Effects of Osmotic Stress and Ionic Toxicity on Growth and Ion Allocation in Transgenic Bt Cotton Seedlings

Abstract:

The seeds of transgenic Bt cotton (Gossypium hirsutum L.) 99B were treated with osmotica and salt solution, such as CaCl₂, NaCl, Na₂SO₄ and PEG (6000), the effects of osmotic and salt stresses on the growth and ion allocation in cotton seedlings were studied. The results showed that the growth of transgenic Bt cotton seedlings were inhibited under stresses, in which PEG had the most significant effect, and the inhibition effects of three kinds of salt was in order as CaCl₂>NaCl>Na₂SO₄. Toxicity of Cl^- was greater than SO₄^2- under the same content of Na⁺. Under osmotic stress, the contents of Na⁺ and Cl^- in the roots, stems and leaves increased, but the contents of K⁺, Ca²⁺ and SO₄^2- and K⁺/Na⁺, Ca²⁺/Na⁺and SO₄^2-/Cl^- decreased, and the change range of ion contents in aerial part was greater than those in under-ground part. The effect of PEG on ion contents was the most significant, followed by CaCl₂, and Na₂SO₄ was the weakest. It suggested that the transgenic Bt cotton had low salt tolerance.