Salinity thresholds and genotypic variability of cabbage (Brassica oleracea L.) grown under saline stress

Two botanical varieties of cabbage, namely Savoy (Brassica oleracea var. Sabauda L.) and White (Brassica oleracea var. Capitata L.) were used in order to understand the morphological, physiological and biochemical elements of functional salt stress response. Thirteen salt concentrations (range, 0 to 300 mmol L(-1) NaCl) were considered in Experiment 1 and, of these 13, three (0, 100 and 200 mmol L(-1) NaCl) were used in Experiment 2.

Experiment 1 enabled the definition of two salinity thresholds (100 and 200 mmol L(-1) NaCl), associated with morphological and physiological adaptations. In Experiment 2, moderate salinity (100 mmol L(-1) NaCl) had lower effects on Savoy than in White cabbage yield (respectively, -16% and -62% from control). Concurrently, 100 mmol L(-1) NaCl resulted in a significant increase of antioxidant enzymes from control conditions, that was greater in Savoy (+289, +423 and +88%, respectively) as compared to White (+114, +356 and +28%, respectively) cabbage. Ion accumulation was found to be a key determinant in tissue osmotic adjustment (mainly in Savoy) whereas the contribution of organic osmolites was negligible.

Higher antioxidative enzymatic activities in Savoy versus White cabbage after treatment with 100 mmol L(-1) NaCl were associated with improved water relations, thus suggesting a possible physiological pathway for alleviating perceived salt stress.