Amaranth (Amaranthus tricolor L.) is a plant that is rich in vitamins, minerals, and phytochemicals. It is grown as a leafy vegetable in marginal environments, but high salinity levels in the soil can have a detrimental effect on its growth. These deleterious effects of salinity can be alleviated by exogenously applying signaling compounds such as salicylic acid (SA) and calcium (Ca), which can improve plant adaptation to stressful conditions. The present study evaluated the physiological and phytochemical responses of red amaranth (Amaranthus tricolor L.) to foliar-applied salicylic acid (SA; 0.005 mM) and calcium (CaSO 4 •2H 2 O; Ca, 2.5 mM) either alone or in combination (SA + Ca) under conditions of 100 mM NaCl salinity. The setup was placed under greenhouse condition from May to October 2017. Treatments without salinity and applied with SA or Ca were used as controls for comparison. Salinity stress reduced the growth and biomass, total chlorophyll contents, and increased electrolyte leakage with Na + and Cl − accumulation in shoot and roots. Nonetheless, exogenous applied SA and/or Ca 2+ reduced the adverse effects of salinity by modulating growth, Na + exclusion from roots, and increased total phenolics, flavonoids, and antioxidant activity in red amaranth. The combined application of salicylic acid and calcium can be a better strategy for improving the salinity tolerance of amaranth under salt-stressed conditions.

The flux of Ca2" at the apical or basal ends of short sunflower (Helianthis alluus L.) hypocotyl segments was monitored using a Callspecific electrode. A higher Ca2" efflux was observed at the apical end relative to the basal end, indicating a net polar flux of Ca2". The extreme low mobility of Ca2' in the isolated segment makes it likely that the observed Ca2" fluxes are of localized origin, that is, from the parenchyma cells close to the exposed cut ends and may represent acropetal transport of Ca2" at the cellular level. Madison, WI) seeds were germinated on wet paper towels overnight. Approximately 60 seeds were selected for good radicle break and then placed on fiberglass netting stretched over plastic dishes with about 450 ml one-fifth strength Hoagland solution (1 mm Ca), unless indicated otherwise. The dishes with seeds were placed in a transparent tray lined with wet paper towels at the bottom. A transparent plastic cover placed ajar over the tray provided for medium humidity and aeration.The seedlings were grown under a bank of fluorescent and incandescent lamps with a net intensity of 13.5 J.m-2. s-' at the level of the cotyledons; the light regime was 16 h light/8 h dark. The temperature in the growth chamber was about 30°C when the lights were on and about 25°C when off.Preparation of Stock Solutions. Measured amounts of IAA, TIBA, and a-and ,B-NAA were dissolved in 0.30 ml of 1 N KOH and made up to 250 ml using deionized distilled H20 to yield stock solutions of 1 mm. The pH of the solutions was adjusted to 5.7 to 5.9 with 1 N HCI. In the course of the experiments, it was found that potassium could stimulate Ca2' flux; since then, care was taken to equalize the K+ concentration in the hypocotyl segment media.Determination of Endogenous Ca2' Flux. A 2-cm hypocotyl segment was taken from each seedling, beginning about 1 cm below the cotyledonary node, washed in deionized distilled H20 for 1 h and gently blotted dry before it was transferred to the treatment solution. Each replication consisted of 20 segments held in a vertical position by embedding 1 to 2 mm of either the apical or basal end ofthe segment in lanolin in planchets attached to glass slides. The segments were then inverted into small plastic beakers containing 3 to 10 ml solution, henceforth called 'segment medium'. Only about 1 to 2 mm of the segments came in contact with the segment medium which always contained an initial concentration of 10 tLM CaC12. The segments were placed inside a moist chamber and kept in the dark at 26°C.At periodic' intervals, or at the end of the experiment, thesegment medium was monitored for Ca24 using a Ca2+-specific electrode

Calcium flux in sunflower (Helianthus annuus L. cv Russian mammoth) hypocotyl was measured with a Ca2" electrode as the increase or decrease in Ca" in an aqueous solution (10 micromolar CaC12) in contact with either the basal or apical end of 20 millimeter segments. Ca2' efflux was significantly higher at the apical end compared with the basal end; this apparent polarity was maintained even when the segments were inverted. No significant difference was observed in the cation exchange capacity of apical and basal cell walls that could explain the difference in Ca2 efflux at opposite ends of the hypocotyl segment. The presence of exogenous indoleacetic acid (IAA) in the segment medium resulted in the promotion of both Ca2' efflux and segment elongation. However, osmotic inhibition of the IAA-induced elongation did not result in inhibiting the IAA-induced Ca2' efflux. Ca2' efflux was inhibited by cyanide. Lowering the temperature from 25°C also caused the gradual reduction of Ca2' efflux; at 5°C the hypocotyl segments showed a net absorption of Ca21 from the segment medium. These findings support the suggestion that: (a) the observed Ca2e efflux in hypocotyl segments is probably the manifestation of the system which maintains the transmembrane Ca2l gradient at the cellular level. Figure 1 was made by stretching two layers of Parafilm between two 20 ml plastic beakers with bottoms removed. Holes smaller than the diameter of the hypocotyl were made through the Parafilm. To ensure fresh, clean cuts at the segment ends, the desired 2 cm region was not excised from the hypocotyl until it was completely inserted through the tight holes in the Parafilm. Seven segments were used per replication. The upper and lower beakers were stabilized in position by pieces of modeling clay. The transverse cuts at the end of the segments were washed with ddH20 for 1 h and then changed to 3 ml of the regular segment medium at the start of the experiment.Isolation

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.

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