Main content area

Interactions between temperature and intercellular CO2 concentration in controlling leaf isoprene emission rates

Monson, Russell K., Neice, Amberly A., Trahan, Nicole A., Shiach, Ian, McCorkel, Joel T., Moore, David J.P.
Plant, cell and environment 2016 v.39 no.11 pp. 2404-2413
carbon dioxide, chloroplasts, emissions, growing season, hybrids, isoprene, leaves, monsoon season, phosphates, photochemistry, summer, temperature, trees, weather, Sonoran Desert, Southwestern United States
Plant isoprene emissions have been linked to several reaction pathways involved in atmospheric photochemistry. Evidence exists from a limited set of past observations that isoprene emission rate (Iₛ) decreases as a function of increasing atmospheric CO₂ concentration, and that increased temperature suppresses the CO₂ effect. We studied interactions between intercellular CO₂ concentration (Cᵢ) and temperature as they affect Iₛ in field‐grown hybrid poplar trees in one of the warmest climates on earth – the Sonoran Desert of the southwestern United States. We observed an unexpected midsummer downregulation of Iₛ despite the persistence of relatively high temperatures. High temperature suppression of the Iₛ:Cᵢ relation occurred at all times during the growing season, but sensitivity of Iₛ to increased Cᵢ was greatest during the midsummer period when Iₛ was lowest. We interpret the seasonal downregulation of Iₛ and increased sensitivity of Iₛ to Cᵢ as being caused by weather changes associated with the onset of a regional monsoon system. Our observations on the temperature suppression of the Iₛ:Cᵢ relation are best explained by the existence of a small pool of chloroplastic inorganic phosphate, balanced by several large, connected metabolic fluxes, which together, determine the Cᵢ and temperature dependencies of phosphoenolpyruvate import into the chloroplast.