Enzymatic and Non-Enzymatic Response of Sphenostylis stenocarpa to Cadmium Stress

Enzymatic and Non-Enzymatic Response of Sphenostylis stenocarpa to Cadmium Stress

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  • March 8, 2019
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Background and Objective: Environmental stress such as heavy metal is a major factor affecting reduction in agricultural productivity. Heavy metals at toxic levels hamper normal plant functioning and act as an impediment of metabolic processes by the production of Reactive Oxygen Species (ROS). Plant has evolved various enzymatic and non-enzymatic mechanism to cope against the ROS produced. This study investigated the biochemical response of S. stenocarpa  to cadmium stress. Materials and Methods: S. stenocarpa  (Fabaceae) seeds were sown in the control (0 ESV) and the different concentrations (2.5, 5 ESV) of cadmium chloride (CdCl2). The soil samples were collected from 10 different points at a depth of 0-30 cm using a soil auger, pooled together, air-dried and grind to pass through a 2 mm sieve before subjecting to physico-chemical analysis. The five accessions consisted of 3 blocks, 15 treatments per block, two plant per polythene bag arranged in a RBD. Enzymes such as superoxide dismutase (SOD), catalase (CAT), malondialdehyde (MDA), proline as well as non-enzymes such as tocopherol, ascorbate were determined. Results: Increased cadmium concentration resulted in increased translocation of the metal in the plant leaves and decreased chlorophyll a/b content of  TSs-accessions. Increase in cadmium concentration results to variability in enzymatic and non-enzymatic response of the studied accessions. Take for instance overall MDA, SOD and proline activities were significantly increased in the Cd-5ESV as compared to the control. However, the accessions varied in their response to cadmium. For instance, the SOD of TSs-95 was reduced with increased cadmium concentration. Similarly, the ascorbate and tocopherol content decreased in TSs-92 and TSs-95, respectively with increased Cd concentration. Individual plants showed different antioxidant responses either between the plants or among the accessions. The MDA activity significantly increased in leaves with metal increase while SOD activity was heighten in TSs-91  whereas  in  TSs-95  there  were  no  significant  difference  in  SOD  activity  between  control  and Cd-exposed plant.

Conclusion: The increase in antioxidant activities of the metal exposed plants compared to their control counterpart suggested possibility of free radicals instigated by metal presence. This further gave trendies to plants’ resistance capacities with SOD been the first line of defense.

Key words: Environmental stress, biochemical response, reactive oxygen species, antioxidant activities, heavy metal, non-enzymatic response, cadmium stress