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Relationship between CO2 assimilation, photosynthetic electron transport, and active O2 metabolism in leaves of maize in the field during periods of low temperature. [Erratum: May 1998, v. 117 (1), p. 335.]

Fryer, M.J., Andrews, J.R., Oxborough, K., Blowers, D.A., Baker, N.R.
Plant physiology 1998 v.116 no.2 pp. 571-580
Zea mays, leaves, chilling injury, cold stress, photosystem II, oxygen, metabolism, antioxidants, quantitative analysis, tocopherols, ascorbic acid, peroxidase, dehydroascorbic acid, oxidoreductases, glutathione reductase (NADPH), superoxide dismutase, enzyme activity, lipoxygenase, lipid peroxidation, cell membranes, electron transfer, stress response, United Kingdom
Measurements of the quantum efficiencies of photosynthetic electron transport through photosystem II (phi(PSII)) and CO2 assimilation (phi(CO2)) were made simultaneously on leaves of maize (Zea mays) crops in the United Kingdom during the early growing season, when chilling conditions were experienced. The activities of a range of enzymes involved with scavenging active O2 species and the levels of key antioxidants were also measured. When leaves were exposed to low temperatures during development, the ratio of phi(PSII)/phi(CO2) was elevated, indicating the operation of an alternative sink to CO2 for photosynthetic reducing equivalents. The activities of ascorbate peroxidase, monodehydroascorbate reductase, dehydroascorbate reductase, glutathione reductase, and superoxide dismutase and the levels of ascorbate and alpha-tocopherol were also elevated during chilling periods. This supports the hypothesis that the relative flux of photosynthetic reducing equivalents to O2 via the Mehler reaction is higher when leaves develop under chilling conditions. Lipoxygenase activity and lipid peroxidation were also increased during low temperatures, suggesting that lipoxygenase-mediated peroxidation of membrane lipids contributes to the oxidative damage occurring in chill-stressed leaves.