Root Anatomy and Growth Responses of Soybean (Glycine max (L.) Merr.) ‘Wilis’ to NaCl Stress

Abstract

Soybean (Glycine max (L.) Merr.) is a very important agricultural commodity for food ingredients. Soybean production decreases every year due to field area constriction. Utilization of marginal lands with high salt content is one of the alternatives for growing soybean. This research aimed to determine root anatomy and growth responses of soybean under NaCl treatment. Volumes of 200 mL NaCl at concentrations of 0 mg · L−1, 2000 mg · L−1, 4000 mg · L−1, 6000 mg · L−1, 8000 mg · L−1, or 10,000 mg · L−1 were individually administered to 15-day-old seedlings. The treatment was repeated every 3 days and parameter observation was done 5 weeks after the first treatment. The data obtained were analyzed using ANOVA and differences between treatments were tested using a Duncan test at a significance level of 5%. The results showed that increases in NaCl concentrations caused smaller diameters of roots, steles, and xylem tissues as well as cortex thickness. However, high concentrations of NaCl tended to increase the diameter of xylem vessels and ruptured the peripheral layers of roots. The soybean growth was also inhibited by higher concentrations of NaCl, as observed by reductions in plant height, root length, leaf number, dry biomass, and chlorophyll content. It was found that the NaCl tolerance limit of soybean ‘Wilis’ was around 2000 mg/L.