The influence of reduced photorespiration on long-term growth and development of wheat

The long-term role of photorespiration was investigated by comparing growth, development, gas exchange characteristics and mineral nutrition of a wheat crop ( Triticum aestivum L. cv. Courtot) cultivated in a culture chamber during a life cycle, either in 4% O₂ or in normal O₂ Low O₂ pressure reduced photorespiration, but CO₂ was controlled so that net photosynthesis remained the same as in the control crop. The growth and development of the low O₂ crop was slowed down. Ear appearance was 16 days late, but the rate of tillering was the same as in the control and was maintained longer so that the final number of tillers was doubled. Pigment, ribulose bisphosphate carboxylase (EC 4.1.1.39) and soluble sugar contents were similar. The response of photosynthesis to CO₂ and O₂ was not appreciably changed by the low O₂ treatment. There was almost no seed formation, and the senescence of the leaves was delayed. It appears that in non-stress conditions most of the photorespiration can be suppressed without damage to the photosynthetic apparatus. Retardation of development and inhibition of reproduction are likely due to other effects of O₂.