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Cold stress is an important factor affecting chickpea (Cicer arietinum L.) plants in winter and early spring. We evaluated the effects of cold stress by measuring lipid peroxidation, membrane permeability, and some enzyme activities involved in the ROS scavenging system under acclimation and non acclimation con ditions in black chickpea Kaka, a popular genotype planted, and accession 4322, as a landrace genotype. Under non acclimation conditions, the genotype 4322 prevented the H 2 O 2 accumulation more efficiently, which led to a decrease in lipid peroxidation and membrane permeability compared to Kaka. Studying the activities of antioxidant enzymes showed that catalase was more effective enzyme in cell protection against H 2 O 2 in 4322 plants. Such response in acclimated plants was more pronounced than in control and non acclimated plants. In this study, the increase in guaiacol peroxidase and ascorbate peroxidase activities did not preserve cell membranes from oxidative damage in Kaka plants. It was observed that short term acclima tion can induce greater cold tolerance upon the increase of oxidative stress in chickpea plants. This was due to low levels of MDA and electrolyte leakage index, indicating the lower lipid peroxidation and higher mem brane stability under the cold stress compared to non acclimated plants.

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This experiment was conducted in order to determine the effects of different concentrations of manganese (Mn) on the levels and correlations of multiple primary and secondary metabolites in Mentha aquatica. With this aim, four levels of Mn concentrations were used as follows: basic Hoagland's solution (control), 40, 80, and 160 μM of Mn supplied as MnSO.HO. The results indicated that the biomass and the contents of photosynthetic pigments and soluble carbohydrates were higher in the plants that were treated with the moderate concentrations of Mn (40 and 80 μM) than the control and 160 μM-treated plants. On the other hand, the contents of flavonoids, anthocyanins, malonaldehyde (MDA), hydrogen peroxide (HO), and the activities of antioxidant enzymes (total superoxide dismutase (SOD), catalase (CAT), and peroxidase (POX)) were progressively increased with the enhancement of Mn concentration in the nutrient solution. In addition, there were clear differences in the content and chemical composition of essential oils among the control and treatment groups. In this study, 1,8-cineole, menthofuran, and β-caryophyllene were the most abundant constituents of essential oils in both the control and Mn-treated plants. The correlation analysis between pairs of the primary and secondary metabolites showed that there were positive and negative correlations among the variables when the Mn concentration was increased in the nutrient solution. These findings clearly display a positive effect of Mn up to 80 μM in the nutrient solution on the growth of M. aquatica.