Comparison of romaine, loose leaf and iceberg lettuces grown in saline

Abstract

The effects of intermediate salt stress on different types (longifolia: romaine, crispa: loose leaf and capitata: iceberg) of lettuce were investigated. Three commercially available lettuce varieties Lital, Caipira, and Savula which belonged to romaine, loose leaf, and iceberg types were used as plant material. Plants were grown in cocopeat slabs in an open soilless system and irrigated by the nutrient solution with or without 50 mM NaCl. Experimental period was autumn-winter in the Mediterranean climate. Plant growth and yield were compared for the different lettuce types in saline and non-saline conditions. The results indicate that lettuce types and cultivars differ in their salt reponses, which would be useful for growers to lettuce choose type and to improve lettuce adaptation to salinity stress. The reduction in leaf area in salt in romaine and iceberg lettuce were 17 and 20%, respectively while in loose leaf lettuce was increased by 3%. Stomatal conductance in salt was decreased by 8.8 and 18% in the loose leaf and iceberg lettuces while 41% increased in the romaine lettuce. The best performance under salt stress in terms of yield was taken from the loose leaf lettuce 'Capira'. Yield reduction in salt was 28, 11 and 18% in romaine, loose leaf and iceberg lettuce types, respectively. Total soluble solids were increased by salt stress in the romaine, loose leaf and iceberg lettuces by 25, 16, and 30%, respectively. Increased brix in salt may improve the taste of lettuce.