Improvements in Morpho-Anatomical Traits of Adventitious Roots of Hedyotis biflora (L.) Lam. using Silicon Nanoparticles

The poor rooting of in vitro-raised shootlets is a major bottleneck and severely affects the survival rate of plantlets in field conditions. Hedyotis biflora is used as a model plant to study the impact of Silicon nanoparticles (SiNPs) on in vitro adventitious root formation and their structural developments in this study. The in vitro proliferated shootlets cultured on ½ strength Murashige and Skoog (MS) medium containing 2.0 mg L−1 indole-3 butyric acid (IBA) and 3.0 mg L−1 SiNPs promoted the morpho-anatomical improvements in roots. Morphologically, the roots of SiNPs treatment were significantly superior, thick, and sturdy with increased biomass (1.298 g fresh weight and 0.614 g dry weight) and more in numbers (33.0 roots with 5.0 cm average length) from that of the fragile control roots (21.0 roots with 3.8 cm average length with reduced biomass of 0.735 g FW and 0.319 g DW). Light microscopic monitoring of roots revealed that SiNPs-derived roots were fully differentiated into periderm, exodermis, and secondary cortex and vascular tissues. Such structures were absent and only primary structures were detected in the control roots (derived from the medium without SiNPs). It was observed that the proportion of secondary xylem was significantly higher in the SiNPs-treated roots than the control roots, which correlated positively with the adaptation of roots toward field conditions. Furthermore, the acclimatization efficiency and survival of SiNPs-derived plantlets were higher (100%) relative to the control plantlets (91.0%). The present findings demonstrate that SiNPs mediated anatomical traits facilitated the adaptation of micropropagated plantlets of H. biflora to the ex vitro/in vivo environments, allowing them to survive successfully post-transplantation.