title: Physiological and biochemical responses of the forage legume Trifolium alexandrinum to different saline conditions and nitrogen levels.
abstract: Salinity stress reduces plant productivity, but low levels of salinity often increase plant growth rates in some species. We herein describe the effects of salinity on plant growth while focusing on nitrogen use. We treated Trifolium alexandrinum with two nitrogen concentrations and salinity levels and determined growth rates, mineral concentrations, nitrogen use efficiency, photosynthesis rates, and nitrate reductase (NR, E.C. 1.6.6.1) and glutamine synthetase (GS, EC 6.3.1.2) activities. The T. alexandrinum growth rate increased following treatment with 100 mM NaCl in low nitrogen (LN) and high nitrogen (HN) conditions. Salt treatment also increased root volume, intrinsic water use efficiency, and nitrogen use efficiency in LN and HN conditions. These changes likely contributed to higher biomass production. Salinity also increased accumulations of sodium, chloride, and phosphate, but decreased potassium and calcium levels and total nitrogen concentrations in all plant organs independently of the available nitrogen level. However, the effect of salt treatment on magnesium and nitrate concentrations in photosynthetic organs depended on nitrogen levels. Salt treatment reduced photosynthesis rates in LN and HN conditions because of inhibited stomatal conductance. The effects of salinity on leaf NR and GS activities depended on nitrogen levels, with activities increasing in LN conditions. In saline conditions, LN availability resulted in optimal growth because of low chloride accumulation and increases in total nitrogen concentrations, nitrogen use efficiency, and NR and GS activities in photosynthetic organs. Therefore, T. alexandrinum is a legume forage crop that can be cultivated in low-saline soils where nitrogen availability is limited.
authors.affiliation: Laboratoire des Plantes Extrêmophiles, Centre de Biotechnologie de Borj-Cedria, Université de Tunis El Manar, B.P. 901, Hammam-Lif, 2050, Tunisia. barhoumi_zou2000@yahoo.fr.|Biology Department, King Khalid University, P.O. Box 9004, Abha, 61413, Kingdom of Saudi Arabia. barhoumi_zou2000@yahoo.fr.
authors.forename: Barhoumi
authors.initials: B
authors.lastname: Zouhaier
authors.affiliation: Laboratoire des Plantes Extrêmophiles, Centre de Biotechnologie de Borj-Cedria, Université de Tunis El Manar, B.P. 901, Hammam-Lif, 2050, Tunisia.
authors.forename: Maatallah
authors.initials: M
authors.lastname: Mariem
authors.affiliation: Laboratoire des Plantes Extrêmophiles, Centre de Biotechnologie de Borj-Cedria, Université de Tunis El Manar, B.P. 901, Hammam-Lif, 2050, Tunisia.
authors.forename: Rabhi
authors.initials: R
authors.lastname: Mokded
authors.affiliation: Laboratoire des Plantes Extrêmophiles, Centre de Biotechnologie de Borj-Cedria, Université de Tunis El Manar, B.P. 901, Hammam-Lif, 2050, Tunisia.
authors.forename: Aida
authors.initials: A
authors.lastname: Rouached
authors.affiliation: Biology Department, King Khalid University, P.O. Box 9004, Abha, 61413, Kingdom of Saudi Arabia.
authors.forename: Khaldoun
authors.initials: K
authors.lastname: Alsane
authors.affiliation: Laboratoire des Plantes Extrêmophiles, Centre de Biotechnologie de Borj-Cedria, Université de Tunis El Manar, B.P. 901, Hammam-Lif, 2050, Tunisia.
authors.forename: Abdelly
authors.initials: A
authors.lastname: Chedly
authors.affiliation: Laboratoire des Plantes Extrêmophiles, Centre de Biotechnologie de Borj-Cedria, Université de Tunis El Manar, B.P. 901, Hammam-Lif, 2050, Tunisia.
authors.forename: Smaoui
authors.initials: S
authors.lastname: Abderrazek
authors.affiliation: Laboratoire des Plantes Extrêmophiles, Centre de Biotechnologie de Borj-Cedria, Université de Tunis El Manar, B.P. 901, Hammam-Lif, 2050, Tunisia.
authors.forename: Atia
authors.initials: A
authors.lastname: Abdallah
mesh_terms: D018533:Biomass; D057075:Enzyme Assays; D005974:Glutamate-Ammonia Ligase / Q000378:metabolism; D008903:Minerals / Q000032:analysis; D050901:Nitrate Reductase / Q000378:metabolism; D009584:Nitrogen / Q000494:pharmacology*; D010788:Photosynthesis / Q000187:drug effects; D018515:Plant Leaves / Q000187:drug effects / Q000201:enzymology; D018517:Plant Roots / Q000033:anatomy & histology / Q000187:drug effects / Q000201:enzymology; D018547:Plant Stems / Q000033:anatomy & histology / Q000187:drug effects; D054046:Plant Stomata / Q000187:drug effects / Q000502:physiology; D018526:Plant Transpiration / Q000187:drug effects; D054712:Salinity; D012965:Sodium Chloride / Q000494:pharmacology*; D013312:Stress, Physiological / Q000187:drug effects; D029921:Trifolium / Q000033:anatomy & histology / Q000187:drug effects / Q000254:growth & development / Q000502:physiology*
chemical_list: D008903:Minerals; D012965:Sodium Chloride; D050901:Nitrate Reductase; D005974:Glutamate-Ammonia Ligase; D009584:Nitrogen
keywords: Enzyme activity; Mineral status; Nitrogen; Photosynthesis; Salinity; T. alexandrinum
references.citation: New Phytol. 2005 Sep;167(3):645-63
references.pmid: 16101905
references.citation: Plant Physiol. 1995 Nov;109(3):735-742
references.pmid: 12228628
references.citation: Plant Cell Environ. 2002 Feb;25(2):239-250
references.pmid: 11841667
references.citation: Environ Exp Bot. 2001 Apr;45(2):155-163
references.pmid: 11275223
references.citation: Plant Physiol. 1979 Sep;64(3):495-8
references.pmid: 16660996
references.citation: Biochem J. 1970 Oct;119(4):715-25
references.pmid: 4321854
references.citation: J Exp Bot. 2007;58(9):2369-87
references.pmid: 17556767
references.citation: Plant Physiol. 2004 Sep;136(1):2483-99
references.pmid: 15375205
references.citation: Ann Bot. 2005 Aug;96(2):261-7
references.pmid: 15928009
references.citation: J Plant Physiol. 2004 Aug;161(8):921-8
references.pmid: 15384403
references.citation: Ying Yong Sheng Tai Xue Bao. 2008 Jul;19(7):1475-82
references.pmid: 18839906
references.citation: Trends Ecol Evol. 2008 Feb;23(2):95-103
references.pmid: 18191280
references.citation: Plant Cell. 1995 Jul;7(7):859-68
references.pmid: 7640524
references.citation: Plant Cell. 2000 Aug;12(8):1491-509
references.pmid: 10948265
references.citation: Plant Physiol. 1994 Aug;105(4):1409-1418
references.pmid: 12232296
references.citation: Ecotoxicol Environ Saf. 2005 Mar;60(3):324-49
references.pmid: 15590011
references.citation: Plant Cell Environ. 2002 Feb;25(2):275-294
references.pmid: 11841670
references.citation: Plant Physiol. 1979 Feb;63(2):232-6
references.pmid: 16660703
references.citation: Proteomics. 2007 Nov;7(21):3964-79
references.pmid: 17922516
references.citation: J Plant Physiol. 2007 Mar;164(3):303-11
references.pmid: 16545490
references.citation: Plant Physiol. 1982 Apr;69(4):771-5
references.pmid: 16662294
references.citation: Plant Physiol. 1985 Aug;78(4):821-5
references.pmid: 16664333
references.citation: Annu Rev Plant Physiol Plant Mol Biol. 2000 Jun;51:463-499
references.pmid: 15012199
references.citation: Plant Physiol. 1994 Nov;106(3):1033-1039
references.pmid: 12232384