title: CO2 enrichment modulates ammonium nutrition in tomato adjusting carbon and nitrogen metabolism to stomatal conductance.
abstract: Ammonium (NH4(+)) toxicity typically occurs in plants exposed to high environmental NH4(+) concentration. NH4(+) assimilating capacity may act as a biochemical mechanism avoiding its toxic accumulation but requires a fine tuning between nitrogen assimilating enzymes and carbon anaplerotic routes. In this work, we hypothesized that extra C supply, exposing tomato plants cv. Agora Hybrid F1 to elevated atmospheric CO2, could improve photosynthetic process and thus ameliorate NH4(+) assimilation and tolerance. Plants were grown under nitrate (NO3(-)) or NH4(+) as N source (5-15mM), under two atmospheric CO2 levels, 400 and 800ppm. Growth and gas exchange parameters, (15)N isotopic signature, C and N metabolites and enzymatic activities were determined. Plants under 7.5mM N equally grew independently of the N source, while higher ammonium supply resulted toxic for growth. However, specific stomatal closure occurred in 7.5mM NH4(+)-fed plants under elevated CO2 improving water use efficiency (WUE) but compromising plant N status. Elevated CO2 annulled the induction of TCA anaplerotic enzymes observed at non-toxic NH4(+) nutrition under ambient CO2. Finally, CO2 enrichment benefited tomato growth under both nutritions, and although it did not alleviate tomato NH4(+) tolerance it did differentially regulate plant metabolism in N-source and -dose dependent manner.
authors.affiliation: Department of Plant Biology and Ecology, University of the Basque Country (UPV/EHU), Apdo. 644, E-48080 Bilbao, Spain. Electronic address: izargiaida.vega@ehu.eus.
authors.forename: Izargi
authors.initials: I
authors.lastname: Vega-Mas
authors.affiliation: Department of Plant Biology and Ecology, University of the Basque Country (UPV/EHU), Apdo. 644, E-48080 Bilbao, Spain; Ikerbasque, Basque Foundation for Science, E-48011 Bilbao, Spain. Electronic address: daniel.marino@ehu.eus.
authors.forename: Daniel
authors.initials: D
authors.lastname: Marino
authors.affiliation: Department of Plant Biology and Ecology, University of the Basque Country (UPV/EHU), Apdo. 644, E-48080 Bilbao, Spain. Electronic address: joseba.sanchez@ehu.eus.
authors.forename: Joseba
authors.initials: J
authors.lastname: Sánchez-Zabala
authors.affiliation: Department of Plant Biology and Ecology, University of the Basque Country (UPV/EHU), Apdo. 644, E-48080 Bilbao, Spain. Electronic address: carmen.gmurua@ehu.eus.
authors.forename: Carmen
authors.initials: C
authors.lastname: González-Murua
authors.affiliation: Department of Plant Biology and Ecology, University of the Basque Country (UPV/EHU), Apdo. 644, E-48080 Bilbao, Spain. Electronic address: jm.estavillo@ehu.eus.
authors.forename: Jose María
authors.initials: JM
authors.lastname: Estavillo
authors.affiliation: Department of Plant Biology and Ecology, University of the Basque Country (UPV/EHU), Apdo. 644, E-48080 Bilbao, Spain. Electronic address: mariabegona.gonzalez@ehu.eus.
authors.forename: María Begoña
authors.initials: MB
authors.lastname: González-Moro
mesh_terms: D002244:Carbon / Q000378:metabolism; D002245:Carbon Dioxide / Q000378:metabolism*; D018551:Solanum lycopersicum / Q000502:physiology*; D009566:Nitrates / Q000378:metabolism*; D009584:Nitrogen / Q000378:metabolism; D054046:Plant Stomata / Q000378:metabolism
chemical_list: D009566:Nitrates; D002245:Carbon Dioxide; D002244:Carbon; D009584:Nitrogen; C006568:ammonium nitrate
keywords: Ammonium tolerance; Elevated CO(2); Nitrate nutrition; Nitrogen assimilation; Solanum lycopersicum L.; TCA cycle