PARENT SESSION
Organized Oral Session 52: Casting light on nocturnal stomatal and canopy conductance
Organizer(s): NG Phillips and M Barbour
Friday, August 12, 8:00 AM - 11:30 AM, Meeting Room 510a, Level 5, Palais des congrès de Montréal
Implications of nocturnal stomatal conductance for modelling the oxygen isotope composition of leaf-respired carbon dioxide.
Cernusak, Lucas*,1, Barbour, Margaret2, Wong, Suan Chin1, Stuart-Williams, Hilary1, Farquhar, Graham, 1 Environmental Biology Group, Canberra, ACT, Australia2 Landcare Research, Lincoln, New Zealand
ABSTRACT- We present data and theory relating to the controls over the oxygen isotope composition of carbon dioxide respired by leaves in the dark. Modeling oxygen isotope effects during leaf dark respiration involves, among other things, predicting the nighttime leaf water oxygen isotope enrichment and the one-way, or gross, efflux of carbon dioxide out of the respiring leaf. Both of these processes depend on how open the stomata are in the dark. Contemporary models predicting nighttime leaf water enrichment and the oxygen isotope composition of leaf dark respiration will be described, paying particular attention to the role of nighttime stomatal conductance. It will be shown that in both cases, it is the one-way, or gross, efflux of water vapor or carbon dioxide out of the leaf that is the relevant flux term, as opposed to the net efflux. Thus, even in the case where the nighttime canopy air space is saturated with water vapor, and leaf transpiration is therefore very small or absent, the extent of stomatal opening can still have a large impact on the nighttime leaf water oxygen isotope composition and on the oxygen isotope composition of leaf dark respiration.
Key words: nocturnal conductance, oxygen isotope, leaf respiration