Influence of salinity on growth and organic compounds content of carrot (Daucus carota L.)

Carrot production of valuable carotenes, carbohydrate and protein are hindered by elevated salinity levels in many parts of the world. To assess this problem, germination and growth of two carrot cultivars (Daucus carota cvs Jordan and Napoli) were studied in vivo and in vitro under different salt stress concentrations (0, 75, and 150 mM NaCl). Seeds were directly or gradually exposed to these salt concentrations. With elevated salinity levels, significant reductions in growth parameters (dry shoot weight, fresh shoot weight, shoot length, root length, and root number) were observed. Also, significant difference in germination percentage was observed at 150 mM NaCl in both cultivars when compared with control treatment (90% germination percentage in Napoli and 71% in Jordan cultivar). Growth rate, tolerant index, and relative water content (RWC) declined as salinity increased. The 150 mM NaCl salinity treatment significantly reduced the shoot chlorophyll and protein content, but increased carbohydrate content. Lesser impairment by the gradual exposure of seedling to salinity provides an opportunity to study the acquirement of salt tolerance.