The changes in the antioxidant enzymes activity, total protein and proline content and their correlations with freezing tolerance (FT) (expressed as LT 50 ) were investigated at 11 different olive cultivars at cold-acclimation (CA, in February) and non-acclimation (NA, in August) stages. Leaf samples were collected from each cultivar and were divided into two groups. The first group was immediately frozen in liquid nitrogen for further biochemical analysis. The second ones was subjected to different freezing temperatures (-5, -10, -15 and -20°C) for 10 h, in order to determine their FT. The unfrozen control samples were kept at 4°C. The results showed that Fishomi, Mission and Shengeh were the most freezing tolerant among other cultivars. In contrast, Zard, Manzanilla and Amigdalolia were the most sensitive ones. The cold acclimation enhanced the activities of superoxide dismutase (SOD), peroxidase (POD), ascorbate peroxidase (APX), catalase (CAT), polyphenol oxidase (PPO) and total protein content. However, proline content and phenylalanine ammonia-lyase (PAL) activity did not change or even decreased slightly at CA stage, compare to those samples at NA stage. It was found that LT 50 to be closely correlated to POD, CAT, and PPO activity at CA and NA stages. Overall, higher leaf POD, CAT, and PPO activity could be used as important selection criteria in screening tolerant olive cultivars for cold zone climatic.

No abstract

No abstract

The freezing hardiness (expressed as LT 50 ) as well as changes in the antioxidant enzymes activity, total protein and lipid peroxidation (MDA content), total phenolic and flavonoid content, antioxidant capacity, chlorophyll fluorescence (F v /F m ) of Echinacea purpurea (L.) Moench were investigated. Five month old purple coneflower seedlings were kept at 4°C for two weeks to induce cold acclimation. The acclimated seedlings were treated with freezing temperatures (0, -4, -8, -12, -16, and -20°C) for 6 h. The unfrozen control plants were kept at 4°C. The results with lowering freezing temperatures showed a sharp increase of ion leakage and MDA content at -20°C as compared to the nonfreezing temperature. Exposing seedlings to freezing temperatures were accompanied by decreasing dark adapted chlorophyll fluorescence (F v /F m ). Freezing stress significantly reduced superoxide dismutase (SOD), ascorbate peroxidase (APX), and catalase (CAT) activity of seedling leaf except at 0°C. With lowering freezing temperature, peroxidase (POD) and polyphenol oxidase (PPO) activity showed a sharp decline to -20°C. Furthermore, total protein and antioxidant capacity of Echinacea leaves were declined significantly after exposure to freezing temperature, and thereafter reached to the highest at ⎯8°C. Total phenolic content of freezing treated seedlings was significantly lower than that of the nonfreezing seed lings. Total flavonoid content increased significantly with lowering freezing temperatures. It was found that per centage of freezing injury closely correlated to antioxidant enzymes activity (POD and PPO; r = -0.93) and F v /F m ratio (r = -0.77). Based on our results, the freezing tolerance (LT 50 ) of Echinacea seedlings under artifi cially simulated freezing stress in the laboratory was -7°C.

In this study, qualitative traits and bioactive compounds of edible oil that extracted from three olive promising genotypes (T2, T7, and T18) and two cultivars (Zard and Koroneiki) from Tarom olive collection in Zanjan province were evaluated during two crop seasons (2017)(2018). Edible oil quality traits including free fatty acids (FFA), peroxide value (PV) and extinction coefficients (K232 and K270), total chlorophyll, total carotenoids, total phenols, total flavonoids and antioxidant capacity were measured. The results of analysis of variance of year  cultivar / genotype on oil qualitative traits showed that their interactions on all traits except K270 were significant at 1% probability level. The results showed that edible oil of T7 genotype (0.79% as oleic acid) and Zard cultivar (0.43% as oleic acid) in 1997 had the lowest and highest FFA contents, respectively. Edible oil of T7 in 2018 (17.22 m Eq / kg of oil) and T2 in 2017 (96.67 m Eq / kg) showed the highest and lowest PV levels, respectively. The K232 extinction coefficient of T18 oil was the lowest in both years (0.8 and 1.03 for 2017 and 2018, respectively). Edible oil of Zard cultivar had the highest amount of total phenol in 2017 (243.94 mg gallic acid per kg of oil). T7 genotype had the highest amounts of total flavonoids in 2018 (21.45 mg of quercetin per kg of oil). Koroneiki cultivar with 90.55% had the highest antioxidant capacity in 2017 and T7 genotype with 41.65% had the lowest value of this index. T2 genotype in both years in terms of antioxidant capacity was in a statistical group with commercial cultivars.