Atmospheric CO2 enrichment effect on water use efficiency in chickpea (Cicer arietinum L.)

Effect of atmospheric CO2 enrichment on crop water relations was evaluated in an open-top chamber experiment on kabuli chickpea (Cicer arietinum L.; Pusa 1,105). Increase in atmospheric CO2 concentration (e[CO2], 580 +/- 20 mu mol/mol) resulted in 21%-46% increase in leaf water potential, and 7%-11% in relative leaf water content, indicating higher water content in leaves, compared to the ambient level (a[CO2], 384 +/- 12 mu mol/mol). Higher leaf water status was connoted through spectral indices over the growing period. A rise in CO2, however, brought increase in leaf diffusive resistance and canopy temperature by 15%-35% and 3%-11%, respectively, potentially indicating partial closure of stomata. Increase in leaf area index (13%-73%), and higher spectral vegetation index suggested improved growth of chickpea under e[CO2]. An increase in leaf area compensated the decrease in diffusive resistance, and therefore seasonal total water use was similar between enriched and ambient conditions. Although water use efficiency (WUE) increased by 30% (p < .05) due to an increase in crop biomass under e[CO2], the canopy conductance remained unaffected. Results suggest a possibility of improved plant water status, enhanced biomass production and increased WUE for chickpea, with similar crop water use under future e[CO2] levels.

Automated summary

Increasing atmospheric CO2 concentration has significant impacts on crop water relations in kabuli chickpea, resulting in higher leaf water potential and relative leaf water content, but also increased leaf diffusive resistance and canopy temperature. Despite the increase in leaf area compensating for the decrease in diffusive resistance, the seasonal total water usage is similar between enriched and ambient conditions.