AMELIORATIVE EFFECT OF CALCIUM CHLORIDE ON GROWTH, ANTIOXIDANT ENZYMES, PROTEIN PATTERNS AND SOME METABOLIC ACTIVITIES OF CANOLA (BRASSICA NAPUSL.) UNDER SEAWATER STRESS

The effect of calcium chloride (CaCl2) as an ameliorating agent on seawater stress was studied in canola (Brassica napus L.). Plants were raised in pots and exposed to seawater stress (30%) with or without 200 ppm CaCl2. Seawater-stressed plants showed decreased growth, water content, leaf area, photosynthetic pigments, total sugars, potassium (K), calcium (Ca), K/ sodium (Na) ratio and ascorbate peroxidase (APX activity), and increased total protein, free amino acid, proline, Na, the activity of catalase (CAT), peroxidase (POD), glutathione reductase (GR) and malondialdehyde (MDA) content. Application of 200 ppm of CaCl2 by seed soaking was accompanied by higher values of water content, leaf area, photosynthetic pigments, total sugars, total protein, K, Ca, K/Na ratio and the activity of CAT, POD, APX and GR. In contrast, treatment with CaCl2 resulted mostly in a decrease in free amino acids, proline, Na and MDA as compared with the seawater plants, which partially alleviated the adverse effect of seawater salinity on growth. Seawater stress led to the appearance of four protein bands of molecular weights 94, 27, 25 and 13 KDa. Seed treatment with CaCl2 led to the appearance of six polypeptides with molecular weights 235, 87, 43, 27, 25 and 13 KDa. The 100, 57, 19, 17 and 14 KDa protein bands which were no longer apparent with salinity were apparent under the interactive effects of salinity and CaCl2.