International Journal of Farming and Allied Sciences Available online at www.ijfas.com ©2015 IJFAS Journal-2015-4-7/585-593/ 30 September, 2015 ISSN 2322-4134 ©2015 IJFAS Biochemical and Morphological Response of Common Bean (Phaseolus vulgaris L.) to Salinity Stress and Vitamin B 12 Hamed Keshavarz * and Seyed Ali Mohammad Modares Sanavy Corresponding author: Hamed Keshavarz ABSTRACT: The effects of saline water irrigation and cyanocobalamin (vitamin B12) priming were evaluated on some growth parameters and biochemical attributes of common bean ( Phaseolus vulgaris L.). Effects were determined by leaf area, root and shoot length, root and shoot dry matter, antioxidant enzyme activity, protein content, chlorophyll and carotenoids, lipid peroxidation and proline accumulation. The results demonstrated that application of vitamin B12 provided significant protection against salinity stress compared with non treated plants. In addition, vitamin B12 application showed a significant effect on morphological characteristics. According to the outcomes, antioxidant enzyme activity, lipid peroxidation, carotenoid and proline accumulation increased due to NaCl stress while protein, chlorophyll and carotenoids decreased. Seed priming with vitamin B12 induced these stimulatory effects on all the measured parameters. Root protein content and leaf carotenoid content were not affected by vitamin treatment under conditions of salinity stress. These results suggest that, vitamin B12 may have a critical role as an effective antioxidant and regulates osmotic balance thereby enhancing bean pl ant’s resistance to salinity stress. Keywords: Antioxidant activity, Common bean, Cyanocobalamin, Dry matter, Photosynthetic pigments, Plant height Abbreviations: CAT: Catalase; Dry matter: DM; POX: Peroxidase; ROS: Reactive Oxygen Species; SOD: Superoxide dismutase INTRODUCTION Plants are usually exposed to different environmental stresses that limit their growth and productivity, of which salinity stress is the most severe. It has been well documented that salinity significantly inhibits plant growth (Saqib et al. 2005). An adverse effect on biochemical processes has also been reported in many species (Zhang et al. 2011). Salt stress is known to change the composition of N-containing compounds, especially proteins (Saqib et al. 2005). In addition, sodium chloride stress inhibits the uptake and transportation of K + that causes an ion imbalance between Na + and K + causing ion toxicity and osmotic stress in plant cells (Sivritepe et al. 2005, Khan and Panda 2008). Photosynthesis, as a key metabolic pathway in plants is a process that is particularly susceptible to salt stress. It is likely that salt stress limits gaseous exchange causing a disruption to stomatal closure and limits CO2 supply to leaves (Harris and Outlaw 1991; Fendina et al. 1994). Over reduction of the photosynthetic electron transport chain induces the generation of reactive oxygen species (ROS), such as superoxide anion (O2 •− ), hydrogen peroxide (H2O2) and hydroxyl radical (OH • ) (Ghosh 2011). The levels of ROS are regulated by the rate at which they are generated, the rate of reaction and the potential rate of degradation on interaction with target substances such as proteins, lipids and nucleic acids. The rate of scavenging/neutralizing by enzymatic and non-enzymatic antioxidants also affects the regulation of ROS (Hasanuzzaman 2011).