biologia plantarum

Biologia plantarum 53:764-768, 2009 | DOI: 10.1007/s10535-009-0140-x

Involvement of cation channels and NH₄⁺-sensitive K⁺ transporters in Na⁺ uptake by cowpea roots under salinity

E. L. Voigt², R. F. Caitano¹, J. M. Maia¹, S. L. Ferreira-Silva¹, C. E. C. De Macêdo², J. A. G. Silveira^1,*

¹ Laboratório de Metabolismo de Plantas, Departamento de Bioquímica e Biologia Molecular, Universidade Federal do Ceará, Fortaleza, Ceará, Brazil

² Departamento de Biologia Celular e Genética, Universidade Federal do Rio Grande do Norte, CEP 59072-910, Natal, Rio Grande do Norte, Brazil

Na⁺ accumulation was investigated in the roots of 11-d-old cowpea [Vigna unguiculata (L.) Walp.] plants. The relative contribution of different membrane transporters on Na⁺ uptake was estimated by applying Ca²⁺, K⁺, NH₄ ⁺, and pharmacological inhibitors. Na⁺ accumulation into the root symplast was decreased by half in the presence of 1 mM Ca²⁺ and it was almost abolished by 100 mM K⁺. The inhibitory effect of external NH⁴⁺ on Na⁺ accumulation was more pronounced in the roots of NH₄ ⁺-free growing plants. Na⁺ accumulation was reduced about 73 % by 0.1 mM flufenamate and it was almost blocked by 2 mM quinine. In addition, 20 mM tetraethylammonium and 1.0 mM Cs⁺ decreased Na⁺ accumulation by 28 and 30 %, respectively. These results evidenced that low-affinity Na⁺ uptake by cowpea roots depends on Ca²⁺-sensitive and Ca²⁺-insensitive pathways. The Ca²⁺-sensitive pathway is probably mediated by nonselective cation channels and the Ca²⁺-insensitive one may involve K⁺ channels and to a lesser extent NH₄ ⁺-sensitive K⁺ transporters.

Keywords: Ca²⁺-sensitive and Ca²⁺-insensitive pathways; K⁺ channels; Na⁺ accumulation; nonselective cation channels; salt stress; Vigna unguiculata

Subjects: calcium; cation channels; cowpea; potassium; salinity; sodium; Vigna unguiculata

Received: November 23, 2008; Accepted: May 11, 2009; Published: December 1, 2009  Show citation