Elevated carbon dioxide and water stress effects on potato canopy gas exchange, water use, and productivity
2008
Fleisher, David H. | Timlin, Dennis J. | Reddy, V.R.
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 (370μmolmol⁻¹) and elevated (740μmolmol⁻¹) [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 1600μmolphotonsm⁻² s⁻¹ 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⁻¹. 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.
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