Change in Physio-Biochemical Responses Induced by Cold Stress in Common Bean

Metabolic acclimation through alternation in oxidative damages and defense system activity establishes cold tolerance in plants. In this study, the metabolic responses of seven cultivars of common bean (Phaseolus vulgaris L.), including the Ghaffar, Khomein, Saleh, Kousha, Azarakhsh, Pakoutah, Seddei were examined at 1 and 3 days after the onset of cold stress (DAS) at 3°C. In contrast with a continuous gradual increase in the H2O2 content in all the cultivars, the lowest H2O2 content was belong to the cultivar Kousha by 40% increase at 3 DAS compared to the control conditions. During cold stress, the highest activity of superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX), guaiacol peroxidase (GPX) and polyphenol oxidase (PPO) was related to the cultivar Kousha. The cultivar Kousha had the highest total phenolic compounds (TPC) and flavonoids content (3- and 1.5-fold, respectively) at 3 DAS compared to the control conditions. Leaf chlorophylls (chl) content showed decreasing trends in all the cultivars, while the cultivar Kousha performed well in maintaining the stability of the photosynthetic apparatus with a regulated decrease in its chl content (4.6% in chl a and 53.9% in chl b) and the highest induction of chl a/b ratio and carotenoids (2.34- and 2.5-fold, respectively) at 3 DAS. A positive correlation of carotenoids paralleled with cellular damage pattern (H2O2 results) confirmed their defensive role along with antioxidative activities especially in the cultivar Kousha. Except the cultivar Kousha, incapability of regulating in signaling (H2O2 content) and defense systems were limiting factors, determining the low acclimation capacity of common bean cultivars to cold stress.