Effect of soil pH on plants growth, phytochemical contents and their antioxidant activity

Abstract

Phytochemicals or secondary metabolites are non-nutritive plants derivatives required for a variety of animal bodily functions. Plant growth and available soil nutrients decide the primary and secondary metabolites. Soil pH has a significant impact on both soil nutrient availability, plant uptake, and growth. Soil pH also decide the distribution of plant species in around the world. Still, the significance of soil pH on phytochemical concentration has not been reported. The goals of this study were to find out how soil pH affects phytochemical content and their antioxidant activity. The model's accuracy in predicting phytochemical effects in various soil pH (3.8, 4.7, 5.7, 6.5, 7.6, and 8.3) was tested in a pot experiment. The soil's pH was adjusted using Ca(OH)₂ and HNO₃ (pH 3.8-8.3) and soil nutrients were maintained by KCl (8.3), MgSO₄ (2.5), Ca(HPO₄) (5) (mg kg^-1 soil. Monocot species viz Oryza sativa, and Zea mays, and dicot species viz Cicer arietinum, Macrotyloma uniflorum were selected for study. Whole plants were collected between 5^th to 8^th day and analysed for growth and phytochemicals like phenols, tannins, flavonoids, saponins, and alkaloids. The result showed acidic soil pH (5.7) and a slightly acidic pH (6.5) is suitable for O. sativa and Z. mays, C. arietinum growth respectively. Whereas slightly alkaline soil pH (7.6) is best for M. uniflorum growth. Phytochemical scarcity in plants was observed despite the presence of all nutrients in the soil.  The quantity and quality of phytochemicals are affected by soil pH. DPPH, ABTS, and anti-lipid peroxidation activity also directly proportional to plant growth and soil pH. This suggests that soil pH has a direct impact on nutrient uptake and phytochemical constituents of plants.