Cover Illustration: Drought-induced effects on photosynthesis and photorespiration in three wheat varieties: Canon, Cadenza, and BobWhite. The main figure shows the relationship between leaf CO2 assimilation rates, stomatal conductance, and intercellular CO2 contents in 5-week-old plants as they experienced progressive drought (up to an 80% decrease in soil water content). Leaf catalase activities were increased in response to drought as the stomata closed and CO2 became limiting for photosynthesis and hence rates of O2 uptake into the substrate, ribulose-1,5-bisphosphate (RuBP) were enhanced as illustrated in the image to the right. This reaction produces phosphoglycollate as well as phosphoglycerate (PGA). The metabolism of phosphoglycollate liberates hydrogen peroxide in the peroxisomes and this is metabolized by catalase. The back drop shows wheat ears on plants growing in the fields at Rothamsted Research, Harpenden, UK. For more details see Luna et al. 'Drought controls on H2O2 accumulation, catalase (CAT) activity and CAT gene expression in wheat'. pp. 417-423. in this volume. These authors thank Nicola Seymour and Lynda Castle for their assistance in the production of this figure. The full version of the cover illustration can be seen at JXB online.
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