Estimating photosynthetic parameter values of rice, wheat, maize and sorghum to enable smart crop cultivation

Abstract

Crop models can support the design of smart crop management practices. The Farquhar-von Caemmerer-Berry (FvCB) model is increasingly being used in these models for quantifying leaf photosynthesis. Nitrogen (N) is required for many functional machineries of photosynthesis, thus relationships between FvCB-model parameters and leaf N content (LNC) should be established. We conducted combined gas exchange and chlorophyll fluorescence measurements on fully expanded leaves of two C₃ crops, rice (Oryza sativa) and wheat (Triticum aestivum), and two C₄ crops, maize (Zea mays) and sorghum (Sorghum bicolor), grown under three N levels. Photosynthetic parameters were estimated and linear relationships between these parameters and LNC were quantified in both C₃ and C₄ crop types. The efficiency of converting incident light into linear electron transport for C₃ crops or into ATP production for C₄ crops showed a weak increase with LNC. The maximum electron transport rate (J_max) for C₃ crops or the maximum ATP production rate (J_max,atp) for C₄ crops significantly increased with LNC. The increase in Rubisco carboxylation capacity (V_cmax) with LNC was significantly higher in C₃ than in C₄ crops. Triose phosphate utilization for C₃ crops and PEP carboxylation capacity (V_pmax) for C₄ crops increased significantly with LNC as well. Except for J_max at 21% O₂ and V_cmax of C₃ crops, there was no significant difference among crops in the relationship between estimated photosynthetic parameters and LNC. The tight associations of photosynthesis parameters with LNC were discussed in view of decision making on N management in the context of smart farming.