Relationships between nutrients and plant density in liquid media during micropropagation and acclimatization of turmeric

To improve micropropagation and acclimatization of turmeric (Curcuma longa L.), we evaluated the effects of media volume, plant density, macronutrient ion concentrations, cationic ratios NH₄ ⁺]/K⁺], and sucrose concentration. Multiplication was highest with low bud density. Yield of new plants was highest with high bud density, the most sucrose, the highest concentration of macronutrients, and the greatest volume of medium. However, maximum plant size required low-density, reduced sucrose and elimination of NH₄ ⁺. The largest plants grew quickest during greenhouse acclimatization when macronutrients were lowered to 20 mM. In a follow-up experiment, media volume was set at 40 mL with 5% sucrose with NH₄ ⁺ reduced to 5 mM, and the effects of varying P, Ca, Mg, KNO₃, and bud densities were assessed. The largest plants were produced at low density. More importantly, at high density the optimal concentrations of P, Ca, Mg, and KNO₃ predicted plant size that was nearly equal to the maximum value from low-density cultures in the prior experiment. Growth of plants during greenhouse acclimatization was increased by modifications of in vitro medium with plants cultured with 3.32 mM P, 4.5 mM Mg, and 37 mM KNO₃ predicted to grow most rapidly. The effect of starter fertilizer in the greenhouse mix was much less than the effects of P, Mg, and KNO₃ in vitro. These results showed (1) optimal media formulae for different stages of micropropagation and (2) process-related factors such as plant density and media volume affected the optimal nutrient concentrations.