Nickel toxicity to safflower seed germination and seedling morpho-anatomy

Abstract

The safflowers (Carthamus tinctorius L. cv Olas) grown hydroponically under nickel (Ni) conditions have been studied in this work. The effects of 0, 0.75, 1.0, 3.0, 5.0, 10.0-, and 15.0-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’ roots, stems, and leaves were determined. While Ni (especially higher than 3.0 mM) adversely affected the germination rate, radicle length, protein, and pigment content of safflower seeds, it also negatively affected the biomass production, plant length, leaf number, 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 revealed 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 highly affected at concentrations higher than 3.0 mM Ni.