Improvements in morphometric and structural traits of Vitex trifolia L. to exogenous application of nano-silicon in vitro

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The present study aimed to analyze the effect of silicon nanoparticles (SiNPs) on the in vitro proliferation of shoots, biomass production, foliar micro-structural features, and root-inducing ability in Vitex trifolia L. Bud breaking was achieved from axillary meristems on 2.5 mg L−1 of 6-benzylaminopurine (BAP) in Murashige and Skoog's (MS) medium. The shoots were proliferated (18.0 ± 0.39 shoots) on 0.75 mg L−1 BAP with 0.2 mg L−1 1-Naphthaleneacetic acid (NAA). Among the varied concentrations of Aerosil300 (hydrophilic silica) used, 6.0 mg L−1 SiNPs with optimal growth regulators into the medium had a positive impact on shoot proliferation (24.0 ± 0.30 shoots) and fresh biomass production. The light microscopic evaluation showed that the leaves developed without SiNPs possessed underdeveloped cuticle, trichomes, stomata, epidermal cells, and photosynthetic and vascular tissues. The SiNPs treatment resulted in well-differentiated tissue systems and favored an increase in width of the lamina, differentiation of palisade and spongy tissues, thickening of cell walls, increased density of trichomes, organized guard cells in stomata, and improved xylem and phloem tissues. The shoots were effectively rooted on half-strength MS medium containing 3.0 mg L−1 NAA, and the shoots derived from SiNPs treatment had the highest rooting efficiency (8.0 roots per shoot). The findings highlight that the use of SiNPs significantly promoted tissue systems and morphology of V. trifolia, which favored the survival of plantlets under in vivo conditions.