Cadmium metal effects physiological and anatomical Variations for aquatic plant Hydrilla verticillata (L. f.) Royle

The cadmium effect on Hydrilla verticillata (L. f.) Royle was tested to understand their physiological and anatomical variations and plant response to cadmium over a period of 21 days. The plant was treated with different concentrations of cadmium (three replicates) of (0,1,2,4,8) mg/l. Some physiological criteria such as Catalase enzyme (CAT), Superoxide Dismutase (SOD) and Malondialdehyde (MDA) enzyme were investigated. The anatomical variations were studied by preparing histological sections of the H. verticillata shoot on (1st, 7th, 14th and 21st) days. The Catalase enzyme values were increased gradually during the experiment period compared to the control treatment and the values were ranged between (33–217) Unit/ mg and the highest values were reported at 8 ppm during the 14th day. A gradual increase in SOD values was reported during the 14 and 21 days for the experiment compared to control; and the values were ranged between (0.018–0.093) Unit/mg. MDA enzyme values were decreased during the 14th day, ranging from 137 to 817 µmol. Anatomical variations of the plant at the low concentration of cadmium (1 ppm) were seen to be thickening for the vascular bundles and central pore during the 7th day, whereas during the 14th and 21st days of the experiment, the number of parenchyma cells decreased and of internal cells of aerenchyma tissue was decadent. The thickness of the outer epidermis was also increased and had multilayers under high concentration (8 ppm) during the 21st day. Moreover, tortuosity in the epidermis surface decreased with parenchyma cells thickening and there was an increase in the cell wall thickness with increasing the carotene pigment concentration.