Keywords: Photosynthesis, Pre-anthesis, In vivo, Rubisco specificity factor, Wheat
Photosynthesis could be improved by increasing photosynthetic rate per unit leaf area and by optimizing light interception and utilization through modified canopy architecture, and also by modifying photosynthetic duration. The yield potential of wheat is determined by the accumulated photosynthates over the entire growing season or the fraction of the total biomass partitioned into grain at harvest. Significant correlation between grain yield and net photosynthesis rate was found under controlled environmental condition (in vitro) but similar relationship under open field conditions is not established. However, phenotyping of photosynthetic traits based on biochemical models can provide accurate physiological information, and thus connecting those traits with yield at crop level would only make crop improvement feasible involving photosynthetic manipulations. At this perspective, the present investigation was undertaken with ten diverse wheat genotypes to characterize pre-anthesis photosynthetic traits and its possible relationship with wheat productivity under in vivo condition. Genotypes were found to have high natural variations for pre-anthesis photosynthetic traits under in vivo condition. Genotypes like DPW-621-50, K 0307, HW 2044 were having high value of Vcmax, Jmax and Cc and thus expected to have better photosynthetic efficiency under ambient atmospheric CO2 condition. Rubisco specificity factor (τ) was found high in KRL-210, HD 2009, KRL-19 and thus expected to have better carboxylase activity under normal condition. Maximum genetic distance was recorded between KRL-210 and DPW-621-50. Rubisco specificity factor (τ) was found as highly correlated with fraction of photorespiration (F) and chloroplast CO2 concentration (Cc). Positive correlation of Cc with fraction of photorespiration (F), mesophyll conductance (gm) and Rubisco specificity factor (τ) indicated high value of CO2 compensation point (Г*). However, correlation between flag leaf photosynthesis rate and grain or biological yield was found non-significant in the present wheat genotypes.
This research work was financially supported by providing Innovation in Science Pursuit for Inspired Research (INSPIRE) Fellowship (IF-150559) to the first author from Department of Science and Technology under Ministry of Science and Technology, Government of India.