Solute accumulation and distribution during shoot and leaf development in two sorghum genotypes under salt stress Claudivan Feitosa de Lacerda a, *, Jose ´ Cambraia b , Marco Antonio Oliva b , Hugo Alberto Ruiz b , Jose ´ Tarquı ´nio Prisco a a Departamento de Bioquı ´mica e Biologia Molecular, Universidade Federal do Ceara ´, Fortaleza, CE 60. 451-970, Brazil b Departamento de Biologia Geral, de Biologia Vegetal e de Solos, Universidade Federal de Vic ¸osa, Vic ¸osa, MG 36571-000, Brazil Received 22 January 2002; received in revised form 8 August 2002; accepted 19 August 2002 Abstract Seedlings of two forage sorghum genotypes (Sorghum bicolor (L.) Moench) differing in salt tolerance were subjected to 0 and 100 mM NaCl and shoot development, leaf elongation, and organic and inorganic solutes contents in leaves were measured. Salt stress reduced both shoot development and leaf elongation and enhanced leaf senescence and injury. It also led to accumulation of toxic ions (Na  and Cl  ), organic solutes (carbohydrates, amino acids and proline), and reduction of K  content in leaf blades. Toxic ion accumulation was higher in the basal zone of the leaf blade and occurred during the period of intense leaf growth while organic solutes accumulation, mainly proline, was higher in the apical zone and occurred when the leaves practically had reached their final size. All these changes were more conspicuous in the sensitive than in the tolerant genotype. The latter also retained more toxic ions in leaf sheath tissue than the former. It is suggested that the reduction in shoot development and leaf elongation were related to toxic ion accumulation and depletion of K  ions in the leaf blades. The accumulation of organic solutes in leaves did not appear to be related to salt tolerance. Proline accumulation appears to be a reaction to salt stress damage and not a plant response associated with salt tolerance. # 2002 Elsevier Science B.V. All rights reserved. Keywords: Genotypes; Cl  ; Na  ; Non-structural carbohydrates; Proline; Salinity; Sorghum bicolor 1. Introduction Soil salinity is considered one of the most important limitations for food production in irrigated soils of the arid and semi-arid areas of the world (Munns, 2002). In Brazil, this problem occurs especially in its northern region, where approximately 25 percent of irrigated areas had become saline (Gheyi, 2000). Salinity reduces plant shoot growth and devel- opment, and in grasses this effect is conspicuous on the leaves. NaCl inhibition of leaf expansion may be associated with reduction in leaf turgor, reduction in net CO 2 assimilation, excessive accu- mulation of toxic ions and/or disturbance in * Corresponding author. Tel.:  /55-85-288-9822; fax:  /55- 85-288-9829 E-mail address: cfeitosa@ufc.br (C.F. de Lacerda). Environmental and Experimental Botany 49 (2003) 107  /120 www.elsevier.com/locate/envexpbot S0098-8472/02/$ - see front matter # 2002 Elsevier Science B.V. All rights reserved. PII:S0098-8472(02)00064-3