Interactive Effects of Carbon Dioxide and Water Stress on Potato Canopy Growth and Development

Reductions in potato ( Solanum tuberosum L.) canopy growth are observed with mild water stress. Potato growth is enhanced by elevated atmospheric carbon dioxide ([CO 2 ]), but interactions of [CO 2 ] and water stress on canopy formation and dry matter partitioning have not been studied. Two soil‐plant‐atmosphere research (SPAR) experiments were conducted at 370 or 740 μmol mol −1 [CO 2 ] and six different irrigations from 10 to 100% of the daily water uptake of the control. Increases in plant length from 23 to 111 cm at 60 d after emergence (DAE), leaf appearance duration from 38 to 71 d, leaf appearance rate from 0.5 to 0.93 leaves d −1 , individual leaf area from 50 to 175 cm 2 , and lateral branch elongation were observed as irrigation increased. Values were generally smaller for elevated [CO 2 ] plants under water stress. Biomass increased with irrigation from 73 to 346 g plant −2 . The percentage allocated to the canopy increased with irrigation from 50 to 80% in ambient and 30 to 80% in elevated [CO 2 ]. Despite decreased canopy size, elevated [CO 2 ] plants produced similar total biomass, but higher yield, at most irrigations. Reduced canopy mass in elevated [CO 2 ] plants was attributed to suppressed lateral branch development due to an interactive effect of [CO 2 ] and water stress on tuber sink strength. These results indicate that water stress predicted by climate change models will be mediated somewhat under [CO 2 ] enrichment.