Physiological and phytochemical responses of red amaranth (Amaranthus tricolor L.) and green amaranth (Amaranthus dubius L.) to different salinity levels

The physiological and phytochemical responses of red amaranth (Amaranthus tricolor L.) and green amaranth (Amaranthus dubius L.) to different salinity levels were determined in two experiments conducted in Vietnam. Both experiments were performed in a net house involving pot experiments arranged in randomized complete block design (RCBD) with three replications. Two genotypes of amaranth were grown in garden soil, saline soil, 50% garden soil: 50% saline soil and 25, 50 and 100 mM NaCl. Salinization was imposed at 7, 14 and 21 days after transplanting. Results indicated that salt stress decreased growth parameters and biomass production in all treatments except for 25 mM NaCl. Na+ and Cl- content accumulated in both shoot and root, however, root had greater NaCl content than shoot. Total phenolics, total flavonoid content and antioxidant activity increased with increasing salinity levels from 25 mM to 50 mM NaCl; however, at 100 mM NaCl, all these parameters decreased. These results showed that red amaranth was more tolerant to salinity stress than green amaranth.