Light Spectra and 6-Benzylaminopurine in the In Vitro Cultivation of Epidendrum lilas

Luciana CNL, et al. Light Spectra and 6-Benzylaminopurine in the In Vitro Cultivation of
Epidendrum lilas. Adv Agri Tech Plant Sciences 2022, 5(1): 180088.
Copyright © 2022 Luciana CNL, et al.
Advances in Agricultural Technology & Plant Sciences
ISSN: 2640-6586
Research Article Volume 5 Issue 1
Light Spectra and 6-Benzylaminopurine in the In Vitro Cultivation
of Epidendrum lilas
Luciana CNL*, Rocha SS, Calaes JG and Pimenta S
EMBRAPA Mandioca e Fruticultura, Brazil
*Corresponding author: Luciana Cardoso Nogueira Londe, Empresa de Pesquisa Agropecuária de Minas Gerais - EPAMIG,
Campo experimental do Gorutuba, Nova Porteirinha - MG, Brazil; Email: luciana@epamig.br
Received Date: February 01, 2021; Published Date: February 23, 2022
Abstract
In order to supply the growing market demand for orchids (Epidendrum Lilas), is usually recommended the micropropagation
technique, mainly, for the production of quality seedlings in a short time and in large numbers. Since, the propagation of this
species is slow through conventional means, factors such as the phytoregulators and the light spectrum that may interfere in
the effectiveness of this technique. The objective of the work was to evaluate different concentrations of cytokinin and the use
of different light spectra in the in vitro propagation of orchid Epidendrum lilas. Two factors were evaluated: concentrations of
benzylaminopurine (BAP): (1.0; 1.5; 2.0; 2.5 and 3.0 mg L-1) and the light spectra: white, red, blue and green. After two months
of establishment, the following characteristics were evaluated: plant height (H), number of leaves (NL), leaf length (LL) and
shoots (S). The data obtained were submitted to analysis of variance and the means compared by the Tukey test (p <0.05). There
was a significant difference only for the light spectra. The red spectrum was more efficient for the development of the aerial
part and leaf length. While the blue spectrum promoted a greater number of leaves. Higher shooting rates were observed using
the white spectrum. It is concluded that during the orchid growth phase the red and blue spectra are more efficient, and in the
multiplication phase the white spectrum is recommended.
Keywords: Orchid; Micropropagation; Light; Cytokinin
Introduction
The commercial production of flowers and ornamental
plants has increased over the years, in all regions of Brazil
[1]. Highlighting the orchid trade, which generates a
commercialized amount of approximately US $ 20 billion
per year [2]. Being highly appreciated by consumers, due
to its exotic flowers of vibrant colors and floral longevity
[3]. Despite the great demand in the market, the spread of
orchid species is considered slow, requiring a long period
to reach the reproductive stage, making the production of
new seedlings time-consuming [4]. In natural conditions,
the multiplication of these plants occurs through the natural
propagation of the seeds, which do not have a functional
endosperm. So that, under natural conditions, they depend
on mycorrhizal fungi for symbiotic germination, which are
necessary until adulthood for their survival [5]. In addition,
seeds have relatively low germination rates, around 5% [6].
In view of the importance of orchids in the economic sector
and due to the difficulty of their natural propagation, it is
necessary to seek techniques that help the rapid propagation
of this species. The micropropagation technique being the

2
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most used, since it allows the use of all the seeds produced
and the regeneration of adult plants from them [7].
In in vitro growth, the nutrient media are supplemented
with growth regulators [8]. Highlighting the cytokinins,
responsible for cell division, stretching and differentiation
[9]. Among the most used cytokinis in in vitro cultivation,
stands out the benzylaminopurine (BAP) [10]. However, the
addition of these growth regulators is a factor that increases
the costs of in vitro seedling production. An alternative would
be manipulation of the cultivation environment through
spectral quality [11]. In which it has proven action on plant
development [12]. Spectral quality is essential in in vitro
propagation, since light is essential for photomorphogenesis
in plants [13]. With the variation in the light spectrum, the
in vitro growth of several species can be manipulated, in
an alternative way to the addition of phytoregulators to the
culture medium [14]. In view of these aspects, the objective of
the work was to evaluate the development and multiplication
of the E. Lilas orchid under different light spectra associated
to BAP doses.
Materials and Methods
Location of the Experiment
The experiment was conducted at the Plant Biotechnology
Laboratory of the Agricultural Research Company of Minas
Gerais-EPAMIG, EPAMIG Norte-Gorutuba Experimental
Field, Nova Porteirinha-MG, during the years 2018/2019.
The geographical location is defined by the coordinates
15o
148’263” south latitude and 43o
17’650” west longitude,
the average altitude is 526 m.
Seed Establishment in Vitro
Orchid plants were previously established in vitro using
seeds from their fruits (capsules). The collected capsules
underwent a disinfection process and then brought to a
laminar flow cabinet in which they were opened and the
seeds removed to perform in vitro sowing. These seeds were
placed in bottles with solid medium MS [15], supplemented
with 0.5 mg L-1
of 6-benzylaminopurine (BAP), 30 g L-1
of
sucrose, 0.1 g L-1
of inositol, with pH adjusted to 5.8 ± 0.1.
After sowing, the flasks containing the seeds remained in a
growth room for 60 days, or until sprouting, under irradiance
of 40 µmol m-2
s-1
provided by cold white light, with 16 hours
of photoperiod at 25 ± 2o
C. After 60 days, sprouts were used
for the experiment.
In Vitro Cultivation Conditions
The obtained sprouts were individualized and transferred to
300 mL flasks containing 50 mL of MS medium supplemented
with the following doses of BAP: 0.5, 1.0, 1.5, 2.0, 2.4 and 3.0
mg L-1
. Then the explants were taken to the growth room and
subjected to different light spectra: white spectrum (cold
white fluorescent light), red, blue and green spectrum. To
obtain the colored spectra, the white lamps were wrapped
with colored films of regenerated cellulose (cellophane),
in the red (~ 625-440nm), blue (~ 440-485nm) and green
(~ 500-565nm) colors. The material was kept in a growth
room for 60 days at a temperature of 25 ± 2ºC and 16
hours of photoperiod (1,800 LUX). At 30 and 60 days after
in vitro establishment, plant height (cm), leaf number, leaf
length (cm) and shoots were evaluated. The experiment
was conducted in a completely randomized design in a 6x5
factorial scheme (Doses of BAP x Colored spectra), with five
replications.
Statistical Analysis
The variables were submitted to the Shapiro-Wilk normality
test and the Bartlett test, both p <0.05, to verify the normality
of the data and homogeneity of the variances, respectively.
All variables were transformed by the x + 1 root. After
confirming the requirements for an analysis of variance,
it was performed at a probability of 5% error. Significant
differences were observed for the sources of variation
involved in the experiment, the means of the variables were
subjected to the Tukey test (p> 0.05) to detect the differences
between treatments. All statistical analyzes were performed
using the Genes software [16].
Results and Discussion
There was no significant interaction (p <0.05) among the
factors dose and light spectra for any of the characteristics
evaluated at 30 and 60 days of cultivation. There was a
significant difference only for single factor spectra for the
following: plant height, number of leaves and shoots. For
characteristic leaf length there was a significant difference
only at 60 days of cultivation. There was no significant
difference for BAP doses. This fact may be associated with
the balance between endogenous and exogenous cytokinin,
the endogenous being sufficient to supply the needs of the
plants [17]. It can also be related to luminosity. According to
Chee and Pool, [18] high light intensity leads to photoxidation
causing degradation of cytokinins. The plants showed greater
growth when submitted to the red spectrum, at 30 and 60
days of cultivation Table 1. Similar results were observed
by Rocha, et al. [19] working with forage palm cv. Gigante
(Opuntia ficus indica Mill.).

3
Espectra
30 days 60 days
H (cm) NL S H (cm) NL LL (cm) S
Blue 4.86 ab 1.77 ab 1.31 b 5.57 ab 2.36 a 3.77 ab 1.78 b
White 4.48 b 1.99 a 1.65 a 5.26 ab 2.58 a 3.33 b 2.13 a
Red 5.43 a 1.79 ab 1.22 bc 5.94 a 2.07 b 4.1 a 1.45 c
Green 4.43 b 1.70 b 1.04 c 4.78 b 1.81 b 3.52b 1.11 d
Table 1: Height (H), number of leaves (NL), leaf length (LL) and shoots (S) means of orchid Epidendrum Lilas, at 30 and 60 days
of in vitro cultivation under different light spectra.
Means followed by the same letter do not differ statistically
by Tukey’s test (p <0.05) for each variable. Some studies
have concluded that the red spectrum promotes the growth
of the aerial part of plants [20]. This is because the process
of light absorption by plants (photomorphogenic route) is
similar to the mechanism of action of hormones [13]. Rosa,
et al. [21] working with Dendrobium phalaenopsis obtained
plants with a length of 3.33 cm using 3.0 mg L-1
of BAP.
Rodrigues, et al. [22] observed greater plant growth (2.36
cm) with 1.0 mg L-1
, BAP in Oncidium baueri. In this work,
using only the red spectrum, the plants had a height of 5.43
and 5.94 cm at 30 and 60 days of cultivation, respectively.
Based on the similarity of the responses, it appears that
it is possible to manipulate the in vitro growth of orchids,
in an alternative way to the addition of phytoregulators to
the culture medium. Plants grown under white spectrum
showed a higher number of leaves (1.99 cm), at 30 days of
cultivation. And at 60 days, more leaves were obtained with
the blue (2.36) and white (2.58) spectrum.
Similar results for these spectra were observed by Cunha,
et al. [23], working with Mentha spicata and Santos, et al.
[24] observed similar averages using 3.6 mg L-1
of BAP
in Epidendrum ibaguense, confirming the efficiency of
the spectra. These results may be related to the influence
of these spectra on in vitro photosynthesis. Since leaves
irradiated with white light absorb more blue, red and
green wavelengths, which are necessary for energy gains
through photosynthesis, as well as for other physiological
processes [25]. Blue light is also essential in the processes
of synthesis of pigments, enzymes, development of
chloroplasts, stomatal opening and closing and several other
photomorphogenic processes [26]. That may have favored
the orchid leaf formation process. Plants exposed to the red
spectrum showed greater leaf length (4.10 cm), at 60 days of
cultivation. The red light generally emits a spectrum near to
the maximum absorption of chlorophylls and phytochromes,
being important for the development of the photosynthetic
apparatus and for the accumulation of starch [27].
Shooting induction in orchids occurs more intensely when
growninwhitespectrum,at 30(1.65shoots/explant) and60
days (2.13 shoots / explant). Similar results were observed
by Ferrari, et al. [28] in Curcuma longa. Camargo, et al. [3]
working with Oncidium baueri observed a close average
(1.87 shoots / plant) using 2.0 mg L-1
of BAP. In general,
plants grown in white light, an environment that is similar
to the natural environment, present thicker leaves with
longer and juxtaposed palisade parenchyma cells [26]. This
may have favored in vitro photosynthesis and, consequently
a higher shooting rate. Plants grown under green spectrum
showed less development. Studies with Arabidopsis have
reported that the green light causes similar effects when
the plants are shaded, that is, they lead to etiolation and
cause differences in the architecture of the plant such as
lengthening of petioles, reorientation of leaves and reduction
of leaf area [30]. Different results were observed by Rocha,
et al. [31] working with three banana cultivars (Musa sp.),
observed higher shooting rates using green light. However,
the influence of spectral quality in relation to plant growth
and development may be directly linked to the species,
the stage of plant development and other environmental
characteristics [32]. Which may justify the different results
verified in this work. Since there was no influence of the
phytoregulator used, the luminosity was the determining
factor for the in vitro development of the orchid. These
results indicate new possibilities for the micro propagation of
E. Lilas, and can be considered as a starting point for further
research on protocols, involving the cultivation environment,
in order to improve the quality of the seedlings produced.
Conclusion
Under the conditions in which this experiment was carried
out, the following conclusions were reached:
• The light spectra influences in the in vitro development
and multiplication of orchids.
• The red spectrum provides greater aerial part
development and leaf length. Whereas, plants exposed
under the blue and white spectra have a higher number
of leaves.
• Cultivation in a growth room under a white spectrum
induces higher shooting rates.
• For economic matter, it is recommended to use the red
and blue spectra in the growth phase and the white
spectrum in the Epidendrum Lilas multiplication phase.

4
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