Changes in the Activities of Carboxylating Enzymes, Organic Acids and Carbohydrates Content in Cadmium-Treated Methallothionein Overexpressing Transgenic Tobacco Plants

ABSTRACT

Cadmium-treated methallothionein overexpressing transgenic tobacco plants exhibited higher RuBPCO and PEPC activities, similar titratable acidity, and smaller proline and carbohydrates content in the leaves in comparison with the non-transgenic plants. The PEPC activity in the roots of these plants increased more than twice. The titratable acidity increased too, but proline and soluble sugars content diminished by about 60%. The development of resistance strategies of plants to heavy metal stresses induced production of complex agents to avoid and tolerate the phytotoxicity of these ions. The results are discussed in the view of the possibilities of the photosynthetic apparatus of the tobacco plants to tolerate excess of Cd²⁺ and the involvement of the defense mechanisms in the detoxication of this heavy metal.