Response of Ajowan to water stress induced by polyethylene glycol (PEG) 6000 during seed germination and seedling growth.

Seed germination and subsequent metabolic changes in Ajowan (Trachyspermum ammi L.) (NRCSS AA-2) seedlings was studied under water limiting conditions, imposed by increasing concentrations of polyethylene glycol (PEG 6000). Five water stress conditions (0, -0.05, -0.1, -0.15 and -0.2 MPa) were created in the laboratory in a completely randomized design. The results revealed that water stress (-0.2 MPa) significantly reduced seed germination components like final germination percent (80%) radical (64%) and plumule (63%) length, fresh (63%) and dry (74%) weight of seedlings and vigor index (SVI) by 92% over control. Decrease in osmotic potential resulted in decreased protein content (56%) with concomitant increase in total sugars (55%) at -0.2 MPa as compared to control. Significant increase in free proline and glycine betaine content by 1.5 to 2 folds was observed at the highest water stress condition. The seedlings exhibited increased activity of superoxide dismutase and peroxidase under stressed condition. In the present study, it was found that Ajowan was a moderately drought tolerant species at laboratory level.