CO2 enrichment modulates ammonium nutrition in tomato adjusting carbon and nitrogen metabolism to stomatal conductance.
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.
['Vega-Mas|Izargi|I|', 'Marino|Daniel|D|', 'Sánchez-Zabala|Joseba|J|', 'González-Murua|Carmen|C|', 'Estavillo|Jose María|JM|', 'González-Moro|María Begoña|MB|']
D002244:Carbon D002245:Carbon Dioxide D018551:Lycopersicon esculentum D009566:Nitrates D009584:Nitrogen D054046:Plant Stomata
Nitrogen assimilation Ammonium tolerance Elevated CO(2) Nitrate nutrition Solanum lycopersicum L. TCA cycle