Combined effect of elevated CO2 and temperature on growth, biomass and secondary metabolite of Hypericum perforatum L. in a western Himalayan region

Rising carbon dioxide [CO2] levels and air temperature influence overall growth and production pattern of crop plants, and thus they help in understanding the functional relationship between the environment and crop performance. The present experiment was conducted to study the simultaneous effect of elevated CO2 (550 +/- 50 mu mol mol(-1)) and air temperature (2.5 +/- 0.5 degrees C above ambient) on Hypericum perforatum growth, biomass and carbon-based plant secondary metabolite concentrations at free air CO2 enrichment (FACE) and free air temperature increase (FATI) facilities of CSIR-Institute of Himalayan Bioresource Technology, Palampur, India during 2016-2017. Experiment was laid out in factorial CRD (completely randomized design) with five replications. Results showed that the growth and biomass were significantly affected by elevated CO2 and temperature. Plant height at 140 days after exposure (DAE) and 280 DAE was 8.49% and 6.90% higher in FACE + FATI as compared to ambient, respectively. Total dry biomass was 35.70% and 55.20% higher in FACE + FATI as compared to ambient at 140 DAE and 280 DAE, respectively. Application of vermicompost recorded 8.50% higher biomass and 20.65% higher hypericin content as compared to control. Hypericin concentration reduced significantly by 22.00% in elevated CO2, while under combined effect of elevated CO2 and temperature it reduced by 19.30% when compared to ambient. Phenological stages i.e. bud and flower formations were advanced by 4 and 5 days, respectively, under FACE as compared to ambient.