Accumulation of Proline under Salinity and Heavy metal stress in Cauliflower seedlings

Salinity and heavy metals affect the growth and development of higher plants and also their productivity. In the present study, Cauliflower (Brassica oleracea var botrytis) seeds were allowed to germinate andgrow in the absence (control) and presence of different concentrations (50, 100, 250, 500, 750 and 1000 ìM) of NaCl, CdCl2, HgCl2 and ZnCl2. Seed germination and growth parameters of seedlings of cauliflower were observed after 5, 10 and 15 days of exposure to salinity and heavy metals. In case of salinity, maximum inhibition of seedling growth was observed at 250 ìM of NaCl which resulted into 66%, 67%, 61%, 56% and 25% inhibition in seed germination, shoot length, root length, fresh weight and dry weight, respectively after 5 days of germination. NaCl at500-ìM concentration and above completely inhibited seed germination. In case of heavy metals, HgCl2 was found to be the most toxic one with 94% inhibition in seed germination at 250 ìM concentrations. Shoot length, root length, fresh weight and dry weights were inhibited by 69%, 88%, 66% and 71% respectively, after 5 days of growth in presence of HgCl2 (250 ìM). On the other hand, only 66% and 55% inhibition in seed germination was observed with as high concentration as 1000 ìM of both CdCl2 and ZnCl2 respectively, after 5 days of seed growth. Further, the extent of reduction in shoot length, root length, fresh weight and dry weight in presence of both CdCl2 and ZnCl2 was found to be less than HgCl2. In general development of root system was severely inhibited in presence of NaCl,CdCl2, ZnCl2 and HgCl2 at all the concentration tested as evidenced by decrease in root length. Increase in the level of proline accumulation was observed in presence of all heavy metals studied and sodium chloride.