Agu Laisk (born 3 May 1938) is an Estonian plant physiologist and physicist. He is a professor emeritus at the University of Tartu and a member of the Estonian Academy of Sciences (elected 1994).
His research has focused on the physiology and biophysics of photosynthesis and photorespiration, including gas-exchange measurement approaches and mathematical modelling of leaf CO<sub>2</sub> exchange.
Laisk studied physics at the University of Tartu, graduating in 1961. He earned a Soviet-era Candidate of Sciences degree (physics and mathematics) in 1965 and a Doctor of Sciences degree in biology in 1975, with research on the kinetics of leaf photosynthesis and photorespiration.
From the 1960s to the early 1990s, Laisk worked in research institutes of the Estonian Academy of Sciences, where he led work linking plant-canopy radiation physics with physiological interpretation of photosynthesis. From 1992 he worked at the University of Tartu (Institute of Molecular and Cell Biology), becoming professor and heading plant physiology, and later serving as senior researcher and professor emeritus.
He has held visiting research positions at several universities and research institutes, including the Australian National University and other European and U.S. institutions, as documented in institutional CV material.
LaiskâÂÂs work addresses quantitative limitations and regulation of photosynthetic CO<sub>2</sub> assimilation in C3 plants, including the interaction between photosynthesis and photorespiration and the interpretation of gas-exchange signals under varying light and CO<sub>2</sub> conditions.
In plant ecophysiology, the term Laisk method commonly refers to a gas-exchange procedure based on measuring net CO<sub>2</sub> assimilation at low intercellular CO<sub>2</sub> (A/C<sub>i</sub>) across multiple irradiances and using the intersection properties of these relationships to estimate respiration in the light (and related CO<sub>2</sub>-exchange parameters used in modelling). The method is widely discussed and compared with alternative approaches in the peer-reviewed literature, including assessments of assumptions and applicability across conditions.