Effects of different silicon sources on the plant tissue culture of Vanilla planifolia Jacks. ex-Andrews

Abstract Vanilla planifolia Jacks. is one of the world’s most economically important orchids, as it is the main natural source of vanillin. Currently, plant tissue culture has become established as a strategy for the mass propagation of promising genotypes of this species to meet the growing demand of the vanilla market. Although silicon (Si) has been widely recognized for enhancing plant growth, nutrient uptake, and tolerance to biotic and abiotic stresses in plant tissue culture, information regarding its application in V. planifolia remains limited. Therefore, the objective of this study was to evaluate the effect of different chemical forms and concentrations of Si on the in vitro propagation of V. planifolia . Nodal segments (1–2 cm) derived from in vitro plantlets were cultured on plant growth regulator-free MS medium using six concentrations (0, 1, 2, 3, 4, and 5 mmol·L -1 ) of silicic acid (H₄SiO₄) and (or) sodium silicate pentahydrate (Na₂SiO₃·5 H₂O) following a completely randomized design with five replicates per treatment. After 90 days, morphological variables (survival rate, size, and number and length of shoots, roots, and leaves), as well as relative chlorophyll content and dry matter, were recorded. The results showed that H₄SiO₄ promoted the development and greater growth of plantlets than Na₂SiO₃·5 H₂O under the conditions evaluated. A concentration of 1 mmol·L -1 of H₄SiO₄ increased shoot size and the formation of shoots, leaves, and roots; however, these parameters decreased with increasing concentration. It is concluded that the chemical form of Si significantly influences the morphological and physiological response of in vitro grown plantlets; therefore, the use of H₄SiO₄ at 1 mmol·L⁻¹ is recommended due to its stimulatory effect.