salinity effects on mineral nutrients and performance of turnip (brassica rapa l.) at different growth stages

in order to study the effects of different salinity levels on turnip (brassica rapa l.), an investigation was conducted at yasouj university, iran, in 2010. the effects of four salinity levels including 1.92, 9.87, 19.6 and 21.94 ds m-1 (20:1 ratio of nacl: cacl2 in hoagland solution) on germination, vegetative and maturity stages of turnip (baherghan landrace) were investigated. the results revealed that the measured traits at the germination stage were significantly affected by salinity treatments. the effect of salinity stress was only significant for leaf area, sodium and potassium contents at the vegetative stage. salinity had significant effects on all the recorded traits of turnip roots, except for ca2+, zn and fe contents. based on stress intensity values, salinity affected germination percentage (si=1.0) on the second day and the seedling root length (si=0.93) more than other measured traits. the results of si (stress intensity) showed that salinity affected na+ content more than other traits at the maturity stage (si=0.74). ca2+ showed an inverse response and had the lowest si (si=0.001). based on this study, vegetative growth and root elongation stages were more tolerant and sensitive to salinity, respectively. in addition, seedling root length at germination stage and tissue na+ content at subsequent growth stages were the most important traits, recommended to be used as selection criteria in turnip breeding programs.