Foliar Application of Salicylic Acid Improved the Growth, Yield and Leaf's Bioactive Compounds in Red Amaranth (Amaranthus tricolor L.)

This study was conducted to determine the effect of foliar salicylic acid (SA) applications on growth, yield and bioactive compounds of red amaranth grown under greenhouse conditions in 2008 at Gifu University, Japan. SA was applied at three different concentrations (10^-3, 10^-4 and 10^-5 M), three times during the vegetation at 7-day intervals one week after sowing. Growth parameters (plant height, stem length, number and size of leaves, root length) and yield (fresh and dry matter weight) were recorded from treated and control plants on 28 days after sowing. Among bioactive compounds, betacyanins, chlorophyll, total polyphenol and antioxidant activity were the determined from the leaves of treated and control plants. All of three doses SA application enhanced the plant growth, yield and leaf's bioactive compounds compared to the control. The growth parameters and yield of red amaranth was significantly influenced by foliar SA applications. The highest yield, antioxidant activity, amount of betacyanins, chlorophyll and total polyphenol occurred in 10^-5 M SA treatment. According to our results, applications SA at rate of 10^-5 M should be recommended in order to improve yield and bioactive compounds in red amaranth.