Soil Sodicity Induced Changes in Aromatic Plants: Effects on Growth, Water Relation, Photosynthetic Pigments, Antioxidative Enzymes, Cations Concentration and Quality of Ocimum sanctum

To assess the salt tolerance mechanism in aromatic plants, a soil pot experiment was conducted on Ocimum sanctum (shyama tulsi). The plants were raised on natural sodic soils having different levels of Exchangeable Sodium Percentage (ESP) i.e.,: 4.37 (control), 15.7 (low), 35.6 (medium) and 54.5 (high) ESP levels in complete randomized design. Results indicated that increased in ESP significantly decreases vegetative growth and dry matter yields of the plant. The pH and EC of cell sap and proline content were increased than the control while water potential decreases (became more negative). Activities of enzymatic and some non-enzymatic anti-oxidant like catalase (CAT), peroxidase (POD), superoxide dismutase (SOD) and total phenol content were increased while Glutathione Reductase (GR) and H2O2 content were reduces that imply oxidative stress as a consequences increased soil ESP. The concentration of chloroplastic pigments like chlorophylls, carotenoids and carotenoids/chlorophyll ratio were decreased on increasing ESP. The reducing sugars and total carbohydrate were also decreased on increasing ESP. The protein content and essential oil content were increased on increasing the ESP levels. The Na concentration in root and stem of plant were increased while in leaf it was decreased. The K concentration was decreased on increasing the soil sodicity in root while in stem and leaf it was increased. The Na/K ratio was decreased on increasing the soil sodicity in stem and root while in leaf it was decreased. The concentration of iron (Fe), manganese (Mn), zinc (Zn) copper (Cu) and lead (Pb) were observed maximum in leaves which increases in low and medium ESP than the control while in high ESP these were decreases except Zn. Thus Ocimum plant showed tolerance mechanism in sodic stress environment.