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Effects of low ozone exposure of spring wheat on net CO2 uptake, Rubisco, leaf senescence and grain filling

Published online by Cambridge University Press:  01 March 1998

KATINKA OJANPERÄ
Affiliation:
Institute of Resource Management, Agricultural Research Centre of Finland, FIN-31600 Jokioinen, Finland
EIJA PÄTSIKKÄ
Affiliation:
Plant Physiology and Molecular Biology, Department of Biology, University of Turku, FIN-20014 Turku, Finland
TOIVO YLÄRANTA
Affiliation:
Institute of Resource Management, Agricultural Research Centre of Finland, FIN-31600 Jokioinen, Finland
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Abstract

Effects of ozone on spring wheat (Triticum aestivum L. cv. Satu) were studied in an open-top chamber experiment during two growing seasons (1992–1993) at Jokioinen in south-west Finland. The wheat was exposed to filtered air (CF), non-filtered air (NF), non-filtered air+35 nl l−1 ozone for 8 h d−1 (NF+) and ambient air (AA). Each treatment was replicated five times. Two wk after anthesis, after 4 wk of ozone treatment (NF+, 45 nl l−1 1000–1800 hours, seasonal mean) the net CO2 uptake of wheat flag leaves was decreased by c. 40% relative to CF and NF treatments, both initial and total activity of Rubisco and the quantity of protein-bound SH groups were decreased significantly. Added ozone also significantly accelerated flag leaf senescence recorded as a decrease in chloroplast size. The effect was significant 2 wk after anthesis, and senescence was complete after 4 wk. In the CF and NF treatments senescence was complete 5 wk after anthesis. The significant effect of ozone on the chloroplasts and net CO2 uptake 2 wk after anthesis did not affect the grain filling rate. However, since the grain filling period was shorter for ozone fumigated plants, kernels were smaller. The decrease in 1000-grain weight explained most of the yield reduction in the plants under NF+ treatment. The results indicate that wheat plants are well buffered against substantial decrease in source activity, and that shortened flag leaf duration is the major factor causing ozone-induced yield loss.

Type
Research Article
Copyright
© Trustees of the New Phytologist 1998

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