Nano-silicon enhanced root micro-structural developments and lignin deposition in Aechmea bracteata (Sw.) Griseb.

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Aechmea bracteata is a vascular, symbiotic epiphyte that holds potential ornamental and ecological values. In vitro propagation techniques significantly enhance the rapid production of high-quality planting materials. However, highly sophisticated physico-chemical environments often suppress the normal growth and development of plants. Tissue density, velamen tissue, and cell wall thickening of roots confer mechanical support and are crucial for plants to achieve epiphytic adaptations. This study analyzed the impact of silicon nanoparticles (SiNPs) on anatomical development in adventitious roots of A. bracteata. Cultures were established by inoculating surface-disinfected seeds (n = 24 explants per treatment × 3) on Murashige and Skoog’s medium containing 0.5 mg·L−1 6-benzylaminopurine (BAP), and shoots were proliferated using 0.25 mg·L−1 BAP and 0.15 mg·L−1 α-naphthalene acetic acid (NAA). The resulting shoots were subjected to rooting on half-strength MS medium containing altered concentrations of indole-3-butyric acid and NAA. The shoots were rooted on 1.0 mg·L−1 NAA along with 3.0 mg·L−1 SiNPs (hydrophilic silica). A completely randomized design was employed to conduct statistical analysis. The micro-structural analyses (n = 10 samples per treatment) of roots revealed that the application of SiNPs significantly improved rhizogenesis, velamen tissue, root cortex density, endodermis, and stele diameter. An elevated cell wall thickening was detected in the cells of SiNPs-derived roots. These features demonstrate the epiphytic adaptational developments in A. bracteata imposed by the SiNPs, supporting the survival of the plantlets in the in vivo environment. Further study could help to establish SiNPs as a functional nano-tool for enhancing epiphytic adaptation, acclimatization efficiency, and resilience in bromeliads.