Abstract
•Polyethylene glycol improved in vitro morphogenesis in Spathoglottis plicata.•Exogenous application of PEG exhibited superior anatomical traits compared to control.•Mild osmotic stress increased the dimensions of leaf mesophyll and vascular tissues.•PEG-derived plantlets performed better during in vitro rooting and ex vitro hardening.•Genetic uniformity of the regenerates was confirmed using SCoT markers.
In vitro propagation is extremely important for the rapid multiplication of a wide range of orchids. This study aimed to investigate the effects of polyethylene glycol (PEG) on morpho-anatomical improvements and ex vitro development of Spathoglottis plicata, a terrestrial orchid. Various concentrations of PEG (100-500 mg L−1) were incorporated with the optimized medium composition [Murashige and Skoog's medium with 2.0 mg L−1 6-benzylaminopurine (BAP) and 0.25 mg L−1 indole-3-acetic acid (IAA)] to study the morpho-anatomical developments of cultures. Results showed that PEG at 300 mg L−1 in the nutrient medium had a significant effect on the development of plantlets with superior morphometric and anatomical characteristics. It improved the rate of shoot multiplication (83 shoots), shoot length (10 cm), fresh weight (4.0 g), and dry weight (1.5 g) of shoots per culture vessel than the control experiment (devoid of PEG). Light microscopic analysis revealed that PEG-derived leaves possessed improved leaf thickness, differentiation in dermal, ground, and vascular tissue systems than the leaves developed without PEG in the medium. Such shoots were responded significantly better during rooting (11.0 roots with 6.2 cm length) and acclimatization stages. Start Codon Targeted (SCoT) markers analysis confirmed the genetic uniformity of the regenerates with the mother plant. The improvements in morpho-anatomical structures of in vitro raised plantlets due to PEG-induced mild drought stress in ground orchid S. plicata could be a useful tool for its large-scale production and survival success in the field.