In vitro acclimatization of Curcuma longa under controlled iso-osmotic conditions.

In vitro acclimatization has been validated as the successful key to harden the plantlets before transplanting to ex vitro conditions. In the present study, we investigated the potential of different sugar types (glucose, fructose, galactose, sucrose) in regulating morphological, physiological and biochemical strategies, survival percentage and growth performance, and rhizome traits of turmeric under iso-osmotic potential. Leaf greenness (SPAD value) in acclimatized plantlets (4% glucose; -1.355 MPa osmotic potential) of 'ST018' was retained and greater than in 'PB009' by 1.69-fold, leading to maintain high Fv/Fm (maximum quantum yield of PSII), ΦPSII (photon yield of PSII) and Pn (net photosynthetic rate) levels, and retained shoot height, leaf length, leaf width, shoot fresh weight and shoot dry weight after one month upon transplanting to ex vitro conditions. In addition, Pn, Ci (intracellular CO2), gs (stomatal conductance) and E (transpiration rate) in acclimatized plantlets (6% sucrose; -1.355 MPa osmotic potential) of 'PB009' were stabilized as physiological adapted strategies, regulating the shoot and root growth and fresh and dry weights of mini-rhizome. Interestingly, the accumulation of total curcuminoids in mini-rhizome derived from 6% sucrose acclimatized plantlets of 'ST018' was greater than in 'PB009' by 3.76-fold. The study concludes that in vitro acclimation of turmeric 'PB009' and 'ST018' using 6% sucrose and 4% glucose, respectively, promoted percent survival, physiological adaptations, and overall growth performances under greenhouse conditions.