Ameliorative Effects of Hydrogel Polymer on Micropropagation Performance of Russelia equisetiformis Schltdl. & Cham. under Salinity Stress

Micropropagated Russelia equisetiformis Schltdl. & Cham. were examined using two different types of culture media (MS and WPM) at full strength to optimize the suitable proliferation medium. The optimized culture medium (MS medium + 0.5 mgl-1 of BA) was selected for in vitro shooting and root formation. Based on the tested hydrogel polymer at five rates (0, 12.5, 25, 37.5, and 50% instead of agar percentage), the addition of 25% hydrogel polymer (2 gl-1) caused an increase in all shooting characters. Using hydrogel at 25% in the culture medium under various salinity levels (NaCl at 0, 1000, 2000, 3000, and 4000 ppm) showed a positive response of all recorded characters (shooting and rooting) and in the estimated pigments content in shootlets grown on each salinity level. The secondary metabolites (total tannins, flavonoids, and phenols) as well as proline were highly influenced by saline conditions. Meanwhile, using 25% hydrogel polymer in the culture medium individually or in combination with various salinity levels decreased these compounds. The increased antioxidant activity was obtained at 4000 ppm NaCl and 0% hydrogel polymer, while unstressed shootlets on MS culture medium with added 25% hydrogel caused the lowest antioxidant activity using DPPH or phosphomolybdenum. Using hydrogel led to alleviating salinity stress on the micropropagated russelia plant, and this finding is relatively new.