Adaptive Responses to high CO2 by Oil seed crop plants Brassica juncea and Brassica compestris grown in Free Air carbon dioxide enrichment (FACE) environment

Adaptation of oil seed crop plants to climate change was studied in Brassica juncea , cv Pusa Jaikisan, and Brassica compestris cv Pusa Gold grown in free air carbon dioxide enrichment (FACE) (600 μmol mol -1 ) (eCO 2 ) environment for three consecutive years. The eCO 2 plants had higher leaf area, biomass, and yield per plant as compared to ambient air-grown plants. The dark respiration increased in eCO 2 to support better crop growth. The light response curves of carbon assimilation demonstrated a 30%-40% increase in the light-saturated photosynthesis rate and higher quantum yield of carbon assimilation by leaves of eCO 2 -plants mostly due to reduced photorespiration. The A-Ci curves demonstrated that the maximum carboxylation efficiency, Vcmax was not reduced in eCO 2 plants due to unaltered rubisco abundance. A decrease in stomatal conductance in eCO 2 reduced the transpiration rate and increased the water use efficiency. However, an increased leaf area index in eCO 2 would have offset the gains due to reduced transpiration. Proteomics and genomics profiling revealed an increase in the expression of proteins/genes involved in photosynthesis, nitrogen assimilation, ribosome biogenesis, signal transduction, antioxidative response and a decrease of those involved in photorespiration, amino acid metabolism, Fe-S cluster cofactor, and protein degradation as adaptation to eCO2.