Alterations in morphological parameters and photosynthetic pigment responses of Catharanthus roseus under soil water deficits

An experiment was conducted in two varieties, rosea and alba, of Catharanthus roseus plants with two watering treatments viz., 100 and 60% of field capacity, to understand the effects of water deficit on early growth, biomass allocation and photosynthetic pigment responses. We found that there were significant differences in early growth, dry matter accumulation and pigment variations between the two varieties. The root length, shoot length, total leaf area, fresh and dry weights were significantly reduced under water stress treatments. There was a significant reduction in the photosynthetic pigment contents in both the varieties. The rosea variety was more affected due to water deficit when compared to alba variety.     

Induction of drought stress tolerance by ketoconazole in Catharanthus roseus is mediated by enhanced antioxidant potentials and secondary metabolite accumulation

A pot culture experiment was conducted to estimate the drought stress mitigating effect of ketoconazole (KCZ), a fungicide cum plant growth regulator, in Catharanthus roseus plants. The plants under pot culture were subjected to drought stress and drought stress with KCZ from 30 days after sowing (DAS) and regular irrigation was kept as control. Antioxidant contents and activities of antioxidant enzymes were estimated from root, stem and leaf of both control and treated plants. The alkaloid ajmalicine was extracted and estimated from the roots of control, drought stressed and KCZ treated plants. Individual and combined drought stress and KCZ treatments increased ascorbic acid, -tocopherol contents, superoxide dismutase, ascorbate peroxidase, catalase and polyphenol oxidase activities when compared to control. There was a significant enhancement in ajmalicine production under KCZ treated plants under drought stress when compared to well watered control as well as drought stressed plants. The KCZ treatment resulted in partial mitigation of drought stress by increasing the antioxidant potentials in C. roseus plants.     

Alterations in osmoregulation, antioxidant enzymes and indole alkaloid levels in Catharanthus roseus exposed to water deficit

Catharanthus roseus (L.) G. Don plants were grown in different water regimes in order to study the drought induced osmotic stress and proline (PRO) metabolism, antioxidative enzyme activities and indole alkaloid accumulation. The plants under pot culture were subjected to 10, 15 and 20 days interval drought (DID) stress from 30 days after sowing (DAS) 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). The drought stressed plants showed increased aminoacid (AA), glycine betaine (GB) and PRO contents and decreased proline oxidase (PROX) and increased γ-glutamyl kinase (γ-GK) activities when compared to control. The antioxidative enzymes like peroxidase (POX) and polyphenol oxidase (PPO) increased to a significant level in drought stressed plants when compared to control. The drought stressed C. roseus plants showed an increase in total indole alkaloid content in shoots and roots when compared to well-watered control plants. Our results suggest that the cultivation of medicinal plants like C. roseus in water deficit areas would increase its PRO metabolism, osmoregulation, defense system and the level of active principles.