Proline Induced Modulation in Gas Exchange and Antioxidant Defense of Aniseed ( Pimpinella anisum L.) Seedlings Exposed to Cadmium Stress

Soil contamination with heavy metals is a widespread global problem. Cadmium (Cd) is a highly bioavailable HM that causes toxicity to plants and deteriorates the vital biochemical processes. Osmoprotectants, such as proline (Pro), play a significant role in the physio‐biochemical processes of plants, particularly under stress conditions. The role of Pro in the regulation of Cd stress tolerance in aniseed was investigated in this study. Two Cd (5 and 10 mM) and one Pro (50 mM) levels were applied in sole and combined form in the solution culture experiment to investigate the potential of Pro regarding Cd stress resistance. Results show that Cd stress imparted strong negative impacts on plant growth, photosynthetic rate, crude proteins, and fiber contents. Furthermore, Cd exposure causes an increase in H 2 O 2 contents, Cd accumulation in root and shoot while suppressing the activities of antioxidant enzymes. However, exogenous Pro mitigated the toxic effects of Cd by altering plant growth attributes, restricting Cd uptake by plant roots, and enhancing activities of antioxidant enzymes. The application of Pro with low Cd stress (5 mM) presents an increase in dry biomass (19%), relative water contents (22%), photosynthetic rate (18%), and a pronounced increase in the activities of antioxidant enzymes. These results suggest that Pro possesses the potential to induce Cd tolerance in aniseed. This work opens new dimensions to achieve sustainable production from Cd‐contaminated soils.