Despite the agronomic importance of potato (Solanum tuberosum L.), the interaction of atmospheric carbon dioxide concentration ([CO₂]) and drought has not been well studied. Two soil-plant-atmosphere research (SPAR) chamber experiments were conducted concurrently at ambient (370Îơmolmol⁻℗£) and elevated (740Îơmolmol⁻℗£) [CO₂]. Daily irrigation for each chamber was applied according to a fixed percentage of the water uptake measured for a control chamber for each [CO₂] treatment. We monitored diurnal and seasonal canopy photosynthetic (A G) and transpiration rates and organ dry weights at harvest. Plants grown under elevated [CO₂] had consistently larger photosynthetic rates through most of the growth season, with the maximum A G at 1600Îơmolphotonsm⁻℗ø s⁻℗£ 14% higher at the well-watered treatments. Water stress influenced ambient [CO₂] plants to a larger extent, and reduced maximum canopy A G, growth season duration, and seasonal net carbon assimilation up to 50% of the control in both [CO₂] treatments. Water use efficiency increased with water stress, particularly at elevated [CO₂], ranging from 4.9 to 9.3gdrymassL⁻℗£. Larger photosynthetic rates for elevated [CO₂] resulted in higher seasonal dry mass and radiation use efficiency (RUE) as compared with ambient [CO₂] at the same irrigation level. This extra assimilate was partitioned to underground organs, resulting in higher harvest indices. Our findings indicate that increases in potato growth and productivity with elevated [CO₂] are consistent over most levels of water stress. This work can support various climate change scenarios that evaluate different management practices with potato.

climate change, drought, plant-water relations, wateruptake, irrigation rates, net assimilation rate, radiation useefficiency, harvest index, dry matter partitioning, photosynthates,duration, crop yield, transpiration, photosynthesis, elevatedatmospheric gases, plant response, soil-plant-atmosphere interactions,carbon dioxide, Solanum tuberosum, potatoes, canopy, growing season,water use efficiency, dry matter accumulation, seasonal variation, waterstress, gas exchange, diurnal variation

• Journal Article

• Drought
• Irrigation Management