The physiological and biochemical responses of eastern purple coneflower to freezing stress

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.

Physio-Biochemical Insights into the Cold Resistance Variations among Nectarine (Prunus persica (L.) Batsch var. nectarina) Cultivars

“…In this study, the contents of PRO, SS and SP in shoots of LR nectarine cultivars were found to be lower than MR and HR cultivars at all timepoints during overwintering, suggesting that the high contents of these three osmoregulatory substances contributed positively to the cold resistance of nectarine. In addition to them, MDA can also be used as an important index for the cold resistance evaluation of plants [17] and its content was generally negatively correlated with cold resistance [43]. Consistently, our study found that the MDA contents of HR cultivars were lower than MR and LR cultivars.…”

Physiochemical Responses and Ecological Adaptations of Peach to Low-Temperature Stress: Assessing the Cold Resistance of Local Peach Varieties from Gansu, China

“…Low-temperature stress can induce an increase in ROS content in plants, and with the deepening of stress, the accumulation of ROS exceeds the range that plants can tolerate, leading to adverse effects [ 60 ]. In this study, CAT activity increased rapidly at −10 °C and then decreased slowly; the trend of CAT activity change was the same as that of Echinacea under LT induction [ 61 ], and both peaked at LT stress. SOD decreased after rising at −10 °C, and then rose rapidly to reach a peak at −25 °C, while POD gradually increased with the decrease in temperature.…”

Ornamental potential and freezing tolerance of six Thymus spp. species as ground-covering plants in the landscape

“…The reduction of POD activity might be due to the inhibition of enzyme synthesis or change in the assembly of enzyme subunits under stress conditions (Abedi, Pakniyat, 2010). Decreased enzyme activity has been reported under low temperature (Asadi-Sanam et al, 2015), insecticide stress (Bashir et al, 2007) and drought (Abedi, Pakniyat, 2010). The higher activity of POD, SOD and APX under freezing conditions is a sound indication of Thymus species ability to cope with ROS.…”