Author
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Sicher Jr, Richard |
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Submitted to: Metabolites
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 7/30/2015 Publication Date: 8/5/2015 Citation: Sicher Jr, R.C. 2015. Temperature shift experiments suggest that metabolic impairment and enhanced rates of photorespiration decrease organic acid levels in soybean leaflets exposed to supra-optimal growth temperatures. Metabolites. 5:443-454. Interpretive Summary: Carbon dioxide is increasing in the atmosphere and this has increased temperatures around the globe. This is a major problem because crop growth at above optimal temperatures causes heat stress that diminishes yields. We investigated the combined effects of elevated carbon dioxide and air temperatures on soybean. Our results indicated that acidic components of soybean leaves decreased dramatically in response to increased growth temperatures. Furthermore, this process was reversed by increasing carbon dioxide levels in the air surrounding the leaf. The above results suggested that elevated growth temperatures stimulated a wasteful side reaction of photosynthesis that could be overcome by carbon dioxide enrichment. In the absence of carbon dioxide enrichment, increased growth temperatures completely altered the metabolism of soybean leaves. These results should benefit agricultural scientists and crop modelers studying the effects of global climate change on major crops. Technical Abstract: Citrate, malate, malonate, fumarate and succinate in soybean leaflets decreased 40 to 80% when plants were grown continuously in controlled environment chambers at 36/28 compared to 28/20 °C. Glycerate was not temperature responsive in this study. Temperature effects on the above mentioned organic acids were partially reversed 3 d after soybean plants were reciprocally transferred among the two growth temperature treatments. Effects of enhanced growth temperatures on five of six soybean leaflet organic acids also were mitigated by CO2 enrichment. Malate, malonate and fumarate were increased by CO2 enrichment on all four harvest dates when plants were grown in the 36/28 °C temperature treatment, although glycerate decreased. Glycerate functions in the photorespiratory pathway, which accelerates at the expense of CO2 assimilation in response to elevated leaf temperatures. Collectively, the above information suggested that the depletion of foliar organic acids in response to elevated growth temperatures and the observed mitigation by CO2 enrichment was likely caused by enhanced rates of photorespiration. Evidence also suggested that differing leaf development rates among growth temperature treatments affected foliar organic acid concentrations. |
