Nitrogen availability modulates CO2-induced responses of Catharanthus roseus: Biomass allocation, carbohydrates and alkaloids profile

•Stimulation in growth under elevated CO2 correlates with increasing N supply.•Elevated CO2 increased foliar carbon pool with greater extent in higher N.•Under no supplemental N condition elevated CO2 reduces foliar N.•Elevated CO2 increased total alkaloids content in all rates of N supply.•Vincristine and vinblastine increased maximally under moderate supply of N.

The effects of elevated CO2 (560 ± 25 ppm) and N supply (no supplemental N: 0 kg N ha−1, recommended N: 50 kg N ha−1, double recommended N: 100 kg N ha−1) on biomass allocation and alkaloids production in periwinkle (Catharanthus roseus L.) were examined using open top chambers. Elevated CO2 significantly stimulated total biomass of the plant grown in moderate and high N condition. Further, change in pattern of biomass partitioning was also observed under different CO2 and N treatments and plant allocated its maximum biomass toward stem under elevated CO2 at all N treatments. Leaf biomass showed its highest proportion with high N, under elevated CO2. Elevated CO2 rather significantly increased starch, organic carbon, while it decreased soluble sugar in higher N supply. Plants grown with low level of N showed significant reduction in total foliar nitrogen due to CO2 enrichment. Under elevated CO2, total alkaloids, vinblastine and vincristine were highest at moderate N; however, catharanthine content was increased linearly with increasing supply of N. On the other hand, vindoline content was reduced under elevated CO2 with high N. Principal component analysis and factor rotation were conducted to understand the cumulative response of all the variables to elevated CO2 and N availability. The differential response of the test plant under varying CO2 and N levels concluded that C-allocation toward biomass and metabolites synthesis under future projected level of CO2 will be greatly modified by soil nitrogen availability. Furthermore, moderate N supply would be more beneficial for medicinal value of the test plant.