Response of Potato Gas Exchange and Productivity to Phosphorus Deficiency and Carbon Dioxide Enrichment

Abstract

ABSTRACTThe degree to which crops respond to atmospheric CO2 enrichment may be influenced by nutrition. To determine the extent to which dry matter production, canopy and leaf photosynthesis, and transpiration are influenced by P and CO2, potatoes (Solanum tuberosum L. cultivar Kennebec) were grown in outdoor soil–plant–atmosphere research (SPAR) chambers at two levels of CO2 (400 or 800 μmol mol−1) and three levels of P fertilization. Total dry matter declined an average 42% between high and low P fertilizer and increased 13% in response to elevated CO2 when averaged across the P treatments. This enhancement effect did not vary with level of P treatment. Leaf level photosynthetic rate was reduced 58% and stomatal conductance 43% between high and low P treatments. Biochemical model parameters for carboxylation rate, ribulose bisphosphate regeneration, and triose phosphate use were reduced by P deficiency but scarcely influenced by growth CO2. After tuber initiation, canopy assimilation rate increased under elevated CO2 particularly at the middle levels of P fertilization, and diurnal canopy evapotranspiration showed a significant reduction in response to elevated CO2 and declining P fertilizer. Lack of interactive effects between CO2 and P on most measured responses suggests the effect of CO2 enrichment on potato growth and assimilation is similar at each P‐treatment level; however, such effects may also be correlated with plant N status.