Elevated Carbon Dioxide Improves Plant Iron Nutrition through Enhancing the Iron-Deficiency-Induced Responses under Iron-Limited Conditions in Tomato

Abstract

The increases in atmospheric carbon dioxide (CO 2 ) 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 CO 2 (800 mL L 21 ), their biomass and root-to-shoot ratio were greater than plants grown in ambient CO 2 (350 mL L 21). 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 CO 2 , 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 CO 2 . The biomass of plants grown in Fe-sufficient medium was also increased by the elevated CO 2 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 CO 2 are caused by interactions between elevated CO 2 and Fe deprivation. Elevated CO 2 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 Fedeficiency-induced responses when Fe limitation and elevated CO 2 occur together. We propose that the combination of elevated CO 2 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.

Long-Term Exposure to Combined Treatment of Elevated CO₂ and Salt Induces Iron Deficiency Responses in <i>Porteresia coarctata</i>

“…slight reduction in transcript level of all the genes compared to ambient control. This finding is similar to an earlier observation in tomato, where elevated CO 2 did not induce the expression of iron deficiency-responsive genes LeIRT1, LeFRO1 and FER in Fe-sufficient roots 12 . Interestingly, however, with 200 mM NaCl at eCO 2 , transcripts level increased for all the genes except for OsYSL2-like gene.…”

“…Till date, there are only few reports on the response of plants to iron deficiency under eCO 2 condition. In tomato grown in Fe-limited medium, the iron deficiency-induced responses like ferric chelate reducatse activity, proton extrusion and subapical root hair development were more pronounced when exposed to eCO 2 for a short duration of 2-3 days compared to the ambient CO 2 condition 12 . Also at the molecular scale, the expression of iron deficiency-responsive genes like FER, FRO1 and IRT1 was more induced under eCO 2 condition 12 .…”

“…In tomato grown in Fe-limited medium, the iron deficiency-induced responses like ferric chelate reducatse activity, proton extrusion and subapical root hair development were more pronounced when exposed to eCO 2 for a short duration of 2-3 days compared to the ambient CO 2 condition 12 . Also at the molecular scale, the expression of iron deficiency-responsive genes like FER, FRO1 and IRT1 was more induced under eCO 2 condition 12 . Over a long-term exposure to 550 l l -1 of (CO 2 ) for more than one growing season, rice and legumes showed a significant drop in iron and zinc content in grains compared to ambient condition 13 .…”

Putrescine Alleviates Iron Deficiency via NO-Dependent Reutilization of Root Cell-Wall Fe in Arabidopsis

“…Stimulation of the plasmalemma NADPH-ferric chelate reductase (FCR; Robinson et al, 1999) activity and extrusion of proton to the rhizosphere, which can be measured as changes in pH value of the growth solution (Jin et al, 2007(Jin et al, , 2009, are hallmark responses to Fe deficiency in dicots (Robinson et al, 1999;Curie and Briat, 2003). Here, we found that the pH of the -Fe solution was decreased greatly after 1 d of Put treatment (Fig.…”

Effects of elevated CO2 levels on root morphological traits and Cd uptakes of two Lolium species under Cd stress

“…The changes in root morphology are often associated with a variation in nutrient uptake (Jia and Gray, 2007;Jin et al, 2009;Jin and Evans, 2010), though considerable variation between species and systems exists (Bowes, 1993;Kimball et al, 2002;Franzaring et al, 2008). Previous studies have shown the effect of elevated levels of CO 2 on plant uptakes of essential micronutrients, such as Cu, Fe, Mn, and Zn Yang et al, 2007;Zheng et al, 2008;Högy and Fangmeier, 2009;Jin et al, 2009;Li et al, 2009), but little is known about the effect of elevated levels of CO 2 on the uptakes of non-essential elements such as Cd (Li et al, 2010). Few studies have addressed heavy metal uptakes by plants under elevated levels of CO 2 in terms of alterations in root morphological traits.…”