aided early establishment, and especially so in cuttings which were initially less vigorous.
INTRODUCTION O r e g a n o (Origanum vulgare L.), p e p p e r m i n t (Mentha piperita L. vat. ' M i c h a m ' ) a n d b a l m (Melissa officinalis L.), 3 i m p o r t a n t L a b i a t a e spices, usually g r o w wild a n d v e r y little is k n o w n o n h o r t i c u l t u r a l p r a c t i c e s concerning t h e i r g r o w t h a n d d e v e l o p m e n t (Parry, 1 9 6 2 ; R o s e n g a r t e n , 1 9 6 9 ; P u t i e v s k y a n d Barker, 1 9 7 7 ; P u t i e v s k y et al., 1977). T h e s e spices are u s u a l l y p r o p a g a t e d v e g e t a t i v e l y since seed p r o p a g a t i o n is difficult: p e p p e r m i n t d o e s n o t p r o d u c e seeds d u e t o a n h e x a p l o i d s t a t e ( M u r r a y et al., 1 9 7 1 ) , o r e g a n o seeds are v e r y small a n d , thus, d i f f i c u l t t o handle, a n d seed p r o d u c t i o n a n d g e r m i n a t i o n in b a l m are p o o r . In a d d i t i o n , p r o p a g a t i o n o f t h e s e spices f r o m seeds m a y result in a c o n s i d e r a b l e d e l a y in yield p r o d u c t i o n . A l t h o u g h m o s t o f t h e L a b i a t a e species are easily p r o p a g a t e d
54
vegetatively through cuttings or stolons, some problems occur in commercial cultivation with lack of r o o t formation and delayed establishment of cuttings (Putievsky et al., 1977). Thus, the rooting-behavior and early establishment of stem cuttings of the above-mentioned species were investigated in relation to hormonal treatment. M A T ER I ALS AND METHODS
Apical stem cuttings, 12 cm in length, were removed in December from one-year-old plants, which were grown in a dark brown vertisol soil under Mediterranean conditions (Newe Ya'ar Regional Experiment Station). Leaves were removed from the lower half of the cuttings. In the case of balm, the remaining leaves were trimmed to a b o u t half-size in order to prevent excessive transpiration by the relatively large leaves. The basal 4 cm of all cuttings were dipped for 4 s in solutions of 500--4000 mg 1 -' IBA (~-indole butyric acid), or 500--2000 mg 1-1 IAA (~-indole acetic acid), as specified in the figures and tables. In addition, Hormex, a commercial rooting-powder containing 0.1% IBA, was applied to the basal cut surface of the cuttings. Two types of stems were observed on oregano, those with visible r o o t primordia on the surface ( " r o o t initials"), and those without visible primordia; cuttings were prepared from the second t y p e only. After treatment, the cuttings were planted in propagation beds in a rootingmedium composed o f horticultural grade peat: perlite (1:1), and maintained in a heated greenhouse. Each experimental treatment consisted of 5 randomized replicates, 8 cuttings in each replicate. After 69 days, all cuttings were removed from the propagatingmedium, rinsed in tap water, and the number of roots per cutting was recorded. Shoot fresh weight, which included the original cutting and the new growth (and in the case of peppermint the stolons also), r o o t fresh weight and length of the longest branch were measured. At various time intervals during the rooting-period, 2 cuttings from each replicate (total 10 cuttings for each treatment) were csxefully removed from the medium and their roots were counted, after which they were inserted back into the propagation beds. In the case of peppermint and balm, root counting was discontinued after 27 and 31 days, respectively. Standard errors of the means of all treatments for the entire period were calculated. RESULTS
Oregano. -- All cuttings rooted. However, treatment with IAA and IBA, at various concentrations, resulted in a slight increase in the number of roots during the first 3 weeks, but the final number of roots after 69 days was similar in each treatment (Fig. 1). There was a slight reduction in the number of roots per cutting during certain dates, and this is related to the samplingm e t h o d (see Materials and Methods).
55
I
I
I
l
I
I
I
40--
~.j-
30-
Z F-
D.
2o
O 0 rr
10
/ 10
1
I
I
I
1
20
3O
40 DAYS
50
60
I 70
Fig. 1. R o o t formation in oregano cuttings in response to hormonal treatments. Cuttings were treated with various concentrations of I B A or IAA, or with Hormex. Root n u m b e r was recorded over a period of 69 days, and data represent average root n u m b e r per cutting. I B A series: 1=500 m g l-I ; 2 = 1 0 0 0 m g 1-1 ; 3 = 2 0 0 0 m g l-I ; 4 = 4 0 0 0 m g l-I . I A A series: 5=500 m g I-I;6 = 2 0 0 0 m g l-I. H o r m e x : 7.
While only a slight effect of hormonal treatment on r o o t formation was found, it markedly affected the initial establishment of cuttings, as judged by the fresh weight of the r o o t and the shoot systems (Table I). IBA, IAA, and especially Hormex increased r o o t fresh weight. The effect of IAA on increasing shoot weight was, however, greater than that of IBA which is clearly reflected in the s h o o t - - r o o t ratio. Final stem length was not affected by hormonal treatment o f cuttings. Peppermint. - - While almost 100% of untreated peppermint stem cuttings formed adventitious roots after 27 days in the rooting-medium, the number of roots per cutting was increased b y hormonal treatment (Fig. 2). This effect was, however, dependent on the t y p e and concentration of the growth substance. IAA at 2000 mg 1-1 (Treatment 6) doubled the number of roots per cutting as compared with control. For reasons that will be discussed later,
56 TABLE I The effect o f h o r m o n a l t r e a t m e n t of oregano cuttings on their initial growth and establishment. Cuttings were u p r o o t e d 69 days after h o r m o n a l t r e a t m e n t , and the fresh weight o f the roots and shoot, as well as s t e m length, were determined. S h o o t / r o o t ratio was calculated f r o m fresh weight data
Control mg mg mg mg
Fresh weight (g) Roots Shoot
Shoot/root ratio
Stem length (cm)
10.1
24.5
2.42
19.9
IBA,
500 1000 2000 4000
1-1 1-1 1-1 1-1
11.9 14.9 13.1 16.2
29.4 26.4 26.9 31.2
2.47 1.77 2.05 1.92
18.7 16.0 22.2 18.7
IAA,
500 mg 1-1 2000 mg 1-1
16.1 14.9
35.3 33.6
2.19 2.25
18.6 21.6
20.2
28.1
1.40
19.3
Hormex
,sI I
I
/D61
SE
z° 10 I.I...-
•
/
#a
(.J ¢,.. I.U Q. I-
o
~
~_.~
I
10 Fig. 2. R o o t f o r m a t i o n in were treated with various see legend to Fig. 1. R o o t sent average r o o t n u m b e r
~
I
20 DAYS
CONTROL
I
30
p e p p e r m i n t cuttings in response to h o r m o n a l t r e a t m e n t . Cuttings c o n c e n t r a t i o n s of I B A or IAA, or with H o r m e x . F o r treatments n u m b e r was r e c o r d e d over a period of 27 days, and data repreper cutting.
57
the major effect of the growth substances was evident from the 19th day on, following an arrest of root development in the preceding week. The reduction in the number of roots per cutting in that week is related to the samplingmethod. Although other morphological observations were made until 69 days, counting of roots was discontinued after 31 days because of massive formation of stolons in addition to regular root initiation. Both root and shoot growth were dependent on initial treatment of cuttings (Table II). Stem length increased by more than, or almost 100% in response to IBA, IAA, and Hormex at the higher concentrations. In addition, the number of axillary branches T A B L E II The e f f e c t o f h o r m o n a l t r e a t m e n t o f p e p p e r m i n t c u t t i n g s o n t h e i r initial g r o w t h a n d e s t a b l i s h m e n t . Cuttings were uprooted 69 days after hormonal treatment and the fresh weight of the roots and shoot, as well as s t e m l e n g t h a n d n u m b e r o f n e w l y - f o r m e d a x l l l a r y b r a n c h e s a n d s t o l o n s , w e r e d e t e r m i n e d . Shoot/roo+. ratio was calculated from fresh weight data F r e s h w e i g h t (g)
Control mg mg mg mg
Shoot/root ratio
Stem length (cm)
No. of branches
No. of stolons
Roots
Shoot
3.4
14.0
4,12
5.0
0,4
0.3
IBA,
500 1000 2000 4000
I-Ii I I II- I
4.7 2.8 2.1 6.5
24.5 16.7 7.3 31.7
5,21 5,96 3.48 4,88
7.2 6.3 4.0 11.3
1.5 0.9 0.6 2.1
0.7 0.3 0.2 0.6
IAA,
500 mgl -I 2 0 0 0 m g ]-I
3.1 4.0
14.1 23.4
4,55 5.85
4.6 II.I
1.0 1.5
0.4 0.6
3.6
26.2
7.27
9.0
1.3
0.7
Hormex
TABLE III The effect of hormonal treatment of balm cuttings on their initial growth and establishment. Cuttings were uprooted 69 days after hormonal treatment, and the fresh weight of the roots and shoot, as well as stem length, were determined. S h o o t / r o o t ratio was calculated from fresh weight data
Fresh weight (g) Roots Shoot Control
Stem length (cm)
6.3
27.0
4.3
8.3
IBA,
500 1000 2000 4000
1-1 1-1 1-1 1-1
12.5 11.1 6.2 9.4
39.1 45.2 18.1 32.6
3.13 4.07 2.92 3.46
9.4 9.5 8.8 9.1
IAA,
500 mg 1-1 2000 mg 1-1
7.8 8.8
32.0 34.9
4.10 3.96
9.5 8.9
11.8
44.1
3.74
10.4
Hormex
mg mg mg mg
Shoot/root ratio
58
and of newly formed stolons increased in response to hormonal treatment. Balm. - - R o o t formation in balm-stem cuttings increased with time and was p r o m o t e d by the application of growth substances (Fig. 3). Thus, a 3-fold increase in the number of roots was found in cuttings pre-treated with 1000 mg 1-' IBA or Hormex, while other concentrations were less effective. R o o t and shoot fresh weights were increased by 500 mg 1-1 IBA and by Hormex (Table III) b u t the response to various concentrations of IBA and IAA was inconsistent. No significant differences in s h o o t / r o o t ratio and stem length were found.
30
I
I
I
SE
~ /
o20 I-I,-
/
I.)
2
4
,
/
rr" LI,J
7
,76
o
o~0
t"
I 0
10
20
30
DAYS
Fig. 3. R o o t f o r m a t i o n in b a l m c u t t i n g s in r e s p o n s e t o h o r m o n a l t r e a t m e n t . C u t t i n g s were t r e a t e d w i t h various c o n c e n t r a t i o n s o f I B A or I A A , o r w i t h H o r m e x . F o r t r e a t m e n t s see legend t o Fig. 1. R o o t n u m b e r was r e c o r d e d over a p e r i o d o f 31 days, a n d d a t a r e p r e s e n t average r o o t n u m b e r p e r c u t t i n g .
DISCUSSION
The need for vegetative propagation of oregano, peppermint and balm brings a b o u t several practical problems with regard to early establishment and growth under field conditions. This is especially so in the above mentioned spices since, in contrast with most other vegetatively propagated plants, their commercial cultivation has many similarities with that of forage plants which are produced from seeds (Putievsky et al., 1977). Early establishment and vigorous growth of the cuttings are especially important in view of: (a) the need
59
for frequent irrigation of rootless cuttings; (b) the attainment of a well-rooted plant before the start of an early new vegetative growth in order to get more than one harvest during the spring; (c) the need for fast ground-covering to avoid weed establishment. All the cuttings of the 3 species that were studied rooted relatively easily, which is characteristic of the Labiatae (Rosengarten, 1969). However, significant differences in the rate of root formation, final number of roots and shoot growth were found in response to hormonal treatment of cuttings. These differences are related to the specific growth habits of the plants, as may indeed be expected in view of the numerous physiological and morphological traits which affect r o o t formation in cuttings (Girouard, 1967; Altman, 1972; Haissig, 1974; Hartmann and Kester, 1975). Thus, the increase in root formation in oregano, due to hormonal treatment, is reflected in a decreased s h o o t / r o o t ratio which seems to be advantageous for initial cutting establishment. The same holds true with s h o o t / r o o t ratio of balm cuttings, though to a lesser degree due to the extensive shoot development which is a characteristic of this species. In the case of peppermint, the marked increase in s h o o t / r o o t ratio in most treatments resulted from the effect of hormones on shoot develo p m e n t via extensive stolon development. The differences in rooting-patterns of the 3 species, evincing various periods of an accelerated r o o t formation (Figs. 1--3), are probably also related to inherent differences in growth characteristics, and this is especially evident in the case of peppermint. Thus, the 2 distinct waves of root formation during a 27-day period reflect competitive growth of roots and of the shoot and stolons. The observed decrease in the number of roots in certain cases is due to the sampling-method, and was evident mainly during the period of initial and slow r o o t formation. The reason for the inconsistent response to different concentrations of IBA in certain cases was not investigated.
REFERENCES Altman, A., 1972. The role of auxin in root initiation in cuttings. Proc. Int. Plant Propag. Soc., 22: 280--294. Girouard, R.M., 1967. A n a t o m y of adventitious root formation in stem cuttings. Proc. Int. Plant Propag. Soc., 17: 289--302. Haissig, B.E., 1974. Influence of auxin and auxin synergistics on adventitious root primordium initiation and development. N . Z . J . For. Sci., 4: 311--323. Hartmann, H.T. and Kester, D.E., 1975. Plant Propagation, Principles and Practices. Prentice Hall, New Jersey. Murray, J.M., Marble, M.P. and Lincoln, D.E., 1971. Inter-sub-generic hybrids in the genus Mentha. J. Hered., 62: 363--366. Parry, J.W., 1962. Spices, their Morphology, Histology and Chemistry. Chemical Publishing Co., New York. Putievsky, E. and Barker, D., 1977. Experimental cultivation of marjoram, oregano and basil. J. Hortic. Sci., 52: 181--188. Putievsky, E., Kuris, A. and Barker, D., 1977. (Research on spice crops, 1973--1976.) Special Publication No. 87, Volcani Center, Bet Dagan, Israel (in Hebrew). Rosengarten, F., 1969. The Book o f Spices. Livingstone, Philadelphia, PA.