Impact of cadmium and nickel on morpho-anatomy and physiology of two native grasses [(Cynodon dactylon (L.) Pers. and Cenchrus ciliaris L.].

Abstract

In order to investigate the toxic effect of heavy metals (cadmium and nickel) on morpho- anatomy and physiology of two grass species (Cynodon dactylon(L.) Pers. and Cenchrus ciliaris L.), three factor factorial experiment was laid out in the Old Botanic Garden, University of Agriculture, Faisalabad. The levels of cadmium and nickel (0, 20, 40 and 60 mg L-1) were selected for all ecotypes collected from Faisalabad, the Salt Range and Pakka Anna. Soils of the Faisalabad were not affected by heavy metals, while that of the Salt Range moderately affected and Pakka Anna heavily affected by both Ni2+ and Cd2+. The data was recorded for different morpho-anatomical, physiological and biochemical attributes. The growth of the both grass species was reduced under Cd2+ and Ni2+ stress. A significant reduction in gas exchange parameters was noted in all ecotypes under both Cd2+ and Ni2+ stresses. Biochemical attributes like total soluble sugars, and total free amino acids increased at high levels (60 mg L-1) of Cd2+ and Ni2+, while proteins were reduced in both types of stresses. Ion uptake was retarded in most of the ecotypes of C. ciliaris and C. dactylon. Zn2+ and Fe2+ uptake was increased with increasing level of Cd2+ and Ni2+ contaminated medium. There was a marked impact on anatomical features of both grass species under Cd2+ and Ni2+ stresses. Cell size of root and shoot decreased in all ecotypes; however, increased vascular bundle area was recorded in the ecotypes of C. ciliaris. Epidermal area decreased while mechanical tissue area increased in all the ecotypes under metal stress. Cadmium stress showed positive influence on stem and leaf anatomy while nickel showed damaging effect on parenchyma, where disintegration was seen in endodermis and pith tissues of C. ciliaris. However, the ecotypes of C. dactylon remained unaffected by Ni2+ stress. The ecotypes of C. dactylon collected from Faisalabad and Pakka Anna performed better in metal (Cd2+ and Ni2+) stress while C. ciliaris from the Salt Range was adversely affected when subjected under Cd2+ and Ni2+ stresses.