Effects Of Low Temperature On Photosynthesis And Antioxidant Enzyme Activities Of Panax Notoginseng During Seeding Stage

In order to find out the low temperature (LT) meteorological disaster index of Panax notoginseng. One-year-old P. notoginseng seedlings were used as experimental materials. The LT treatments were 9,6,3 and 0 degrees C, with 25 degrees C as control. The experiments lasted for 7 d, and then all plants were moved to 25 degrees C for 5 d of recovery. The leaves of P. notoginseng showed different degrees of chlorosis after the LT treatment. With the extension of low temperature stress (LTS) time, the contents of Chlorophyll a (Chl a), Chlorophyll b (Chl b), superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT) in the leaves of P. notoginseng showed a tendency to increase first and then decrease. At 9 and 6 degrees C, all maxima appeared at 5d, but at 3 and 0 degrees C, appeared at 3d. Non-photochemical quenching (NPQ) at 9 and 6 degrees C increased with the prolongation of LT stress time, while at 3 and 0 degrees C, it increased first and then decreased, and both maxima appeared at 3d. Carotenoid, Chl a/b, maximum photosynthetic rate (P-ma(x)), apparent quantum efficiency (AQE), electron transport rate (ETR) and light saturation point (LSP) decreased under LTS. At 3 degrees C for 3d, these values were significantly lower than the control. Malondialdehyde (MDA) and light compensation point (LCP) were contrary to the P. After 5 d of recovery, the values of Net photosynthetic rate (Pn), stomatal conductance (Gs), intercellular carbon dioxide concentration (Ci), and stomatal limitation value (Ls) at 9 and 6 degrees C were recovered to normal levels, while 3 and 0 degrees C failed to recover. The results suggested that the key low temperature threshold point for P. notoginseng seedlings was 3 degrees C for 3d. (C) 2019 Friends Science Publishers