Response of Sunflower (Helianthus annuus L.) Plant at Early Growth Stage to Cadmium Exposure

The study carried out in greenhouse conditions at daylight in order to evaluate the effects ofincreasing Cd exposure on growth and physiological characteristics of sunflower at early growth stage as wellthe accumulation of some metal nutrient ions. Accordingly, the soil treated with six levels of Cd (0, 50, 100,250, 500, and 1000 µM CdCl2.H2O). The plant growth and root elongation unfavorably affected by Cd exposureand detrimental effect of Cd on plant growth was appeared shoot more than roots. Growth tolerance index(GTI), relative water content (RWC), the contents of chlorophyll (Chl a+b) and carotenoids (Car), the uptakes ofzinc (Zn), potassium (K), and calcium (Ca) in shoot and root, and total accumulation rate (TAR) of Zn weredecreased by Cd exposure as well as bioaccumulation and translocation of Cd. Furthermore, increasing Cddoses augmented the concentrations and uptakes of Cd in shoot and root, net accumulation of Cd via roots,the TAR of Cd, membrane permeability (MP) and the rate of Car/Chl caused by its toxic effects. This studydemonstrated that Cd exposure cause a reduction in growth due to affecting morphological and physiologicalcharacteristics of sunflower in the initial stages of plant development.