Synergistic effects of growth regulators and silicon nanoparticles on enhancing morpho-structural stability in Vitex agnus-castus L. plantlets

Abstract

This study aimed to analyze the impact of silicon nanoparticles (SiNPs) on the in vitro proliferation efficiency and micro-structural developments of the Vitex agnus-castus L. tree. Aerosil³⁰⁰, hydrophilic silica was used to create SiNPs suspension. It was found that Murashige and Skoog (MS) medium containing 1.0 mg L⁻¹ kinetin (Kn) generated a maximum number of shoots (6.0 ± 0.58 shoots per node explants). Shifting these buds to 1.0 mg L⁻¹ Kn and 0.15 mg L⁻¹ Indole-3-acetic acid (IAA) promoted shoot proliferation (14.7 ± 1.20 shoots with 5.00 ± 0.21 cm length per explant). Significant improvements in the morphology and number of shoots (21.0 ± 1.53 shoots with 7.5 ± 0.21 cm length per explant), leaf area (1.7 ± 0.17 cm length × 0.8 ± 0.15 cm width), and fresh weight (5.8 ± 0.17 g) were recorded when this media combination was enriched with 4.0 mg L⁻¹ SiNPs, surpassing the results reported with the control and other concentrations of SiNPs. The microscopic analysis of SiNPs treated leaf and stem revealed the successful formation of tissue systems including stomata, trichomes, dermal tissues, chlorophyllous palisade and spongy parenchyma, xylem and phloem, and increased lignification in sclerenchyma within 8-weeks of incubation, leading to the subsequent development of mature vegetative shoots. The cultures from the control treatment showed thin shoots, reduced leaf area, and underdeveloped tissue systems. The shoots were rooted (100 % rooting) using half-strength MS medium fortified with 1.0 mg L⁻¹ α-Naphthalene acetic acid (NAA), and 98.3 % survival was achieved during the acclimatization of these plantlets. It is determined that incorporating a small quantity of SiNPs into the nutrient medium can increase shoot production, improve micro-morpho-anatomical features, and enhance the survival rate of plantlets of V. agnus-castus during the hardening phase.