Interactive Effects of <scp>CO₂</scp> Enrichment and Nitrogen Levels on Leaf Gas Exchange Capacities of Sweet Potato

ABSTRACT Different nitrogen ( N ) doses may stimulate the photosynthetic responses of sweet potato under CO 2 ‐enriched environment (ECO 2 ). The photosynthetic responses of two varieties, Sree Arun and Sree Kanaka, were adjudicated under varying nitrogen levels (0%, 25%, 50%, 100%, and 125% of the recommended N dose), exposed to ambient CO 2 (400 ppm) and elevated CO 2 (600 and 800 ppm). The results indicated that, compared to ambient CO 2 , the net photosynthetic rate ( P n ) and intercellular CO 2 ( C i ) were significantly increased at ECO 2 , while stomatal conductance ( g s ) and transpiration ( E ) were significantly exacerbated. This resulted in an improved intrinsic ( P n / g s ) and instantaneous water use efficiency ( P n / E ). Relative humidity and vapour pressure deficit during the time of measurements remained at 73%–85% and ~0.95–1.42 kPa, respectively, at 28°C ± 2°C leaf temperature. Furthermore, the results demonstrated that higher N doses increased photosynthesis and improved plant water relations by modulating stomatal conductance and transpiration rate. Overall, the responses of sweet potato plants to ECO 2 and N supply were genotypic‐dependent, and nitrogen application could play an important role in modulating these responses under ECO 2 . The findings from this study provide valuable insights for tailoring nitrogen‐based management practices for sweet potato in a carbon‐enriched environment.