Scientia Horticulturae 75 (1998) 103±111
Description of Syzygium paniculatum Gaertn.
`Verlaine' and its propagation by stem cuttings
A. Lebruna,*, A.N. Toussaintb,1, J. Roggemansc,2
a
b
Hortiforum asbl, Rue Verlaine 9, B-5030, Gembloux, Belgium
Unite d Horticulture GeÂneÂrale, .Faculte Universitaire des Sciences Agronomiques de Gembloux,
Avenue de la Faculte d0 Agronomie 2, B-5030, Gembloux, Belgium
c
Laboratoire d0 Applications Phytotechniques, Haute Ecole de LieÁge-Verviers-Huy-Gembloux,
Rue Verlaine 9, B-5030, Gembloux, Belgium
0
Accepted 10 February 1998
Abstract
Expanding the market for house plants is linked to increasing the diversity on offer to consumers.
Accordingly, experiments were done to introduce a new plant onto the market: the cultivar
`Verlaine' derived from Syzygium paniculatum. This cultivar has a dense foliage and an attractive
aspect. It presents interesting characteristics like annual flowering and colorful fruits. The best
results of propagation by cuttings were obtained when using cuttings from the basal part of the
mother plant, placed in a 1±1 or 2±1 peat±perlite substrate, with a bottom heat around 228C. Auxins
do not affect rooting. The origin of the adventitious roots is endogenous. # 1998 Elsevier Science
B.V.
Keywords: Syzygium; Cutting; Cultivar
1. Introduction
The market for ornamental plants is increasing rapidly in Europe as a result of
the economics of their production and their diversity.
* Corresponding author. Fax: +32 81 625638
1
Tel.: +32 81 622417; fax: +32 81 622427; e-mail: [email protected]
2
Tel.: +32 81 625613; fax: +32 81 611202; e-mail: [email protected]
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 2 - 8
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A. Lebrun et al. / Scientia Horticulturae 75 (1998) 103±111
With a view to increasing the range of foliage plants, we are studying the genus
Syzygium (Myrtaceae). This genus includes numerous trees and shrubs grown for
their foliage and ornamental berries or their edible fruits. In Germany, another
research group is studying Syzygium oleosum, with the intention of exploiting it
as a house plant (Von Hentig and Ehlers, 1992).
The present study focuses on Syzygium paniculatum Gaertn., a species native to
Australia. S. paniculatum was first described by the botanist Gaertner in 1789
who named it Eugenia paniculata. Subsequently, it was referred to under
different names including Myrtus paniculata and Eugenia myrtifolia.
This species is easily propagated by seed but the new cultivar, S.p. `Verlaine',
can only be multiplied vegetatively. In this paper we describe this cultivar and
determine the best conditions for ensuring the rooting of stem cuttings. Four
experiments were performed: (i) to examine the effect of the nature of the
substrate and bottom heating, (ii) to examine the influence of auxins on rooting of
the cuttings, (iii) to examine the effect of the position of the cuttings on the
mother plant, (iv) to examine the influence of the period of the year in which the
cuttings were taken on rooting.
2. Materials and methods
2.1. Influence of different factors on rooting of cuttings
Experiments were performed with softwood leafy lateral cuttings, taken on
greenhouse-grown 2 year-old stock plants, pruned 3 months earlier. Except for
the experiment relative to the position of the cuttings on the stock plant, cuttings
were taken from the apical part. The cuttings were 10 cm long with 4 nodes.
Batches of 30 cuttings were used for each treatment in each experiment. All
experiments were conducted in a greenhouse, under mist and at an air temperature of 258C. The four experiments were performed 3 times and the results are the
means of the 3 replicates. In all experiments, the batches of cuttings were
distributed randomly and observed weekly over a 90-day period. The statistical
analysis was based on one-way or two-way analysis of variance (ANOVA), for
fixed and crossed patterns (Dagnelie, 1992) after the normality of the data had
been confirmed. The means were compared by Student's t-test at P<0.05.
2.1.1. Influence of substrates and bottom heat
The substrates most frequently used to root cuttings (Rein et al., 1991) were
tested: peat±coarse sand in the ratio 1±1, 2±1, 3±1 and 4±1 (pH 4.1±4.2);
vermiculite±perlite: 1±1 (pH 7.3), peat±perlite: 1±1, 2±1, 3±1 and 4±1 (pH 3.3±3.5).
The experiment was conducted with or without a constant average bottom heat of
220.58C.
A. Lebrun et al. / Scientia Horticulturae 75 (1998) 103±111
105
2.1.2. Influence of auxins
Indole-3-acetic acid (IAA) and naphthalene acetic acid (NAA) are the two
growth regulators that best promote rooting (Hartmann et al., 1990; Smalley et
al., 1991). Preliminary experiments showed that there was no interaction between
substrates, growth regulators and rooting.
In our experiment using IAA, concentrations of 500, 1000, 1500 and 2000 ppm
were tested. The basal part of the cuttings was dipped in a freshly prepared
solution for 5 s before striking in the 1±1 peat±perlite substrate. In the experiment
with NAA, the lower 3 cm of the cuttings were coated with a preparation of 2%
NAA in talc and the excess powder was then shaken off. Cuttings were struck in
the same substrate. A bottom heat of 220.58C was maintained.
2.1.3. Influence of the position of the cuttings on the mother plant
To determine the effect of the position of the cuttings on the mother plant, three
positions were selected: the apical part of the stock plant, the median part and the
basal part. The cuttings were struck in the 1±1 peat±perlite mixture. A bottom
heat of 220.58C was maintained.
2.1.4. Influence of the period of the year in which the cuttings are taken
Preliminary observations showed that the cv `Verlaine' could easily be
propagated by cuttings in spring and summer. Indeed, softwood cuttings taken
during spring and summer usually tend to root more easily than cuttings taken in
the winter (Hartmann et al., 1990; Wilson, 1993). Furthermore, propagation by
stem cuttings of Eugenia Smithii, a closely related species, is very good from
June to September, but very poor in November (Toussaint et al., 1991).
In order to determine the possibility to root cuttings in less favourable periods,
every month, from September to April, experiments were conducted on a peat±
perlite 1±1 mixture, with a bottom heat of 220.58C.
2.2. Microscopy
To determine where the adventitious roots are initiated, basal parts of rooted
cuttings were fixed, dehydrated, embedded in paraffin following Heinemann's
technique (1980) and sectioned at 15±20 mm. Sections were stained with malachite
green and congo red.
3. Results and discussion
3.1. Description of the cultivar `Verlaine'
For about 15 years, seeds from a Syzygium paniculatum plant were harvested
every year and sown. One of the resultant seedlings differed quite noticeably from
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Fig. 1. 18-month-old Syzygium paniculatum `Verlaine' (approximate height: 1 m).
the parental type, presenting stable characteristics: smaller leaves (4 to 6 cm long
by 1.5 to 2 cm wide) and shorter internodes (Fig. 1). Table 1 lists the main
features that distinguish cv `Verlaine' from the species (Curtis, 1969; Schmid,
1972; Hyland, 1983; Whistler, 1988). The main asset of this plant is its denser
foliage, which is pale green when young, darker green when mature, while its
young leaves and stems are tinged with red. The general appearance of the plant
can be compared to that of Ficus benjamina `Exotica'. Another asset of S.p.
`Verlaine' is its great propensity for flowering after 1 or 2 years of culture. The
axillary peduncles that grow laterally or at the top of the shoots, develop at least 3
to 5 flowers in a loose trichotomous panicle. The fruits are magenta, globular or
ovoid berries, 1.5 cm in diameter, topped by a persistent calyx.
3.2. Influence of different factors on rooting of cuttings
3.2.1. Influence of substrates and bottom heat
The cuttings tested on non-heated substrates (average temperature 16.08C)
failed to root. However, when the substrate was heated (average temperature of
220.58C), the mean rooting rate exceeded 75% on the best substrates.
A. Lebrun et al. / Scientia Horticulturae 75 (1998) 103±111
107
Table 1
Main characters distinguishing Syzygium paniculatum and S. p. `Verlaine'
Distinctive criteria
Syzygium paniculatum
S. p. `Verlaine'
Shoots
Internodes
15 to 50 mm long
15 to 40 mm long
Leaves
Length
Width
Primary veins
45 to 90 mm
15 to 30 mm
16 to 22 pairs
25 to 65 mm
12 to 24 mm
10 to 16 pairs
Flowers
Inflorescences
Terminal and axillary towards
the top; cymes and sometimes
panicles with 3, 7 or 11 flowers
Most often terminal; 3 to 5
flowers per panicle
Fruits
Drupes
Ovoid, 16 to 26 mm in diameter
Globular to ovoid, 15 to 22 mm
in diameter
The experiments concerning the nature of the substrates showed that the 1±1
vermiculite±perlite mixture was not suitable as it caused the loss of over 90% of
the cuttings due to rot.
The results of the experiment done on 8 different substrates based on peat, sand
and perlite are given in Fig. 2. The rooting percentage and speed of root production were higher on peat±perlite 1±1, 2±1 and 3±1 mixtures than on peat±sand
ones but the loss of cuttings by rotting was higher on the 3±1 peat±perlite mixture
Fig. 2. Average rooting speed of cuttings of Syzygium paniculatum `Verlaine' depending on the
nature of the substrate.
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A. Lebrun et al. / Scientia Horticulturae 75 (1998) 103±111
(18%) than on the 1±1 and 2±1 ones (5.6%). The good rooting rates observed on
peat±perlite substrates can be attributed to a lower pH in these mixtures and/or to
the increase in aeration in substrates containing perlite, favouring rhizogenesis
(Hartmann et al., 1990). The rooting rate was low on peat±sand 2±1, 3±1 and 4±1
substrates. In peat±sand substrates with a high peat-content, the poorer rooting
rate observed could be due to the compaction of peat by water, which
consequently would prevent proper aeration of the mixture and lead to rot in the
cuttings. This also occurred in the 3±1 and 4±1 peat±perlite substrates but to a
lesser extent, thanks to the favourable effect of perlite. The greater length of the
root system observed on the peat±perlite mixtures could be attributed to the
earlier development of the roots and/or excellent substrate aeration. The ease with
which cuttings can be removed from this medium is a distinct advantage.
3.2.2. Influence of auxins
There was no significant difference between IAA and NAA in their affect on
rooting. No exogenous input of the growth substance seemed to affect rooting of
Syzygium cuttings except for the 2000 ppm treatment which caused the highest
percentage of loss of cuttings by rotting (18% for the 2000 ppm treatment against
an average 2% to 5% for the lower concentrations) and the lowest rooting
percentage (52%). This high concentration added to the endogenous auxin of the
plant, which itself increases as a consequence of taking cuttings (Favre, 1977)
might have led to a level which disturbed the hormonal metabolism and inhibited
rhizogenesis.
3.2.3. Influence of the position of the cuttings on the mother plant
The rooting success of cuttings taken from the three positions on the stock
plants are shown in Fig. 3. The proportion of cuttings that developed roots was
significantly higher among those taken from the median and lower parts of the
plant than from the apical part. Furthermore, roots developed earlier on cuttings
originating from the basal and median parts of the stock plants than on those from
the apex. Rooting was initiated as early as the third week on basal cuttings, in the
fourth week on the median ones and in the sixth on the apical ones. Only 73% of
the apical cuttings had rooted after 13 weeks whereas 99% of the basal ones had
rooted after only 7 weeks.
The natural accumulation of endogenous auxin, favourable to the development
of roots, in the basal part of the stock plants (Wilson, 1993) along with the
influence of the nearby root system which encourages juvenility (Chaperon,
1979; Bonga, 1982) are both likely to explain the results obtained.
3.2.4. Influence of the period of the year in which the cuttings are taken
The rooting percentage and speed of production of roots were similar on
cuttings of S.p. `Verlaine' at whatever time between September and April they
A. Lebrun et al. / Scientia Horticulturae 75 (1998) 103±111
109
Fig. 3. Average rooting speed for cuttings of Syzygium paniculatum `Verlaine' depending on the
position of the cutting on the mother plant.
were struck. The percentage of rooted cuttings ranged from 64% to 71%. For
November, the results are much better than those obtained for Eugenia Smithii
(20±28% rooted cuttings), a closely related species (Toussaint et al., 1991). In
other Myrtaceae like Chamaelaucium sp., the rooting of cuttings is unaffected by
season (Curir et al., 1993). The fact that stock plants are grown in a greenhouse
could favour rooting of cuttings (Macdonald, 1986; Marczynski and Joustra,
1993). Stoutemyer (1961) suggested that this could be due to increased air
humidity and temperature or to the absence of UV rays in a greenhouse.
3.3. Microscopy
Sections of the basal part of a rooted cutting exhibited the classical structure of
a stem but with scar tissue consistent with a cutting, schizogenous spaces,
tanniferous cells characteristic of the Myrtaceae, and cells with vacuoles
containing much calcium oxalate. The sections showed that the adventitious roots
originated endogenously in the young secondary phloem.
4. Conclusion
The cultivar `Verlaine' of Syzygium paniculatum, originating from a seedling of
Syzygium paniculatum has smaller leaves and shorter internodes than the parent
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species, resulting in dense foliage and a very attractive appearance. It offers
additional interesting and original characteristics including annual flowering,
colourful fruits and red colour of the young leaves.
Rooting of cuttings of Syzygium paniculatum `Verlaine' ranged from fair to
good depending on the technique applied. Several factors influence the rooting of
cuttings: (i) bottom heat is needed (228C was found to be suitable); (ii) the nature
of the substrate affects rooting of cuttings by its physical and/or chemical
properties. An acid (pH value of about 3.5) well-aerated substrate was best. The
results show the advantages of peat±perlite substrates (at 1±1 or 2±1 mixtures)
over peat±sand mixtures. Considering the relatively high cost of perlite, it is
advisable to choose the 2±1 peat±perlite mixture; (iii) the best position from
which to take cuttings on stock plants in order to accelerate rooting is as close as
possible to the root system. The addition of auxins does not affect rooting.
Throughout the period from September to April, propagation by stem cuttings is
successful.
The histological study showed that root initiation is endogenous.
Propagation by cuttings appears to be a reliable way of multiplication, but
financial returns are likely to be modest because of the few shoots produced by
each stock plant. Further work is needed to examine the influence of the age of
stock plants on rooting of cuttings. In Eucalyptus sp., Jacobs (1977) noted that the
rooting rate of cuttings from 3 year-old stock plants was less than of those from
younger plants.
Acknowledgements
We thank the Ministry of the Walloon Region (Belgium) ± General Direction
for Economy and Employment ± for its contribution to this research by PRIME
projects.
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