The Effect of Humic Acid on Seed Germination and Seedling Growth Characteristics of Three Varieties of Radish in salinity stress

To reduce the effects of salt stress in plants used different ways at different stages of plant growth, including germination .Humic acid is a natural substance and has positive effects on plant growth. In this experiment was investigated the effects of humic acid on germination characteristics of three varieties of radish under salinity stress. A factorial experiment in a completely randomized design with three replications. Treatments include three varieties of radish(Cherry bell, Sparkler and Scarlett Cincinnati as the first factor and humic acid on four levels (control, 0.5, 1.5 and 2 grams per liter) as the second factor and salinity at four levels (control, 1.5, 5 and 7.5 dS/m) as a third factor. In this experiment was evaluated germination characteristics such as Shoot and root lenght, fresh and dry weight of seedling, allometric coefficient, speed and percentage of germination. Under salt stress, the use of humic acid increased the shoot length, fresh weight of seedling and speed of germination in radish varieties but the length of root, allometric coefficient, dry weight of seedling and percentage of germination was a non-significant . In salt stress conditions, the use of humic acid at 1.5 g /L was increased maximal effect on root length and fresh weight of seedling and concentration of 2 g /L increased germination rate. The results revealed radish varieties showed different responses. Scarlett allocated to the highest shoot length, fresh weight of seedling, speed and percentage of germination and The highest root lenght and allometric coefficient was related to the Sparkler. Cherry bell had least germination characteristics in salinity salinity even with the application of humic acid.