Nickel toxicity to safflower seed germination and seedling morphoanatomy

The safflowers (Carthamus tinctorius L. cv Olas) grown hydroponically under nickel (Ni) stress were examined in this study. T he effects of 0, 0.75, 1, 3, 5, 10, and 15 mM Ni on seed germination rate, protein, and pigment content of germinating seeds were investigated. Also, the toxicity of 0.75 mM Ni on plant growth, malondialdehyde (MDA) amount, and anatomy of 21-day-old safflower seedlings were studied. Ni adversely affected the germination rate, radicle length, protein, and pigment content of safflower seeds, particularly when higher than 3 mM. It also negatively affected the biomass production, plant length, leaf number, and MDA amount, as well as some cell size/structure of roots (endodermis, phloem, trachea), stems (trachea and tracheid), and leaves (epidermis and sponge parenchyma) of safflower seedlings. Our results showed that seedling growth was more sensitive to Ni exposure than germination. Although severe toxic effects were observed in 0.75 mM Ni treatment for plant growth parameters, seed germination only started to be strongly affected at concentrations higher than 3 mM Ni.