ORIGINAL PAPER Salt tolerance is unrelated to carbohydrate metabolism in cowpea cultivars Sidney Carlos Praxedes • Claudivan Feitosa de Lacerda • Thalita Montoril Ferreira • Jose ´ Tarquinio Prisco • Fa ´bio Murilo DaMatta • Ene ´as Gomes-Filho Received: 5 July 2010 / Revised: 8 September 2010 / Accepted: 15 September 2010 Ó Franciszek Go ´rski Institute of Plant Physiology, Polish Academy of Sciences, Krako ´w 2010 Abstract Under salinity stress, plants commonly accu- mulate carbohydrates for osmotic adjustment to balance the excess accumulated ions and to protect biomolecules. We selected two cowpea cultivars with contrasting response to salinity, Pitiu ´ba (salt-tolerant) and TVu (salt-sensitive), to investigate whether the salt tolerance could be associated with changes in carbohydrate accumulation and metabo- lism in leaves and roots during a long-term experiment. Two salt treatments (0 and 75 mM NaCl) were applied to 10-day-old plants grown in nutrient solution for 24 days. Despite some changes in carbohydrate accumulation and carbohydrate metabolism enzymes induced by salt stress, no consistent alterations in carbohydrates could be found in leaves or roots in this study. Therefore, we suggest that tolerance to salt stress is largely unrelated to carbohydrate accumulation in cowpea. Keywords Carbon metabolism Á Salt stress Á Sugars Á Vigna unguiculata Introduction Salinity is one of the main stresses in agriculture, partic- ularly in arid and semiarid regions, where salt content of the soil is naturally high and rainfall can be insufficient for leaching the excess salt. A common response of organisms to salinity is the accumulation of compatible solutes, which are important for the osmotic balance of the cytosol when plants accumulate excess ions during osmotic adjustment (Hare et al. 1998; Hasegawa et al. 2000). These solutes may also protect biomolecules (Yancey et al. 1982; Hare et al. 1998). A major category of organic osmotic solutes is comprised of simple sugars (mainly fructose and glucose), sugar alcohols, and complex sugars (Bohnert and Jensen 1996). In fact, up to 50% of the total osmotic potential in some glycophytes subjected to saline conditions may be associated with sugar accumulation (Cram 1976). The production of assimilates in leaves and their trans- location to growing organs are regulated by partitioning of starch and sucrose biosynthesis (Taiz and Zeiger 2006). In plants, sucrose phosphate synthase (SPS) is thought to catalyze the rate-limiting step of sucrose synthesis (Huber and Huber 1996). Sucrose is the main carbohydrate trans- ported from source to sink organs; in storage sinks, sucrose is chiefly degraded by sucrose synthase (SS) whereas in growing sinks the vacuolar acid invertase plays a pivotal role in sucrose utilization (Sung et al. 1989), whereas the Communicated by J. Zwiazek. S. C. Praxedes Departamento de Fitotecnia, Universidade Federal do Ceara ´, Fortaleza, Ceara ´, Brazil Present Address: S. C. Praxedes Unidade Acade ˆmica Especializada em Cie ˆncias Agra ´rias, Universidade Federal do Rio Grande do Norte, Macaı ´ba, Rio Grande do Norte, Brazil C. F. de Lacerda Departamento de Engenharia Agrı ´cola, Universidade Federal do Ceara ´, INCTSal/CNPq, Fortaleza, Ceara ´, Brazil T. M. Ferreira Á J. T. Prisco Á E. Gomes-Filho (&) Departamento de Bioquı ´mica e Biologia Molecular, Universidade Federal do Ceara ´, INCTSal/CNPq, Caixa Postal 6039, Fortaleza, Ceara ´ 60455-970, Brazil e-mail: egomesf@ufc.br F. M. DaMatta Departamento de Biologia Vegetal, Universidade Federal de Vic ¸osa, Vicosa, Minas Gerais 36571-000, Brazil 123 DOI 10.1007/s11738-010-0615-6 Acta Physiol Plant (2011) 33: – 887 896 / Published online: 1 October 2010