Photosynthetic and Respiratory Characteristics of Peanut Cultivars Adapted to Varying Night Temperatures1

Abstract

Abstract Relatively mild night temperatures can reduce leaf carbon dioxide exchange rates (CER) and dry matter (DM) accumulation in peanut (Arachis hypogaea L.). To investigate differences among cultivars in response to long-term exposure to a range of night temperatures, three peanut cultivars (OAC Ruby, Chico, and Early Bunch) with known differences in chilling sensitivity were grown in controlled-environment cabinets at the University of Guelph, Ontario. Effects of long-term exposure to night temperatures from 9 to 20 C were assessed in terms of leaflet and whole plant CER, DM accumulation, and phenological development. Effects of night temperature on rate of phenological development and DM accumulation were consistent with differences in accumulation of degree-days. Cultivars did not differ in daytime leaf CER response to all night temperatures except 9 C, at which CER for OAC Ruby was higher than for Early Bunch or Chico. CER in the 9 C treatment was 92% of the CER at 20 C for OAC Ruby and 80% for Early Bunch and Chico. Continuous exposure to night temperatures of 10C reduced CER sensitivity to low daytime temperature in OAC Ruby, but Early Bunch was unaffected. Specific respiration rates were higher for plants of OAC Ruby than Early Bunch in the 10 C treatment, with indications that these differences were due to increased maintenance requirements. The ability of OAC Ruby to adapt to cool-night conditions may have a significant impact on crop performance in cooler environments.