Journal
Journal of Applied Horticulture, 19(3): 222-225, 2017
Appl
Auxin application and cutting length affect rooting in Cuphea
hyssopifolia stem cuttings
L. Sabatino, F. D’Anna and G. Iapichino*
Department of Agricultural, Food and Forest Sciences, University of Palermo, Viale delle Scienze, Palermo, Italy.
*E-mail: giovanni.iapichino@unipa.it
Abstract
The effect of cutting length and indole-3-buyric acid (IBA) application on adventitious root formation of stem cuttings was studied in
Cuphea hyssopifolia. Softwood terminal cuttings of a clone grown in Sicily were trimmed to three lengths (2, 4 or 6 cm) and inserted
to a 1-cm depth in bottom heated plastic trays containing a humidified peat-vermiculite mixture 1:2 (v/v). To verify the cutting response
to different auxin concentrations, cuttings were dipped to a 1.0 cm depth in a 500 ppm or 1000 ppm IBA solutions for 10 seconds.
Cutting survival percent was 100 %. Regardless of cutting length, the highest rooting percentage was obtained with IBA at 1000 ppm
(86.7%), whereas rooting significantly declined to 73 and 81 %, in absence of IBA and at 500 ppm IBA, respectively. Percentage rooting
averaged over IBA treatment accounted for 93.3 and 90 % in 6 and 4 cm long cutting treatments, respectively. The lowest percentage of
rooting was recorded with the 2 cm cutting treatments (59 %). Cutting length and IBA application significantly interacted as percentage
rooting ranged from 43 % in 2 cm long cuttings in absence of IBA to 100 % in 4 cm long cuttings with 1000 ppm IBA. The highest
number of roots was observed from cuttings exposed to IBA at 500 and 1000 ppm (19.7 and 19.6 roots per cutting, respectively).
Root number significantly declined in absence of IBA (16.8 roots per cutting). Our results demonstrated that the use of 4 or 6 cm long
cuttings and the application of 1000 ppm IBA for 10 seconds could induce optimal adventitious root formation in C. hyssopifolia. The
application of the technique described would enhance propagation of this valuable ornamental species.
Key words: Mexican heather, adventitious root, Indole-3-butyric acid, ornamental plant, percent rooting
Introduction
The genus Cuphea (Lythraceae) includes approximately 260
species of annual, evergreen perennials, and short shrubs native to
central and south America and distributed from Mexico to Brazil
(Graham and Kleiman, 1985; Martínez-Bonfil et al., 2013). The
primary interest in Cuphea genus is for its seed as a potential
source of medium chain triglycerides (C12, C10, C8) (Thompson,
1984; Graham and Kleiman, 1992; Phippen, 2009; Tisserat et
al., 2012), and as folk medicine (Wang et al., 1999; Braga et al.,
2000; Biavatti et al., 2004; Schuldt et al., 2004; Barbosa et al.,
2007). However, several cuphea species are available for use
in landscapes and in the potted plant industry (Pottberg, 1984;
Thompson et al., 1987; Brown, 1989; Jaworski and Phatak, 1990,
1991a, 1991b). Cuphea hyssopifolia also known as Mexican
heather is a small shrub with several small lavender flowers used
in low borders, ground covers and in potted color plants.
Due to the difficulty in seed collection (1.3 million of seeds
per kg), C. hyssopifolia is commonly propagated by cutting,
even though propagation by air and ground layers is also
possible (Francis, 2004). According to Dole et al. (2006),
2-4 cm C. hyssopifolia terminal stem cuttings root in ten to
fourteen days at 21-24 C°. However, to our knowledge, no
published data is available concerning the potential beneficial
effects of IBA treatment on adventitious root formation in C.
hyssopifolia cuttings as well as the influence of the morphological
characteristics of the cuttings on rooting. Investigation of factors
controlling C. hyssopifolia propagation by cutting would improve
the efficiency of commercial ornamental nursery.
Based on the above considerations, the aim of our study was
to assess rooting of C. hyssopifolia stem cuttings in relation to
cutting length and IBA application.
Materials and methods
The research was conducted at the Department of Agricultural,
Food and Forest Sciences (SAF) of the University of Palermo, in
the northern coast of Sicily (Italy). Softwood terminal cuttings,
@ 12 cm in length were collected on April 2016 from a clone of
C. hyssopifolia located in the landscape at the SAF Horticulture
and Floriculture experimental farm near Palermo (longitude 13°
19’ E, latitude 38° 9’ N, altitude 14 m). Cuttings were stored
over night at 10 °C in polyethylene bags. The day after, prior
to planting, the bases of cuttings were trimmed to three lengths:
2, 4 or 6 cm and the leaves removed from the basal end. Node
number and average diameter of 2, 4 or 6 cm long cuttings
ranged from 3 to 8 nodes and from 0.5 to 1.0 mm, respectively.
Propagation was performed in an unheated greenhouse covered
with clear polyethylene (PE) and external 70% shade-cloth. Air
temperature in the greenhouse was maintained between12-14°C
during the night and 16-20°C during the day. To test adventitious
root formation, randomly selected 2, 4, or 6 cm long cuttings
were inserted to a 1-cm depth in bottom heated plastic trays
containing a humidified peat-vermiculite mixture 1:2 (v/v) at a 5
cm spacing. Basal heat was provided at constant temperature of 22
± 2ºC. All trays were covered with polyethylene (PE) to maintain
cutting turgidity. To verify the cutting response to different auxin
concentrations, cuttings were dipped to a 1 cm depth in 1000
ppm or 500 ppm indole-3-butyric acid (IBA) solutions for 10
Journal of Applied Horticulture (www.horticultureresearch.net)
Rooting in Cuphea hyssopifolia stem cuttings
sec. Untreated cuttings were dipped in distilled water (control).
Ventilation of the cuttings was increased with time by increasing
size of the holes made in the plastic. A 3 × 3 [three cutting lengths
(2, 4 or 6 cm) × three IBA (0, 500 or 1000 ppm)] concentrations
factorial set of treatments within a complete randomized block
design was used with 3 replications per treatment and 10 cuttings
per experimental unit.
The percentage rooting averaged over IBA treatment accounted
for 93.3 and 89 % in 6 and 4 cm long cuttings, respectively.
The lowest percent of rooting was observed in the 2 cm cutting
treatment (59 %). The IBA application × cutting length interaction
was highly significant (Table 1). The percentage of rooted cuttings
ranged from 43% in 2 cm long cuttings rooted in absence of
IBA to 100% in 4 cm long cuttings exposed to 1000 ppm IBA
(Fig. 1). Furthermore, increasing IBA concentration from 0 to
500 ppm, increased rooting percentage in 2 cm long cuttings
(from 43.3 to 66.7 %), but not with the 4 and 6 cm long cuttings.
Moreover, increasing IBA concentration from 500 ppm to 1000
ppm increased rooting percentage in 4 cm long cuttings, but not in
6 cm long cuttings. In fact, under both IBA applications, rooting
percentage in 6 cm long cuttings accounted for 93 %.
Two weeks after cutting insertion in the rooting medium,
cuttings were evaluated for percent survival, percent rooting,
number of roots per rooted cutting, length of the five longest
roots. Cuttings with non-withered stems (with and without roots)
were considered to have survived. Cuttings with necrotic tissue
without roots were classified as dead. Percentage data were
subjected to arcsin transformation before ANOVA analysis. Mean
separation was performed by Duncan Multiple Range Test. All
the statistical analysis were performed using SPSS software
version 14.0 (StatSoft, Inc., Chicago, USA). After two more
weeks acclimatized rooted cuttings were transplanted into each
plastic pot (diameter 16 cm) containing the same growing mix;
all plants were pinched leaving 4 nodes on each and kept for five
weeks in a lath house covered with 70% shade-cloth. Plants were
thereafter transplanted in the open field and were evaluated for
their clonal fidelity.
Irrespective of the cutting length, IBA application significantly
affected the number of roots per cutting (Table 1). The highest
number of roots was displayed from cuttings exposed to IBA at
500 and 1000 ppm (19.7 and 19.6 roots per cutting, respectively).
Root number significantly declined in absence of IBA (16.8 roots
per cutting) (Table 2). Root number per cutting averaged over IBA
treatment concentration accounted for 21.6 roots in 6 cm long
cuttings. Significantly lower values were revealed from 4 and 2
cm long cuttings (16.9 and 17.4 roots per cutting, respectively).
No significant interaction was found between cutting length and
IBA treatment in terms of roots per cutting.
Results and discussion
The effects of the cutting length and IBA treatment on C.
hyssopifolia stem cuttings after 2 weeks from insertion in the
rooting medium are reported in Tables 1 and 2. The cutting percent
survival was 100%; no significant effect of IBA treatment and
cutting length was observed on cutting survival. Regardless of
cutting length, the highest rooting percentage was obtained with
IBA at 1000 ppm (86.7%). Rooting significantly declined to 73%
and 81%, in absence of IBA and at 500 ppm IBA, respectively.
The length of the five longest roots was significantly influenced by
the treatments tested. Root length generally increased as cutting
length increased (Tables 1 and 2). Exposure of cuttings to IBA
favored root growth and elongation although concentration higher
than 500 ppm seemed to be inhibitory. Cutting length and IBA
treatment concentration significantly affected root length (Table
1). Six cm long cuttings exposed to 500 ppm IBA showed the
highest root length (22.5 mm; Figs. 2 and 3), although this value
was not significantly different from that observed in untreated 6
cm long cuttings. The lowest root length values were found in
2 cm long cutting either untreated or exposed to 1000 ppm IBA
(7.0 and 5.6 mm, respectively).
Table 1. Analysis of variance for means of adventitious root formation
in Cuphea hyssopifolia cuttings of various length and exposed to 0, 500
ppm or 1000 ppm indole-3-butyric acid (IBA)
Parameters
Cutting length
Significance
IBA
Survival
NS
NS
Rooting
***
**
*
Roots per cutting
**
*
NS
Root length
***
***
***
223
Cutting length
x IBA
NS
In our study, the application of IBA improved rooting percentage
and root number. Auxin application via cut surface of cuttings to
promote rooting is well documented (Blazich, 1988; Hartmann et
al., 2002) and there are reports of auxins markedly increasing the
number of roots in many species in vitro and ex vitro (De Klerk et
al.,1999; Iapichino et al., 2015). The auxin IBA has been largely
used to induce adventitious shoot formation in other ornamental
shrubs (e.g., Thymus ssp, Iapichino et al., 2006a; Teucrium
flavum, Prasium majus, Micromeria fruticulosa, Iapichino et al.,
The significance is designated by asterisks as follows: *statistically
significant differences at P-value below 0.05; **statistically significant
differences at P-value below 0.01; ***statistically significant differences
at P-value below 0.001. NS = not significant.
Table 2. Effect of indole-3-buyric acid (IBA) and cutting length on Cuphea hyssopifolia cutting survival and rooting after 2 weeks from insertion
in the rooting medium
Parameters
Cutting length (cm)
IBA (ppm)
2
4
Survival (%)
100ns
Rooting (%)
Roots per cutting (n)
6
0
100ns
100ns
100ns
58.9b
88.9a
93.3a
73.3c
17.4b
16.9b
21.6a
16.8b
1
1
1
1
1
1
500
1000
100ns
100ns
81.1b
86.7a
19.7a
19.6a
Root length (mm)
9.8c1
12.6b
19.5a
14.8a1
16.0a
12.9b
Different letters in rows denote significant differences in treatments. 1The significance levels of the principal factors (cutting length and IBA
concentration) are reported in Table 1.
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Rooting in Cuphea hyssopifolia stem cuttings
Fig. 1. Effect of indole-3-buyric acid (IBA) application and cutting
length on Cuphea hyssopifolia rooting percentage after two weeks
from insertion in the rooting medium. Different letters correspond to
significantly different values based on the Duncan Multiple Range Test
(P<0.05)
Fig. 2. Effect of indole-3-buyric acid (IBA) application and cutting
length on Cuphea hyssopifolia root length per cutting after two weeks
from insertion in the rooting medium. Different letters correspond to
significantly different values based on the Duncan Multiple Range Test
2006b; Teucrium fruticans, Sabatino et al., 2014). Our results are
in line with those obtained by Henry et al. (1992) who reported
that cutting length positively affected root count in Juniperus
virginiana and to those obtained by Caruso and Iapichino (2014)
who found that increase in the length of the cutting resulted in
a parallel increase in adventitious root formation in Plumeria
rubra. The efficacy of longer cuttings in inducing superior
rooting performances compared with shorter cuttings has been
attributed to their higher carbohydrate reserves (Beyl et al.,
1995). In the present study, all plants of C. hyssopifolia obtained
from softwood terminal cuttings grew vigorously and are under
evaluation for their ornamental performances. To summarize,
our results demonstrated the use of 4 or 6 cm long cuttings and
the application of 1000 ppm IBA for 10 sec to induce optimal
adventitious root formation in C. hyssopifolia. As high percent
rooting and adequate root number are fundamental prerequisites
to ensure propagation efficiency, rapid plant growth in pot and
landscape suitability, the application of the technique described
would enhance use of this valuable ornamental species.
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Received: March, 2016; Revised: January, 2017; Accepted: February, 2017
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