Monday, November 13, 2006 - 1:00 PM

Potato Gas Exchange and Canopy Development Responses to Drought and Atmospheric Carbon Dioxide Concentration.

David H. Fleisher, Dennis Timlin, and V.R. Reddy. USDA-ARS, Crop Systems and Global Change, 10300 Baltimore Ave, Beltsville, MD 20705-2350

Potato is very sensitive to drought with yields reduced under even moderate amounts of water stress.  The interaction of long-term drought with atmospheric carbon dioxide concentration ( [CO2]) on potato whole plant gas exchange and canopy development has not been well studied.  A 12 SPAR (soil plant atmosphere research) growth chamber research experiment was conducted at facilities in USDA-ARS Beltsville, MD in the summer of 2005.  Six SPAR chambers were maintained at ambient [CO2] (370 ppm) and six chambers at elevated [CO2] (740 ppm).  Within each set of chambers, daily irrigation was varied to 90%, 75%, 50%, 25%, and 10% of a control chamber that received 100% of daily water uptake throughout the growth season.  Water uptake in each chamber was measured with 15 time-domain reflectometry probes.  Measurements of whole plant photosynthetic and transpiration rates were made at 5 minute intervals throughout the season.  Biweekly measurements of leaf appearance and expansion rates and stem elongation were recorded to further assess differences in potato growth and development in response to the degree of drought stress.  The results indicate that plant growth, yield, and canopy expansion were more strongly correlated with irrigation amount than [CO2].  Little difference was observed in gas exchange and total biomass production between 75, 90, and 100% treatments; however, canopy expansion, and thus total plant growth, was linearly correlated with 10, 25, and 50% irrigation amounts.  The [CO2] primarily influenced partititioning between above and below-ground plant organs at most levels of irrigation.