Impacts of drought on leaf respiration in darkness and light in Eucalyptus saligna exposed to industrial-age atmospheric CO2 and growth temperature

Abstract

Our study assessed the impact of a wide range of industrial-age climate scenarios on leaf respiration (R) in Eucalyptus saligna. Well-watered or sustained drought-treated plants were grown in glasshouses differing in atmospheric CO2 concentration ([CO2]) (280, 400 and 640μll-1) and temperature (26 and 30°C). Rates of R in darkness (Rdark) and light (Rlight), photosynthesis (A) and related leaf traits (mass area relationships, and nitrogen, phosphorus, starch and sugar concentrations) were measured. Light inhibited R in all cases (Rlight<Rdark) (well-watered: 40%; drought-treated: 73%). Growth [CO2] and temperature had little impact on area-based rates of Rdark or Rlight, with Rlight exhibiting minimal thermal acclimation. By contrast, sustained drought resulted in reduced Rdark, Rlight and A, with the inhibitory effect of drought on A and Rlight (c. 50-70%) greater than that on Rdark (c. 15%). Drought effects were fully reversible after watering. Variability in Rlight appeared to be dependent on the underlying rate of Rdark and associated Rubisco activity. Collectively, our data suggest that there is an asynchronous response of leaf carbon metabolism to drought, and a tighter coupling between Rlight and A than between Rdark and A, under both past and future climate scenarios. These findings have important implications for ecosystem/global models seeking to predict carbon cycling. Show more