High-Nitrogen Supply Enhances Leaf Photosynthesis Capacity of Chickpea (Cicer arietinum L.) Under Elevated CO2

Abstract

Background

Nitrogen (N) limitation may reduce the CO₂-fertilization effect on photosynthesis and crop productivity. The mechanisms by which N supply influences photosynthetic capacity under elevated CO₂ (eCO₂) are not well understood, particularly in chickpea.

Aims

This study examined the interactive effects of CO₂ and N supply on chickpea's photosynthetic capacity and leaf N status, and to understand the regulatory role of N in photosynthetic capacity under eCO₂.

Methods

Non-inoculated chickpea plants were grown under two CO₂ levels (400 vs. 800 µmol mol⁻¹) and two N rates (21 vs. 189 mg N kg⁻¹ soil) for 65 days. Photosynthetic activity and plant N uptake were investigated at the flowering and podding stages of growth.

Results

Adequate N supply maintained the maximum Rubisco carboxylation capacity (V_c,max25) and the electron transport rate supporting ribulose–1,5-bisphosphate (RuBP) regeneration (J₂₅) under eCO₂ by increasing leaf N concentration per unit area and chlorophyll synthesis and reducing photosynthetic acclimation in chickpea under eCO₂ at the flowering and podding stages. Low N decreased the leaf N concentration and SPAD (soil and plant analyzer development of chlorophyll meter readings) and limited the eCO₂-driven increases in V_c,max25 and J₂₅. High-N supply increased plant biomass and N accumulation to a greater extent under eCO₂ than under ambient CO₂, leading to significant CO₂ × N interactions.

Conclusion

Adequate N supply is critical to enhance photosynthetic capacity by maintaining V_c,max25 and J₂₅ in non-inoculated chickpea at the flowering and podding stages under eCO₂. The findings highlight the importance of optimizing N management for maximizing the CO₂-fertilization effect in future climate change.