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. 'Georgia Jet') on biomass production and plant-water relationships in an enriched CO2 atmosphere. Plants were grown in pots containing sandy loam soil (Typic Paleudult) at two concentrations of elevated CO2 and two water regimes in open-top field chambers. During the first 12 d of water stress, leaf xylem potentials were higher in plant grown in a CO2 concentration of 438 and 666 micromol mol(-1) than in plants grown at 364 micromol mol (-1). The 364 micro mol mol(-1) CO2 grown plants had to be rewatered 2 d earlier than the high CO2-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 CO2 than at 364 micromol mol(-1), the increase, however, was not linear with increasing CO2 concentrations. In well-watered plants, biomass production and storage root yield increased at elevated CO2, and these were greater as comapred to water-stressed plants grown at the same CO2 concentration