Environmental Effects on Peppermint (Mentha piperita L.). II. Effects of Temperature on Photosynthesis, Photorespiration and Dark Respiration in Peppermint With Reference to Oil Composition

Abstract

Net CO₂ exchange was investigated at several photon flux densities and day temperatures in both 21% and 2% O₂. Light saturation occurred between 400 and 500 µEm^-2, s^-1 in attached, fully expanded leaves of peppermint. Maximum rates of 'apparent' photosynthesis occurred at 20°C. The important determinants of 'apparent' photosynthesis were an increase in 'true' photosynthesis when temperature was increased to 25°C, a steady increase in dark respiration with increased temperature and a rapid increase in photorespiration between 15 and 30°C. Such net CO₂ exchange characteristics of peppermint support the photosynthate model proposed to explain environmental effects on oil composition.