ORIGINAL PAPER Calcium can moderate changes on membrane structure and lipid composition in cowpea plants under salt stress Francisco Valderez Augusto Guimara ˜es • Claudivan Feitosa de Lacerda • Elton Camelo Marques • Maria Raquel Alca ˆntara de Miranda • Carlos Eduardo Braga de Abreu • Jose ´ Tarquinio Prisco • Ene ´as Gomes-Filho Received: 28 May 2010 / Accepted: 9 February 2011 / Published online: 20 February 2011 Ó Springer Science+Business Media B.V. 2011 Abstract The effects of supplemental Ca 2? on mem- brane integrity and lipid composition of cowpea plants submitted to salt stress (75 mM NaCl) were evaluated. The experimental design was factorial (2 9 6 ? 1) corre- sponding to six saline treatments supplemented with CaCl 2 and six saline treatments supplemented with CaSO 4 , both at 0.5, 1.25, 2.5, 5.0, 7.5 and 10.0 mM, plus control treatment (plants grown in half-strength Hoagland’s nutri- ent solution without supplemental calcium addition). Samples of leaves and root tips were analyzed for total lipid, glycolipid and fatty acid contents and membrane damage symptoms. Salt stress greatly reduced total lipid content in leaves and roots and caused great damage to membrane structures. In leaves, the glycolipid content was differently influenced by calcium treatments. Moreover, salinity increased the saturated/unsaturated fatty acid ratio in leaves and an increase in the concentration of calcium intensified this response. In roots, only saturated fatty acids were detected and their content was strongly influenced by salinity and very little by calcium treatments. Supplemental Ca 2? was unable to ameliorate the negative effects of salinity on the structural integrity and fluidity of plant membranes in cowpea. Keywords Supplemental Ca 2? Á Membrane lipids Á Salinity Á Vigna unguiculata Introduction Salinity is one of the most important abiotic stress affecting crop yield worldwide (Hasegawa et al. 2000). The adverse effects of salinity on plant growth are associated with (1) low osmotic potential of soil solution, (2) ion toxicity, (3) nutritional imbalance, or (4) a combination of these factors (Ashraf and Harris 2004; Munns and Tester 2008). These stressing factors can disturb biochemical and physiological processes such as water relations, ionic and redox homeostasis, hormonal and nutritional balance, and mem- brane permeability, which may result in reduced growth (Parida and Das 2005). In plants, changes in lipid bilayer composition and membrane permeability due to salt stress were reported by various authors (Kerkeb et al. 2001; Elkahoui et al. 2004; Lope ´z-Pe ´rez et al. 2009). Such modifications of the lipid bilayer result in alterations of membrane fluidity and H ? -ATPase activity, influencing the passive influx of potentially toxic ions such as Na ? and Cl - (Kerkeb et al. 2001; Mansour and Salama 2004). Plasma membrane permeability is a reflex of the lipid composition and the lipid-protein interaction (Mansour and Salama 2004). When two maize cultivars contrasting in salt tolerance were grown at 100 mM NaCl, there was a decrease in unsaturated/saturated fatty acid ratio of the PM, but it was higher in salt tolerant cultivar (Salama et al. F. V. A. Guimara ˜es Fundac ¸a ˜o Cearense de Meteorologia e Recursos Hı ´dricos, FUNCEME, Fortaleza, Ceara ´ 60115-221, Brazil C. F. de Lacerda Departamento de Engenharia Agrı ´cola and Instituto Nacional de Cie ˆncia e Tecnologia em Salinidade (INCTSal/CNPq), Universidade Federal do Ceara ´, CP 12168, Fortaleza, Ceara ´ 60020-970, Brazil E. C. Marques Á M. R. A. de Miranda Á C. E. B. de Abreu Á J. T. Prisco Á E. Gomes-Filho (&) Departamento de Bioquı ´mica e Biologia Molecular and Instituto Nacional de Cie ˆncia e Tecnologia em Salinidade (INCTSal/ CNPq), Universidade Federal do Ceara ´, CP 6039, Fortaleza, Ceara ´ 60440-970, Brazil e-mail: egomesf@ufc.br 123 Plant Growth Regul (2011) 65:55–63 DOI 10.1007/s10725-011-9574-1