TThe 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.
The ethyl acetate extract of the Bacillus sp. EJ-121 culture broth exhibited growth inhibitory activity on a lettuce (Lactuca sativa L.) seedlings assay. Bacillus sp. EJ-121 was identified as Bacillus cereus by the morphological characteristic and nucleotide sequence of the 16S rDNA. The bioassay-guided fractionation of the ethyl acetate extract led to the isolation of two compounds. Their structures were deduced by spectroscopic methods and determined as sodium vanillate (1) and 2-aminobenzoic acid (2). Both compounds 1 and 2 inhibited more than 90% of root length at 50 ppm (0.26 and 0.36 mM, respectively) while they had a limited effect on shoot growth at the same concentration level. Roots and shoots of lettuce seedlings showed severe deterioration at 100 ppm. In order to study the fundamental structure-activity relationship, several structurally related benzoic acid derivatives were also assayed. The existence of a polar carboxyl moiety seemed to be responsible for the stronger activity.
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