The Effect of Different Seawater Ratios on Germination Indices and Morpho-Physiological Traits of Milkweed in Vitro and Nursery Conditions

The milkweed shrub, in addition to ecological functions, has special industrial and medicinal values. This plant is widely planted for afforestation in arid lands in the south of Iran. Regard to scarcity of fresh water, using of seawater as a vital and alternative source of water for irrigating of halophyte plants was suggested. Thus, the current research was carried out to investigate the efficiency of diluted seawater on seed germination, growth and physiology parameters of milkweed seedling. For this purpose, an experiment was conducted in completely randomized design with three replications in two separate experiments; in vitro and nursery, with different levels of diluted seawater i.e. 0, 12.5, 25 and 50% using saline meter. The results of seed germination test showed that germination parameters and seed vigor index significantly decreased by increasing seawater concentration to more than 12.5%. The results of nursery experiment revealed that concentrations of more than 25% of seawater significantly reduced growth performance and gas exchange of seedling. The survival rate 55%, height 19.9 cm, specific leaf area 190.7 g/cm2 and root length 22.54 cm as well as photosynthesis rate 2.83 µmol, transpiration rate 0.42 mmol, chlorophyll 20.45% and relative water content 43.95% were observed in 25% seawater treatments. It is recommended that researchers conduct a broader study of the salinity-tolerant physiology of this valuable medicinal plant to obtain more comprehensive information for afforestation programs.