Interaction of enriched CO₂ and water stress on the physiology of and biomass production in sweet potato grown in open‐top chambers

The objective of this study was to investigate the effects of water stress in sweet potato ( Ipomoea batatas L. [Lam] ‘Georgia Jet’) on biomass production and plant‐water relationships in an enriched CO 2 atmosphere. Plants were grown in pots containing sandy loam soil (Typic Paleudult) at two concentrations of elevated CO 2 and two water regimes in open‐top field chambers. During the first 12 d of water stress, leaf xylem potentials were higher in plants grown in a CO 2 concentration of 438 and 666 μmol mol −1 than in plants grown at 364 μmol mol −1 . The 364 μmol mol −1 CO 2 grown plants had to be rewatered 2 d earlier than the high CO 2 ‐grown plants in response to water stress. For plants grown under water stress, the yield of storage roots and root: shoot ratio were greater at high CO 2 than at 364 μmol mol −1 ; the increase, however, was not linear with increasing CO 2 concentrations. In well‐watered plants, biomass production and storage root yield increased at elevated CO 2 , and these were greater as compared to water‐stressed plants grown at the same CO 2 concentration.