Water deficit stress mitigation by calcium chloride in Catharanthus roseus: Effects on oxidative stress, proline metabolism and indole alkaloid accumulation

The present investigation was conducted to determine whether CaCl2 increases Catharanthus roseus drought tolerance and if such tolerance is correlated with changes in oxidative stress, osmoregulation and indole alkaloid accumulation. C. roseus plants were grown under water deficit environments with or without CaCl2. Drought induced oxidative stress was measured in terms of lipid peroxidation (LPO) and H2O2 contents, osmolyte concentration, proline (PRO) metabolizing enzymes and indole alkaloid accumulation. The plants under pot culture were subjected to 10, 15 and 20 days interval drought (DID) stress and drought stress with 5 mM CaCl2 and 5 mM CaCl2 alone from 30 days after planting (DAP) and regular irrigation was kept as control. The plants were uprooted on 41 DAS (10 DID), 46 DAS (15 DID) and 51 DAS (20 DID). Drought stressed plants showed increased LPO, H2O2, glycine betaine (GB) and PRO contents and decreased proline oxidase (PROX) activity and increased γ-glutamyl kinase (γ-GK) activity when compared to control. Addition of CaCl2 to drought stressed plants lowered the PRO concentration by increasing the level of PROX and decreasing the γ-GK activities. Calcium ions increased the GB contents. CaCl2 appears to confer greater osmoprotection by the additive role with drought in GB accumulation. The drought with CaCl2-treated C. roseus plants showed an increase in total indole alkaloid content in shoots and roots when compared to drought stressed and well-watered plants.