Anatomy of non-uniform leaf photosynthesis

Since 1986, non-uniform photosynthesis over the leaf area that may be attributed to patchy stomatal closure, has been an important issue in stress physiology of photosynthesis. In this review, I first outline the gaseous environment within the intercellular spaces, because this is the most fundamental background of this problem. Then, recent studies approaching non-uniform photosynthesis are reviwed. After examining techniques for the detection of non-uniform photosynthesis or non-uniform stomatal aperture, results of the relevant studies are discussed for respective stress factors, seeking causes and consequences of non-uniform photosynthesis. From these, mechanisms responsible for, and consequences of non-uniform photosynthesis, are considered. The problems which should be challenged are also pointed out.Abbreviations A rate of photosynthetic CO₂ fixation (assimilation rate) - ABA abscisic acid - g conductance for CO₂ or H₂O - p_a partial pressure of CO₂ in the ambient air - p_i partial pressure of CO₂ in the intercellular space - p_i p_i estimated by the conventional gas exchange techniques - q_N non-photochemical quenching - q_p photochemical quenching