title: Tomato responses to ammonium and nitrate nutrition under controlled root-zone pH.
abstract: Tomato (Lycopersicon esculentum L. Mill. 'Vendor') plants were grown for 21 days in flowing solution culture with N supplied as either 1.0 mM NO3- or 1.0 mM NH4+.  Acidity in the solutions was automatically maintained at pH 6.0.  Accumulation and distribution of dry matter and total N and net photosynthetic rate were not affected by source of N.  Thus, when rhizosphere acidity was controlled at pH 6.0 during uptake, either NO3- or NH4+ can be used efficiently by tomato.  Uptake of K+ and Ca2+ were not altered by N source, but uptake of Mg2+ was reduced in NH4(+)-fed plants.  This indicates that uptake of Mg2+ was regulated at least partially by ionic balance within the plant.
authors.affiliation: Dept. of Horticultural Science, North Carolina State University, Raleigh 27695-7609, USA.
authors.forename: M M
authors.initials: MM
authors.lastname: Peet
authors.forename: C D
authors.initials: CD
authors.lastname: Raper
authors.forename: L C
authors.initials: LC
authors.lastname: Tolley
authors.forename: W P
authors.initials: WP
authors.lastname: Robarge
mesh_terms: D018533:Biomass; D002118:Calcium / Q000493:pharmacokinetics; D003470:Culture Media; D006863:Hydrogen-Ion Concentration; D018527:Hydroponics; D008027:Light; D018551:Solanum lycopersicum / Q000254:growth & development / Q000378:metabolism / Q000502:physiology*; D008274:Magnesium / Q000493:pharmacokinetics; D009566:Nitrates / Q000378:metabolism* / Q000493:pharmacokinetics / Q000502:physiology; D009584:Nitrogen / Q000378:metabolism* / Q000493:pharmacokinetics / Q000502:physiology; D010788:Photosynthesis / Q000502:physiology; D018517:Plant Roots / Q000254:growth & development / Q000378:metabolism* / Q000502:physiology; D011188:Potassium / Q000493:pharmacokinetics; D000644:Quaternary Ammonium Compounds / Q000378:metabolism* / Q000493:pharmacokinetics
chemical_list: D003470:Culture Media; D009566:Nitrates; D000644:Quaternary Ammonium Compounds; D008274:Magnesium; D009584:Nitrogen; D011188:Potassium; D002118:Calcium