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.

Centella asiatica L. as a traditional medicinal plant is popular in several Asian countries and characterized by the presence of phytochemicals, such as phenolics and flavonoids. Soil salinity can affect the growth and phytochemical composition in this plant species. In this study, the effects of incremental soil salinity (0, 25, 50, 75, and 100 mM NaCl) on growth, physiological characteristics, total phenolic and total flavonoid contents, including the antioxidant activity of Centella asiatica L., were evaluated under greenhouse conditions. Salinity stress reduced growth, biomass production, and total chlorophyll contents, while increasing electrolyte leakage, Na+ and Cl− contents in the shoots and roots. With the increase of salt concentration, total phenolic, total flavonoid content and antioxidant activities were increased. The results showed that centella can tolerate saline conditions up to 100 mM NaCl. Na+ exclusion from the roots, and that increases of phytochemical content in the shoots were related to the salt tolerance of this species.

Background: Centella asiatica L. is a traditional medicinal plant popular in several Asian countries. The cultivation of this herb is facing the problem of overuse of chemical fertilizers and quality deterioration. The aim of this study was to evaluate the effect of organic and non-organic fertilizer on growth, yield and phytochemical content of centella. Methods: The set-up was performed in the field from June to November 2021. The treatments were: no fertilizer (control); inorganic fertilizer (the famer’s recommended rate; 150 kg N ha-1:50 kg P ha-1: 50 kg K ha-1); organic compost (10 tones ha-1); inorganic fertilizer (a half of recommendation rate; 75 kg N ha-1:25 kg P ha-1: 25 kg K ha-1);organic compost (5 tones ha-1) plus inorganic fertilizer (a half of recommendation rate; 100 kg N ha-1:25 kg P ha-1: 25 kg K ha-1). Result: The application of fertilizer increased the plant growth, biomass production and total chlorophyll content of centella. Nonetheless, the high amount of inorganic fertilizer led to a reduction in the phytochemical content and antioxidant activity in centella leaf. The combination of organic compost and inorganic fertilizer produced maximum growth and increased the total phenolic content and antioxidant activity.