Monochromic radiation through light-emitting diode (LED) positively augments in vitro shoot regeneration in Orchid (Dendrobium sonia)

Abstract

ORIGINAL RESEARCH PAPER OPEN ACCESS50 AbstractMonochromatic lights emitted by light-emitting diodes (LEDs) have generated great interest for efficient and controlled growth in vitro, especially of plants which are endangered or require specific intensity and wavelength of light. In the present study, we have evaluated the effect of monochromatic LEDs on in vitro morphogenesis: growth, proliferation of shoot cultures, and rooting of Dendrobium sonia. Different light sources viz. white LEDs (W), blue LEDs (B), yellow LEDs (Y) and red LEDs (R) were tested under photoperiod of 16 h of exposure and 8 h of dark. The frequency of morphogenesis depended on the wavelength of the applied monochromatic light. Higher wavelength monochromatic light (yellow light) was observed to induce higher shoot proliferation (98%), early PLB (protocorm-like bodies) formation, differentiation into green buds and shoot initiation as compared to red, blue and white light treatments. Yellow light also yielded higher number of shoots per explants (29 shoots/explant) than red, blue and white light treatments. The results suggest that the monochromatic light sources stimulate morphogenic effects on in vitro culture of Dendrobium sonia, and that yellow light treatment can be used to enhance the efficiency of micropropagation.

Gamma irradiation induced effects on in vitro shoot cultures and influence of monochromatic light regimes on irradiated shoot cultures of Dendrobium sonia orchid

“…Mutations could generate phenotypic variations in both vegetative and reproductive characteristics and the approach is particularly useful for Dendrobium improvement because it is highly heterozygous and is genetically diverse. In our earlier study, we reported effects of monochromatic lights on growth and morphogenesis of D. sonia [21]. It is essential to study the radiosensitivity in each case to estimate lethal dose (LD50) to focus on the effective doses at which higher frequency of the mutants can be isolated [1,2].…”

“…Rhizome buds from the ex vitro plants were used as explants to initiate in vitro shoot cultures. These explants were thoroughly washed in running tap water for 10 min, surface sterilized with 0.1% mercuric chloride for 3 min followed by 70% alcohol for 30 s and finally rinsed thrice with sterilized distilled water [21]. These surface sterilized explants were then cultured on to Murashige and Skoog’s (MS) [30] basal medium supplemented with sucrose (3% w/v), 6-benzylaminopurine (BAP 2 mg/l) and gelling agent agar-agar (0.6% w/v).…”

“…The individual shoots measuring 1–2 cm long were transferred onto MS medium containing 3% sucrose fortified with 3 mg/L IAA for root induction. The plants with 3–4 roots in number and approximately 1 inch in length were selected for hardening and acclimatization [21]. The well established plantlets were transplanted into small pots containing coco-peat for two weeks and kept under 70–80% relative humidity at 24–28℃, followed by transfer to large sized pots containing coco-peat under greenhouse conditions.…”

“…In this regard, partial desiccation has been shown to favour regeneration response of high dose gamma irradiated in vitro cultures of sugarcane [18]. Since monochromatic light treatment has shown stimulatory effect on in vitro morphogenesis in different plant species [19] including orchids [20,21], we have applied this method to augment in vitro regeneration of mutagenized orchid tissue cultures.…”

“…Terrestrial orchids need stronger light than epiphytic orchids [28]. Reports on the effect of artificial light spectral intensities on plant growth, particularly in orchids are limited [21]. In other plants, blue light treatment improved the efficiency of favourable adventitious rooting [29].…”