Responses of periwinkle (Catharanthus roseus L.) to CO₂ enrichment: Chlorophyll florescence, pigments, metabolites, growth and biomass

The present field experiment was conducted to investigate the effects of elevated CO₂ (560 ± 25ppm) on selected physiological, metabolic and growth parameters of Catharanthus roseus (L.) G Don, compared to ambient (375 ± 30 ppm) CO₂ at different developmental stages, using the open top chamber. Photosynthetic efficiency of plants measured in terms of F_v/F_m ratiowas enhanced under elevated CO₂. Total chlorophyll, protein, total phenolics and total alkaloid contents were also increased under elevated CO₂; however, the ascorbic acid content was declined. Increments in total chlorophyll and protein contents were higher at early growth stage, while increments in phenolics, carotenoids and alkaloid contents were greater at a late growth stage. Root length, shoot length, numbers of branches and leaves and total biomass also showed significant increments under elevated CO₂ compared to ambient. The study concluded that CO₂ enrichment will improve the medicinal yield of plant by enhancing biomass accumulation as well as the alkaloids content.