Chilling Dependent Photoinhibition of Photosynthetic CO₂ Uptake

Abstract

Several studies have shown that chilling (exposure to temperatures between 0°C and 12°C) increases the susceptibility of the photosynthetic apparatus to damage by light (1, 2). Investigations of chilling dependent photoinhibition of photosynthesis have centred on the chilling sensitive annual crops which have been introduced to cool temperate climates from the tropics, e.g. Maize and Tomato (1, 3, 4). However, evergreen crops of Mediterranean climates, although infrequently exposed to freezing conditions for long periods, will be exposed to long periods of chilling during the winter when light levels may be high. In this study gas-exchange techniques are used to compare photoinhibition in three chilling sensitive crops: an annual C₃ species (Cucumber, Cucumis sativus), an annual C₄ species (Maize, Zea mays) and a Mediterranean evergreen C₃ species (Olive, Olea europaea). Changes in the rates of CO₂ uptake under limiting and under saturating conditions of light and/or CO₂ supply are used to examine the kinetics and characteristics of both the development of photoinhibition and recovery from photoinhibition. Two further questions are examined in Maize. 1) To what extent is chilling dependent photoinhibition influenced by light pre-history and by location within the leaf? 2) What genotypic variation in susceptibility to chilling dependent photoinhibition might exist within a species?