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ENVIRONMENTAL STRESS AND ADAPTATION TO STRESS

Elevated Carbon Dioxide Improves Plant Iron Nutrition through Enhancing the Iron-Deficiency-Induced Responses under Iron-Limited Conditions in Tomato^1,[OA]

College of Natural Resources and Environmental Science (C.W.J., Y.S.Z.) and College of Agronomy and Biotechnology (G.X.L.), Zhejiang University, Hangzhou 310029, China; College of Environmental Science and Engineering, Zhejiang Gongshang University, Hangzhou 310035, China (S.T.D.); and State Key Laboratory of Plant Biochemistry and Physiology, College of Life Sciences, Zhejiang University, Hangzhou 310058, China (C.W.J., W.W.C., S.J.Z.)

The increases in atmospheric carbon dioxide (CO₂) concentrations can enhance plant growth and change their nutrient demands. We report that when tomato (Lycopersicon esculentum ‘Zheza 809’) plants were grown in iron (Fe)-limited medium (with hydrous ferric iron oxide) and elevated CO₂ (800 µL L^–1), their biomass and root-to-shoot ratio were greater than plants grown in ambient CO₂ (350 µL L^–1). Furthermore, the associated increase in Fe concentrations in the shoots and roots alleviated Fe-deficiency-induced chlorosis. Despite the improved nutrient status of plants grown in Fe-limited medium under elevated CO₂, the Fe-deficiency-induced responses in roots, including ferric chelate reductase activity, proton secretion, subapical root hair development, and the expression of FER, FRO1, and IRT genes, were all greater than plants grown in the ambient CO₂. The biomass of plants grown in Fe-sufficient medium was also increased by the elevated CO₂ treatment, but changes in tissue Fe concentrations and Fe deficiency responses were not observed. These results suggest that the improved Fe nutrition and induction of Fe-deficient-induced responses in plants grown in Fe-limited medium under elevated CO₂ are caused by interactions between elevated CO₂ and Fe deprivation. Elevated CO₂ also increased the nitric oxide (NO) levels in roots, but treatment with the NO scavenger cPTIO inhibited ferric chelate reductase activity and prevented the accumulation of LeFRO1, LeIRT1, and FER transcripts in roots of the Fe-limited plants. These results implicate some involvement of NO in enhancing Fe-deficiency-induced responses when Fe limitation and elevated CO₂ occur together. We propose that the combination of elevated CO₂ and Fe limitation induces morphological, physiological, and molecular responses that enhance the capacity for plants to access and utilize Fe from sparingly soluble sources, such as Fe(III)-oxide.

The author responsible for the distribution of materials integral to the findings presented in this article in accordance with the policy described in the Instructions for Authors (www.plantphysiol.org) is: Shao Jian Zheng (sjzheng{at}zju.edu.cn).

^[OA] Open access articles can be viewed online without a subscription.

www.plantphysiol.org/cgi/doi/10.1104/pp.109.136721

^* Corresponding author; e-mail sjzheng{at}zju.edu.cn.

Received February 9, 2009; accepted March 21, 2009; published March 27, 2009.

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On the Inside

Peter V. Minorsky
Plant Physiol. 2009 150: 1-2. [Full Text]